4316
Macromolecules 2000, 33, 4316-4320
Articles Activated Monomer Cationic Polymerization of Lactones and the Application to Well-Defined Block Copolymer Synthesis with Seven-Membered Cyclic Carbonate Yuji Shibasaki, Hidetsugu Sanada, Makiko Yokoi, Fumio Sanda, and Takeshi Endo*,† Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan Received December 22, 1999; Revised Manuscript Received March 29, 2000 ABSTRACT: Activated monomer cationic ring-opening polymerization of -caprolactone (-CL) and δ-valerolactone (δ-VL) and the synthesis of di- and triblock copolymers of a seven-membered cyclic carbonate (7CC) and these lactones initiated with n-butyl alcohol/HCl‚Et2O and H2O/HCl‚Et2O were carried out to obtain the corresponding homopolymers and block copolymers with narrow polydispersity ratios in one pot quantitatively. The molecular weights of the obtained polymers could be controlled with the feed ratio of the monomer and initiator.
Introduction
Experimental Section
Ring-opening polymerization of lactones and cyclic carbonates attracts much attention because the resulting polymers are applicable to drug delivery and biodegradable materials.1 Recent development of living ring-opening polymerization has enabled us to obtain the corresponding polymers with controlled molecular weights (Mn’s) and polydispersity ratios (Mw/Mn’s). One of the most powerful methods to control cationic ringopening polymerization is “activated monomer cationic polymerization” reported by Penczek et al.,2 which can suppress unfavorable reactions such as backbiting and deproportionation. This method has been applied to the polymerization of epichlorohydrin and propylene oxide to give the linear polymers free from cyclic oligomers.3 Okamoto has reported that the combination of an alcohol and triethyloxonium hexafluorophosphate is effective for ring-opening polymerization of β-propiolactone, δ-valerolactone (δ-VL), and -caprolactone (-CL) to give the corresponding polymers with controlled Mn’s (
