Ultrasonic degradation is a convenient means of studying the degradation of macromolecules subjected to transient elongational stresses. Cavitation results in non-random, near-midchain scission of linear polymers, which ultimately reach a limiting molar mass Mlim beyond which degradation is no longer possible. The ultrasonic degradation of block, random, and alternating copolymer solutions of styrene-methyl methacrylate was studied, along with the degradation of their respective homopolymers, to isolate the effects of monomeric arrangement on copolymer degradation. Results from the degradation experiments were monitored by means of multi-detector size-exclusion chromatography. Decreases in both molar mass and size were observed for all polymers studied, except for those with molar mass near or below their Mlim. Differences in limiting molar mass were observed between the alternating and the other types of copolymers, indicating that monomeric arrangement influences ultrasonic degradation. Persistence length was identified as a key comparative parameter for a priori prediction of relative Mlim.

Mechanochemical degradation of styrene-methyl methacrylate copolymers

244th National Meeting (2012)

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