Tuning Cleaving Kinetics of Photo-Responsive Polymers Via Solvent-Polymer Interactions

Tuning cleaving kinetics of photo-responsive polymers via solvent-polymer interactions
Authors: Martin Siron, Michele E. Lee, Eda Gungor, Andrea M. Armani
2016 American Institute of Chemical Engineers Conference, San Francisco, CA
Student Poster Competition

Smart materials show a pre-determined response to specific stimuli. These triggers include pH, chemicals, temperature, and electric fields. Due to the selectivity of the response, these materials are of interest in many applications such as drug delivery and environmental sensing. A key component in engineering a material for an application is the ability to tune the material response. In my project, I explored strategies to tune the photo-induced response of the ortho-nitrobenzyl (ONB) group by changing the polymer-solvent interaction. ONB cleaves upon exposure to UV radiation. Using atom transfer radical polymerization (ATRP), I synthesized poly(styrene) (PS), poly(methyl acrylate) (PMA) and poly(ethylene glycol monomethyl acrylate) (MPEGMA) with a photo-cleavable ONB moiety at the center of the polymer (Figure 1). These polymers could be used in topical drug delivery system or UV exposure sensors, but for this use it is imperative that the cleaving rate be well controlled and well defined. I tested solvents with different Flory-Huggins solvent-polymer interaction parameters to test the effect of the solvent-polymer interaction on the cleavage kinetics. Finally, I fit the results to a multi-exponential dose-response curve, and found that the solvent-polymer interaction affects the cleaving kinetics of the polymers. This provides an approach for controlling the cleaving rate of the ONB-functionalized polymer.

Figure 1. Smart polymer with photo-cleavable moiety