University of Zagreb, Croatia, November 3, 2011

Charles YangDepartment of Textiles

The University of GeorgiaAthens, Athens, GA 30602, USA

Chemical Analysis of Polymeric Materials

Using Infrared Spectroscopy

Outlines

Basic Theory of Infrared SpecrtrocopyMolecular vibrational energy, infrared spectroscopy and its selection rulesInterpretation of Infrared spectra, group frequency and finger print region Dispersive versus Fourier transform infrared spectroscopyThe sampling techniques for solids

Applications of FT-IR spectroscopy to polymers: qualitative analysis Applications of FT-IR spectroscopy to polymer: quantitative analysis

M1 M2

Vibrational Energy of A Diatomic Molecule

V - vibrational quantum number, 0, 1, 2…

H - Plank constant

Vm- vibrational frequency

µ- reduced mass

k- force constant

M1M2M2M1

Wavenumber (cm-1) of An IR Absortion Peak

a. Force constant - 105 dynes/cm

b. Reduced mass - 1.673 x 10-24 g

An Absorption Peak in An Vibrational Spectrum

CO (gas)

An Absorption Peak with Rotational Fine Structure in An Vibrational Spectrum

CO (gas)

Electric Magnetic Radiation

Near-, Mid-, and Far-Infrared Region

Selection Rules of Infrared Spectroscopy

Excitations from V=0 (ground state) to V=1 (1st excited state (fundamentals) by absorption of IR radiationAbsorption can occur only when there is a change in the magnitude and direction of dipole moment of the bond

Vibrational Modes

http://en.wikipedia.org/wiki/Infrared_spectroscopy

Infrared Spectra Interpretation: Group Frequency

Start in the group frequency region: 4000-1250 cm-1 (-OH, -NH, =C-H, -CH2, -CH3, >CH-, >P-H, >C=O…) Easy to interpret, little interferencePeak assignment

Peak position (wavenumbers)Peak heightPeak shape

Infrared Spectra Interpretation: Finger Print Region

More complex and more difficult to interpretSmall structural differences results in significant in spectral differencesComplete interpretation impossibleComplete identification requires 100% match between sample’s and standard’s spectra in the finger print region

Infrared Spectroscopy: Group Frequency

http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/InfraRed/infrared.htm

C-H bending &ring puckering

str-med690-900C-H (may be several bands)C=C (in ring) (2 bands)

(3 if conjugated)

varmed-wk

30301600 & 1500

Arenes

C-H deformationstr600-700C-H (usually sharp)C≡C (symmetry reduces

intensity)

strvar

33002100-2250

Alkynes

=C-H & =CH2

(out-of-plane bending)

cis-RCH=CHR

strmedmed

880-995780-850675-730

=C-H & =CH2 (usually sharp) C=C (symmetry reduces

intensity)

C=C asymmetric stretch

medvar

str

3020-31001630-1680

1900-2000

Alkenes

CH2 & CH3

deformationCH3 deformation

CH2 rocking

medmedwk

1350-14701370-1390720-725

CH3, CH2 & CH2 or 3 bands

str2850-3000Alkanes

AssignmentIntensityRange (cm-1)AssignmentIntensityRange (cm-1)Functional Class

Bending VibrationsStretching Vibrations

C-O-H bending

N-H (1°-amide) II band

N-H (2°-amide) II band

med

medmed

1395-1440

1590-1650 1500-1560

O-H (very broad)C=O (H-bonded)

O-C (sometimes 2-peaks)

C=OC=O (2-bands)

O-CC=O

O-C (2-bands)C=O (amide I band)

strstr

med-str

strstrstrstrstrstr

2500-3300 (acids) overlap C-H1705-1720 (acids)1210-1320 (acids)

1785-1815 ( acylhalides) 1750 & 1820 (anhydrides)

1040-1100 1735-1750 (esters)

1000-1300 1630-1695(amides)

Carboxylic Acids& Derivatives

α-CH3 bendingα-CH2 bendingC-C-C bending

strstr

med

1350-13601400-1450 1100

C-H (aldehyde C-H)C=O (saturated

aldehyde) C=O (saturated

ketone)

aryl ketoneα, β-unsaturationcyclopentanonecyclobutanone

medstrstr

strstrstrstr

2690-2840(2 bands)1720-17401710-1720

1690 1675 1745 1780

Aldehydes & Ketones

NH2 scissoring (1°-amines)

NH2 & N-H wagging

(shifts on H-bonding)

med-strvar

1550-1650660-900

N-H (1°-amines), 2 bands

N-H (2°-amines)C-N

wkwk

med

3400-3500 (dil. soln.)3300-3400 (dil. soln.)

