SYNTHESIS AND THERMAL-STABILITY OF NOVEL ANION-EXCHANGE RESINS WITH SPACER CHAINS

Spacer-modified anion exchange resins were prepared by suspension copo lymerization of omega-bromoalkylstyrenes or omega-bromoalkyloxymethyls tyrenes with 2-8 mol % of divinylbenzene, followed by quaternization w ith trimethylamine. The thermal stability of the spacer-modified anion exchangers of the OH form was examined by standing the resins in deio nized water at 100-140 degrees C for 30-90 days. The anion exchangers with alkylene chains such as butylene or heptylene groups between the benzene ring and the quaternary nitrogen exhibited higher thermal stab ility compared with commercial, strongly basic anion exchangers with b enzylic ammonium groups. The thermal stability of the exchangers with butyleneoxymethylene or hexyleneoxymethylene spacers was also higher t han that of the commercial exchangers. The exchanger with the propylen eoxymethylene spacer, however, had less stability than did the commerc ial ones. The decreased stability of this spacer-modified exchanger is due to the accelerated degradation of the spacer chain via Hofmann el imination. The excellent stability of the anion exchangers with alkyle ne or alkyleneoxymethylene spacers, except propyleneoxymethylene, resu lts from the structure of the exchangers, where there are no reactive benzylic carbons, which are attached directly to the quaternary nitrog en. (C) 1997 John Wiley & Sons, Inc.