Oral Presentations: Polymer Characterization · Oral Presentations: Polymer Characterization 12 th...

Oral Presentations: Polymer Characterization

12th National Graduate Research Polymer Conference 2016 | College of Polymer Science and Polymer Engineering at The University of Akron

Auto-exfoliating acid degradable protective polymer layer for chemical and biological threat reduction Abstract: Acid sensitive crosslinker 2,5-dimethyl-2,5-hexanediol dimethacrylate (DHDMA)-containing thin hydrogel films were synthesized as protective layers from chemical and biological (CB) threats. Hydrogels based on poly (ethylene glycol) dimethacrylate (PEGDMA) and 2-hydroxyethyl methacrylate (HEMA) were prepared by free radical crosslinking polymerization. Thermal (60-700C) and UV (λ: 365nm) curing methods were used to cure the thin films and the thicknesses of the films varied from 20-50 (µm) were observed by optical profilometer. The influence of different compositions of PEGDMA and HEMA on the moisture vapor transmission rate (MVTR), mechanical properties, swelling properties and morphology of P(PEGDMA/DHDMA/HEMA) copolymeric hydrogels have been investigated. The MVTR values, mechanical and swelling properties were found to be improved with increased PEGDMA content. Acid sensitive nature of tertiary ester group of DHDMA with crosslinked films, they can be easily cleaved under acidic condition at elevated temperature (90-1000C). The cleavage of crosslinked hydrogel thin films was observed by H1-NMR, DSC and scanning electron microscope (SEM).

1



Specific ion effects on the performance of ion

exchange membranes used in clean energy

applications

Harrison J. Cassady

Abstract

Rapid industrialization over the last two centuries has strained worldenergy supplies and threatens the stability of the global climate. Since1750 atmospheric carbon dioxide levels have increased by 142 %. Thermalexpansion of seawater as well as arctic ice melting at a rate of 2.7 % perdecade has contributed to a rise in global sea level if 1.3 mm/year for thepast twenty years. A study examining climate-induced behavioral changesin plants and animals found 80 % of species to exhibit shifts in directionscongruent with global warming. It is known with high confidence thatanthropogenic emission of greenhouse gases and consequent global warm-ing is responsible for these, as well as other changes. The need for cleanenergy technologies is imperative in slowing the growth of greenhouse gasemissions and ensuring a hospitable world for many generations to come.Ion exchange polymers form a class of materials that can be found inmany clean energy technologies such as the generation of electricity fromionic concentration gradients in reverse electrodialysis, the storage of windenergy produced during non-peak hours in redox flow batteries, and theconversion of hydrogen into electricity in a PEM fuel cell. These technolo-gies rely on ion exchange membranes to provide a barrier to a multitudeof different ions. Despite this, ion exchange polymers are typically char-acterized in pure sodium chloride solutions, and the effect of different ionson their performance is relatively unknown. This talk talk will focus onthe use of ion exchange polymers in clean energy applications, and myrecent work on understanding the effects that specific ions have on theperformance of these materials.

2



Presenter: Jack Chalker, UG

Title: Investigation of Chemical Network Structure of Matrix and Interphase of Polymer Matrix

Composite

Abstract: Understanding the chemical network structure of polymer matrix composite and its

relationship with mechanical performances can lead to a comprehensive understanding of failure mechanisms. This work investigates the nanoscopic nature of PMC matrix as well as interphases in terms

of topography and chemical mapping to find a bridge between nanoscopic, microscopic and macroscopic mechanical properties. It is guided by ongoing simulations aimed at an understanding of bond scission,

interphase structure and mechanical properties at the nanoscale level via a multiscale computational approach. DGEBA epoxy resins with known chemical structures are processed in-house with varying

molecular weight, controlled stoichiometric ratios (resin and cross-linker) and degrees of cure, both in the

presence and absence of carbon fiber. AFM-IR is used to investigate the chemical structure at ~ 100 nm resolution, which is calibrated by controlled experimental characterization at varying conditions using

FTIR (mid-IR and near-IR) in bulk.

3



Synthesis of Main Chain Purine-based Copolymers and Effects of Monomer Design on Thermal and Optical Properties Graham S. Collier,† Lauren A. Brown,† Evan S. Boone,‡ Brian K. Long,† S. Michael Kilbey II†‡* †Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States ‡Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States Abstract Understanding the relationship between monomer design and polymer properties is

essential for developing a “materials-by-design" approach for polymeric materials with

targeted applications. Motivated by the idea that purine-based copolymers could provide

a class of polymeric scaffolds with diverse properties due to the myriad ways they can be

modified, purine-derived monomers were synthesized and introduced directly into a

polymer backbone via metal-catalyzed polymerizations. Variations in substitution pattern

of the purine monomers and benzodithiophene (BDT) comonomer side chains allowed

links between “poly(purine)” design and thermal and photophysical properties to be

examined. Specifically, thermal analyses show that poly(purine)s exhibit high thermal

stability and high glass transition temperatures, depending on the BDT side-chain type

and substitution pattern of the purinyl comonomer. UV-Vis and fluorescence

spectroscopies show that poly(purine)s exhibit intramolecular charge-transfer (ICT)

characteristics and have emission wavelengths spanning ~150 nm of the visible spectrum.

These findings demonstrate the first example of the synthesis of main chain poly(purine)s

and highlights the potential to manipulate the resulting thermal and photophysical

properties and serve as a foundation for further investigations of purine-based polymers.

4



High Tg Polyesters as Potential BPA-Polycarbonate Replacements

Joseph M. Dennis, Josh S. Enokida, Nicole Fazekas, and Timothy E. Long

Macromolecules and Interfaces Institute, Department of Chemistry, Virginia Tech, Blacksburg,

VA 24061

Symposium: New Synthesis & Characterization of Polymers

With increased concerns for BPA-containing materials, a critical area of research remains in

developing BPA-free replacements.1 Recent investigations have identified cycloaliphatic

diesters, such as decahydronaphthalate dimethyl ester, as promising high-impact polyesters.2

The intense beta-relaxations in the glassy regime suggests several local relaxations, and presents

a mode for high-energy dissipation. However, the Tg’s below 100 °C prevent utility of these

amorphous materials in many commercial applications. By introducing rigid, aliphatic diols (e.g.

2,2,4,4-tetramethylcyclobutane-1,3-diol) the glass transition is increased to above 120 °C.

Although introduction of the cyclobutane ring reduces the overall low-temperature local

mobility, the relaxations attributed to the fused decahydronaphthalate rings remain constant. As

a result, these all-aliphatic polyesters maintain modes for high-energy dissipation suggesting

impact-strengths similar to BPA-Polycarbonates. A compilation of analytical techniques derives

structural relationships, while melt rheology and compression molding illustrate the melt

processability of these novel polyesters. Finally, the necessity of certain structural aspects are

highlighted for potential high Tg, high impact, BPA-polycarbonate replacements.

