山东大学：《物理化学》课程教学资源（讲义资料）8.11 solution of macromolecules

88. 11 Solutions of macromolecules

§8.11 Solutions of macromolecules

8.11.1 Macromolecules and their solutions 1. Lyophilic sol and macromolecules Lyophilic sol (1)Spontaneous dissolution/dispersion (2)thermodynamically stable ()Weak Tyndall effect (4)High viscosity Hermann Staudinger Mar:.23,1881-Sep.8,1965 German organic chemist 1953 Nobel prize The existence of macromolecules https://en.wikipediaorg/wiki/hermann_staudiNger

Hermann Staudinger Mar. 23, 1881-Sep. 8, 1965 German organic chemist 1953 Nobel Prize The existence of macromolecules https://en.wikipedia.org/wiki/Hermann_Staudinger 1. Lyophilic sol and macromolecules Lyophilic sol (1) Spontaneous dissolution/dispersion; (2) thermodynamically stable; (3) Weak Tyndall effect; (4) High viscosity. 8.11.1 Macromolecules and their solutions

8.11.1 Macromolecules and their solutions 2. Definition of macromolecules Macromolecules: a chain-like molecule with its molar mass higher than 10000 Natural macromolecules: protein, starch, cellulose Artificial macromolecules: PE, PP, PS, nylon-66

Macromolecules: a chain-like molecule with its molar mass higher than 10000. Natural macromolecules: protein, starch, cellulose; Artificial macromolecules: PE, PP, PS, nylon-66 8.11.1 Macromolecules and their solutions 2. Definition of macromolecules

8.11.2 Viscosity of macromolecular solutions 2. 1 viscosity of macromolecule solutions Newtonian viscosity law: F=nA Relative viscosity Specific -7 7n ty 7 Reduced 7p7 vIscoSity C C Intrinsic VIScOSIty C→)0 C c is concentration in g/l

Newtonian viscosity law: dx du F =A Relative viscosity Specific viscosity Reduced viscosity Intrinsic viscosity 0 r    = r 1 0 0 sp = − − =      c c sp r −1 =     c c sp 0 lim   → = c is concentration in g/ml 8.11.2 Viscosity of macromolecular solutions 2.1 viscosity of macromolecule solutions

8.11.2 Viscosity of macromolecular solutions 2. 1 viscosity of macromolecule solutions Reptation Theory Relationship between intrinsic viscosity and molar mass of macromolecule Slope 3.4 SP M For spherical molecule: a=0 For rod-like molecule. a=2 For flexible thread-like molecule a=0.5-1.0 In good solvent: a>0.5; in bad solvent: as KM 0.5

    = KM Relationship between intrinsic viscosity and molar mass of macromolecule For spherical molecule:  = 0 For rod-like molecule:  = 2 For flexible thread-like molecule:  = 0.5~1.0 In good solvent:  > 0.5; in bad solvent:   0.5 8.11.2 Viscosity of macromolecular solutions 2.1 viscosity of macromolecule solutions

8.11.3 Salting-out of macromolecule 3.1 Salting in and salting out salting out( Can be used for Fractionation) Addition of salt at low ionic strength If the concentration of neutral salts is at a can increase solubility of a protein by high level(>0. 1 mol dm- ), in many instances neutralizing charges on the surface of the the protein precipitates. This phenomenon protein, reducing the ordered water around results because the excess ions(not bound to the protein and increasing entropy of the the protein) compete with proteins for the system solvent. The decrease in solvation and netralization of the repulsive forces allows the proteins to aggregate and precipitate Nacl

Addition of salt at low ionic strength can increase solubility of a protein by neutralizing charges on the surface of the protein, reducing the ordered water around the protein and increasing entropy of the system. 8.11.3 Salting-out of macromolecule 3.1 Salting in and salting out Salting out (Can be used for Fractionation) If the concentration of neutral salts is at a high level (> 0.1 mol dm-3 ), in many instances the protein precipitates. This phenomenon results because the excess ions (not bound to the protein) compete with proteins for the solvent. The decrease in solvation and neturalization of the repulsive forces allows the proteins to aggregate and precipitate

8. 11.3 Salting-out of macromolecule 3.1 Salting in and salting out Adjusting ph of the solution to isoelectric point can weaken the repulsion between color idal particles, helping for pH> I.E.P. pH <I.E.P. coagulation of colloidal particles L.E. P Solubility of a globulin-type protein close to its isoelectric point(IEP

Adjusting pH of the solution to isoelectric point can weaken the repulsion between colloidal particles, helping for coagulation of colloidal particles. 8.11.3 Salting-out of macromolecule 3.1 Salting in and salting out

8. 11.3 Salting-out of macromolecule 3.1 Salting in and salting out Salting-in NaCl lonic strength Salting-out: Ammoniu Used to selectively precipitate proteins, often Sodium Aggregate with(NHa)2 sO4 which is cheap, effective, lonic strength does not disturb structure and is very soluble

8.11.3 Salting-out of macromolecule 3.1 Salting in and salting out Used to selectively precipitate proteins, often with (NH4 )2SO4 which is cheap, effective, does not disturb structure and is very soluble

8.11.4 Osmotic pressure of macromolecular solutions 4.1 Osmotic pressure of macromolecules At low molality H,O I=RT+A,mB 丌=cRT丌=BRT 丌RT M =x+R742 丌RT B M Valid for polymeric nonelectrolyte =RT+A,mB+ M A3i Can be used to determine molar mass of macromolecule within 104 106 g mol Virial factor

 = cRT RT M mB  = M RT mB =        = + + 2 2 3 1 B B B A m A m M RT m  Virial factor At low molality       = + B B A m M RT m 2  1 B B RTA m M RT m = + 2  Can be used to determine molar mass of macromolecule within 104~106 g mol-1 Valid for polymeric nonelectrolyte 8.11.4 Osmotic pressure of macromolecular solutions 4.1 Osmotic pressure of macromolecules P H2O c

8.11.4 Donnan Effect of macromolecular solutions 4.2 Donnan Effect polyelectrolytes 藏NaP NaCl NaP H,O polyelectrolyte Semipermeable membrane (unaCd,=(uNaI(Na'I[cr]=(Na] Nap->Na+p (+x)x=(b-x)b-x) 丌=2cRT 2c+2c6 Rt C+26 C+26 Na p zNa tp Two limiting cases. b>c丌=cRT1 It's hard to determine molar mass of a When a very large amount of Nacl is present, polyelectrol te the donna effect can be completely eliminated

NaP H2O c + − NaP ⎯→Na + P polyelectrolyte  = 2cRT Semipermeable membrane It’s hard to determine molar mass of a polyelectrolyte. + − ⎯→ + z Naz P zNa P  =（z +1）cRT NaCl b NaP c ( ) ( ) NaCl L NaCl R  =  ( ) ( ) L R [Na ][Cl ] [Na ][Cl ] + − + − = (c + x)x = (b − x)(b − x) c b b x 2 2 + = RT c b c cb         + + = 2 2 2 2  Two limiting cases: b>c  = 2cRT  = cRT When a very large amount of NaCl is present, the Donna effect can be completely eliminated. 8.11. 4 Donnan Effect of macromolecular solutions 4.2 Donnan Effect polyelectrolytes