Initiator‐fragment incorporation radical copolymerization of vinyl acetate and 1,2‐polybutadiene as a multivinyl monomer

Abstract

AbstractThe copolymerization of vinyl acetate (VAc) with 1,2‐polybutadiene (1,2‐PB; 85.5% 1,2‐units and 14.5% 1,4‐units) as a multivinyl monomer was carried out at 80 °C in dioxane with dimethyl 2,2′‐azobisisobutyrate (MAIB) at high concentrations (0.10–0.50 mol/L) as an initiator. The copolymerization of 1,2‐PB [0.80 mol/L (monomer unit)] and VAc (1.20 mol/L) with MAIB (0.30 mol/L) for 4 h proceeded homogeneously without gelation to yield a soluble copolymer. The resulting copolymer was divided into methanol‐ and n‐hexane‐insoluble parts, of which the yields based on the total weight of the comonomers and initiator were 46 and 20%, respectively. The methanol‐insoluble part consisted of the fractions of the 1,2‐PB units with (9 mol %) and without (39 mol %) an intact double bond, the 1,4‐PB unit (8 mol %), the VAc unit (32 mol %), and the methoxycarbonylpropyl group (12 mol %) as the MAIB fragment, whereas the hexane‐insoluble one was composed of the fraction of the 1,2‐PB units with (4 mol %) and without (17 mol %) a double bond, the 1,4‐PB unit (4 mol %), the VAc unit (60 mol %), and the methoxycarbonylpropyl group (15 mol %). The use of higher concentrations of 1,2‐PB and VAc and lower concentrations of MAIB resulted in gelation. The cast film from a chloroform solution of the methanol‐insoluble part contained spherical pores organized in a hexagonal way with a monodisperse pore size of 3 μm. The copolymer molecules seemed to be arranged in an ordered way on the surface layer of the pores, as shown by an optical microscopy image under crossed polarizers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2328–2337, 2006