GPC Data Interpretation in Mechanochemical Polymer Degradation

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Abstract
Molecular weight distribution obtained by gel permeation chromatography (GPC) conceals a wealth of mechanistic information which can be disclosed only after adequate data treatment. This paper discusses how GPC chromatograms may be used for the elucidation of polymer degradation kinetics. The case of ultrasonic degradation of dilute polystyrene solutions was investigated in detail. The extent of bond scission was determined as a function of sonication time and initial polymer molecular weight. Different bond scission mechanisms were evaluated by comparing calculated molecular weight distributions with experimental data. Best agreement was obtained when multiple fragmentation was included in the degradation scheme, a result experimentally supported by spectroscopic chain ends titration. The results are rationalized by establishing a parallelism between transient elongational flow and ultrasonic degradation.