Ring - Opening Polymerization 1 Thermodynamic of ring-opening polymerization 1.1 General aspectn -R-Z- -R-Z-,n,comparison with polycondensation/addition polymerization and step/chain polymerization 1) polymerization rate (kinetic) equation similar to that of addition and chain polymerization 2) molecular weight of polymer t curve similar to that ofpolycondensation and step 3) equilibrium of polymerization and depolymerization,types of ring monomers:cyclic alkane -(-CH2-)- n=3, 4, 5cyclic ether -(CH2-)-O- n=2, 3, 4n=2 ethylene oxidepropylene oxiden=3 oxetanen=4 tetrahydrofuranacetals trioxaneamides -(-CH2-)-C-NH n=5 caprolactam,n,n,O,O,CH3,O,O,O,O,O,O,n,O,n,esters -(-CH2-)-C-O n=5 caprolactonO=C-O anhydride (CH2-)-C=Oamines -(-CH2-)-NHsiloxanes -(-Si(CH3)2-O-)- n=3, 4, 5n=4 octamethyl cyclotetrasiloxane (D4),n,n,n,G=H-TS H is affected by:,1) angle strain 2) conformational strain 3) transannular strain 4) steric effect of side group ring-opening polymerization: Tc (THF, 1,3-dioxalane)Tf (S8, Se8)Me 1.2 Homocyclic compounds 1.2.1 Factors affecting H 1.2.1.1 Angle strainmeasure: distortion, strain per CH2, strain energy, H, G,1) distortion of bond angles= (normal valency angle - actual angle between bonds)for 4-member ring, = (109o28 - 90o)=9o44 2) strain energy per CH2= heat of combusion of CH2 in cycloalkane - that of CH2(659 kJ/mol)for 4-member ring, = 686.7 - 659 = 27.7 kJ/mol 3) strain energy of cycloalkane= n strain energy per CH2for 4-member ring, = 4 27.7 = 110.8 kJ/mol 4) enthalpy of polymerization calorimetrically Hfor 4-member ring, -CH2-CH2-CH2-CH2- + Hls,1,2,1,2,for cycloalkane3 60 24o44 697.6 38.6 115.6 115.8 113.1 69 92.5 4 90 9o44 686.7 27.7 109.7 110.8 105.1 55.3 88.8 5 108 0o44 664.5 5.5 26.4 27.5 21.8 42.7 9.2 6 120 -5o16 659.0 0 0.8 0.0 -2.9 10.5 -5.9 7 128o34 -9o33 662.8 3.8 26.8 26.6 21.2 15.9 16.3 8 135 -12o46 664.0 5.0 41.9 40.0 34.8 3.35 34.3 34561112,No. of ring,actual angle,distortion,heat of com-bustion per CH2,strain energy per CH2,strain energy -Hlc -Slc -Glc exp. cal. (25),1.2.1.2 Conformation and transannular strainfrom distortion : r5r6 for polymerization,H,H,H,H,H,H,H,H,H,H,The cyclopentane has a planar ring, and almost no angle strain. But it has a completely eclipsed conformation with ten “oppositions” between adjacent H atoms, and the heat of combustion for cyclopentane is large than that of cyclohexane and cycloheptane.,conformation strain,rn=6, “chair” or “boat” form7 rn 12, “gauche” formrn 15 cycloalkane alkane,transannular strain,no transannular strain,1.2.1.3 Steric effect of side groupscyclo-monomer linear-polymerside groups uncrowded side groups crowdedequilibrium shifts,a,b,or,c,1 - 1,1-dimethyl substituted 2 - methyl substituted 3 - unsubstituted,why?,repulsing force of side groups internal energy Hp Hm H more positivering-opening polymerizability other affecting factors:,for acenaphthalene - H=100.5 kJ/mol5-member ring - H=21.8 kJ/molwhy?planar structure C C 2.34 AC C 1.35 A-C-C- 1.54 A for maleimide - H=87.9 kJ/molHC=CHO=C C=ONH,o,o,o,for cycloalkenestrain energy is less than that of cycloalkane- H5- 6- 7- 8- cycloalkane 25.5 0.4 25.5 40.6 cycloalkene 20.5 4.2 21.0 25.0- H = -92.1 - H = 63.7 more double bondconjugation 1.2.2 S and Gsee table of p.6 for S :,1) S is independent of angle strain, but dependent on configuration of ringS = f(p) = f() possibility of ring-opening and closing mean square end-to-end distance ring member , , - S , ring-opening 2) S ring member: linear,for G: 1) for 3, 4-member rings, H gives main contribution to G 2) for 5, 6, 7-member rings, H gives same contribution as S to G,3) for 6-member ring, G = +, does not polymerization 4) for 3, 4, 5, 7, 8-member rings, G = -, can polymerize in the presence of initiator1.3 Heterocyclic compoundsbond length bond angle C-C 1.54 C-C-C 109o28 C-N 1.47 C-N-C 109o C-O 1.44 C-O-C 111o C-S 1.82 C-S-C 100ofrom bond angle and length: 1) N and O: bond angle and length C,C, N, O angle strain similar 2) S: more different from strain energy, - H kJ/molcycloalkane cycloether cycloimine cyclosulfide 3 116.4 117.2 96.3 77.9 4 109.3 79.15 25.5 28.65 9.21 4.2 -33.5 30.6 -69.0 6 0.4 -79.6 12.1 16.5,