MODIFICATION OF POLY(STYRENE-STAT-ACRYLONITRILE) TO PROMOTE POLYMER BLEND MISCIBILITY THROUGH HYDROGEN-BONDED (2,4-DIAMINO-1,3,5-TRIAZINE)-MALEIMIDE INTERACTIONS

The acrylonitrile units in poly(styrene-<(stat)under bar>-acrylonitril e) (SAN) have been partially converted to the 2,4-diamino-1,3,5-triazi ne (DAT) moiety by the reaction with dicyandiamide in dry dimethyl sul foxide, containing catalytic amounts of potassium hydroxide. This prod uced a range of terpolymers of poly(styrene-<(stat)under bar>-acryloni trile-<(stat)under bar>-vinyl 2,4-diamino-1,3,5-triazine) with mol% co mposition in the range (54.3:43.0:2.7) to (54.3:25.0:20.7). Copolymers of methyl acrylate (MA) and maleimide (MI) were also synthesised and used to prepare blends with the modified SAN terpolymers. Here the tri azine rings and the maleimide units can form complementary pairs of do nor-acceptor-donor (DAD) and (ADA), triple hydrogen bonding sites. It was found that miscible, one-phase, polymer blends could be formed if the DAT content of the modified SAN terpolymers was greater than or eq ual to 10 mol% and the MI content of the (MA-MI) copolymers was > 22 m ol%, or alternatively if the MI content was 9-14 mol% and the correspo nding DAT content in the modified SAN was greater than or equal to 21 mol%. Once formed these secondary interactions were stable up to the o nset of degradation of the blends and there was no evidence of a lower critical temperature for phase separation. (C) 1998 Elsevier Science Ltd. All rights reserved.