Copolymers with soft and hard segments based on 2,2-dimethyltrimethylene carbonate and ɛ-caprolactone

Thermoplastic elastomers with ABA-block structure, A representing the hard segment and B the soft segment, were prepared by ring-opening polymerization from 2,2-dimethyltrimethylene carbonate (DTC, 1) and e-caprolactone (ECL, 2) as monomers. Typical anionic initiators, viz. the dilithium salt of hydroxytelechelic poly(ethylene oxide) 200 (4) and of polytetrahydrofuran 1000 (5) and as an insertion initiator the bis(diethylaluminium) salt of triethylene glycol were used. The soft block is formed by a sequence of random (or tapered) structure comprising equimolar amounts of the two monomers and obtained by simultaneous polymerization of DTC and ECL. The hard blocks consist of highly crystalline poly(2,2-dimethyltrimethylene carbonate) sequences. The thermal properties of the polymers depend on the sequence length, the content of heterodiads in the soft block and the thermal history of the samples. Copolymer films with short end blocks and high content of heterodiads show rubber-elastic properties at normal conditions.