1. Nelson, A. M.; Long, T. E. Polym. Int. 2012, 61, (10), 1485-1491. 2. Dennis, J. M.; Enokida, J. S.; Long, T. E. Macromolecules 2015, 48, (24), 8733-8737.

5



Effect of cooling rate on crystal polymorphism in

beta-nucleated isotactic polypropylene as revealed

by a combined WAXS/FSC analysis

Alicyn Marie Rhoades 1,*, Nichole Wonderling2, Anne Gohn1, Jason Williams 1, Daniela

Mileva3, Markus Gahleitner 3, René Androsch4,*

1 School of Engineering, Penn State Behrend, 4701 College Drive, Erie, PA 16563,

United States

2 Materials Characterization Laboratory, N-003 Millennium Science Complex,

Pennsylvania State University, University Park, PA 16802, United States

3 Borealis Polyolefine GmbH, Innovation Headquarters, A-4021 Linz, Austria

4 Martin-Luther-University

Abstract

The efficiency of linear trans -quinacridone to nucleate formation of -crystals in

isotactic polypropylene (iPP) at rapid cooling conditions has been evaluated by a

combination of fast scanning chip calorimetry (FSC) and microfocus wide-angle X-ray

scattering (WAXS). For samples containing different amount of -quinacridone, FSC

cooling experiments revealed information about a critical cooling rate above which the

crystallization temperature decreases to below 105 °C, that is, to temperatures at which the

growth rate of -crystals is higher than that of -crystals. Microfocus WAXS analysis was

then applied to gain information about the competition of formation of - and -crystals in

samples prepared at well-defined conditions of cooling at rates up to 1000 K/s in the FSC.

For iPP containing 1 and 500 ppm -quinacridone, the crystallization temperature is lower

than 105 °C on cooling faster about 10 and 70 K/s, respectively, which then on further

increase of the cooling rate leads to a distinct reduction of the -crystal fraction. The study

may be considered as a first successful attempt to quantify and interpret -crystal

formation in iPP containing -quinacridone at processing-relevant cooling conditions in the

shed of light of the different temperature-dependence of the growth rates of - and -

crystals.

6



Depletion of functionalized chain ends from polymer surface observed by novel mass spectrometry technique

Jacob A. Hill1, Kevin Endres1, John Meyerhofer3, Qiming He1, Chrys Wesdemiotis1,2, Mark

D. Foster1

1Department of Polymer Science, University of Akron, 302 E Buchtel Ave, Akron, OH

44325 2Department of Chemistry, University of Akron, 302 E Buchtel Ave, Akron, OH 44325 3Department of Chemistry, Saint Vincent College, 300 Fraser Purchase Rd, Latrobe, PA

15650

MALDI mass spectrometry (MS) is able to distinguish polymer molecules that differ in

quite subtle ways, such as differing only in the chemistry of one chain end. A new

technique, Surface Layer-MALDI-ToF Mass Spectrometry (SL-MALDI ToF MS) is able to

provide such precise identification for chains in the top molecular layer of polymer blends.

Conventional MALDI-MS analysis shows that the blend studied contains 9 mol %

hydroxymethyl terminated polystyrene (PS) with the remainder being conventionally

terminated PS. Using SL-MALDI-ToF-MS, we observe complete depletion of this

component from the surface of blend films prepared by spin coating. The percentage of

hydroxymethyl functionalized chains in the molecular layer adjacent to air is below the

noise level (< 1 mol %), providing strong evidence that the presence of the functionalized

chain end alone was sufficient to drive segregation of the entire chains away from the

surface during spin coating. Such depletion is remarkable. The study of such segregation

phenomena by other spectroscopic methods usually requires labelling and thus is more

complicated and cumbersome and the labelling can drive segregation by itself. SL-

MALDI-ToF-MS has the ability to observe behavior of chains differing by only the terminal

end group when that group accounts for less than 0.5 % of the chain's mass.

7



High Performing Polyethylene oxide-PDMS Membranes for Carbon Dioxide

Separation

Tao Hong1, Sophia Lai2, Shannon Mahurin3, De-en Jiang4, Brian Long1, Jimmy Mays1,3, Alexei

Sokolov1,3, Tomonori Saito3

1. Department of Chemistry, University of Tennessee, Knoxville, TN 37996

2. Department of Chemistry, Cornell University, Ithaca, NY 14850

3. Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831

4. Department of Chemistry, University of California, Riverside, CA 92521

8



Abstract:

A climate change caused by a greenhouse effect is one of the most challenging problems we face

today, and the development of high performance materials for CO2 separation and capture will

significantly contribute to solution of the problem. Passive membranes present one of the

promising and energy efficient solutions. However, materials with high CO2 permeability and

good selectivity are needed for these membranes to be used in a practical field, and only few

materials have been developed to meet the requirement. Based on our previous study on cross-

linked (Bicycloheptenyl) ethyl terminated polydimethylsiloxane (PDMSPNB) membranes [1],

we herein report the study on the incorporation of the CO2-philic polyethylene oxide (PEO)

group into the PDMSPNB matrix. The Ab initio calculations were carried out and used to

identify the binding energies of the CO2-PEO complexes[2] .The membranes were synthesized

using in-situ ring-opening metathesis polymerization. The CO2 permeability and CO2/N2

selectivity were largely influenced by the PEO composition. Our highest performing PEO-

PDMSPNB membranes showed excellent CO2 permeability and achieved the performance on the

Robeson upper bound line (CO2 premeability ~3500 Barrer and CO2/N2 ~22). The gas solubility

measurements are carried out to elucidate the correlation between binding energies and CO2

solubility. This study contributes to foster the fundamental understanding of gas transport

through polymer membranes for CO2 separation as well as many other applications.

101

102

103

104

105

10

100

XL-C

4EO-40

CO

2/N

2 S

ele

ctivity

CO2 Permeability (Barrer)

Figure 1. Representative data of cross-linked PDMSPNB (XL-C) [1], and PEO-PDMS (4EO-40)

membranes in the Robeson plot.

[1] Hong et al. ChemSusChem 2015, 8, 3595 – 3604.

[2] Tian et al. J. Phys. Chem. A 2015, 119, 3848−3852.

9



“High-throughput investigation of polymer crystallization in thin films via flowcoating” Giovanni M. Kelly, Julie N. L. Albert Tulane University, New Orleans, Louisiana Semi-crystalline polymers exhibit mechanical, optical, and chemical properties that have made these materials invaluable for applications in consumer packaging, organic photovoltaics, and drug delivery. As the materials for these applications continue to increase in complexity, a greater fundamental understanding of the physical phenomena that dictate polymer crystallization is needed. These phenomena include the way changing macromolecular architecture alters crystallization kinetics, confinement-driven orientational changes in crystalline nano-, micro-, and macro-structures, and the role blending plays on crystallization in two and three dimensions. Whereas the majority of the literature reports the use of spincoating to generate polymer thin films, flowcoating has allowed us to create gradient thickness films that can be quickly and easily characterized to study the morphological and physical changes that occur over single-nanometer variations in film thickness. Using this technique, we seek to elucidate the relationship between morphology and degree of confinement (film thickness), which can be further correlated to molecular dimensions such as the radius of gyration and the crystalline lamellar thickness. Furthermore, these gradients have revealed novel, film thickness-dependent morphologies in polymer blends and permitted us to study the conditions under which these morphologies occur most readily and reproducibly.

