RAFT Iniferter Photopolymerization of PNIPAM based Block Copolymers

Poly(N-isopropyl acrylamide) (PNIPAM) has been studied for various biomedical applications such as drug delivery, wound dressings, and, specifically, sensing via hydrogels due to a characteristic phase transition around 32°C. Previous work focused on the fabrication and characterization of PNIPAM based microfibers. The fibers were subsequently processed into a fibrous hydrogel to be used as biosensor. The fibrous structure was maintained as it functions as an avenue to improve the sensitivity of the biosensor by increasing the surface area. Current work focused on improving the viscoelastic behaviors of the hydrogel through the synthesis of block copolymers (BCPs) containing PNIPAM. These BCPs were synthesized using photo reversible addition-fragmentation chain transfer (RAFT). While RAFT is a commonly used controlled polymerization technique, photoinitiated RAFT can yield polymers with ultra-high molecular weights and can be performed under mild conditions. Therefore, photoinitiated RAFT is promising for synthesizing polymers ideal for ultra-thin fibers and hydrogels due to enhanced viscoelastic and mechanical properties. Alongside PNIPAM, the highly hydrophilic poly(N,N-dimethyl acrylamide) (PDMA) is a promising candidate as a stabilizing block since it improves the mechanical properties of hydrogels. A compact UV setup was implemented using a commercially available nail curing device, while also varying the distance between the reaction/light bulbs, and the light intensity through the number of said bulbs. The methodology was optimized using common lab equipment to enable widespread implementation. The physical setup was kept intentionally simple with the intent to allow small undergraduate institutions and even high schools to perform polymer synthesis, while maintaining a level of scientific refinement via the use of photo-iniferter RAFT. This project offers an avenue to broaden participation for young students and researchers to engage with and contribute to materials research by validating the potential of using commercially available equipment.