Colloid Chemistrykemszori/KolloidKemia_2018_02_ENG.pdf · Hydrophilic-lipophilic balance (HLB)...
Transcript of Colloid Chemistrykemszori/KolloidKemia_2018_02_ENG.pdf · Hydrophilic-lipophilic balance (HLB)...
Colloid Chemistry
Lecture #2
Association colloid
1Milán Szőri: Colloid chemistryhttps://ilustracionmedica.wordpress.com/2014/08/27/fisicos-haciendo-medicina-john-tyndall/
SolutionClassical vs. Colloid solution
• Classical state functions: • Composition (xi, w%i, ci, cT,i etc.)• (Colour, smell)• T• V• P• U• H• S• G• A
• Further state descriptors:• Particle morphology• Distribution• Dispersity• …
Milán Szőri: Colloid chemistry 2
Tyndall effect
At high c
precipitation (e.g. inorganic chemistry)
5M (≈25 w%)4M (≈20 w%)(3M≈16 w%)
J. Chem. Phys. 2016, 144, 204126.
Increased ion size
NaBr
Association (self-assembled) colloids
• In solution, tensides (molecules having polarand apolar sites) are associated by secondarychemical bond making micelles which are inchemical equilibrium with tenside solution(their formation is spontaneous process andthey achieve thermodynamic stability).
• Transition between classical solution and sols
• Microheterogenous systems with at leasttwo components
3
Phys. Chem. Chem. Phys., 2014, 16, 8594.
hydrophilichydroapathetic
Micelle
equilibrium
J. Phys. Chem. B 2007, 111, 11722.
Sodium dodecyl sulfate (SDS) micelle
Milán Szőri: Colloid chemistry
Classification of tensides I.
• According to their chemical structure:• Nonionic tensides:
• Non dissociable hydrofil group(s) attached to hydroapathetic groups
• Anionic (anion active) tensides: • Anionic group(s) attached to hydroapathetic groups
• Cationic (cation active) tensides: • Cationic group(s) attached to hydroapathetic groups
• Amphoteric tensides:• Zwitterionic group(s) attached to the hydroapathetic
group
4
hydrofilhydroapatic
lipofil
Milán Szőri: Colloid chemistry
large µ(5D<µ)
Classification of tensides II.
5
R: saturated and unsaturated hydrocarbon chain, # of carbon in the chain: 8-18Counter ion:X+: Na+, K+
Y-: Br-, Cl-Milán Szőri: Colloid chemistry
Classification of tensides III.
• According to their origin:• Natural tensides:
• Synthetic tensides:
6
Ramnose lipid Soforose lipid
Optik 2016, 127, 2740.Milán Szőri: Colloid chemistry
Size, shape and structure of micelles
• Depending:• Molecular structure of the tensides• solvent• ctensid
• celectrolyte
• temperature
Dynamic equilibrium (Continuous exchange of tenside between the micelles and the solution, texchange = few ns)Geometric parameters: a,b,tAggregation number: average number of tenside in a micelle
7PLoS ONE 2013, 8, e62488.
Milán Szőri: Colloid chemistry
Classification of the association colloids
• Solvent:• Micelles:
• In aqueous solution
• Inverse micelles: • In nonaqueous solutions
• Size of aggregates are smaller than micelles
• In apolar solvent, only small HLB tensides can be dissolved
8
Inverse micelleMicelle
Milán Szőri: Colloid chemistry
Hydrophilic-lipophilic balance (HLB)
9Journal of Soil Science and Plant Nutrition, 2012, 12, 667.
Water solubility
Lipophilic
HLB scale(Nonionic tenside) Application
Milán Szőri: Colloid chemistry
Hydrophilic-lipophilic balance (HLB)
• ICI standard for selection of the optimal emulsifying agents
• Davies (HLB of the tenside):
𝐻𝐿𝐵𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒 = 7 +𝐻ℎ𝑦𝑑𝑟𝑜𝑝ℎ𝑖𝑙𝑖𝑐 +𝐻𝑙𝑖𝑝𝑜𝑝ℎ𝑖𝑙𝑖𝑐
𝐻𝐿𝐵𝑆𝐷𝑆 = 7 + 38,7 + 12 ∙ −0,475 = 40,0
• Griffin method (for tenside mixtures):
𝐻𝐿𝐵 =(𝐻𝐿𝐵𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒,𝑖∙ 𝑤𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒,𝑖)
Online:
Milán Szőri: Colloid chemistry 10
Hydrophilic group 𝑯𝒉𝒚𝒅𝒓𝒐𝒑𝒉𝒊𝒍𝒊𝒄
-SO4−Na+ 38.7
-COO−K+ 21.1
-COO−Na+ 19.1
N (tertier amine) 9.4
sorbitane ester 6.8
Free ester 2.4
-COOH 2.1
free –OH 1.9
-O- 1.3
Sorbitane OH 0.5
Lipophilic groups 𝑯𝒍𝒊𝒑𝒐𝒑𝒉𝒊𝒍𝒊𝒄
-CH- -0.475
-CH2- -0.475
CH3- -0.475
=CH- -0.475
http://www.al-nasir.com/www/PharmCalc/exec_calc.php?ID=hlb
International Journal of Pharmaceutics 2008, 356, 44.http://www.firp.ula.ve/archivos/historicos/57_Chap_Davies.pdf
Physical chemical properties of association colloids I.
