Syntesis, curing and applications of bioinspired polymers based on vinylbenzil thymine

A. BARBARINI; D. M. MARTINO; M SPONTON; D. A. ESTENOZ; G. MEIRA

Cancun

Congreso; XX International Materials Research Congress (IMRC); 2011

Bioinspired polymers based on a new synthetic monomer, 4-vinylbenzyl thymine (VBT), have been designed to have the ability to photo-crosslink upon irradiation with short-wavelength UV light. Water-soluble environmentally benign, non-toxic and recyclable polymers can be obtained copolymerizing photocrosslinkable VBT with para-substituted charged styrenic monomer vinylbenzyl triethylammonium chloride (VBA). The VBT-based photo-polymers have potential applications in a variety of fields ranging from hair care products to printed circuit boards and photo-imaging systems, as well as controlled release systems for pharmaceutical and agricultural use. Syntheses of VBT–VBA random copolymers at various comonomer ratio and initiator concentrations were carried out at 65 ºC using isopropanol as solvent. Samples were taken along the reactions to determine the monomer conversion, chemical composition and molecular weight distribution. The comonomers exhibited similar reactivities and random copolymers with different chemical compositions were obtained. The curing process involved the irradiation of the copolymer films with short UV light (254 nm) for different times. Cross-linked areas becomes insoluble due to increased molecularweight leading to film immobilization on the substrate, while uncross-linkedregions may beremoved by washing with water. The light-induced crosslinking reaction was followed by UV-vis spectroscopy and the immobilization point was determined. The kinetics of the crosslinking process pointed to a second-order process with respect to thymine concentration [1]. 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. On the other hand, we used controlled radical polymerization techniques (Nitroxide Mediated, NMP and Atom Transfer, ATRP) to produce amphiphilic block copolymers of VBT-VBA. The polymer chains are able to self-assemble into micelles at certain concentrations, where the hydrophobic core of pVBT allows transporting hydrophobic drugs of biomedical interest through hydrophilic media, acting as drug delivery systems. The crosslinking of the core by UV light dimerize adjacent thymines increasing the stability of the micelle and allowing a slower drug release. Bulk polymerizations of styrene (St) in Dimethylformamide (DMF) at 130ºC under N2 atmosphere were carried out using TEMPO as polymerization mediator. Conversion andmolecular weight distribution (MWD), average molecular weights (Mn) (Mw)and polydispersity (Ip) were determined. To obtain di-block copolymers, polymerization of VBT from pSt macro-initiator were carried out in DMF at 130°C under nitrogen atmosphere. The MWD shows an increase in the average molar mass, with low Ip variation. We plan to synthesize VBT-VBA block copolymers in aqueous systems, with the goal of obtaining block amphiphilic copolymers for use in controlled drugs release systems.