10



Synthesis and characterization of novel amphiphilic poly(vinyl ether)s based on soybean oil

Kyle Kingsley,1 Satyabrata Samanta,1 Shane Stafslien,2 Lyndsi Vanderwal,2 and Bret J. Chisholm1

1Department of Coatings and Polymeric Materials

2Research and Creative Activity

North Dakota State University

Fargo, North Dakota

Environmentally friendly amphiphilic copolymers were synthesized using cationic polymerization of a vinyl

ether monomer derived from soybean oil with different poly(ethylene glycol) (PEG) vinyl ethers. The

soybean oil vinyl ether monomer, 2-(vinyloxy)ethyl soyate (2-VOES), was prepared by base-catalyzed

transesterification of 2-(vinyloxy)ethanol and soybean oil. An important feature of this type of

polymerization is the ability to polymerize exclusively through the vinyl ether double bond, while still

maintaining unsaturation from the fatty acid ester pendent groups derived from the soybean oil starting

material. Copolymers were synthesized by cationic polymerization using varying weight ratios of 2-VOES

and PEG vinyl ethers that varied with respect to the number of ethylene glycol units. Coatings were

produced on steel substrates and cured at ambient conditions through autoxidation. The properties that

were analyzed included drying time, solvent resistance, hardness, impact resistance, adhesion, contact

angle, and flexibility. Free films were also produced and used to measure mechanical and viscoelastic

properties of the copolymers. Additional analysis of free films included AFM, protein absorption, water

absorption, and red blood cell hemolysis.

11



Effects of Crosslink Density and Crosslink Inhomogeneity on CO2 Transport in Crosslinked PEO-based

Gas Separation Membranes

Gregory K. Kline and Ruilan Guo

University of Notre Dame, Department of Chemical and Biomolecular Engineering, Notre Dame, IN

46556, USA

Crosslinked poly(ethylene oxide) (PEO) membranes are attractive for performing CO2 separations.

However, CO2 separation performance varies widely among reported crosslinked PEO systems, most

likely because random crosslinking process was applied resulting in rather ambiguous crosslinked

structures. Furthermore, all reported studies focused only on the effects of crosslink density while

leaving crosslink inhomogeneity, the uneven distribution of crosslinks in the network, unexplored. To

obtain a more comprehensive understanding of the effects of crosslinking, this work reports on a series

of PEO-based, model crosslinked membranes with systematically varied crosslink density and crosslink

inhomogeneity. Crosslink density was controlled by end-crosslinking commercial Jeffamine

polyetheramines of specific molecular weight of 148, 600, 900, or 2000 g/mol with an epoxy terminated

PEO. The distribution of crosslinks was controlled through end-linking Jeffamines of different molecular

weight, whereby three types of crosslinked membranes with distinct level of inhomogeneity were

produced: unimodal, bimodal, and clustered. All membranes show high gel contents above 95%.

Furthermore, the membranes show no crystallinity at permeation testing conditions (35°C) and are

thermally stable with Td (10 wt% loss) greater than 312°C. Pure gas permeability was evaluated for CO2

related gas pairs, including CO2/H2 and CO2/N2. It was found that decreasing crosslink density is a

prominent factor in increasing CO2 permeability. Further improvements in CO2 separation performance

were realized by introducing various degrees of inhomogeneity. Both the bimodal and clustered films

outperformed respective unimodal films in terms of CO2 permeability and CO2/H2 selectivity suggesting

the important role of crosslink inhomogeneity in dictating gas transport properties. These crosslinked

films approach or surpass the most recent Robeson upper bounds for CO2/H2 and CO2/N2 separations,

making them attractive membranes for H2 purification and carbon capture.

12



Title: Influence of Humidity on the Structure and Water Uptake in Cationic Polymer

Thin Films

By Douglas Ian Kushner

Increasing energy demand and environmental impact is driving research towards new and

more efficient energy conversion from clean fuel sources. Ion conducting membranes play a

significant role in the operation of these devices resulting in a parallel development of new

polymers for increased membrane ion conductivity and understanding thin film properties under

confinement in the catalyst layer. This work focuses on the thin film response under controlled

humidity for two anion exchange membrane (AEM) polymers developed in our research group.

The first polymer is comb-shaped poly(2,6-dimethyl-phenylene oxide) synthesized with

controlled n-alkyl (n = 0, 6, 10, and 16) side chains tethered pendant to the quaternary ammonium

cation (QA). The role of the side chain is to control phase separation generating ion conduction

pathways and mechanical integrity. The microstructure was characterized using grazing incidence

X-ray scattering (GIXS). The mechanical properties of the thin film were measured using

cantilever bending that is capable of resolving small changes in deflection due to the change in

coating modulus. Spectroscopic ellipsometry (SE) and quartz crystal microbalance (QCM) were

employed to monitor the swelling strain and water uptake, respectively to draw upon the

correlation between modulus and water uptake.

The second polymer of interest is diblock copolymer poly(hexylmethacrylate-b-

quaternized vinyl-benzyl chloride) (PHMA-b-QAPVBC). Block copolymers provide the ability to

tailor specific properties. In the case of AEMs, the hydrophilic block provide ion conduction

pathways while the hydrophobic block acts as the structural block not influenced by water. The

13



phase separated morphology was characterized using atomic force microscopy and GIXS for

surface and bulk morphology, respectively. The swelling and water uptake were monitored using

SE and QCM. The water uptake measurements resulted in pinpointing the morphology transition

from a parallel cylindrical morphology to a lamellar morphology as a function of thickness.

14



Efficient Perovskite Hybrid Photovoltaics via Alcohol-Vapor Annealing Treatment

Chang Liu,1 Kai Wang,

1 Chao Yi,

1 Xiaojun Shi,

2 Adam W. Smith,

2 Xiong Gong

1* and Alan J. Heeger

3

1) Department of Polymer Engineering, The University of Akron, Akron, OH 44325, USA

2) Department of Chemistry, The University of Akron, Akron, OH 44325, USA

3) Center for Polymers and Organic Solids, University of California, Santa Barbara, CA 931006, USA

Abstract

In this work, we report alcohol-vapor solvent annealing treatment on the CH3NH3PbI3 thin films,

aiming to improve the crystal growth and increase the grain size of the CH3NH3PbI3 crystal, thus

boosting the performance of perovskite photovoltaics. By selectively controlling CH3NH3I

precursor, larger-grain size, higher crystallinity and pinhole-free CH3NH3PbI3 thin films are

realized, which result in enhanced charge carrier diffusion length, decreased charge carrier

recombination and suppressed dark currents. As a result, over 43% enhanced efficiency along

with high reproducibility and eliminated photocurrent hysteresis behavior are observed from

perovskite hybrid solar cells (pero-HSCs) where the CH3NH3PbI3 thin films are treated by

methanol vapor as compared with that of pristine pero-HSCs where the CH3NH3PbI3 thin films

without any alcohol vapor treatment. In addition, the dramatically restrained dark currents and

raised photocurrents give rise to over 10 times enhanced detectivities for perovskite hybrid

photodetectors, reaching over 1013 cmHz1/2W-1 (Jones) from 375 nm to 800 nm. These results

demonstrated that our method provides a simple and facial way to boost the device performance

of perovskite photovoltaics.

