One-Shot Block Copolymerization of a Functional Seven-Membered Cyclic Carbonate Derived from L-Tartaric Acid with E-Caprolactone

摘要

Block copolymerization of a seven-membered cyclic carbonate (5S,6S)-dimethy1-5,6-isopropylidene-1,3-dioxepin-2-one (ITC) with e-caprolactone in one-shot feeding" is reported. The cyclic carbonate monomer ITC was synthesized from naturally occurring L-tartaric acid in three steps. Three catalysts—stannous octanoate, Sn(Oct)_2, triisopropoxide aluminum, Al(O~1Pr)_3, and diethylzinc monohydrate, ZnEt_2—H20—were tested for the homopolymerization of ITC monomer at 120 °C for 12 h in bulk. The results show that Sn(Oct)2 was the most effective catalyst to carry out the polymerization (M_n = 24 000 g/mol; PDI = 1.6; [α]_D~(20) = +77.8). The copolymerization of ITC with e-caprolactone (CL) in various feed ratios was also investigated. The detailed spectral and thermal analysis of the copolymers catalyzed by Sn(Oct)2 revealed formation of the block copolymer (poly[44%ITC-block-56%CL], M_n = 24 000 g/mol; PDI = 1.6; [α]_D~(20) = +33.8). Two glass transition temperatures (T0) were observed for poly(44%ITC)-block-poly(56% ε-CL) at —59.1 and —37.2 °C for the poly(CL) and the poly(ITC) block, respectively, confirming the diblock nature of the copolymer. It is the first report of one-shot± block copolymerization of ε-caprolactone with a cyclic carbonate monomer. The deprotection of the ketal groups resulted in copolymers containing free hydroxy groups in the polymer backbone.