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40 Synthesis and linear rheological property of comb-like styrene-based polymers with a high degree of long-chain branching
40 Synthesis and linear rheological property of comb-like styrene-based polymers with a high degree of long-chain branching
A series of model comb-like polymers (PSVS-g-PS) with high branching degree were synthesized by nucleophilic substitution reaction between iodinated copolymer of styrene (St) with 4-(vinylphenyl)-1-butene (VSt) (PSVSI, backbone) and living polystyrene lithium (PSLi, side chain). This method is a facile way for modular synthesis of graft copolymers based on living anionic polymerization and hydrozirconation reaction. The branching density of PSVS-g-PS (the number of branch chain per 100 repeat backbone units) ranged from 2.4 to 20.7%. The backbone length of PSVS-g-PS was larger than the entanglement molecular weight (Me) of PS, while the molecular weight of branch chain was designed to be below or above the Me of PS. The results from the linear rheological properties of the PSVS-g-PS showed hierarchical relaxation process. One appeared in the intermediate angular frequency region, corresponding to the relaxation of the side chain. The other is in the terminal region, which is related to the movement of the whole comb polymer. From scaling law of zero shear viscosity (η0) of PSVS-g-PS with versus molecular weight, it could be seen that the dynamical behavior of PSVS-g-PS was different from those of both poly(macromonomers) and entangled linear polymer chains, indicating that there is certain entanglement for PSVS-g-PS with long branch chain.