*Corresponding author, Email: [email protected]; Fax: (330)9723406

15

mailto:[email protected]



Atomic Scale Observation of Atoms in Nanofibers of Polyvinylidene Fluoride by Electron Microscopy1

Suqi Liu,a Dinesh Lolla,b Joseph Gorse,a Christian Kisielowski,c Jiayuan Miao,d Philip L. Taylor,d

George G. Chaseb and Darrell H. Renekera

aDepartment of Polymer Science, The University of Akron, Akron, OH 44325, USA

bDepartment of Chemical and Biomolecular Engineering, The University of Akron,

Akron, OH 44325, USA

cThe Molecular Foundry and Joint Center for Artificial Photosynthesis, Lawrence

Berkeley National Laboratory, One Cyclotron Rd, Berkeley CA 94720, USA

dDepartment of Physics, Case Western Reserve University, Cleveland, OH 44106, USA

Obtaining the positions of atoms in molecules is a direct and fundamental way to specify

the structure and conformation of the molecules. An aberration corrected electron

microscope was used to observe the morphology and structure of electrospun

polyvinylidene fluoride (PVDF) nanofibers. Similar twists and bends of the PVDF

molecules observed in the electron micrographs were observed in images calculated by

molecular dynamic modeling. Relative movements of segments of PVDF molecules

were also observed. The atomic scale study of PVDF molecules in nanofibers sheds

light on the promising future of electron microscope for the structural and dynamical

study of polymer and other molecules inside or on the surface of nanofibers.

Scanning electron microscope (SEM) is also important in the morphology study of

polymber nanofibers. Stereographic SEM images of mats of nanofibers were observed.

These images showed the diameter and location of the nanofibers and were used to

calculate the average density inside the mat, for comparison with the density measured

by weighing and measuring the volume of the mat.

1Support from Coalescence Filtration Nanofiber Consortium, from the Office of Basic

Energy Sciences Contract No. DE-AC02-05CH1123, and from Akron Ascent

Innovations.

16



Elucidation of Stabilization Pathways of Atactic-Polyacrylonitrile by Solid-State NMR

Spectroscopy

Xiaoran Liu and Toshikazu Miyoshi

(Department of Polymer Science, The University of Akron, Akron, OH, USA 44325-3909)

Atactic-polyacrylonitrile (a-PAN) is used as major precursor to produce carbon fiber.

From a-PAN to carbon fibers, several heat treatment processes including stabilization,

carbonization and graphitization are involved.1 During stabilization, linear polymer structure is

believed to convert to ladder structure, which makes it able to survive during further heat

treatment at even higher temperature. For the past decades, several experimental approaches

including FT-IR, DTA, TGA, etc., have been applied to characterize chemical structures of

stabilized PAN.1,2 However, due to experimental limitations, stabilization process was still not

well understood at the molecular level.

In this talk, we report a novel strategy to characterize a-PAN stabilized as a function of

stabilization temperature and stabilization time by two dimensional 13C-13C and 1H-13C

correlation NMR techniques combined with selectively 13C isotopic labeling. Through-bond

correlation of stabilized a-PAN was successfully obtained to identify different chemical

structures with the change of stabilization temperature. Improved spectral resolutions of 1 and

2D NMR data for the first time revealed different stabilization pathways for PAN stabilized

under air and nitrogen. Meanwhile, degree of stabilization can also be calculated through

quantified 1D NMR spectra, which was plotted as a function of stabilization temperature and

time, respectively.

References

1. Rahaman, A. F.; Ismail, A. F.; Mustafa, A. Polym. Degrad. Stab. 2007, 92, 1421-1432.

2. Wang, Y.; Xu, L.; Wang, M.; Pang, W.; Ge, X. Macromolecules 2014, 47, 3901-3908.

3. Liu, X.; Chen, W.; Hong, Y.; Yuan, S.; Kuroki, S.; Miyoshi, T. Macromolecules 2015, 48,

5300-5309.

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Abstract for National Graduate Research Polymer Conference 2016 (June 19-22, Akron)

Segmented Copolymers of Poly(ethylene oxide) Reinforced with Pentiptycene-containing Polyimide Hard Segments for Highly CO2-Selective Gas Separation

Shuangjiang Luo1, Kevin A. Stevens2, Jae Sung Park2, Joshua D. Moon2, Qiang Liu2, Benny D. Freeman2, Ruilan Guo1,*

1Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556 2Center for Energy and Environmental Resources, Department of Chemical Engineering, Texas Materials Institute, The University of Texas at Austin, Austin, TX 78758

Gas separation using polymeric membranes has attracted substantial attention during the past

decades due to its high energy efficiency, relatively low cost and ease of operation.

Poly(ethylene oxide) (PEO)-containing polymer membranes are highly attractive for CO2-

related gas separations because of their high selectivity towards CO2 due to the favorable

dipole-quadrupole interactions between the EO unit and the CO2 molecules. However, the

development of PEO-rich membranes is frequently challenged by weak mechanical properties

and a high crystallization tendency of PEO that hinders gas transport.

In this study, we report the synthesis, characterization and gas transport properties of a new

series of CO2-selective, amorphous PEO-containing segmented copolymers based on

commercial Jeffamine® polyetheramines and pentiptycene-based polyimide hard segments.

The copolymers are much more mechanically robust than the non-pentiptycene counterparts

due to the molecular reinforcement mechanism of supramolecular chain threading and

interlocking interactions induced by the pentiptycene units, which also effectively suppresses

PEO crystallization leading to a completely amorphous structure even at 60 wt% PEO.

Membrane transport properties are sensitively affected by both PEO weight content and PEO

chain length. A nonlinear correlation between CO2 permeability with PEO weight content was

observed due to the competition between solubility and diffusivity contributions, whereby the

copolymers change from being size-selective to sorption-selective when PEO content reached

40%. CO2 selectivities over H2 and N2 increase monotonically with both PEO content and chain

length, indicating strong CO2-philicity of the copolymers. The copolymer film with the longest

PEO sequence (PEO2000) and highest PEO weight content (60%) showed a measured CO2

pure gas permeability of 39 Barrer, and ideal CO2/H2 and CO2/N2 selectivities of 4.1 and 46,

respectively, at 35 oC and 3 atm, making them attractive for hydrogen purification and carbon

capture.

