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1、Thermodynamics of Polymerization 1 Introduction 1.1 Process and Gibbs free energy state 1 state 2 G1 G2 2nd Law four process in polymer science from thermodynamics 1) Melting of crystalline polymer PP, PA crystalline amorphous,2) Rubber elasticity + force - force tension 45, T10 , S= - (increase in
2、order) 3) Mixing and miscibility polymer - solvent polymer - polymer MW determination polyblend MWD fractionation graft solution polymerization block coating and adhesion solution spinning plasticization,4) Polymerization and depolymerization 1.2 Some phenomena in the polymerization monomer polymer
3、or not,degrade,polymer monomer or cyclic oligomer,polymerization depolymerization,1) monomer-polymer equilibrium at high temperature, some polymer depolymerize to monomer,-CH2-C- n CH2=C,R,R,n,R,R,-CH2-C- n CH2=C,CH3,COOCH3,n,CH3,COOCH3,ex. PMMA,-CF2-CF2- n CF2=CF2,n,PTFE,P(-MS),-CH2-C- n CH2=C,CH3,
4、n,CH3,PMAN,-CH2-C- n CH2=C,CH3,CN,n,CH3,CN,2) ring-polymer interconversion,PVDCN,-CH2-C- n CH2=C,CN,CN,n,CN,CN,Why?,-CH2-C*,R,R,nCH2-CH2 -OCH2CH2-,O,n,nCH2-CH-CH3 -OCH2CH-,O,n,CH3,nCH2 CH2 -OCH2CH2CH2CH2-,O,n,CH2 - CH2,nHN(CH2)5CO -NH(CH2)5CO-,810% 90%92%,3)“unpolymerizable” compound,CH CH -CH=CH-,=
5、,n,1.3 Fundamental of thermodynamics of polymerization M P G1 G2 H1 H2 S1 S2,exo,order,three cases of 1) M P polymerize 2) M P depolymerize 3) M P equilibrium,ceiling temperature,four combinations of and,1) - - - + TTf (floor temp.) Tf =159 for nS8 -S- 3) - + - polymerize no 4) + - + unpolymerize no
6、,8,n,ex.,2 Ceiling temperature,n M Mn,at equilibrium,thermodynamic kinetic,analysis,2.1 Thermodynamic analysis of Tc,equilibrium between polymerization and depolymerization,kp,kdp,at equilibrium for high MW polymer equilibrium constant monomer concentration at equilibrium Standard condition of therm
7、odynamics ( .) solid or liquid, 25 , pure, 1atm, activity=1 (or conc.=1 mol/L),at standard condition, Me=1 mol/L polymerization ceiling temperature at non-standard condition, Me 1 mol/L polymerization equilibrium ceiling temperature,VAc St MMA -MeSt Me mol/L 10-9 10-6 10-3 2.6 Te 536 345 198 61,2.2
8、Kinetic treatment of Tc at ordinary temperature kp high, Ep=2034kJ/mol small, T kp kdp small, Edp=40110kJ/mol high, T kdp at equilibrium, Rp=Rdp,two theories of kinetics:,collision transition state,1) collision theory Arrhenius equation:,introduced into Rp=Rdp comparison with,2) transition state the
9、ory,2.3 Determination of Tc 1) kinetic method T(TTc) polymerization R or DP R=0 or DP=0 Tc,2) equilibrium method T(T 3440 kJ/mol,const?,3.2 Analysis gas monomer gas polymer:,translation (molecular weight) rotation (rotational inertia) vibration (vibrational frequency) internal rotation (steric effec
10、t),ref: (cal/mol.K) monomer polymer unit MW ethylene 28.05 35.9 15.9 0.6 0 52.4 18.4 17.8 34.0 iso-butene 56.10 38.0 23.1 - 9.1 70.2 29.2 20.1 41.5 styrene 104.14 39.8 27.9 10.1 4.7 82.5 47.0 32.2 35.5,3.3 Factors effect the entropy 1) steric effect St: -MeSt:,J/mol.K,J/mol.K,cal/mol.K=-(105125) J/m
11、ol.K const.,2) resonance monomer resonance Svm S 3.4 Determination and estimation of entropy 1) from and,oreder: gc gc gg lc lc most negative least negative,ex: - 25, J/mol.K gc gc gg lc lc ethylene 174 158 142 propylene 167 136 116 1-butene 219 190 167 141 113 styrene 149 111 107 -methyl styrene 14
12、7 110 iso-butene 172 112 2) from Me,intercept=,slope=,curve,3) from,4) from Adp=1012 s-1 Ap=106 s-1,J/mol.K,4 Enthalpy of polymerization 4.1 Basic concept,for most cases H= - from first law of thermodynamics H=E+PV at const volume V=0, H=E enthalpy of polymerization = change of internal energy for:
13、n CH2=CH2 -CH2-CH2- H=E=2E-E=2(-351.7)-(-609.2)=-94.2 kJ/mol thermodynamic possibility heat transfer 4.2 Factors effect the enthalpy 1) resonance (conjugation),n,-H kJ/mol CH2=CH2 94.2 no conjugation CH2=CH 85.8 super conjugation CH3 CH2=CH 69.9 conjugation CH3 CH2=C 35.2 conjugation + super conjuga
14、tion,-H,2) steric effect,CH2=CH 85.8 CH3 CH2=CH 77.5 COOCH3 CH2=CH 69.9,CH3 CH2=C 61.5 CH3 CH3 CH2=C 56.5 COOCH3 CH3 CH2=C 35.2,-H,-H,3) hydrogen bonding,CH2=CH 77.5 COOCH3 CH2=CH 67.0 COOH CH2=CH 60.3 CONH2,CH3 CH2=C 56.5 COOCH3 CH3 CH2=C 42.3 COOH CH3 CH2=C 35.2 CONH2,-H,-H,4) electron negative group,CH2=CH2 94.2 CH2=CH 95.9 Cl Cl CH2=C 75.4 Cl,-H,steric effect,-H,electron negative group,-H,-H,-H,2 Cl steric effect,-H ,electron negative group,-H,steric effect: FH,CH2=CH2 94.2 CH2=CF2 129.8 CF2=CF2 155,-H, H=-(30100) kJ/mol,4.
