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

16

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

22

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

26Milán Szőri: Colloid chemistry