The photo-reversible [4πs+4πs] cycloaddition reaction of pendant anthracene moieties represents a convenient strategy to impart wavelength dependent properties into hydrogenated carboxylated nitrile butadiene rubber (HXNBR) networks. The present article provides the 1H NMR data on the reaction kinetics of the side chain functionalization of HXNBR. 2-(Anthracene-9-yl)oxirane with reactive epoxy groups is covalently attached to the polymer side chain of HXNBR via ring opening reaction between the epoxy and the carboxylic groups. Along with the identification, 1H NMR data on the quantification of the attached functional groups are shown in dependence on reaction time and concentration of 2-(anthracene-9-yl)oxirane. Changes in the modification yield are reflected in the mechanical properties and DMA data of photo-responsive elastomers are illustrated in dependence on the number of attached anthracene groups. DMA curves over repeated cycles of UV induced crosslinking (λ>300 nm) and UV induced cleavage (λ=254 nm) are further depicted, demonstrating the photo-reversibility of the thermo-mechanical properties. Interpretation and discussion of the data are provided in "Design and application of photo-reversible elastomer networks by using the [4πs+4πs] cycloaddition reaction of pendant anthracene groups" (Manhart et al., 2016) [1].
Abstract Herein, we demonstrated the synthesis of multifunctional alkyne building blocks from commercially available acrylate monomers exploiting the carbon and oxa Michael addition reaction. These compounds were obtained in decent yields and show similar or even higher photoreactivity than the initial acrylates. Importantly, selected thiol‐yne formulations can be processed by stereolithography and significantly outperform the corresponding acrylate in terms of modulus and toughness. The high compatibility of such cured materials with osteosarcoma cells makes these photopolymers interesting for hard tissue engineering.
This study deals with the investigation of photocurable thiol‐yne resins covering several important aspects for the production of medical devices by UV‐based manufacturing processes. In this context, the performance of different low‐toxic photoinitiators (PIs) and stabilizers are evaluated in thiol‐yne formulations based on di(but‐1‐yn‐4‐yl) carbonate and various multifunctional thiol monomers. Photodifferential scanning calorimetry measurements reveal that the conversion of all resin formulations is mostly independent on the type and concentration of the applied photoinitiator; however, significant differences in their curing speed are observed. It turns out that the migration of an alkyne derivatized photoinitiator is significantly reduced while providing almost similar photoactivity as its nonfunctionalized reference. Moreover, it is found that lauryl gallate and butylated hydroxytoluene lead to significant stabilization without affecting the overall photoreactivity. Notably, the thermomechanical properties of the investigated photopolymers are only slightly affected by water absorption. Using ester free thiols, water absorption can be reduced and hydrolytically stable polymers are realized. These results highlight the versatility of the present thiol‐yne system for the production of medical materials by photopolymerization. image
