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3.5ThermodynamicsofPolymerization

3.5.1GeneralConceptofThermodynamics3.5.2EnthalpiesofPolymerization3.5.3CeilingTemperatureofPolymer-ization.3.5ThermodynamicsofPolymeri13.5ThermodynamicsofPolymerizationWhethermonomerscanpolymerize,boththermodynamicandkineticfeasibilitiesshouldbetakenintoconsideration.Fromthethermodynamicviewpointtoanalysisthetendencyofpolymerizationordepolymerization.3.5ThermodynamicsofPolymer2Whenpolymerizationisfavorablefromthethermodynamicviewpoint,thenkineticfactorsaretakenintoconsideration.Theenthalpiesofpolymerizationandtheceilingtemperaturearediscussedinthermodynamics..Whenpolymerizationisfavorab3

3.5.1GeneralConceptofThermodynamics

Freeenergycanbeusedtojudgewhetherpolymerizationisfavored.Topolymerization,monomersaretheinitialstate(m),andpolymersarethefinalstate(p).When，monomerspolymerswhen，monomerspolymersWhen，monomerspolymers.

3.5.1GeneralConceptof4Therelationshipbetweenfreeenergyandenthalpy,andentropyis.Therelationshipbetweenfree5△S----Thenegative△Sforpolymerizationarisesfromthedecreasedrandomnessforthepolymerrelativetothemonomer.The△Svaluesfallinthenarrowrangeof-105～-125J/mol·K,andpolymerizationtemperaturefromroomtemperatureto100℃，Soisabout+30～42kJ／mol。.△S----Thenegative△Sforpoly6

Enthalpyvaluesforpolymersarelow,whilethoseformonomersarehigh.Whentheabsolutevalueof△Hisgreaterthan，polymerizationcantakeplace.Thegreater

△Hvalueis,themorepossiblethepolymerizationtakeplace..Enthalpyvaluesforpolyme73.5.2

EnthalpiesofPolymerizationMeasuringmethod:directcalorimetric,heatsofcombustion,thermodynamicequilibriummeasurements.Standardheatofformationalsocanbeusedtoevaluate

.3.5.2EnthalpiesofPolymeriza8Thedifferencesofthesubstituentsonmonomerswillaffectthebondenergy,andtheenthalpiesaredifferent.Theheatofpolymerizationisthedifferencebetweenthebondenergyoftwosinglebondandthatofonedoublebond..Thedifferencesofthesubstit9EffectofStructureFactors

-H=35---163kJ/molThestericeffectofthesubstituentswilldecreasetheenthalpy.Conjugativeeffectdecreasesit,too.

Substituentswithhighelectronegativitywillincreaseit.

Theeffectsofhydrogenbondandsolvationiscomparativelysmall..EffectofStructureFactors10

Thestericeffectofthesubstituentswilldecreasetheenthalpy.

CH2=CH2CH2=C(CH3)2CH2=O

95.051.554.4kJ/mol

CH3CH3CH3CH2=CCH2=CCH=OCOOCH3C6H5

56.5350.0kJ/mol.

Thestericeffectofthes11Conjugativeeffectdecreasestheenthalpyofpolymerization

CH2=CHCH2=CHCH2=C(CH3)C6H5CH=CH2CH=CH2

69.972.874.5kJ/mol

CH2=CHCH2=CHCH3CNCOORCH2=C

72.478.735C6H5.Conjugativeeffectdecreasest12Substituentswithhighelectronegativitywillincreasetheenthalpy.

CH2=CHCH2=CHCH2=CF2CF2=CF2ClNO2

95.890.8129.2154.8kJ/mol

.Substituentswithhighelectro13Itisbecausethatsubstituentswithhighelectronegativitywillgreatlyenhancethebondenergy.Forexample,thebondenergyofC－Csinglebondinhexafluoroethaneis520kJ/mol,whichis350kJ／molhigherthanthatinethane..Itisbecausethatsubstituent14TheeffectsofhydrogenbondandsolvationCH3CH2=CHCH2=CCOOHCOOH

66.942.3kJ/molCH3CH2=CHCH2=CCONH2CONH2

60.235.1kJ/mol.Theeffectsofhydrogenbonda153.5.3

CeilingTemperatureofPolymerizationwhen,，polymerizationcantakeplace

.3.5.3CeilingTemperatureof16Withtemperaturerising，thevalueofapproachestoandreaches,atthispoint，andpolymerizationanddepolymerizationgettoabalance.Thetemperatureofthisbalanceiscalledpolymerizationceilingtemperature(Te)..Withtemperaturerising，theva17ForexampleInthepresencesodiumnaphthaleneorlithiumalkyl，α-methylstyrenecanpolymerizeinbenzenesolution.Whenthetemperatureiselevatedto+40℃andthenloweredto-70℃repeatedly，Theviscosityofthereactingsystemrisesandfallsrepeatedly，whichmeanspolymerizationanddepolymerizationproceedsinareversiblemanner.

