Using a copolymer of styrene (St) with 4-(vinylphenyl)-1-butene (VSt) (PSVS) as the backbone, a series of model comb-like polymers with were synthesized by means of “graft onto” strategy. The branching density of these comb-like copolymers in this work is higher than that of traditional graft copolymer with low branching density, but lower than that of poly(macromolecular monomer). The influences of branching parameters (branching chain length and branching density) and branching chain composition on the rheological properties of comb-like polymers were studied. When the branching chain was polystyrene (PS) chain, which is miscible with the backbone in the PSVS-g-PS, the linear rheological studies showed that PSVS-g-PS presented hierarchical relaxation process, that is, the relaxation of the side chain (intermediate angular frequency region) and the whole comb polymer (the terminal region). At the same time, both the two relaxation processes showed coordination relaxation effect. From scaling law (a) of zero shear viscosity (η<sub>0</sub>) of PSVS-g-PS with molecular weight, a=2.2-2.6, it could be seen that the viscosity behaviour of PSVS-g-PS was different from those of both poly(macromonomers) and entangled linear polymer chains. When the branching chain was polyethylene (PE) chain, which is immiscible with the backbone in the PSVS-g-PE. In this case, the microstructure and linear rheological properties of the melt strongly depended on the branching density and the length of the side chains in PSVS-g-PE. PSVS-g-PE with low branching density showed a microphase-separated structure at the melt state, with the length increasing of side chain, the graft copolymers presented various microphase-separated structures. As a result, the graft copolymers with low grafting density presented a typical rheological characteristic for network-like structure. In contrast, PSVS-g-PE with high branching density showed homogeneous phase structure at the melt state, and presented a normal rheological behavior, which is similar to linear or comb-like homopolymers. We further discussed possible reason about the strong effect of branching parameters and branching chain composition on the rheological properties of comb-like polymers.

Effect of branching chain parameter on rheological behavior of comb-like (co)polymers with high branching degree

253rd National Meeting (2017)

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