1000-1250

Amines

O-H bending (in-plane)

O-H bend (out-of-plane)

medvar-wk

1330-1430650-770

O-H (free), usually sharp

O-H (H-bonded), usually broad

C-O

varstrstr

3580-36503200-3550970-1250

Alcohols & Phenols

http://orgchem.colorado.edu/hndbksupport/irtutor/tutorial.html

Presentation of Infrared Spectra

T% = It/I0 A = -Log10T%

Instrumentation of Infrared Spectrometer

SourceMonochromator (dispersive IR spectrometer) or Interferometer (FT-IR spectrometer) Sample deviceDetectorData processing, presentation and storage device

Dispersive Infrared Spectrometer

FT-IR Spectrometer

FT-IR Spectrometer

Advantages of FT-IR Spectrometry

Multiplex advantage, shorter data acquisition time, high S/N ratio by multiple scansHigh throughput advantageHigh resolutionMore accurate frequency/wavelength measurement

Sampling Techniques for Solids: Transmission Spectra

Pressed KBr pellet methodUsed for all solid samplesWater interferenceSample/matrix quantity (2-3%, 200 mg KBr)Fully grinding for sample homogeneity for chemically treated fabrics/fibers

Cast film For polymeric sample soluble in a volatile organic solventChoosing the right window materials

KBrZnSe

Infrared Spectroscopy Window Materials

Sampling Techniques for Solids: Reflectance Methods

Diffuse reflectance (DRIFTS)Good for samples which can be ground to fine particlesCan be used as a quantitative methodHigh energy throughput and fast data collectionHomogeneous particle size, accessory alignment and sample mounting are important experimental parameters

Sampling Techniques for Solids: Reflectance Methods

Diffuse reflectance (DRIFTS) Quantitative Analysis

F(R∞) – maximum peak valuec – concentrationK’ – related to particle size and molar absorptivity

Use of KBr to collect a reference spectra

F(R∞) = c/k’

Sampling Techniques for Solids: Reflectance Methods

Internal total reflection A thin and flexible film (e.g., elastomer) is placed with pressure against the crystal, good optical contact is necessary. It can be used as a near-surface method (left)Single bounce, small area diamond crystal is developed for a variety of solid samples (right)

Sampling Techniques for Solids:Photoacoustic Method

FT-IR Photoacoustic Spectroscopy

µs – Thermal diffusion length (cm)

α – Thermal diffusivity (cm2·s-1)

ω – Angular modulation frequency (redians· s-1)

k – Thermal conductivity (cal·cm-1·s-1·°C-1)

ρ – Density (g·cm-3)

C – Specific heat (cal·g-1·°C-1)

f – modulation frequency (Hz)

FT-IR Photoacoustic Spectroscopy

No sample preparationNear surface analysisDepth profilingLow sensitivityInterferences (water, vibration…)

C. Q. Yang, Ind. Eng. Chem. Res., 31, 617-621 (1992)

C. Q. Yang, Appl. Spectrosc., 45, 102-108 (1991)

Qualitative Analysis of Polymers and Textiles by FT-IR Spectroscopy: Part 1

Identification of unknown contaminants of rayon fiberUV-induced oxidation of polyethylene nonwoven fabric

