1、Thermodynamics of Polymerization 1 Introduction 1.1 Process and Gibbs free energystate 1 state 2G1 G2 2nd Lawfour process in polymer science from thermodynamics 1) Melting of crystalline polymerPP, PAcrystalline amorphous,2) Rubber elasticity+ force- forcetension 45, T10 , S= - (increase in order) 3
2、) Mixing and miscibilitypolymer - solvent polymer - polymerMW determination polyblendMWD fractionation graftsolution polymerization blockcoating and adhesionsolution spinningplasticization,4) Polymerization and depolymerization1.2 Some phenomena in the polymerizationmonomer polymer or not,degrade,po
3、lymer monomer or cyclic oligomer,polymerization depolymerization,1) monomer-polymer equilibriumat 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,n,CH3,PMAN,-CH2-C-
4、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-,=,n,1.3 Fundamental
5、of thermodynamics of polymerizationM PG1 G2H1 H2S1 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 =159for nS8 -S- 3) - + - polymerize no 4) + - + unpolymerize no,8,n,ex.,2 Ceiling tempe
6、rature,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 polymerequilibrium constantmonomer concentration at equilibriumStandard condition of thermodynamics ( .)solid or liqu
7、id, 25 , pure, 1atm, activity=1 (or conc.=1 mol/L),at standard condition, Me=1 mol/Lpolymerization ceiling temperature at non-standard condition, Me 1 mol/Lpolymerization equilibriumceiling temperature,VAc St MMA -MeSt Me mol/L 10-9 10-6 10-3 2.6 Te 536 345 198 61,2.2 Kinetic treatment of Tcat ordin
8、ary temperaturekp high, Ep=2034kJ/mol small, T kpkdp small, Edp=40110kJ/mol high, T kdpat equilibrium, Rp=Rdp,two theories of kinetics:,collision transition state,1) collision theoryArrhenius equation:,introduced into Rp=Rdpcomparison with,2) transition state theory,2.3 Determination of Tc 1) kineti
9、c methodT(TTc) polymerization R or DPR=0 or DP=0Tc,2) equilibrium method T(TTc) polymerization x or Mex=0 or Me=M0Tc,3) calculation methodref: ,2.4 Effect of pressure on Tcqualitative: P VTc polymerizationquantitative:Clapeyron - Clausius equation,2,1,5,3,4,lnTcP: P, Tc ex: -MeSt -V=14.1 mL/mol-H=34
10、.0 kJ/mol mL/kJ,3 Entropy of polymerization 3.1 Basic conceptM P ,?,at equilibrium - (105125) J/mol.K ex: polymerization at 50, -TS=323(105125)=3440 kJ/mol - H 3440 kJ/mol,const?,3.2 Analysisgas monomer gas polymer:,translation (molecular weight) rotation (rotational inertia) vibration (vibrational
11、frequency) internal rotation (steric effect),ref: (cal/mol.K)monomer polymer unitMW 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 effectSt:-MeSt:,J
12、/mol.K,J/mol.K,cal/mol.K=-(105125) J/mol.K const.,2) resonancemonomer resonance Svm S3.4 Determination and estimation of entropy 1) from and,oreder: gc gc gg lc lc most negative least negative,ex: - 25, J/mol.Kgc gc gg lc lc ethylene 174 158 142 propylene 167 136 116 1-butene 219 190 167 141 113 sty
13、rene 149 111 107 -methyl styrene 147 110 iso-butene 172 1122) from Me,intercept=,slope=,curve,3) from,4) fromAdp=1012 s-1Ap=106 s-1,J/mol.K,4 Enthalpy of polymerization 4.1 Basic concept,for most cases H= -from first law of thermodynamicsH=E+PVat const volume V=0, H=Eenthalpy of polymerization = cha
14、nge of internal energy for: n CH2=CH2 -CH2-CH2-H=E=2E-E=2(-351.7)-(-609.2)=-94.2 kJ/molthermodynamic possibilityheat transfer4.2 Factors effect the enthalpy 1) resonance (conjugation),n,-H kJ/mol CH2=CH2 94.2 no conjugation CH2=CH 85.8 super conjugationCH3 CH2=CH 69.9 conjugationCH3 CH2=C 35.2 conju
15、gation + super conjugation,-H,2) steric effect,CH2=CH 85.8 CH3CH2=CH 77.5COOCH3CH2=CH 69.9,CH3 CH2=C 61.5 CH3CH3 CH2=C 56.5COOCH3CH3 CH2=C 35.2,-H,-H,3) hydrogen bonding,CH2=CH 77.5 COOCH3CH2=CH 67.0COOHCH2=CH 60.3 CONH2,CH3 CH2=C 56.5 COOCH3CH3 CH2=C 42.3COOHCH3 CH2=C 35.2 CONH2,-H,-H,4) electron n
16、egative group,CH2=CH2 94.2 CH2=CH 95.9ClCl 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,4.3 Determination and estimation of enthalpy 1) direct calori
17、metryadiabatic system 2) from heat of formation or heat of combustionex: St PSHfmg=149 kJ/mol, Hfpg=67.4 kJ/mol,Hfpc=34.3 kJ/mol, Hv=44.8 kJ/molHgg=Hfpg-Hfmg=67.4-149= - 81.6 kJ/molHlc=Hfpc-Hfml=Hfpc-(Hfmg-Hv)=34.3-(149-44.8)= - 69.9 kJ/mol,CH2=CH + 10O2 8CO2 + 4H2O8C + 8O2 4H2 + 2O2,H3,H2,H1,HfM,Hf
18、M= H1 + H2 - H3,5 Gibbs free energyG= H-TSG=-RTlnke=RTlnMeat 50 -TS=3440 kJ/molbut H=-(30100) kJ/mol G is mainly dependent on H,6 Application of polymerization thermodynamics-MeStH=-35.2 kJ/molS=-104 J/mol.KTc=61T=25, Me=2.6 mol/Lanionic polymerizationemulsion polymerization with redox initiator system at 530copolymerization heat resistant polymer,poly(-MeSt),St/AN (72/28 by wt%) Tg=100 -MeSt/AN (69/31 by wt%) Tg=113,
