Synthesis and characterization of hyperbranched polystyrene copolymers by atom transfer radical self-condensing vinyl copolymerization

A series of hyperbranched polystyrene copolymers were synthesized by atom transfer radical self-condensing vinyl copolymerization (ATR-SCVCP) of p-chloromethylstyrene (CMS) and styrene using the complex CuCl/2,2'-bipyridyl as catalyst. The composition and structures of these hyperbranched polystyrene copolymers were characterized by (1)H-NMR and (13)C-NMR spectroscopy, gel permeation chromatography (GPC), and elemental analysis. The thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The influence of the reaction conditions, including comonomer ratios, reaction time, and polymerization temperature, on the molecular weight and degree of branching (DB) of the resulting copolymers were investigated in detail. With increasing ratios of styrene in total monomers from 10 to 90%, the resulting copolymers have number-average molecular weights that change from 6.0 to 10.5 kDa, polydispersities from 2.96 to 4.74, and a degree of branching from 0.01 to 0.45. The experimental results indicated that the structures and properties can be controlled by adjusting the reaction conditions. The concentrations of styrene in the copolymers slightly affect the copolymer structures and T(g) when they are less than 50 mol%, but have a large effect at greater concentrations. The results also show that the ATR-SCVP reaction does not follow a complete ATRP feature, but has some characteristics of step-growth polymerization. Copyright (c) 2009 John Wiley & Sons, Ltd.