Degradation of poly(butyl methacrylate) model compounds studied via high-resolution electrospray ionization mass spectrometry

Abstract

This study investigates the degradation behavior of poly(n-butyl methacrylate) (p(HFBMA)), poly(tert-butyl methacrylate) (p(tBMA)), and poly(hexafluoro butyl methacrylate) (p)HFBMA)) on a molecular level under extreme environmental conditions. The polymers chosen are readily applicable in the formulation of surface coatings and were degraded under conditions which replicated the harsh Australian climate, in which surface coatings may reach temperatures of up to 95 degrees C and are exposed to broad-spectrum UV radiation of up to 1 kW m(-2). The degradation profiles were mapped with high-resolution electrospray ionization mass spectrometry (ESI-MS) with a LCQ quadrupole ion trap mass analyzer, with the peak assignments confirmed to within 3 ppm using ESI-MS with a LTQ-Orbitrap mass detector. It was found that in all the butyl ester polymers analyzed herein regardless of their tertiary side-chain structure the loss of the butyl ester group and subsequent formation of acid side groups are a component of the overall degradation pathway of poly(butyl methacrylate)s under these harsh conditions. However, it is also demonstrated that the magnitude of this pathway is intimately linked to the side-chain structure with the propensity for degradation decreasing in the order p(tBMA) > p(nBMA) > p(HFBMA). The degradation mechanisms identified in this study, in combination with the previous end-group degradation studies of poly (methyl methacrylate) and poly(n-butyl acrylate), have allowed a much deeper understanding of the molecular degradation behavior of poly(acrylate)s and poly(methacrylate)s in an extreme natural environment. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 848-861, 2011