References:

Luo, S.; Stevens, K.A.; Park, J.S.; Moon, J.D.; Liu Q.; Freeman, B.D.; Guo, R.*: Highly CO2-selective gas separation membranes based on segmented copolymers of poly(ethylene oxide) reinforced with pentiptycene-containing polyimide hard segments. ACS Applied Materials & Interfaces, 2016, 8, 2306-2317. 18



Effects of Stereoregularity on Local Dynamics and Structure of

Hydrogenated Polynorbornenes (hPNBs) as Studied by Solid-State NMR

Yuta Makita†, Yuki Nakama‡, Shigetaka Hayano‡, and Toshikazu Miyoshi*,† †

Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, United States ‡

Zeon Corporation R&D Center, 1-2-1 Yako, Kawasaki-ward, Kawasaki City, Kanagawa Prefecture 210-9507, Japan

ABSTRACT

Solid-State (ss) NMR spectroscopy can be used to study both the structure and dynamics of

macromolecular systems that exhibit different degrees of order to understand the fundamental

properties of materials.1 One such point of interest is to determine the difference of a polymer’s

structure, local dynamics and phase transition between various isomers of semicrystalline

polymers. For example, the relationship between stereoregularity and packing structure has

been studied for poly(methylene-1,3-cyclopentane) using X-ray diffraction (XRD).2 Recently,

a thorough study on stereospecific ring-opening metathesis polymerization (ROMP) has been

conducted on norbornenes (NBs) making the synthesis and the study of hPNB stereoisomers

possible.3 This presentation will focus on using ssNMR to characterize the stereoregular effects

on molecular dynamics and packing of hPNB samples under various temperatures below

melting temperature (Tm). The atactic-hPNB exhibited the most unique behavior with fast

dynamics and reversible crystallization while isotactic- and syndiotactic-hPNB exhibited fixed

crystal features. The relationship between chemical structure, crystalline structure, and

molecular dynamics of the h-PNBs will be discussed.

References

1. Hansen, M. R. et al. Chem. Rev., 2016, 116, pp 1272-1308.

2. Ballestros, O. R. et al. Macromolecules, 1995, 28, pp 2383-2388.

3. Hayano, S. and Nakama, Y. Macromolecules, 2014, 47, pp 7797-7811.

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In Situ Determination of Polymer Diffusion in Nanocomposites

In situ neutron reflectivity is used to monitor the effect of a variety of different

soft polystyrene nanoparticles on the interdiffusion of deuterated and protonated

polystyrene bilayers. The in situ temperature cell was designed with two separate,

individually controlled temperature plates that allow for precise control of the

temperature increase from 90C to 130C in less than 15 minutes with no overshoot or

fluctuation. Over 17 minute intervals, reflectivity profiles were measured sequentially at

130C over a limited Q range. For a bilayer containing similar molecular weight

polystyrenes, the diffusion of the polymers is symmetric. Therefore the time dependence

of the interfacial width, w, between the two layers is fit to Fick’s second law to determine

the diffusion coefficient of the PS chain. Analysis of the time dependence of the

interfacial width shows t1/4 behavior at early times, which changes to t½ behavior in the

diffusive regime. When the soft nanoparticles are dispersed homogeneously within both

layers of the bilayer to form a nanocomposite, the diffusion coefficient is faster than that

of the neat film when the radius of gyration of the nanoparticle is smaller than that of the

polymer matrix.

80

90

100

110

120

130

140

0 5 10 15 20

Temperature vs Elapsed Time for In Situ Cell

Tem

pera

ture

(o C

)

Elapsed Time (min)

20



High Performance Perovskite Hybrid Solar Cells with E-beam-Processed TiOx

Electron Extraction Layer

Abstract Perovskite hybrid solar cells (pero-HSCs) have drawn great attention in the last 5 years.

The efficiencies of pero-HSCs have been boosted from 3.8% to over 20%. However, one

of the bottlenecks for commercialization of pero-HSCs is to make high electrical

conductive TiOx electron extraction layer (EEL). In this study, we report high performance

pero-HSCs with TiOx EEL, where the TiOx EEL is fabricated by electron beam (e-beam)

evaporation, which has been proved to be a well-developed manufacturing process. The

resistance of the e-beam evaporated TiOx EEL is smaller than that of sol-gel processed

TiOx EEL. Moreover, the dark current densities and interfacial charge carrier

recombination of pero-HSCs incorporated with e-beam processed TiOx EEL is also smaller

than that of pero-HSCs incorporated with sol-gel processed TiOx EEL. All these result in

efficient pero-HSCs with high reproducibility. These results demonstrate that our method

provides a simple and facile way to approach high performance pero-HSCs.

Meng, Tianyu

21



Effect of Chain Length on the Equilibrium Melting Temperature

and Spherulitic Growth Rate of Poly(ethylene oxide)

Hadi Mohammadi, Zhenyu Huang and Herve Marand

Department of Chemistry

Center for Soft Matter and Biological Physics

Virginia Polytechnic Institute and State University

Blacksburg, VA 24061

The equilibrium melting temperature, , was estimated for five narrow molecular

weight distribution poly(ethylene oxide) samples using the non-linear Hoffman-Weeks

treatment. The resulting were 3-8 degrees higher than those predicted by Buckley and

Kovacs, leading to a limiting equilibrium melting temperature for infinite molar mass of 82.5 oC.

Our results also suggest that the constant C2 in the expression for the undercooling dependence

of the initial lamellar thickness (lg*= C1/ΔT + C2) increases linearly with chain length. Using the

dependence of on Mn, we analyzed the spherulitic growth rate data for poly(ethylene oxide)

in the context of Lauritzen-Hoffman theory. The undercooling for the I II regime transition,

, increases with chain length. Both the nucleation constant in regime I, KgI, and the ratio

KgI/KgII increase linearly with chain length, the latter toward a limiting value of 2 at high

molecular weights. Finally, spherulitic growth rates at constant undercooling display a power law

relationship with chain length, , where the exponent s decreases from 4 to 1 with

increase in . These results parallel these obtained recently for linear polyethylene fractions.

22



Real-time Mechano-Optical Behavior and Structural Evolution of Polyimide

(BTDA-DAH) during Uniaxial\Biaxial Deformations.