CH3CH3nCH2=C-[-CH2-C-]n-.ForexampleInthepresence18Inmostcasespolymerizationtakeplaceatlowtemperature.Athightemperaturemoremonomersaredepolymerized.Withinawiderangeoftemperature，monomersandpolymersareinabalancestateandthereseemstobeaseriesofceilingtemperatures，soceilingtemperaturesTehasrelationtomonomerconcentration..Inmostcasespolymerizationt19PropagationanddepolymerizationarereversiblereactionsPropagationanddepolymerizationrateequationAtbalancestateDPisverygreat

.Propagationanddepolymerizati20Inthermodynamics

investigationastandardstateshouldbechosen.Forsolidandliquidthestandardstateisdefinedaspuresubstance，at1atmandwhosedegreeofactivityequals1，thermodynamicfunctionsatstandardstateismarkedwitha“0”atitstoprightcorner.Inthermodynamicsinvestigatio21Atnonstandardstate

Atbalance

BalancetemperatureTeisdefinedasthebalancetemperaturewhen[M]e＝1mol/L.AtnonstandardstateAtbalanc22CeilingtemperatureTe-----BalancemonomerconcentrationThereisacorrespondingbalancemonomerconcentrationatacertainceilingtemperatureTe..Ifthebalancemonomerconcentrationisverylowthepolymerizationmaybelookonasaverythoroughprocess..CeilingtemperatureTe-----Bal23At25℃，forvinylacetate[M]e＝1.4×10-11mol/L，forSt2×10－8，forMMA2.86×l0－5，forα-methylSt[M]e=2.6mol／L，At130℃，forMMA[M]e=0.5mol/L，.At25℃，forvinylacetate.24

thermodynamic

analysisandkinetics

deed

PolymerizationceilingtemperaturecanbeestimatedbythedataofandAtacertaintemperature，andarenotquitedifferent.Andonecanbeasubstituteforanothersometimes..thermodynamicanalysisandki25Whethersomemonomercanpolymerizeshouldbejudgedbyboththermodynamicandkineticanalysiskineticanalysisisnousewhendynamicanalysisresultisnopolymerizationfeasibility.Whethersomemonomercanpolym26Ifpolymerizationcantakeplacefromthethermodynamicviewpoint,appropriateinitiatorsarethensearchedtosolvetherateofpolymerizationproblem..Ifpolymerizationcantakepla27Takepropyleneforexample,theheatofpolymerizationofpropyleneis85.8kJ/mol.Thus,thepolymerizationcantakeplace,however,thepolymerizationtakesplaceonlyafterthecomplexationinitiationsystembeenfound..Takepropyleneforexample,th283.5ThermodynamicsofPolymerization

3.5.1GeneralConceptofThermodynamics3.5.2EnthalpiesofPolymerization3.5.3CeilingTemperatureofPolymer-ization.3.5ThermodynamicsofPolymeri293.5ThermodynamicsofPolymerizationWhethermonomerscanpolymerize,boththermodynamicandkineticfeasibilitiesshouldbetakenintoconsideration.Fromthethermodynamicviewpointtoanalysisthetendencyofpolymerizationordepolymerization.3.5ThermodynamicsofPolymer30Whenpolymerizationisfavorablefromthethermodynamicviewpoint,thenkineticfactorsaretakenintoconsideration.Theenthalpiesofpolymerizationandtheceilingtemperaturearediscussedinthermodynamics..Whenpolymerizationisfavorab31

3.5.1GeneralConceptofThermodynamics

Freeenergycanbeusedtojudgewhetherpolymerizationisfavored.Topolymerization,monomersaretheinitialstate(m),andpolymersarethefinalstate(p).When，monomerspolymerswhen，monomerspolymersWhen，monomerspolymers.

