Morphological and Property Analyses of Multicomponent Block Copolymer Nanocomposites Gels

Abstract

Thermoplastic elastomer gels (TPEGs), molecular networks composed of a microphase-separated multiblock copolymer swollen to a large extent by a low-volatility midblock-selective solvent, are ubiquitous in a wide range of contemporary technologies, including home and office products, athletic equipment and telecommunications devices. In this work, we investigate the effect of several network-forming nanoscale modifiers — two different silica nanoparticles, 3 different nanoclays, a multiwalled carbon nanotube and a semicrystalline homopolymer — on the property development of a TPEG prepared from a microphase-ordered poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) triblock copolymer imbibed with an EB-compatible aliphatic mineral oil. Dynamic rheological measurements of the resultant nanocomposite TPEGs (NCTPEGs) confirm that addition of these modifiers tends to increase the linear viscoelastic threshold, the dynamic elastic modulus (G') and the flow onset temperature (where G' plummets) of the parent TPEG. Variable-temperature stress-relaxation studies indicate that these NCTPEGs undergo substantial relaxation irrespective of added modifier at temperatures above ~60°C. Complementary x-ray diffraction analysis reveals that the nanoclay particles used to generate three series of the NCTPEGs examined here are swollen with copolymer and/or solvent and are therefore intercalated.