Identification the functional groupsDistribution of the functional groups

Thermal oxidation of polyethylene nonwoven fabric

Identification the functional groupsDistribution of the functional groups

The Dyed 2-ply Rayon Yarn with Unknown Contaminations

Previously scoured Dyed with a fiber reactive dyeContaminant unknown

Spin finishAnother contaminant unknown

The yarn was extractedMethylene chloride (polar solvent)Hexane (nonpolar solv

DRIFTS Spectra of the Dyed 2-ply Rayon Yarns

C. Q. Yang, Ind. Eng. Chem. Res., 33,2836-2839 (1994).

Photo Oxidation of Polyethylene Film

L. Martin, C. Q. Yang*, J. Environ. Polym. Deg., 2, 153-160 (1994).

Thermal Oxidation of PE Film

L. Martin, C. Q. Yang, J. Appl. Polym. Chem., 51, 389-397 (1994).

Qualitative Analysis of Polymers and Textiles by FT-IR Spectroscopy: Part 2

Esterification of cellulose by polycarboxylic acidsReactant Productintermediate

Mechanism of esterification of cotton by polycarboxylic acidsDevelopment of new and more effective DP finishing systemIn-situ polymerization of unsaturated bifunctionalcarboxylic acidsCatalysis of NaH2PO2 for estertification of cellulose by polycarboxylic acids

C. Q. Yang, Textile Res. J., 61, (1991), pp433-440.

Esterification of Cotton by a Polycarboxylic acid

C CCO

HO

H

C

H

OH

O

C C

CO

HO

H C

H

OHO

Maleic Acid (cis-isomer)

Fumaric Acid (trans-isomer)

C. Q. Yang, Textile Res. J., 61, (1991), pp433-440.

Succinic Acid Maleic Acid

C. Q. Yang, J. Polym. Sci. Part I Polym Chem, 31, (1993), pp1187-1193.

Cis-Aconitic Acic (CAA)

C. Q. Yang, X. Wang, Textile Res. J., 66, (1996), pp595-603.

BTCA

BTCA Bifunctional Acids

cis-1,2-cyclo-hexanedicarboxylic acid

(cis-1,2-CHA)

C. Yang, G. Zhang, Res. Chem. Intermediates, 26, 515-528 (2000).

cis-1,2-CHA

NaH2PO2

trans-1,2-cyclo-hexanedicarboxylic acid

(trans-1,2-CHA)

1,3-hexanedicarboxylic acid(1,3-CHA, mixtures of cis-

and trans-isomers)

Formation of Cyclic Anhydride of CHA

Cis-1,2-CHA forms 5-membered anhydride at temperatures significantly lower than trans-1,2-CHANaH2PO2 catalyzes the formation of anhydride of cis-1,2-CHA1,3-CHA forms 6-membered cyclic anhydride at much higher temperatures1,3-CHA forms could not for cyclic anhydride

C. Q. Yang, J. Polym. Sci. Part A Polym Chem,31, (1993), pp1187-1193.

C. Q. Yang, X. Wang, J. Polym. Sci. Part A Polym Chem, 34, (1996), pp1570-1580.

trans-aconitic acid

(TAA)

X. Gu, C. Yang, Re. Chem. Intermediates, 24, 979-997 (1998).

Formation of the Cyclic Anhydride by Polycarboxylic Acids

A polycarboxylic acid, which can form both 5-and 6-membered cyclic anhydride intermediates on cotton, forms 5-membered cyclic anhydride The hydrogen-bonded carboxyl groups in a polycarboxylic acid forms its anhydride at high temperatures than the free carboxyl groups

Esterification of Cotton by a Polycarboxylicacid: Reaction Mechanism

COOHHOOC

COOH

HOOC

O

O

OCOOH

HOOC

COOHHOOC

O

O

OBTCA

O

O

OCOOH

HOOC

COOHHOOC

O

O

O

Or Cellulose

HO

OH O

O

OH

HO

O

HO

OH

O

O

OH

O

HOOCCOOH

HOOC

O

Esterification of Cotton by a Polycarboxylic acid: Reaction Mechanism

Esterification of Cotton by a Polycarboxylicacid: Reaction Mechanism

Cellulose

HO

OH O

O

OH

HO

O

HO

OH

O

O

OH

O

HOOC

O

O

HO

OH O

O

OH

HO

O

HO

OH

O

O

OH

O

COOH

HO

OH O

O

OH

HO

O

HO

OH

O

O

OH

O

HOOC

O

O

O

O

The Formation of 5-Membered Cyclic Anhydride Intermediate

CH

CH

CH

COOH

COOH

COOH

2

2

CH

CH

CH

CH2

2

2COOH

COOH

COOH

1,2,3-Propanetricarboxylic Acid (PCA)

1,2,4-Butanetricarboxylic Acid (BTA)

Scheme 1

Mao Z., Yang, C. Q.,J. Appl. Polym. Sci., 81, (2001), pp2142-2150.

