A general strategy for adhesion enhancement in polymeric composites by formation of nanostructured particle surfaces

In this work we present a general methodology to enhance the interfacial adhesion in polymeric composites by creating nanoscale morphologies on the surfaces of particles. The surface morphology, which appears as inorganic whiskers, is achieved by treating silicate particles (zeolites 4A) with thionyl chloride, followed by subsequent reaction with methylmagnesium bromide (Grignard reagent). Poly(vinyl acetate) and Ultem composites containing this type of modified particles exhibit defect-free interfaces. Dynamic mechanical analysis testing reveals that such composites have higher moduli as compared to those embedded with nontreated fillers with the same loadings. Furthermore, gas permeation measurements demonstrate that these materials also show impressive enhancements in gas separation efficiency. The dramatic increase in the topological roughness (physical heterogeneity) on the sieve surfaces is proposed to provide improved interaction at the interface via thermodynamically induced adsorption and physical interlocking of polymer chains in the nanoscopic inorganic whisker structure. The presented strategy need not be tailored to a specific polymer/ filler pair and therefore has potential to be extended to many other polymeric composites for a variety of applications, where tailoring polymer/solid interface compatibility is important.