• Association colloids differ from classical solution at high concertation:• Surface tension
• Specific and equivalent electric conductivity
• Osmotic pressure
• Decrease in vapor pressure
• Increase in Freezing point
11http://www.dataphysics.de/2/start/understanding-interfaces/basics/surfactants-and-critical-micelle-concentration-cmc/
J. Colloid Interface Sci. 2012, 370, 102.
CMC
Micelle formation
Milán Szőri: Colloid chemistry
Concentration
Freezing point
Surface tension
Eq. electric conductivity
Specific electric conductivity
Osmotic pressurePh
ysic
al p
rop
erti
es
• Surface tension (γ)• Adsorption of tenside molecules at the air/solution interface• Decrease in the surface tension compared to the neat solvent• At c > CMC, there is no change in the tenside coverage at the
interface since „new” tenside molecules are involve in the micelle formation. No change in the surface tension
• Specific and equivalent electric conductivity• In the case of c < CMC: the ion concertation increasing with the
adding ionic tensides to the solution, therefore the electric conductivity increases
• By the micelle formation, the ion mobility is decreased therefore the conductivity is only slightly increasing by adding tensides to the solution.
• Osmotic pressure, decrease in vapor pressure, increase in freezing point• Colligative properties depends only from the ion concertation which
is affected by the micelle formation
12Milán Szőri: Colloid chemistry
Physical chemical properties of association colloids II.
Critical micelle concentration (CMC)
• Other notation (IUPAC): c.m.c., cmc, cM
• Unit:• mM (mmol/dm3)
• mg/l (mg/dm3)
Milán Szőri: Colloid chemistry 13Further cmc values: https://nvlpubs.nist.gov/nistpubs/Legacy/NSRDS/nbsnsrds36.pdf
PLoS ONE 2011, 6, e19850.
[Xn]
[X]
Thermodynamic of the aggregation I.
• Equilibrium of the aggregate formation :
∆G𝑎𝑔𝑔= −𝑅𝑇𝑙𝑛𝐾𝑎𝑔𝑔 = −𝑅𝑇𝑙𝑛𝑋𝑛𝑋 𝑛
∆G𝑎𝑔𝑔= −𝑅𝑇𝑙𝑛 𝑋𝑛 + 𝑛𝑅𝑇𝑙𝑛 𝑋• Formation of aggregate from tenside solution:
𝑋𝑛 = 10−10𝑀 (small, existence of the aggregates)
𝑋 = 10−3𝑀 = 1𝑚𝑀 (typical CMC value)
𝑛 > 50 (small aggregation number)
∆G𝑎𝑔𝑔= −𝑅𝑇𝑙𝑛 𝑋𝑛 + 𝑛𝑅𝑇𝑙𝑛(𝐶𝑀𝐶)
∆G𝑎𝑔𝑔= 57𝑘𝐽
𝑚𝑜𝑙+ 50 × −17
𝑘𝐽
𝑚𝑜𝑙≈ −800
𝑘𝐽
𝑚𝑜𝑙
Milán Szőri: Colloid chemistry 14
http://cdn.intechweb.org/pdfs/13118.pdf
𝑛[𝑋] [𝑋𝑛]
𝐾𝑎𝑔𝑔
(𝐾𝑎𝑔𝑔 = 10140)
𝑅𝑇𝑙𝑛(𝐶𝑀𝐶): average molar free energy contribution of tenside molecule
𝐶𝑀𝐶 = 𝑛 𝑋𝑛 + 𝑋 ≈ 𝑋
Thermodynamic of the aggregation II.
• Isothermal titration calorimetry (ITC)
Milán Szőri: Colloid chemistry 15Colloid Polym. Sci. 2011, 289, 3.
Frontiers in Microbiology, 2015, 6, 1049.
CMC determination of SDS by ITC
Integration
CMC
Factors changing CMC
• Accociaiton behavious depends on theintermoleculari nteractions:
• CMC decreases by increasing the carbon chain length (𝑵𝑪) :lg 𝐶𝑀𝐶 = 𝑎 − 𝑏𝑁𝐶
tenside-tenside interaction increases
• The non—ionic tenside has lower CMC value compared to the ionic tenside in the same sizeSmaller tenside-solvent interaction
• Higher the charge in the counterion smaller the CMCLarger tenside-counterion interaction
• CMC decreases by the decresing solvation of the counterionSmaller solvent-counterion interaction
• By adding electrolyte the CMC decreaseslg 𝐶𝑀𝐶 = 𝑎 − 𝑏𝑙𝑔𝑐𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑙𝑦𝑡𝑒
Smaller the dissociation of the ionic tenside
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Solvent-counterioninteraction
Tenside-solventinteraction
Tenside-tenside interaction
Solvent-solventinteractionTenside-counterion
interaction
Milán Szőri: Colloid chemistry
∆G𝑎𝑔𝑔= −𝑅𝑇𝑙𝑛 𝑋𝑛 + 𝑛𝑅𝑇𝑙𝑛 𝐶𝑀𝐶
∆G𝑎𝑔𝑔 + 𝑅𝑇𝑙𝑛 𝑋𝑛
𝑛= ∆G′𝑎𝑔𝑔= 𝑅𝑇𝑙𝑛(𝐶𝑀𝐶)
Composition of Surface and bulky tenside solution
High purity material with contaminated surface
• CMC(SDS)=8.2 mM
• Am(SDS)=0.25nm2=2.5·10-17dm2
• V=1dm3
• A=1dm2
Is there case when CMC does depend on the surface?