Ido Offenbach,1 Greg Treich,2 Gregory A. Sotzing, 2 Robert B. Weiss,1 Miko Cakmak,1

1 Department of Polymer Engineering, The University of Akron, Akron, OH

2 Institute of Materials Science, University of Connecticut, Storrs, CT

The study of energy storage systems has received much attention lately. Electromagnetic

(EM) railguns1-2 and batteries of electrical cars3 are just some of the products of this new

focus. In order to use these products, electricity will need to be stored in pulse power

systems (such as capacitors) which have short charge times and high-energy release rates.4-

5 Today's metalized biaxially oriented polypropylene (BOPP) is the most dominant

polymer for capacitors. BOPP provides a low dielectric constant of ~2.26 and a low-energy

density of 5 at breakdown (which occurs at ~720V/μm for films ~10 μm thick);6its

breakdown strength is reduced above 85°C.7 Polyimide (BTDA-DAH) (3,3′,4,4′-

benzophenone tetracarboxylic dianhydride (BTDA) 1,6-diaminohexane(DAH)) was

synthesized. It has a high dielectric constant, a high band gap and a high range of

temperature stability. Therefore, it is a suitable candidate to replace the BOPP for capacitor

applications. The processing techniques of thin-film Polyimide (BTDA-DAH) were

optimized by studying the mechano-optical behavior of Polyimide (BTDA-DAH) in

various temperatures and rates during uniaxial and biaxial deformation. This study used

integrated systems that combined uniaxial stretching and biaxial stretching with real-time

spectral birefringence measurements. Different regimes of stress optical behavior were

revealed as functions of temperatures and stretching rates. First, at the early stage of

deformation the stress optical rule was observed; birefringence linearly increased with a

stress-regime I. Second, a deviation from linearity took place. At higher temperatures and

lower stretching rates the deviation was positive and the birefringence rapidly increased

while the stress slowly increased- regime II. Third, this transformation was followed by a

negative deviation of birefringence and reached a plateau while stress rapidly increased-

regime IIIc. According to off-line characterization techniques DSC and WAXD, stress

induced crystallization is associated with regime II.

23



1. Office of Naval Research Science & Technology NR Home Page.

http://www.onr.navy.mil (accessed Feb.29, 2016).

2. Pacella, R. M; Nasa engineers propose combining a rail gun and a scramjet to fire

spacecraft into orbit, http://www.popsci.com/technology/article/2010-11/nasa-

engineers-propose-combining-rail-gun-and-scramjet-fire-spacecraft-orbit (accessed

March.2, 2016).

4. Karden, E.; Ploumen, S.; Fricke, B.; Miller, T.; Snyder, K.; Journal of power source

2007, 168, 2-11.

5. Ribeiro, P. F.; Johnson, B. K.; Crow, M. L.; Arsoy, A.; Liu, Y. Proceedings of the

IEEE, 2001, 89,1744-1756.

6. Chen, H.; Cong, T. N.; Yang, W.; Tan, C.; Li, Y.; Ding, Y. Progress in Natural Science,

2009,19, 291-312.

7. Wang, C. C.; Ramprasad, R. J. Mater. Sci. 2011, 46, 90−93.

8. Barshaw, E. J.; White, J.; Chait, M. J.; Cornette, J. B.; Bustamante, J.; Folli, F.;

Biltchick, D.; Borelli, G.; Picci, G.; Rabuffi, M. IEEE Trans. Magn. 2007, 43, 223−225.

24



Trehalose-Based Diblock Copolymers as Excipients for Enhancing Solubility of Poorly Water Soluble Drugs

Anatolii Purchel, Swapnil Tale, Molly C Dalsin, Theresa Reineke

Oral administration is the most preferable route of drug delivery, especially during prolonged therapy of chronic diseases. Unfortunately, many effective pharmaceuticals are poorly water-soluble, which leads to decreased bioavailability and shelf life. One of the ways to improve drug solubility and efficacy is to prepare an amorphous solid dispersion (ASD) with a polymer excipient. It is important that the polymer matrix of an ASD will stabilize the drug in the amorphous state and maintain its supersaturated concentration long enough in the dissolution media. Some of the commercial polymeric systems have shown a positive impact on drug dissolution, but most of them are difficult to characterize due to high polydispersity and system complexity. This makes it difficult to understand the structure property relationships and to quantify the effect of drug-polymer specific interactions. Also, most of the available excipients that improve dissolution of poorly water-soluble drugs tend to Hydrogen-bond to the drug while in solution, thus preventing its crystallization. Therefore, a series of block copolymers were synthesized with varied composition of H-bonding monomers including N-isopropylacrylamide, N,N-dimethylacrylamide, and 2-methacrylamidotrehalose using addition-fragmentation chain transfer (RAFT) polymerization. This family of diblock copolymers offers hydrophobic, hydrophilic, or H-bonding functionalities to serve as noncovalent sites for model drug Probucol binding. Role of each binding moiety as well as overall excipient performance was assessed using in-vitro dissolution testing.

25



Title: Tuning Morphology in Hierarchically Porous Polymer Monoliths

Authors: Stacey A. Saba, Department of Chemical Engineering and Materials Science

Marc A. Hillmyer, Department of Chemistry

Affiliation: University of Minnesota

Hierarchically porous polymer monoliths, uniform rigid materials containing both macropores

(>50 nm) and mesopores (2-50 nm), are useful for applications including liquid separations,

bioengineering, and catalysis. In these monoliths the percolating macropores facilitate mass

transport whereas the mesopores provide high surface area. The production of hierarchically

porous polymers, however, is limited because the materials are difficult to synthesize. Here, we

demonstrate a simple strategy to control the morphology of a cross-linked porous polymer using

the dual approach of polymerization-induced macro- and microphase separation. Specifically,

styrene and divinylbenzene are copolymerized from a macro-chain transfer agent in the presence

of a nonreactive additive of varying volume fraction and molecular weight. The tuning of these

parameters produces a diverse portfolio of monolith nanostructures, ranging from mesoporous to

hierarchically porous morphologies. This straightforward approach has great potential to enhance

the production of porous polymer monoliths for applications.

26



Elucidating the Underlying Structure of Methylcellulose Fibrils

Peter W. Schmidt,1 Amanda L. Maxwell,2 Frank S. Bates,1 Timothy P. Lodge1,2

1Department of Chemical Engineering & Materials Science and 2Department of Chemistry

University of Minnesota

Minneapolis, MN 55455, USA

Abstract:

Cellulose ethers are a large class of chemically modified celluloses used in a diverse

range of applications from food to construction materials. Methylcellulose (MC), a cellulose

ether which is partially methoxy substituted, is one of the simplest cellulose ethers. Many

applications of MC take advantage of the ability to form an aqueous solution at low temperatures

and to transition into a turbid hydrogel upon heating. Despite the structural simplicity there has

been debate over the mechanism of gelation.

Recently it has been shown by cryogenic transmission electron microscopy and small

angle neutron scattering (SANS) that methylcellulose forms 15 ± 2 nm diameter fibrils upon

heating. The conversion of polymer chains in solution to a fibrillar network measured by SANS

fitting correlates with an increase in the elastic modulus measured by rheology, demonstrating

that the gelation mechanism is a result of the formation of fibrils. Additionally, a filament based

mechanical model has been applied to predict the critical stress in MC gels in large amplitude

oscillatory shear experiments to corroborate the fibril structure as measured by SANS. While

recent efforts have investigated the overall fibril structure of these materials, the underlying sub-

fibril structure remains unknown.