PCA heated 140-200ºC for 2 min.

200ºC

180ºC

160ºC

150ºC

140ºC

BTA heated 140-200ºC for 2 min.

200ºC

180ºC

160ºC

150ºC

120ºC

Ester carbonyl band intensity of the cotton fabric treated with 6% PCA and that treated with 6.5% BTA versus curing temperature.

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

150 160 170 180 190 200

Curing Temperature (oC)

Este

r Car

bony

l Ban

d In

tens

ity

BTA

PCA

Figure 4

Esterification of Cotton by PCA and BTA

PCA Forms Two 5-membered Anhydride Intermediates

CH

CH

CH

OCOOH

COOH

COOH

CH

CH

CH

C

C

COOHO

O

HO-Rcellulose2

2

2

2

2-H OCH

CH

CH

COO-Rcellulose

COOH

COOH

2

2

-H2

O

CH COO-Rcellulose

CH

CH

OO

O

2

2

C

C 2

2COOH

COO-Rcellulose

CH

CH

CHHO-Rcellulose

COO-Rcellulose

PCA

Scheme 2

BTA Forms only One 5-membered Anhydride Intermediate

BTA

COO-Rcellulose

COOHHO-Rcellulose

2

2

COOH

CH

CH

CH

CH22CH

2O-H

2

2

2 CH

CH

CH

C

C

COOH

O

O

2

2

OCOOH

COOH

CH

CH

CH

CH

COOH

Scheme 3

PCA Forms Two 5-membered Anhydride Intermediates

CH

CH

CH

OCOOH

COOH

COOH

CH

CH

CH

C

C

COOHO

O

HO-Rcellulose2

2

2

2

2-H OCH

CH

CH

COO-Rcellulose

COOH

COOH

2

2

-H2

O

CH COO-Rcellulose

CH

CH

OO

O

2

2

C

C 2

2COOH

COO-Rcellulose

CH

CH

CHHO-Rcellulose

COO-Rcellulose

PCA

Scheme 2Second Anhydride

First Anhydride

(A) Cotton/PCA; (B) 180ºC 2min; (D) Cotton/PCA/NaH2PO2, 150ºC 2min, washed, (E) sample above, 180ºC 2min.

First Anhydride

Second Anhydride

1. C. Q. Yang, "FT-IR Spectroscopy Study of the Ester Cross-linking Mechanism of Cotton Cellulose," Textile Research Journal, 61, 433-440 (1991).

2. C. Q. Yang, "Infrared Spectroscopy Studies of the Cyclic Anhydride as the Intermediate for the Ester Cross linking of Cotton Cellulose by Polycarboxylic Acids: I. Identification of the Cyclic Anhydride Intermediate,"Journal Polymer Science, Part A: Polymer Chemistry Edition, 33, 1187-1193 (1993).

3. C. Q. Yang, X. Wang, "Infrared Spectroscopy Studies of the Cyclic Anhydride as the Intermediate for the Ester Cross linking of Cotton Cellulose by Polycarboxylic Acids: II. Comparison of Different PolycarboxylicAcids", Journal Polymer Science, Part A: Polymer Chemistry Edition, 34, 1567-1580 (1996).

4. C. Q. Yang, X. Wang, "Formation of the Cyclic Anhydride Intermediates and Esterification of Cotton Cellulose by Multifunctional Carboxylic Acids: An Infrared Spectroscopy Study", Textile Research Journal, 66, 595-603(1996).

5. X. Gu, C. Yang, “FT-IR and FT-Raman Spectroscopy Study of the Cyclic Anhydride Intermediates for the Esterification of Cellulose: I. Formation of Anhydride without A Catalyst”, Research on Chemical Intermediates, 24, 979-997 (1998).

