Reversible addition fragmentation chain transfer (RAFT) polymerization was used in the cyclopolymerization of a symmetrical difunctional monomer, tert-butyl α-(hydroxymethyl)acrylate ether dimer. Cumyl dithiobenzoate (CDB) was chosen as the RAFT agent and N,N′-azobis(isobutyronitrile) (AIBN) was employed as the initiator. Polymerizations were carried out in xylene at 70 °C. Under tuned conditions, cyclic soluble polymers with six-membered tetrahydropyran repeat units were obtained. Polydispersities of the polymers were relatively low and molecular weights were close to the theoretical values. Factors affecting the RAFT mediated cyclopolymerization were investigated. The results indicate that initial monomer concentration, [CDB]/[AIBN] ratios, and reaction temperatures change the rate and the control of the RAFT cyclopolymerization. The livingness of the cyclopolymers was shown through successful block copolymerization with n-butyl acrylate where the formers were used as the macro-chain transfer agents.
Atom transfer radical polymerization (ATRP) was used in the cyclopolymerizaton of a symmetrical dimethacrylate, the ether dimer of tert-butyl R-(hydroxymethyl)acrylate (TBHMA). The cyclopolymerization was succesfully carried out with high cyclization efficiency in xylene using CuBr/PMDETA at 70°C. Cyclopolymers with six membered tetrahydropyran repeat units were obtained in high conversions with controlled molecular weights and low polydispersities. It was found that at higher temperatures (100°C), the polymerization became less controlled and polydispersities increased slightly whereas at lower temperatures (50°C) the intermolecular reactions lead to pendent vinyl groups and cross-linking. The livingness of the propagating cyclopolymers was shown through successful block copolymerization with tert-butyl acrylate where the former was used as macroinitiator. The physical properties of the cyclopolymers were investigated and it was found that ring microstructures and polymer polydispersities affected the glass transition temperatures of the polymers obtained.
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