STRENGTHENING POLYMER INTERFACES

Interfaces between immiscible glassy homopolymers are normally weak as there are few chains which can penetrate far enough into the opposite side of the interface to become entangled there. To overcome this pro blem a number of strategies for strengthening can be pursued, all of w hich involve adding a third polymeric component to the system, which e ither segregates to or reacts at the interface. We have examined the e ffect of small additions of diblock copolymers, random copolymers and reactive end-functional chains to interfaces between polystyrene and o ther glassy polymers on the interfacial fracture toughness. By labelli ng portions of the polymer additive with deuterium, we can use forward -recoil spectrometry on the fracture surfaces to determine (1) the are al chain density, Sigma, of the additive at the interface and (2) the mechanism of interface failure. We outline how the important failure m echanisms, chain pull-out, crazing and chain scission, depend on Sigma and the architecture of the polymer additive and discuss strategies f or maximizing the interfacial fracture toughness.