Effects of Photodegradable o‐Nitrobenzyl Nanogels on the Photopolymerization Process. Issue 9 (21st June 2018)

• Record Type: Journal Article
• Authors: Liu, Tao; Shah, Parag K.; Liu, Zhenzhen; Gao, Guangzhe; Bowman, Christopher N.; Stansbury, Jeffrey W.
• Is Part Of: Macromolecular materials and engineering. Volume 303:Issue 9(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-06-21
• Subjects: networks -- o‐nitrobenzyl nanogels -- photodegradation -- photopolymerization -- polymerization shrinkage; Plastics -- Periodicals; Polymers -- Periodicals; Polymerization -- Periodicals; 547.705
• DOI: 10.1002/mame.201800206
• Languages: English
• ISSNs: 1438-7492

Abstract

Abstract: A series of partially photodegradable o ‐nitrobenzyl nanogels (NBNG) with different caged functional groups (COOH, OH, SH) are prepared and compared with a nondegradable nanogel as additives in photocurable materials. Photoinduced nanogel network disruption and photoinitiated polymerization of infiltrating and dispersing monomer could be controlled independently. In triethylene glycol dimethacrylate (TEGDMA), o ‐NBNGs that release a COOH or OH functional group upon photodegradation of the o ‐nitrobenzyl crosslinker, the reduced chemical crosslinking density of the nanogel network allows greater penetration of monomer into the partially degraded nanogel network, which results in an increase in volumetric shrinkage and polymerization stress. In contrast, the formulation of o ‐NBNGs with caged SH groups also can be photodegraded but is able to rebuild the chemical crosslinking through thiol‐based chain transfer reactions when photocured as a dispersion in TEGDMA. As such, it behaves like a photo‐inert nanogel. Dynamic thermomechanical analysis and testing by three‐point bending further confirms the photoinduced crosslink density variation influences mechanical properties of the final polymer networks. This work demonstrates the inherent properties of the nanogel network and the type of crosslinking can alter the performance of the photocured resin while a separate photochemical process can be used to regulate photoinduced polymerization. Abstract : Three photodegradable o ‐nitrobenzyl nanogels with different caged functional groups (COOH, OH, SH) are prepared and used as additives in photocurable materials. This work demonstrates that the inherent properties of photodynamic nanogels can influence the performance of photocured resins, and an additional separated photochemistry process can be used to regulate the photoinduced polymerization.