Milán Szőri: Colloid chemistry 17
1dm2
1dm
6,6·10-8mol SDS
8,2·10-3mol SDS
1dm1dm
Interfacial structure of tenside solutions
Milán Szőri: Colloid chemistry 18
Monolayer coverage
SDS
DTAB
C12E10
J. Phys. Chem. B 2011, 115, 2518.Langmuir, 2014, 30, 10600.
A: a representative SDS in high surface concentration zoneB: a representative SDS in low surface concentration zone
Langmuir 2010, 26, 5462.
7 nm2/SDS molecule 0.52 nm2/SDS molecule
Temperature effect on the solubility & micelle formation of ionic tensides• By increasing the temperature
the solubility of the ionic tensides will:• Slightly increase
• At ctenside> CMC: rapidly increasing
• The average mass of the micelles decreases by the increasing temperature
19T(°C) c te
nsi
de
Krafft point tenside solution
Saturatedtenside
solution +
Solid tenside Micelles
+Tenside solution
Saturated tensidesolution
+solid
tenside+
Micelles
https://www.stevenabbott.co.uk/practical-surfactants/cloud-krafft.php
Milán Szőri: Colloid chemistry
Temperature effect of the solubility and micelle formation ability of nonionic tensides• The CMC of nonionic tensides decreases by the increasing
temperature
• The average mass of the micelle increases dramatically by the evaluation of the temperature
• At a characteristic temperature, the solubility of nonionic tensides drops
• After the size of micelle increased (cloudy), phase separation
20
T(°C)
c ten
sid
e
b
Concentration of the micelle
solution
Concentration of the tenside
solution
a
Two-phase system
CMC(T)Tensidesolution
Micelle+
Tensidesolution
Tenside solution
Micelles
Physicochemical and Engineering Aspects 2001, 183 – 185, 95.Current Opinion in Colloid & Interface Science, 2016, 22, 23.Milán Szőri: Colloid chemistry
Analogy - solubility
• Formation of spatial discontinuation
Concentrated NaCl solution (saturated 26% at 25⁰C)
21Milán Szőri: Colloid chemistry
5M (≈25 w%)4M (≈20 w%)(3M≈16 w%)
NaCl percolation network
https://www.tf.uni-kiel.de/matwis/amat/iss/kap_6/illustr/i6_2_2.html
J. Chem. Phys. 2016, 144, 204126.
Solubilisation
• Make a solution form a poorly soluble materials by means of tensides
• This is due to the micelle formation
• Spontaneous
• The formed solubilisatum can be either fluid or solid
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Apolarsolubilisatum
Amphiphatic solubilisatum
Solubilisatum molecules adszorb on the surface of micelle
Solubilisatum molecules inserted into the void of the
nonionic tenzids
Szolubilizátum:Tenzid:
Milán Szőri: Colloid chemistry
https://femina.hu/otthon/kezi_mosas/
Phase equilibrium L – lamellar phase;
H1 – hexagonal phase (normal type);
H2 –hexagonal phase (reversed type);
I1 – isotropic solution (normal micelles);
I2 – isotropic solution (reversed micelles);
K – liquid crystalline phase, presumably with rod-like reversed micelles (non-hexagonal packing
23Soft Matter, 2012, 8, 11022.Biochemical Society Transactions, 2011, 39, 725.
Cetyl-trimethylammonium-bromideGlycerine-monooleate
Milán Szőri: Colloid chemistry
Applications
• Solubilizing agent
• Detergents
• Emulsifying agent
• Wetting and spreading agent
• Antifoaming agent
24https://www.ihs.com/products/chemical-surfactants-scup.htmlhttp://tudasbazis.sulinet.hu/hu/szakkepzes/kereskedelem-es-marketing/kereskedelmi-es-marketing-modulok/mososzerek/mososzerek-fogalma-osszetetele
Overall growth on a volume basis in the major
world areas is expected to average almost 3%
annually during 2015–20.
Milán Szőri: Colloid chemistry
Colloids
25Milán Szőri: Colloid chemistryhttp://kolloid.unideb.hu/wp-content/uploads/Pharmacy/colloid1_intr.pdf