PNNL

Abstract

Hyperbranched and linear poly(alkyl methacrylate)s with and without polycaprolactone grafts were designed and prepared via a core-first strategy, then evaluated with respect to their rheology and shear stability performance. The focus of this work was to study the effect of architecture on mechanical shear stability, as it relates to lubricant performance. The polymers were prepared from functionalized macroinitiators subsequently subjected to ATRP/ARGET-ATRP conditions with dodecyl methacrylate and 2-ethylhexyl methacrylate mixtures. As expected, most compounds displayed an increased viscosity index along with increasing molecular weights. The inclusion of polycaprolactone appears to have enhanced the viscosity index in select samples. Although the hyperbranched polymers studied here varied in the number of arms from about twenty to one (linear), the data presented supports the empirical understanding that shear stability is mainly influenced by molecular weight and not architecture or topology. The polymers with caprolactone blocks demonstrated a positive effect on the shear stability, as in possessing the lowest viscosity loss values which were four times lower than the other compounds included in this study as well as the benchmark.