Add time:08/17/2019         Source:sciencedirect.com

Poly(alkyl methacrylate)s (alkyl = methyl, ethyl, n-butyl and n-hexyl) synthesized by Atom Transfer Radical Polymerization (ATRP) using 2,2,2 tribromoethanol as initiator present a first mass loss below 200 °C in thermogravimetric experiments. In order to investigate the possible mechanism of this degradation step, the polymers were subjected to thermal treatment at 150 °C under argon atmosphere. The volatiles were analyzed by gas chromatography coupled to mass spectrometry, while the thermally treated polymers were analyzed by thermogravimetry, 1H and 13C nuclear magnetic resonance and size exclusion chromatography. The main mechanism of the first step of degradation is HBr elimination from initiator fragments attached to the chain ends, resulting in vinylidene, lactone and aldehyde terminal groups of the polymer chains. Moreover, volatiles produced by the chain-end elimination were mainly alkyl bromides, alkyl alcohols, alkyl methacrylates and products successive to HBr elimination and polymer chain scission. The amount of monomer release at 150 °C varied with the alkyl group in the range of 3–17 wt %; however, polymer chain configuration, molar mass and dispersity did not significantly change. Polymer chains free of the ATRP initiator were thermally stable at least up to 250 °C.

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