To probe the underlying structure, synchrotron X-ray scattering is used to investigate MC

solutions. Mid-angle and wide-angle X-ray scattering (MAXS and WAXS) from MC give peaks

at 0.55, 0.92, and 1.5 Å-1, independent of concentration, temperature, molecular weight, and

27



substitution pattern. Small-angle X-ray scattering (SAXS) exhibits similar scattering to the fibril

form factor previously reported in SANS. The formation of the structures probed by MAXS

coincides with the increase in scattered intensity in SAXS indicating the peaks in MAXS and

WAXS correspond to structures present within MC fibrils.

28



Hybrid thiol-ene and conventional free radical photopolymer system

for sequential molecular weight growth and photo-crosslinking

Justin M. Sirrine*, Nicholas G. Moon, and Timothy E. Long

Department of Chemistry, Macromolecules Innovation Institute (MII)

Virginia Tech, Blacksburg, VA 24061-0212

Abstract: Stereolithography (SLA) is a type of additive manufacturing (AM) or three-

dimensional (3D) printing where a UV-curable liquid oligomer or polymer is photocured in a

layer-by-layer fashion, producing a 3D object. Conventional photopolymer compositions

typically possess low viscosity and accompanying low molecular weight between crosslinks

(Mc), resulting in the formation of a brittle or rigid object upon photocuring. The 3D fabrication

of flexible and elastic objects requires higher Mc, which carries a concomitant increase in

photopolymer viscosity, resulting in prohibitively high layer recoat and print times. In this work,

a novel, low viscosity, hybrid polydimethylsiloxane (PDMS) thiol-ene and conventional free

radical photopolymer system is evaluated for sequential molecular weight growth and

crosslinking upon UV irradiation. In-situ Fourier transform infrared spectroscopy (FTIR) and

photocalorimetry probe the molecular weight growth and crosslinking reaction kinetics.

Photorheology examines the gelation kinetics as a function of UV irradiation time and

demonstrates adequate spatiotemporal control required for SLA. Preliminary 3D printing with

SLA demonstrates adequate print speeds and high print resolution. Dynamic Mechanical

Analysis (DMA) and tensile testing probe mechanical properties as a function of print

orientation, examining interlayer adhesion at the interface between printed layers. This novel,

hybrid photopolymer system enables the fabrication of flexible and elastic objects without the

use of co-solvents, reactive diluents, or plasticizers, preventing issues of shrinkage and low gel

fraction associated with these other systems.

29



30



Chain Folding Structure and Crystallization Mechanism of Poly(l-lactide) in Solution

As Studied by 13C-13C Double-Quantum NMR

Shijun Wang and Toshikazu Miyoshi

Department of Polymer Science, The University of Akron, Akron OH 44325-3909

Crystallization of long polymer chains induces drastically structural change from random coils

to folded chains in thin crystals. Various factors including kinetics, polymer concentration,

entanglements of polymers, flexibility, intermolecular interactions etc. in complexity influence

crystallization process and folded chain structures. To systematically understand crystallization

mechanism, understanding of structural formation process of individual chains is necessary.

However, there is no proper in-situ experimental tool to capture structural formation of polymer

chains at atomic levels. Thus, several experimental approaches are focusing on characterizing

folded chain structures after crystallization. 1-3 Very recently, our group developed a novel strategy

using 13C – 13C double-quantum (DQ) NMR in combination with selective isotope labeling, to

investigate the chain folding structures in the crystallization.4-6 This innovative strategy, giving

details about re-entrance site of the folded chains, and adjacent re-entry fraction <F> and number

<n>. Additionally, blending of 13C labeled and non-labeled polymers does not induce segregations

of two components. Thus, it enabled us to investigate kinetic effects on chain trajectory of

polymers. .Such advantage allows us to investigate chain-folding structures of polymer in single

crystals formed in very wide solution concentration (0.005 -15 wt %).

In this presentation, we investigate chain-folding structure of poly (l-lactide) (PLLA) in single

grown crystals formed in a wide concentration range of 0.005 - 15 wt %. It will be demonstrated

that how polymer concentration and entanglements influence chain-folding structures of PLLA in

solution. Detailed chain-level structure will provide detailed folding and crystallization

mechanism at the molecular level.

References

1. S. J. Spells and D. M. Sadler, Polymer, 1984, 25, 739–748.

2. S. J. Spells, A. Keller and D. M. Sadler, Polymer, 1984, 25, 749–758.

3. K. Liu, Y. Song, W. Feng, N. Liu, W. Zhang and X. Zhang, J. Am. Chem. Soc., 2011, 133,

3326–3329.

4. Y. Hong, T. Koga and T. Miyoshi, Macromolecules, 2015, 48, 3282–3293.

5. Z. Li, Y. Hong, S. Yuan, J. Kang, A. Kamimura, A. Otsubo and T. Miyoshi, Macromolecules,

2015, 48, 5752–5760.

6. W. Chen, S. Wang, W. Zhang, Y. Ke, Y. Hong and T. Miyoshi, ACS Macro Lett., 2015,

1264–1267.

31



DFT Simulation of CO2 Capture on Amine-based Polymer Composites

Erik Willett, Steven S.C. Chuang

Atmospheric CO2 concentrations exceeding 400 ppm require expanded efforts in carbon capture,

utilization, and storage (CCUS) on industrial scales. Water-based alkanolamine scrubbing technology1,2

has been used to remove CO2 from emissions however it is an energy intensive process. By immobilizing

amine capture sites as a thin polymer film on silica, the energy required (0.7 – 1.1 kJ kg-1 K-1) to cycle the

temperature of the material between capture at 40˚C to regeneration at 100˚C is greatly reduced versus

alkanolamine solutions (3 – 4 kJ kg-1 K-1).3

The simulation work presented demonstrates the utility of density-functional theory (DFT) calculation4

in determining the selectivity5 of amine capture on primary and secondary polymeric amine sites,

evaluating process parameters such as regeneration temperature, and the effect of water and polymeric

additives in directing CO2 capture toward higher CO2:amine ratios.

References

(1) Gregory, L. B.; Scharmann, W. G. Industrial & Engineering Chemistry 1937, 29, 514. (2) Rochelle, G. T. Science 2009, 325, 1652. (3) Tanthana, J.; Chuang, S. S. C. ChemSusChem 2010, 3, 957. (4) Friesner, R. A. Proceedings of the National Academy of Sciences of the United States of America 2005, 102, 6648. (5) Danckwerts, P. V. Chemical Engineering Science 1979, 34, 443.

