Singlet Oxygen Generation and Adhesive Loss in Stimuli-Responsive, Fullerene-Polymer Blends, Containing Polystyrene-Block-Polyutadiene-Block-Polystyrene and Polystyrene-Block-Polyisoprene-Block-Polystyrene Rubber-Based Adhesives

J. Paige Phillips Buchanan, University of Southern Mississippi
Xiao Deng, University of Southern Mississippi
Meredith L. Todd, University of Southern Mississippi
David T. Heaps, University of Southern Mississippi

Abstract

The adhesive properties, as measured by bulk tack and peel strength analysis, were found to decrease in polystyrene-block-polybutadiene-block-polystyrene (SBS) and polystyrene-block-polyisoprene-block-polystyrene (SIS) PSA films containing common singlet oxygen generators, acridine, rose bengal, and C-60 fullerene, when irradiated with a tungsten halogen light in air. The addition of the singlet oxygen quencher, beta-carotene, to the C-60 fullerene samples was found to significantly deter the rate of adhesive loss in the fullerene-SBS and -SIS PSA nanocomposites. The presence of oxygen was essential to the mechanism of adhesive loss and, in combination with the effects of singlet oxygen generators and a singlet oxygen scavenger, strongly supports a singlet-oxygen mediated process. FTIR investigations of fullerene-SBS and -SIS systems suggest the initial formation of peroxides which, upon further irradiation, lead to the generation of carbonyl-containing compounds of a ketonic type after crosslinking. Rates of SBS and SIS C-H abstraction were comparable and found to decrease when the high-pressure, mercury xenon irradiation source was filtered to allow only light of lambda > 390 nm. (C) 2008 Wiley Periodicals, Inc.