ROLE OF FUNCTIONAL-GROUPS IN STRENGTHENING POLYMER-POLYMER INTERFACES- RANDOM COPOLYMERS WITH HYDROGEN-BONDING FUNCTIONALITIES

Two series of random copolymers, poly(styrene-d(8)-co-4-vinylbenzamide ) and poly(styrene-d(8)-co-4-vinyl-N-ethylbenzamide), were prepared wi th varying compositions. The functionalized random copolymers were tes ted for their abilities to reinforce the weak interface between immisc ible polymers: polystyrene and poly(2-vinylpyridine). The effect of th e hydrogen-bonding groups with different interaction strengths (primar y or secondary benzamide) was studied through the evaluation of interf acial fracture toughness and fracture surface characteristics, For the compositions investigated, the copolymers with the primary benzamide functionality were shown to attain higher fracture toughness values th an the substituted benzamide copolymers. Additionally, the composition at which maximum interfacial strengthening was attained was much lowe r in the primary benzamide case (f(max) = 0.06) than in the substitute d benzamide case (f(max) = 0.25). However, in both cases the observed strengthening was lower than our previous results using copolymers bea ring phenolic groups. The effect of the copolymer functionality, inclu ding such variables as steric constraints and degree of self-associati on, and composition drift on the measured interfacial properties are d iscussed.