Morphology and linear rheology of comb-like copolymer melts with high grafting density: Ⅰ. PVSt-g-(PS-b-PE) comb-like block copolymers

Abstract

Comb-like block copolymers PVSt-g-(PS-b-PE) (PVSt: poly(4-(vinylpheneyl)-1-butene)) with high grafting density were successfully synthesized based on “Graft onto” strategy. The grafting density of PVSt-g-(PS-b-PE) was 35–39% (branch chain number per 100 repeating units of the backbone). By introducing PS block in the side chains, the total PS volume fraction in the copolymers could be adjusted to explore the influence of the volume fraction of total PS component (PVSt backbone + PS block) on morphology (at melt state) and linear rheological response of the copolymers. Compared to PSVS-g-PE copolymers with similar grafting density in the previous work (Macromolecules, 2015, 48, 7640), PVSt-g-(PS-b-PE) copolymers showed a microphase-separated structure at the melt state. The volume fraction of total PS in the comb-like block copolymers determined the type of morphology. When the volume fraction of PS changed from 11% to 55%, the microphase-separated structure changed from poor-order spherical structure to poor-order lamellar morphology, and all the samples of PVSt-g-(PS-b-PE) showed a typical rheological behavior of network-like structure. At the same time, the G′ curve and G″ curve were more away from each other at intermediate frequency with the increasing of PS content. The reason resulted from the formation of different microphase-separated structure types in the PVSt-g-(PS-b-PE).