,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,3,.5 Thermodynamics of Polymerization,3.5.1 General Concept of Thermodynamics,3.5.2 Enthalpies of Polymerization,3.5.3 Ceiling Temperature of Polymer-,ization,.,3.5 Thermodynamics of Polymeri,1,3,.5,Thermodynamics of Polymerization,Whether monomers can polymerize,both,thermodynamic and kinetic feasibilities,should be taken into consideration.,From the thermodynamic viewpoint to,analysis the tendency of polymerization or,depolymerization,.,3.5 Thermodynamics of Polymer,2,When polymerization is favorable from the thermodynamic viewpoint,then kinetic factors are taken into consideration.,The enthalpies of polymerization and the ceiling temperature,are discussed in thermodynamics.,.,When polymerization is favorab,3,3.5.1 General Concept of Thermodynamics,Free energy can be used to judge whether polymerization is favored.,To polymerization,monomers are the initial state(m),and polymers are the final state(p).,When ，,monomers polymers,when ，monomers polymers,When ，monomers polymers,.,3.5.1 General Concept of,4,The relationship between free energy and enthalpy,and entropy is,.,The relationship between free,5,S-,The negative S,for polymerization arises from the decreased randomness for the polymer relative to the monomer.,The S values fall in the narrow range of,-105-125J/molK,and polymerization temperature from room temperature to 100，,So is about+3042kJmol。,.,S-The negative S for poly,6,Enthalpy values for polymers are low,while those for monomers are high.When the absolute value of H is greater than ，polymerization can take place.,The greater,H value is,the more possible the polymerization take place.,.,Enthalpy values for polyme,7,3.5.2,Enthalpies of Polymerization,Measuring method:direct calorimetric,heats of combustion,thermodynamic equilibrium measurements.,Standard heat of formation also can be used to evaluate,.,3.5.2 Enthalpies of Polymeriza,8,The differences of the substituents on monomers will affect the bond energy,and the enthalpies are different.,The heat of polymerization is the difference between the bond energy of two single bond and that of one double bond.,.,The differences of the substit,9,Effect of Structure Factors,-,H=35-163 kJ/mol,The steric effect of the substituents will decrease the enthalpy.,Conjugative effect decreases it,too.,Substituents with high electronegativity will increase it.,The effects of hydrogen bond and solvation is comparatively small.,.,Effect of Structure Factors,10,The steric effect of the substituents will decrease the enthalpy.,CH,2,=CH,2,CH,2,=C(CH,3,),2,CH,2,=O,95.0 51.5 54.4 kJ/mol,CH,3,CH,3,CH,3,CH,2,=C CH,2,=C CH=O,COOCH,3,C,6,H,5,56.5 35 0.0 kJ/mol,.,The steric effect of the s,11,Conjugative effect decreases the enthalpy of polymerization,CH,2,=CH CH,2,=CH CH,2,=C(CH,3,),C,6,H,5,CH=CH,2,CH=CH,2,69.9 72.8 74.5 kJ/mol,CH,2,=CH CH,2,=CH CH,3,CN COOR CH,2,=C,72.4 78.7 35,C,6,H,5,.,Conjugative effect decreases t,12,Substituents with high electronegativity will increase the enthalpy.,CH,2,=CH CH,2,=CH CH,2,=CF,2,CF,2,=CF,2,Cl NO,2,95.8 90.8 129.2 154.8kJ/mol,.,Substituents with high electro,13,It is because that substituents with high electronegativity will greatly enhance the bond energy.For example,the bond energy of C C single bond in hexafluoroethane is 520kJ/mol,which is 350kJmol higher than that in ethane.,.,It is because that substituent,14,The effects of hydrogen bond and solvation,CH,3,CH,2,=CH CH,2,=C,COOH COOH,66.9 42.3 kJ/mol,CH,3,CH,2,=CH CH,2,=C,CONH,2,CONH,2,60.2 35.1 kJ/mol,.,The effects of hydrogen bond a,15,3.5.3,Ceiling Temperature of Polymerization,when ,，polymerization can take place,.,3.5.3 Ceiling Temperature of,16,With temperature rising，the value of,approaches to and reaches ,at this point，and polymerization,and depolymerization get to a balance.,The temperature of this balance is called,polymerization,ceiling temperature,(T,e,),.,.,With temperature rising，the va,17,For example,In the presence,sodium naphthalene or lithium alkyl，-methyl styrene can polymerize in benzene solution.When the temperature is elevated to+40 and then lowered to-70 repeatedly，The viscosity of the reacting system rises and falls repeatedly，which means polymerization and depolymerization proceeds in a reversible manner.,CH,3,CH,3,n CH,2,=C -CH,2,-C-,n,-,.,For exampleIn the presence,18,In most cases polymerization take place at low temperature.At high temperature more monomers are depolymerized.Within a wide range of temperature，monomers and polymers are in a balance state and there seems to be a series of ceiling temperatures，,so ceiling temperatures T,e,has relation to monomer concentration.,.,In most cases polymerization t,19,Propagation and depolymerization are reversible reactions,Propagation and depolymerization,rate equation,At balance state,DP is very great,.,Propagation and depolymerizati,20,In,thermodynamics,investigation a stan,d,ard state should be chosen.For solid and liquid the stan,d,ard state is defined as pur