Abstract:The synthesis of different photo-reactive poly(alkenyl norbornenes) and poly(oxonorbornenes) containing benzophenone (BP) via ring-opening metatheses polymerization (ROMP) is described. These polymers are UV irradiated to form well-defined surface-attached polymer networks and hydrogels. The relative propensity of the polymers to cross-link is evaluated by studying their gel content and its dependency on BP content, irradiation wavelength (254 or 365 nm) and energy dose applied (up to 11 J·cm −2 ). Analysis of the UV spectra of the polymer networks demonstrates that the poly(oxonorbornenes) show the expected BP-induced crosslinking behavior at 365 nm, although high irradiation energy doses and BP content are needed. However, these polymers undergo chain scission at 254 nm. The poly(alkenyl norbornenes), on the other hand, do not cross-link at 365 nm, whereas moderate to good cross-linking is observed at 254 nm. UV spectra demonstrate that the cross-linking at 254 nm is due to BP cross-linking combined with a [2 + 2] cylcoaddition of the alkenyl double bonds. This indicates limitations of benzophenone as a universally applicable cross-linking for polymer networks and hydrogels.

Surface‐attached, degradable polymer hydrogels with potential antimicrobial activity are reported. They are obtained by ring‐opening metathesis copolymerization (ROMP) of a monomer with potential bioactivity and a monomer that carries a benzophenone cross‐linker and a hydrolyzable group. The hydrolyzable group is either an ester or an anhydride group. The copolymers thus obtained are spin‐coated onto silicon wafers and UV‐irradiated to induce C,H cross‐linking of the benzophenone groups and obtain the target polymer networks. Immersion of these networks into aqueous media triggers network degradation. The degradation speed depends on the nature of the intended break points (ester or anhydride groups), the number of cross‐links per polymer chain, and the surrounding medium. By releasing bioactive polymer fragments to the medium (“leaching”) and by regenerating the hydrogel surface during the degradation process, the hydrogels potentially have two ways to prevent biofilm formation on their surface.