Spontaneous Polymerization of Micelle-Forming Styryl Ammonium Derivatives in Water

Abstract

KEY WORDSSpontaneous Polymerization / Micelle-Forming / Styrene Derivative / Radical Polymerization / We have recently found that some amphiphilic methacrylate monomers such as sodium alkyl 2-hydroxy-3-methacryloyloxypropyl phosphates and alkyl-2-methacryloyloxyethyldimethylammonium bromides spontaneously polymerize in the aqueous micellar solution, and the micelle formation is indispensable for the initiation of reaction. 1 • 2 The initiating radical species has been assumed to be produced by the thermal reaction of two monomer molecules giving the dimer diradical (1,4-diradical) followed by a chain-transfer to result the dimer monoradical, just like the thermal polymerization of methyl methacrylate, 3 which would be promoted by the micelle formation.Although styrene is the most well known thermally polymerizable monomer, spontaneous polymerization of the micelle-forming monomer having styryl group has never been reported. This paper concerns with the spontaneous polymerization of alkyldimethyl-p-vinylbenzylammonium chlorides (Cn-VBAC) as the styrene derivatives capable of forming micelles,4 so that the micellar organization would make possible to facilitate the spontaneous polymerization of these monomers like the methacrylic ester derivatives. 1 • 2 EXPERIMENTAL MonomersReagent grade 2-phenylethyl bromide and alkyl amines as starting materials for preparation of the monomers were purchased from Tokyo Kasei Co. and Kishida Chemicals Co. and were used without further purification. p-Vinylbenzyl chloride, which was prepared by chloromethylation of 2-phenylethyl bromide followed by dehydrobromination and was purified by recrystallization from hexane to remove its ortho isomer, 5 was reacted with corresponding alkyldimethylamine as described by Cochin et al. 4 The resulted crude monomers were thoroughly purified by repeated recrystallizations from ethyl acetate containing a small quantity of water for C 16 -and C 12 -VBAC and by reprecipitation using water/acetone system for C 1 -VBAC. The structure and purity of the monomers were confirmed by 1 H NMR spectra 4 recorded in CDC1 3 using a JEOL JNM-A400 spectrometer. Although the monomers contained a small quantity of water (ca. 2%) as already reported, 4 they were used for the polymeriza-1014 tion experiments without further drying.Critical micelle concentration (cmc) of the monomers in aqueous solution was determined by surface tension measurement using a du Noiiy tensiometer at room temperature. PolymerizationThe polymerization was carried out in a sealed glass tube in the dark after removing dissolved oxygen by repeated freeze-thaw cycles using a purified nitrogen. Water as polymerization solvent was distilled after ionexchanged. In the case of C 16 -and C 12 -VBAC, after heating in a thermostated water bath for a given time, the polymerizing solution was freeze-dried. The resulted monomer-polymer mixture was washed to separate each other by acetone which is a solvent for the monomer and a non-solvent for the polymer. The absence of vinyl double bond in the re...