6. C. Q. Yang, X. Wang, "The Formation of Five Membered Cyclic Anhydride Intermediates by PolycarboxylicAcids Studied by the Combination of Thermal Analysis and FT-IR Spectroscopy", Journal of Applied Polymer Science, 70, 2711-2718 (1998).

7. C. Yang, X. Gu, “FT-IR and FT-Raman Spectroscopy Study of the Cyclic Anhydride Intermediates for the Esterification of Cellulose: II. Formation of Anhydride with Sodium Hypophophite as a catalyst”, Research on Chemical Intermediates, 25(5), 411-424(1999).

8. X. Gu, C. Yang, “FT-IR Study of the Formation of Cyclic Anhydride Intermediates of Polycarboxylic Acids Catalyzed by Sodium Hypophosphite”, Textile Research Journal, 70, 64-70 (2000).

9. C. Q. Yang, G. Zhang, “FT-IR and FT-Raman Spectroscopy Study of the Cyclic Anhydride Intermediates for the Esterification of Cellulose: III. Cyclic Anhydrides Formed by the Isomers of CyclohexanedicarboxylicAcid”, Research on Chemical Intermediates, 26, 515-528 (2000).

10.Z. Mao, C. Q. Yang, "IR Spectroscopy Studies of the Cyclic Anhydride as the Intermediate for the Ester Cross linking of Cotton Cellulose by Polycarboxylic Acids: V. Comparison of 1,2,4-Butanetricarboxylic Acid and 1,2,3-Propanetricarboxylic acid", Journal of Applied Polymer Science, 81, 2142-2150 (2001).

Esterification Mechanism of Cotton by Polycarboxyic Acids

The Traditional PMA

CH CH

CC OOO

nBenzoyl Peroxide

CH3

CH CH

COOHCOOHn

n = ~6

H2O

The BTCA-treated cotton shows lower amount of anhydride intermediate, but higher ester formation and higher WRAThe PMA-treated cotton shows higher amount of anhydride intermediate, but lowerer ester formation and lower WRA

C. Q. Yang*, X. Wang, I. Kang, Textile Res. J., 67, 334-342 (1997).

Citric Acid (CA)

No Toxicity and low PriceLow DP Performance Low Laundering DurabilityFabric YellowingAll are contributed to the –OH group CA

C

CH2

CH2

HO COOH

COOH

COOH

CA and Poly(maleic Acid) (PMA)

PMA form 5-membered anhydride intermediate on cotton, but has low reactivity to esterify cotton due to its large molecular weight (M.W. ~ 1,000-2,000)CA has low reactivity because of the hindrance by its -OH groupPMA’s anhydride group esterify CA on cotton under curing conditions

The Synergistic Effect of CA and PMA

The Reaction of CA and PMA eliminates the hydroxy group of CA, thus increasing its reactivity and reduce yellowingThe Reaction of CA and PMA increases the functionality of CA

C

CH2

CH2

O COOH

COOH

COOH

CH

CH COOHC

CH2

CH2

HO COOH

COOH

COOH

+CH

CH

COOH

COOH

PMA CA

1001891840.00Control

582312540.19551000

572432550.19539010

592522640.19738515

572462550.19648020

592512570.19837525

572492620.19567030

612492510.19855050

662372360.19800100

after 10 washesbefore washCATPMA

TensileStrengthRetention

(%, F)

WRA (º, w+f)Total

-COOH (m)

Carboxy Mole Ratio

Table 1. The WRA of the cotton fabric treated with CA/TPMA with different CA-to-TPMA ratios and cured at 185º for 3 min

