New Pathways for Modifying the Surface of High Density Polyethylene: Photochemical Functionalization and Subsequent Surface Chemistry

摘要

Treatment of HDPE by the herein described heterogeneous chemical reaction/photochemical process had the function of adding chlorine to the polymer surface and rendering it adhesive while not affecting the desirable chemical, thermal and mechanical engineering characteristics of the bulk HDPE material, pigment or molded sample geometry. The chlorinated HDPE surface was subsequently exposed to ultra-violet (UV) light and surface al-kene moieties were noted using ATR FT-IR methods along with a concomitant reduction in surface chlorine. The photochemically induced free radical surface dehydrochlo-rination mechanism was observed to follow first-order kinetics and potentially produce a focussed pattern for in- formation storage via UV laser treatment. It is hypothesized that increasing the light intensity using a UV laser with λ<355 nm would increase the efficiency of homolytic C-Cl bond scission and significantly shorten the 600 hours of irradiation required using a soft laboratory UV lamp Dehydrohlorination reaction kinetics using a UV laser treatment on the HDPE surface chlorinated via reaction with NaOCl/(CH_3CO)_2O is currently being investigated in our laboratory. Facile subsequent reactivity of the isolated surface alkene groups was demonstrated using a variety of electrophilic addition reagents including Br_2. Furthermore, poly(4-hydroxy sryrene) architectures were covalently tethered to either the chlorinated or unsaturated HDPE surface in an effort to ultimately tailor surface po larity, hydrophilicity and adhesiveness. In addition, the tethered PHS can be used to create poly(α-olefin)s with laminate coatings via conventional urethane, epoxy, no-volac or resole condensation step-growth polymerization reactions. This economical and benign surface chlorina-tion/photochemical two-step treatment process produced relatively small handling and disposal risks as well as no apparent polymer degradation.