Odian Book Chapter 7

Ring-opening Polymerization (I)

Ring-opening Polymerization Anionic Cationic Ring Opening Metathesis Polymerization (ROMP)

Commercially Important ROP Tg Tm -82 181 cationic anionic -41 66 PTMO -84 (57)

Commercially Important ROP cationic anionic Tg Tm -60 67 Poly(caprolactone) Poly(caprolactam) 53 230 D4, D3, Di -124 -50

Ring-opening Polymerization kP kdp linear cyclic X = ; ; ; ; Heteroatom provide site for coordination w/ appropriate anionic, cationic or coordinating initiator (kinetic accessibility) Keq= kP / kdp = 1 / [Monomer]e G= - R T ln Keq= R T ln [M]e

Ring Strain of Cycloalkanes CYCLOALKANE (kcal/mole) (kJ/mole) Cyclopropane 27.6 115 Cyclobutane 26.4 110 Cyclopentane 6.5 27 Cyclohexane 0.0 0 Cycloheptane 6.4 27 Cyclooctane 10.0 42 Cyclononane 12.9 54 Cyclodecane 12.0 50 Cyclopentadecane 1.5 6

Ring Strain Ring Size 3,4 5,6,7 8

Free Energy G= H -TS  H  S  G [M]e # atoms in Ring 3,4 ext. of pzn @ Equil 3,4

Ring Opening Pzn Types of Ring Compound Mx detected up to x = Propagating Species Cycloalkenes Cyclic Ethers Caprolactam Cyclic Siloxanes 14 9 5 400 Metal Carbene THF w/ CF3SO3H Anionic Anionic KOH Series of Ring Sizes Concentration Distribution % Cyclics  w/ decreasing [M]

(substituents usually will prevent it) Cyclic Ethers polymerization difficult (substituents usually will prevent it) unreactive tertrahydropyran dioxane

Cyclic Ethers 1) Ethylene Oxide Living Polymerization (DMSO) PEO

Cyclic Ethers Monomer is usually a racemic mixture of enantiomers 2) Propylene Oxide Monomer is usually a racemic mixture of enantiomers

Poly(propylene oxide) Initiation Propagation Soft segments in polyurethane Avg Mn limited to ~5,000 g/mol Limited by CT to monomer acidify Termination 1o & 2o

Chain Transfer to Monomer 200 oC Proton abstraction Leads to imperfect networks with “dangling ends” fast allylic structure f = 1 Allylic end group

Functionality Control Polyhydroxy compounds  CTA (CTA) networks fAVG ~ 2.5 f = 3