32



Synthesis and characterization of nanoporous

polyethersulfone membrane as support for composite

membrane in CO2 separation: From lab to pilot scale Dongzhu Wu and W.S. Winston Ho*

William G. Lowrie Department of Chemical and Biomolecular Engineering,

The Ohio State University, 151 West Woodruff Avenue, Columbus, OH 43210-1350, USA

Nanoporous polyethersulfone (PES) membranes were prepared from PES/N-methyl-2-pyrrolidone

(NMP)/2-methoxyethanol (2-ME) casting solutions with water as coagulant by both vapor- and

non-solvent-induced phase inversion steps successively under various preparation parameters. 2-

ME was incorporated into the casting solution as a pore-forming additive because of its high

affinity with water, leading to more open membrane morphology. A detailed study of the effects

of different parameters, including polymer concentration, 2-ME/NMP ratio, relative humidity,

water vapor exposure time, and water coagulation bath temperature, was conducted in lab-scale

experiments to determine the operation guidelines for pilot-scale fabrication. 14-inch wide PES

membranes were fabricated successfully by using a continuous casting machine. Parametric

studies in pilot-scale fabrication were also carried out. Surface morphologies of PES membranes

were characterized by scanning electron microscopy (SEM). The morphological differences

between both scales by the same preparation conditions were compared. Based on the guidelines

established from lab-scale experiments, the casting solution composition and coagulation bath

temperature were optimized in a pilot-scale continuous casting machine to fabricate the 14-inch

wide PES membrane with a desired morphology suitable for use as the substrate of composite

membranes in CO2 separation. The selective layers were coated on the PES substrates and tested

with model flue gas. The effect of the substrate on composite membrane separation performance

was studied, and a suitable PES substrate was selected. The studied fabrication process also

showed the potential for the commercial production of the PES membrane in a larger scale by the

vapor- and non-solvent-induced phase inversion technique.

33



Structure Analysis of Mesomorphic Form

Isotactic Polypropylene at the Molecular Level:

A Solid-State NMR Study

Shichen Yuan,† and Toshikazu Miyoshi†*

† Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, United States

ABSTRACT

Crystallization of small molecules and polymers is an integration process. Polymer crystallization usually results in complex

metastable state due to the nature of the long chain connectivity, where individual chains penetrate both amorphous regions

and thin lamellar crystals.1 However, understanding the structural formation of long polymer chains in the early stage of

crystallization is still one of missing piece in polymer physics. There is a mesomorphic (meso-) form of Isotactic

polypropylene (iPP) that intermediates between crystalline order (α-, β-, γ-) and liquid amorphous. The understanding of

packing structure and formation mechanism of meso- from iPP, which may carry information about the early stage of

crystallization, however, are not satisfactory at all due to a limited resolution for short range ordered systems. Particularly,

little is known about whether iPP chains in such non-equilibrium form go through solidification or nucleation and growth

upon quenching from the melt state. Using solid state NMR, we investigated chain trajectory of iPP in the mesomorphic

nano-domains formed via rapid and deep quenching. Comparison of experimental and simulated 13C-13C double quantum

buildup curves demonstrated that meso- form iPP adopt similar packing structure as β- form.2 Instead of random re-entry

chain trajectory predicted by solidification models, individual chains in the meso- form iPP adopt adjacent re-entry clusters

predicted by nucleation and growth model, with an average folding number of <n> = 3-4 (assuming an adjacent re-entry

fraction of <F> of 100%).3

REFERENCE

(1) Cheng, S. Z. In Phase Transitions in Polymers; Elsevier, 2008.

(2) Yuan, S.; Li, Z.; Hong, Y.; Ke, Y.; Kang, J.; Kamimura, A.; Otsubo, A.; Miyoshi, T. ACS Macro Lett. 2015, 4, 1382–1385.

(3) Yuan, S.; Li, Z.; Kang, J.; Hong, Y.-L.; Kamimura, A.; Otsubo, A.; Miyoshi, T. ACS Macro Lett. 2015, 4, 143–146.

34



The Effect of Water on the Thermal Transition

Observed in Poly(allylamine hydrochloride)-

Poly(acrylic acid) Complexes

Yanpu Zhang,1 Ran Zhang,2 Fei Li,1 Luis D. Valenzuela,1 Maria Sammalkorpi,2*

Jodie L. Lutkenhaus1,3* 1 Artie McFerrin Department of Chemical Engineering, Texas A&M University,

College Station, Texas 77843, United States 2 Department of Chemistry, Aalto University, P.O. Box 16100, 00076 Aalto, Finland 3 Department of Materials Science and Engineering, Texas A&M University, College

Station, Texas 77843, United States

Polyelectrolyte complexes (PECs) are receiving increasing attention because of

their stimuli-responsive behaviors with ionic strength, pH, and temperature. Of these,

temperature is particularly intriguing in that PECs undergo a glass-melt transition

whose origin remains debatable. Here, we present the thermal behavior of PECs

containing weak polyelectrolytes poly(allylamine hydrochloride) (PAH) and

poly(acrylic acid) (PAA) as influenced by water content and complexation pH. These

are investigated using modulated differential scanning calorimetry (MDSC) and

dynamic molecular simulation. MDSC revealed a glass-transition-like thermal

transition (Ttr) that decreases with increasing hydration and with decreasing

complexation pH. It is shown that water has a plasticizing effect by molecular

simulations and comparison with the Fox equation. Simulations show an increasing

number of water-polymer hydrogen bonds within the hydrated complexes as water

content increases. Complexation pH influences the thermal transitions by tuning the

polymer charge density and then the structure and composition of the PEC. These

results support the hypothesis that the transition is caused by a restructuring of the water

hydrogen-bonding network within the PEC that then allows for subsequent chain

relaxation.

35



Title: SO-ATR as a vibrational spectroscopic tool to probe the ordering of thin polymer films

Infrared spectroscopy is a powerful spectroscopic tool in the elucidation of polymer structure

and chemistry but is greatly signal limited when it comes to films with thicknesses of less than

100 nm. In this work using NAFION® as an example, we demonstrate how signal enhanced ATR

can provide vital information about the orientation of thin polymer films, even on nonmetallic

substrates. Spin cast NAFION® samples were prepared on silicon native oxide and gold

substrates with film thicknesses ranging from 5 nm to 250 nm. The influence of NAFION® film

thickness on the infrared spectrum of the polymer was investigated in substrate overlayer

attenuated total reflection (SO-ATR) geometry at incident angles between 60° and 65°. In SO-

ATR geometry, the thickness of the film significantly affected the position and absorbance of

characteristic peaks in NAFION® infrared spectrum. As the thickness of the film decreased from

250 nm to 5 nm, the convoluted vas(CF2) and vas (SO3-) peak at 1220 cm-1 systematically

blueshifted to 1256 cm-1.The same phenomenon was observed with the predominantly vas(CF2)

peak at 1150 cm-1 which shifted to 1170 cm-1. Changes in the NAFION® thin film FTIR

spectrum can be ascribed to ordering of NAFION® at the interface during spin coating (film

formation) and the increase in the p-polarization character of the infrared evanescent wave as the

polymer film became thinner between the ATR element and the film substrate overlayer. An

increase in p-polarization due to the overlayer enhancement of the electric field in the NAFION®

film resulted in the increase in characteristic peak absorbance of dipoles aligned normal to the

substrate. These results demonstrate that the specific thin film sampling geometry, especially in

reflection experiments, must be considered to rationally quantify changes in polymer thin film

structure.

Author: Twawnda Zimudzi

36

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