3.5.1GeneralConceptof32Therelationshipbetweenfreeenergyandenthalpy,andentropyis.Therelationshipbetweenfree33△S----Thenegative△Sforpolymerizationarisesfromthedecreasedrandomnessforthepolymerrelativetothemonomer.The△Svaluesfallinthenarrowrangeof-105～-125J/mol·K,andpolymerizationtemperaturefromroomtemperatureto100℃，Soisabout+30～42kJ／mol。.△S----Thenegative△Sforpoly34

Enthalpyvaluesforpolymersarelow,whilethoseformonomersarehigh.Whentheabsolutevalueof△Hisgreaterthan，polymerizationcantakeplace.Thegreater

△Hvalueis,themorepossiblethepolymerizationtakeplace..Enthalpyvaluesforpolyme353.5.2

EnthalpiesofPolymerizationMeasuringmethod:directcalorimetric,heatsofcombustion,thermodynamicequilibriummeasurements.Standardheatofformationalsocanbeusedtoevaluate

.3.5.2EnthalpiesofPolymeriza36Thedifferencesofthesubstituentsonmonomerswillaffectthebondenergy,andtheenthalpiesaredifferent.Theheatofpolymerizationisthedifferencebetweenthebondenergyoftwosinglebondandthatofonedoublebond..Thedifferencesofthesubstit37EffectofStructureFactors

-H=35---163kJ/molThestericeffectofthesubstituentswilldecreasetheenthalpy.Conjugativeeffectdecreasesit,too.

Substituentswithhighelectronegativitywillincreaseit.

Theeffectsofhydrogenbondandsolvationiscomparativelysmall..EffectofStructureFactors38

Thestericeffectofthesubstituentswilldecreasetheenthalpy.

CH2=CH2CH2=C(CH3)2CH2=O

95.051.554.4kJ/mol

CH3CH3CH3CH2=CCH2=CCH=OCOOCH3C6H5

56.5350.0kJ/mol.

Thestericeffectofthes39Conjugativeeffectdecreasestheenthalpyofpolymerization

CH2=CHCH2=CHCH2=C(CH3)C6H5CH=CH2CH=CH2

69.972.874.5kJ/mol

CH2=CHCH2=CHCH3CNCOORCH2=C

72.478.735C6H5.Conjugativeeffectdecreasest40Substituentswithhighelectronegativitywillincreasetheenthalpy.

CH2=CHCH2=CHCH2=CF2CF2=CF2ClNO2

95.890.8129.2154.8kJ/mol

.Substituentswithhighelectro41Itisbecausethatsubstituentswithhighelectronegativitywillgreatlyenhancethebondenergy.Forexample,thebondenergyofC－Csinglebondinhexafluoroethaneis520kJ/mol,whichis350kJ／molhigherthanthatinethane..Itisbecausethatsubstituent42TheeffectsofhydrogenbondandsolvationCH3CH2=CHCH2=CCOOHCOOH

66.942.3kJ/molCH3CH2=CHCH2=CCONH2CONH2

60.235.1kJ/mol.Theeffectsofhydrogenbonda433.5.3

CeilingTemperatureofPolymerizationwhen,，polymerizationcantakeplace

.3.5.3CeilingTemperatureof44Withtemperaturerising，thevalueofapproachestoandreaches,atthispoint，andpolymerizationanddepolymerizationgettoabalance.Thetemperatureofthisbalanceiscalledpolymerizationceilingtemperature(Te)..Withtemperaturerising，theva45ForexampleInthepresencesodiumnaphthaleneorlithiumalkyl，α-methylstyrenecanpolymerizeinbenzenesolution.Whenthetemperatureiselevatedto+40℃andthenloweredto-70℃repeatedly，Theviscosityofthereactingsystemrisesandfallsrepeatedly，whichmeanspolymerizationanddepolymerizationproceedsinareversiblemanner.

CH3CH3nCH2=C-[-CH2-C-]n-.ForexampleInthepresence46Inmostcasespolymerizationtakeplaceatlowtemperature.Athightemperaturemoremonomersaredepolymerized.Withinawiderangeoftemperature，monomersandpolymersareinabalancestateandthereseemstobeaseriesofceilingtemperatures，soceilingtemperaturesTehasrelationtomonomerconcentration..Inmostcasespolymerizationt47PropagationanddepolymerizationarereversiblereactionsPropagationanddepolymerizationrateequationAtbalancestateDPisverygreat

.Propagationanddepolymerizati48Inthermodynamics

investigationastandardstateshouldbechosen.Forsolidandliquidthestandardstateisdefinedaspuresubstance，at1atmandwhosedegreeofactivityequals1，thermodynamicfunctionsatstandardstateismarkedwitha“0”atitstoprightcorner.Inthermodynamicsinvestigatio49Atnonstandardstate

Atbalance

BalancetemperatureTeisdefinedasthebalancetemperaturewhen[M]e＝1mol/L.

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