The cavitation events produced by ultasonic irradiation of a polymer solution result in non-random, near-midchain scission of linear polymers, as a result of transient elongational (fast transient) flows created during bubble implosion and collapse. The polymers eventually reach a limiting molar mass Mlim beyond which degradation is no longer possible. The ultrasonic degradation of block, random, and alternating copolymer solutions, along with the degradation of solutions the respective homopolymers, was studied by size-exclusion chromatography with on-line multi-angle static light scattering, viscometry, and refractometry detection (SEC/MALS/VISC/DRI). This allowed isolation of the effects of monomeric arrangement on copolymer degradation. 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.

SEC/MALS/VISC/DRI study of mechanochemical copolymer degradation

254th National Meeting (2017)

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