Polymethacrylate macromolecular property skewing via depolymerization.

Ariana M. Tamura,¹ Kevin A. Stewart,¹ James B. Young,¹ Alexander J. Cantor, Nathan B. Wei, Brent S. Sumerlin*

University of Florida

Depolymerization, or the process of breaking down polymers to monomer, is a rapidly growing field that holds promise for sustainability practices and closed-loop recycling. Recent literature demonstrated that polymethacrylates can undergo facile depolymerization via photothermal, metal-catalyzed, and bulk thermal methods. While prior research has primarily emphasized methodology, the effect of depolymerizations on macromolecular properties remains enigmatic. In this project, we use depolymerization methods to tune the rheological properties of blended polymethacrylate samples. Polymethacrylates terminated with chain ends from controlled radical polymerization (CRP) syntheses have previously shown efficient thermal depolymerizations in the bulk. By leveraging this thermal lability of CRP end groups, we selectively depolymerized CRP-terminated polymethacrylates in blended samples of thermally stable and thermally active materials. We coined this targeted depolymerization method the Skew Customization by Unzipping Layered Polymer Traces (SCULPT). Samples depolymerized via SCULPT methods resulted in molecular weight distribution (MWD) shifts, narrowed dispersities, and significant alterations in rheological properties. Materials were skewed to higher and lower MWDs and characterized via size exclusion chromatography (SEC), frequency
dependency, and creep-recovery. Skewing MWDs to higher weight averages resulted in greater storage modulus, resistance to creep, and more creep-recovery. Conversely, skewing MWDs to lower weight averages resulted in a lower storage modulus, and no creep resistance or recovery. When post-depolymerized polymethacrylate blends were compared to virgin, monomodal counterparts of similar MWD averages, the rheological properties were similar. This indicates that SCULPT methods do not affect the material properties of polymers with thermally stable chain ends.