Preparation of P4VP‐g‐PSt Copolymer Microspheres with Controllable Size by Atom Transfer Radical Polymerization Synthesized Poly(4‐vinylpyridine) Macromonomer

Abstract

Poly(4-vinylpyridine) macromonomer (St-P4VP) with a styryl end group was synthesized by atom transfer radical polymerization (ATRP) of 4-vinylpyridine using p-(chloromethyl)styrene (CMSt) as functional initiator, CuCl as catalyst and tris[2-(dimethylamino)ethyl]amine (Me 6 TREN) as ligand in 2-propanol. The structure of St-P4VP macromonomer was identified by proton nuclear magnetic resonance ( 1 H NMR). The result of gel permeation chromatography (GPC) illustrated that the number-average molecular weight of St-P4VP could be controlled by adjusting polymerization conditions. Poly(4-vinylpyridine) grafted polystyrene microspheres (P4VP-g-PSt) were then prepared by dispersion copolymerization of styrene with St-P4VP macromonomers. The effects of polymerization reaction parameters such as medium polarity, concentration of St-P4VP macromonomer and polymerization temperature on the sizes and size distribution of P4VP-g-PSt microspheres were investigated. The results of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and laser light scattering (LLS) indicated that mono-dispersed P4VP-g-PSt microspheres with average diameters of 100-200 nm could be obtained when the molar ratio of St to St-P4VP was 0.25∶100 in ethanol/water mixed solvents (V/V＝80∶20) at 60 ℃. Such kind of graft copolymer microspheres was expected to be applied to many fields such as drug delivery system and protein adsorption/separation system due to their particular structure.