Synthesis and characterization of amphiphilic methoxypoly(ethylene glycol)-polystyrene diblock copolymer by ATRP and NMRP techniques

Abstract

Amphiphilic block copolymers are used in a variety of applications, for example, as stabilizers for emulsions and dispersions or as compatibilizers in polymer blends. Amphiphilic diblock copolymer composed of methoxypoly(ethylene glycol) and polystyrene (MPEG-b-PS) was synthesized using atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMRP). In order to synthesize MPEG-b-PS diblock copolymer using ATRP, monofunctional MPEG macroinitiator (chloroacetylated MPEG [MPEG-Cl]) was prepared from monohydroxyfunctional poly(ethylene glycol) and initiated end group on the basis of chloroacetyl chloride. ATRP was carried out in bulk using MPEG-Cl as the macroinitiator, copper chloride (CuCl)/2,2′-bipyridine (bipy) as the catalyst ([MPEG-Cl]/[CuCl]/[bipy] = 1:1:3), and styrene as the monomer. For preparation of MPEG-b-PS by means of NMRP, firstly, 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-OH) was obtained by reduction of 2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) with sodium ascorbat. Then, TEMPO-OH was coupled with chloroacetylated MPEG (MPEG-Cl) to yield the macroinitiator MPEG terminated with a TEMPO unit (MPEG-CO-TEMPO). At last, MPEG-CO-TEMPO was further used to prepare the diblock copolymer MPEG-b-PS by ‘living’ free radical polymerization of styrene. The products were purified and identified by Fourier transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC).