Synthesis of head-to-tail and head-to-head poly(propylene-alt-methyl methaerylate)s via anionic polymerization of methyl 2,4-alkadienoates. 2. Synthesis and thermal properties

Two methyl 2,4-alkadienoates, i.e., methyl 2,4-dimethyl-2,4-pentadienoate ( MDMPd) and methyl 2-methyl-2,4-hexadienoate (MMHd), were polymerized using t-BuLi or t-BuMgCl as the initiator in toluene. H-1 and C-13 NMR and IR ana lyses demonstrated that complete trans 1,4-addition was achieved in the pol ymerizations. Addition of methylaluminum bis(2,6-di-tert-butyl-4-methylphen oxide) produced polymers with relatively narrow molecular weight distributi ons (M-w/M-n = 1.1-1.2) at 0 degreesC. Hydrogenation of poly(MDMPd) and pol y(MMHd) with p-toluenesulfonylhydrazide produced head-to-tail (H-T) and hea d-to-head (H-H) poly(propylene-alt-methyl methacrylate)s, respectively. The thermal properties of H-H poly(propylene-alt-methyl methacrylate) and H-T poly(propylene-alt-methyl methacrylate) were different. Differential scanni ng calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) measurements i ndicated that both the H-T and H-H copolymers were amorphous. The glass tra nsition temperature of the H-H copolymer is approximately 30 degreesC highe r than that of the H-T copolymer. According to thermogravimetric (TG) analy sis, the H-H copolymer is more thermally stable than the H-T copolymer.