Mechanochemical Degradation of Brush Polymers: Kinetics of Ultrasound-Induced Backbone and Arm Scission

The ultrasonic degradation of polynorbornene-g-polylactide and polynorbornene-g-polystyrene brush polymers was explored. First-order rate constants for backbone scission were obtained for brush polymers with varying arm lengths (ranging ca. 3-8 kDa) and backbone degrees of polymerization (ranging ca. 78-361). Master curves, in which the rate constant trends for all polymers converge, could be generated by accounting for the rate enhancement from the polymer being in an extended conformation and the contour length being equivalent to the combined length of two arms and the backbone. Slow scission of arms from the backbone was also observed, with first-order rate constants being dependent on the arm length.