Photoactive, porous honeycomb films prepared from rose bengal-grafted polystyrene
Résumé
Honeycomb-structured porous polymer films based on photosensitizer-grafted polystyrene are prepared through the breath figure process. Rose Bengal (RB) photosensitizer is first attached to a well-defined poly(styrene-stat-4- vinylbenzyl chloride) statistical copolymer, synthesized by nitroxide-mediated radical polymerization. The RB grafted poly(styrene-stat-4-vinylbenzyl chloride) (ca. 20 000 g mol-1 molar mass, 1.2 dispersity) leads to porous polymer films, with a hexagonal pore pattern, while a simple mixture of poly(styrene-stat-4-vinylbenzyl chloride) and the insoluble RB photosensitizer produced unstructured, nonporous films. The RB-grafted honeycomb films, compared with the corresponding nonporous flat films, are more efficient for oxidation of organic molecules via singlet oxygen production at a liquid/solid interface. The oxidations of 1,5-dihydroxynaphthalene to juglone and α-terpinene to ascaridole are followed in ethanol in the presence of both types of films. Oxidation of the organic molecules is a factor 5 greater with honeycomb compared to the nonporous films. This gain is ascribed to two factors: the specific location of the polar photosensitizer at the film interface and the greater exchange surface, as revealed by fluorescence and scanning electron microscopies.
Mots clés
Chlorine compounds
Exchange surfaces
Film preparation
Free radical polymerization
Grafting (chemical)
Honeycomb structures
Interfaces (materials)
Liquid/solid interface
Molecules
Nitroxide mediated radical polymerization
oxidation
Photosensitizers
Polystyrenes
Porous polymer films
Scanning electron microscopy
Singlet oxygen production
Specific location
Statistical copolymers
Styrene
Vinyl-benzyl chlorides