A novel class of environmentally benign, non‐toxic and recyclable materials based on vinylbenzyl thymine (VBT) and an ionically‐charged vinylbenzyl triethylammonium chloride (VBA) monomers was studied. Several syntheses of VBT–VBA copolymers at various comonomer ratio and initiator concentrations were carried out at 65 °C using isopropanol as solvent. Samples were taken during the reactions to determine the monomer conversion, chemical composition and molecular weight distribution. The comonomers exhibited similar reactivities and random copolymers with similar chemical compositions were obtained. The curing process involved the irradiation of the copolymer films with a short‐wavelength UV light (254 nm) for different times, leading to film immobilization on the substrate. The light‐induced crosslinking reaction was followed by UV‐vis spectroscopy and the immobilization point relative to the gel point was determined. The kinetics of the crosslinking process pointed to a second‐order process with respect to the thymine concentration. The experimental results provide complementary information on photo‐induced immobilization of VBT–VBA films that are crucial for developing new classes of environmentally benign materials and new energy‐saving methods.magnified image

The effect of irradiation light intensity, film thickness, and polymer composition upon photo-irradiation of watersoluble polymers containing thymine was studied by ultraviolet (UV)-vis spectroscopy. Coatings of aqueous solution of the polymer on PET substrates were exposed to UV light at 254 nm through a standard mask. The effect of irradiation dose is similar to the typical behavior of photo-resists: the degree of crosslink increases over the time until it reaches saturation. The polymer composition effect shows an expected trend on the curing process, the more vinylbenzylthymine (VBT) content in the copolymer the higher the degree of crosslinking, a situation that agrees with the fact the VBT is the monomer playing the main role in the photo-reaction. It was observed that the effect of film thickness was as expected, the thicker the film the slower the immobilization of the polymer on the substrate. It was demonstrated that by varying these parameters one could control the crosslinking rate of the polymer.

Polymeric micelles (PMs) composed of self-assembled amphiphilic block copolymers were synthesized from vinylbenzyl thymine (VBT) and vinylbenzyl triethylammonium chloride (VBA) exhibiting improved physical stability. Three diblock copolymers of different chemical compositions and similar molecular weights (polydispersities below 1.5) were obtained via nitroxide mediated radical polymerization. Critical micelle concentration (CMC) was determined by dye micellization method, the shift of the absorption peak of the anionic (EY) due to the interactions with non-assembled chains and auto-assembled copolymers was followed. Polymeric systems exhibited good stability revealing that a higher proportion of cationic monomers in the diblock reduce the CMC. Furthermore,
after the core of PMs was photocrosslinked by UV irradiation, the CMC decreases notably. Kinetic release studies using EY dye as probe demonstrated that both, higher VBA ratios in the polymer and higher UV-irradiation, slow down the dye release.Fil: Barbarini, Alejandro Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); ArgentinaFil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; Argentin