Synthesis and structure-property relationships of polypropylene-g- polystyrene and polypropylene-g-poly(n-butyl acrylate) graft copolymers with well-defined molecular structures

摘要

Several polypropylene-g-polystyrene (PP-g-PS) and polypropylene-g-poly(n- butyl acrylate) (PP-g-PnBA) graft copolymers with well-defined molecular structures, basing on the same PP-Br precursor, were synthesized via a combination of metallocene-catalyzed polymerization and ATRP. The structure-property relationships of the resultant graft copolymers were systematically investigated. The crystallization temperatures of the obtained PP-g-PS and PP-g-PnBA graft copolymers decreased first and increased then with the enhancement of branch lengths. Compared to PP-Br, the introduction of PS or PnBA branches onto PP backbones both led to increased η_0, more pronounced shear-thinning behavior, elevated value of G′ at low shear frequencies, and reduced loss angle. Under the same foaming conditions, the resulting PP-g-PS and PP-g-PnBA foams exhibited closed cell structure, increased cell density, and uniformized cell size distribution compared to the PP-Br foam. The cell density of PP-g-PS foam increased first and decreased then with the enhancement of branch length, and the cell size increased as the branch length increased. However, the cell density of the obtained three PP-g-PnBA foams was almost the same regardless of the PnBA branch length, and the cell size decreased first and increased then with increasing the branch length.