The CA/PMA Nonformaldehyde Durable Press Finishing System: Publication

1. C. Q. Yang, X. Wang, "Infrared Spectroscopy Studies of the Cyclic Anhydride as the Intermediate for the Ester Cross linking of Cotton Cellulose by Polycarboxylic Acids: III. the Molecular Weight of A Cross linking Agent", Journal of Polymer Science, Part A: Polymer Chemistry Edition, 35, 557-564(1997).2. C. Q. Yang, X. Wang, I. Kang, "Ester Cross linking Cotton Fabric by the Polymers of Maleic Acid and Citric Acid", Textile Research Journal, 67, 334-342 (1997).3. C. Q. Yang, L. Xu, S. Li, Y. Jiang, "Nonformaldehyde Durable Press Finishing of Cotton Fabrics by Combining Polymers of Maleic Acid with Citric Acid", Textile Research Journal, 68, 457-464(1998).4. W. Wei, C. Q. Yang, "Polymeric Carboxylic Acid and Citric Acid as A Nonformaldehyde Durable Press Finish", Textile Chemist and Colorist, 32(2), 53-57 (2000). 5. W. Wei, C. Q. Yang, Y. Jiang, "Nonformaldehyde Durable Press Garment Finishing of Cotton Slacks", Textile Chemist and Colorist, 31(1), 34-38 (1999).Yang, C. Q.: Cross linking Agents of Cellulose Fabrics, U.S. Patent 6,165,919, December 26, 2000.

In-situ Polymerization of MA and ITA on Cotton

Choi reported that cotton fabric treated with MA, ITA and a free radical initiator (0.1-0.2% K2S2O8) underwent “in-situ polymerization”(H,-M., Coi, Textile Res. J., 62, 1992, 614-618)Choi claimed such treatment imparted wrinkle resistance to cotton without providing laundering durability data.We studied the system using FT-IR spectroscopy

C. Q. Yang, Y. Lu,”, Textile Res. J., 70, 359-362 (2000).

In-situ Polymerization of MA and ITA on Cotton

We found that the treated cotton had no wrinkle resistance durable to multiple launderingWe found that the in-situ polymerization takes place only in the presence of K2S2O8and NaH2PO2Durable wrinkle resistance is achieved only at high K2S2O8(2%)IR spectra data provide the evidence of polymerization of MA and ITA

S2O82-

2SO4 .-

+H P

O

OM

H SO4.-

+H P

O

OM

.HSO4-

Free Radical Initiation

HP

O

OMx

MA[ ]. + yMA HH P

O

OM

yMA[ ]x

MA[ ]

H P

O

OM

.x

MA[ ] + +H P

O

OM

H H P

O

OM

.HH P

O

OMx

MA[ ]

HH P

O

OMx

MA[ ] + +SO4.-

HSO4-HP

O

OMx

MA[ ].

H P

O

OM

. MAx+ H P

O

OM

.x

MA[ ]

Chain Propogation and Chain Transfer

Beer’s Law

A = εbc

A = log I0/It (absorbance)

ε molar absorbability

c concentration (m/l)

b radiation pass length in sample

FT-IR Spectroscopy Quantitative Analysis

Transmission method should be the best sampling technique for quantitative analysisDRIFTS or photoacoustic methods can also be used as long as the particle sizes are homogeneousFT-IR spectroscopy is a secondary quantitative method. Reference samples or internal references are needed

C. Q. Yang, G. D. Bakshi, Textile Res. J., 66, 377-384(1996).

R2 = 0.982R2 = 0.998R2 = 0.982

R2 = 0.993R2 = 0.984

HO CH2CO

CH CH OH

CH2 ON N H

HO

Conclusions-I

FT-IR can be applied as qualitative, semi-quantitative and quantitative methods for analysis of polymers. It is primary used as qualitative or semi-quantitative method.FT-IR detects functional groups of polymers. The peak frequency and intensity provide qualitative and quantitative information. Peak frequency/shape also provide information related to chemical environment of the functional group.FT-IR is a reproducible, fast and relatively inexpensive analytical method for chemical analysis of polymer. The data base for FT-IR were well established in the literatures.

Conclusions-II

FT-IR can be applied to insoluble and intractable samples. It can be applied to mixture samples without separation. The sampling methods are relatively easy with no or minimum sample preparation.FT-IR is most useful to study the chemical reactions and chemical bonding on solids.FT-IR is a very useful method for identifying organic compounds including polymers. Full identification based solely on FT-IR can be done when a standard sample is available, as discussed hereFT-IR can do more for your research if you have thoroughly understanding all aspects of this analytical method.