Strengthening polymer interfaces

Abstract

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 problem a number of strategies for strengthening can be pursued, all of which involve adding a third polymeric component to the system, which either segregates to or reacts at the interface. We have examined the effect of small additions of diblock copolymers, random copolymers and reactive end-functional chains in to interfaces between polystyrene and other glassy polymers on the interfacial fracture toughness. By labelling portions of the polymer additive with deuterium, we can use forward-recoil spectrometry on the fracture surfaces to determine (1) the areal chain density, Σ, of the additive at the interface and (2) the mechanism of interface failure. We outline how the important failure mechanisms, chain pull-out, crazing and chain scission, depend on Σ and the architecture of the polymer additive and discuss strategies for maximizing the interfacial fracture toughness.