Group Transfer Polymerization of Methacryl-Type Poly(2-oxazoline) Macromonomers

Abstract

Group transfer polymerlzation (GTP) of methacrylate-terminated poly(2-alkyl-2-oxazoline) macromonomers (MA-PROZO-n 3; R = Me and n-Bu; n, degree of polymerization) was examined using 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene and nucleophiles as the initiator and catalyst, respectively, at 24 or 50°C. MA-PROZO-n 3 (R=n-Bu; n=3, 14, and 31) was polymerized using tetra-n-butylammonium fluoride as the catalyst in tetrahydrofuran (THF) to provide poly(MA-PROZO-n)s (4; R=n-Bu) with M_n, up to 37600. GTP of 3 (R = Me; n=14 and 30) was carried out by use of KHF₂ as the catalyst in CH₃CN or CD₃CN to produce 4 (R = Me) with maximum M_n, up to 17300. M_w/M_n of the 4 given from 3 of n≥14 was narrow (1.08—1.12). Rate of the GTP of the macromonomers 3 decreased with increase in n and concentrations of macromonomers. Maximum conversion of macromonomers 3 was obtained at relatively lower concentration of 3, generally 89—95%. Polymer 4 (R=n-Bu) was coupled in situ with p-bis(bromomethyl)benzene or propagating species of living poly(2-n-butyl-2-oxazoline)s, to provide chain extended poly(MA-PROZO-n)s (5; R=n-Bu) or block copolymers (6). From characteristics of the reactivity of 3 and 4 and narrow molecular weight distribution of 4, living nature of present polymerization was suggested.