Thermo-Rheological Behavior of Polyethylene Particle Suspensions in Organic Solutions with Side-Chain Crystalline Block Copolymers

It was found that polyethylene (PE) surfaces, traditionally considered chemically inert, can be modified using block copolymers with solvophobic long alkyl side chains and solvophilic side groups, where the alkyl moieties adsorb to form pseudocrystals on the PE surface. Such side-chain crystalline block copolymers (SCCBCs) serve as agents in thermo-rheological (TR) suspensions of PE particles, though the effect of SCCBCs on the interparticle forces has not yet been investigated directly. Here, the TR behavior of the suspensions was studied by using colloid-probe atomic force microscopy (cpAFM), rheometry, and computational fluid dynamics (CFD) simulations. The addition of SCCBCs decreased the adhesive force between PE surfaces at a low temperature, reducing the viscosity of the PE suspension. At a high temperature, however, the adhesive force and viscosity increased to levels similar to those of the suspension without SCCBCs. CFD simulations supported the observed behavior, and a molecular mechanism was proposed using Hansen solubility parameters.