Effect of amphiphilic copolymer containing ruthenium tris(bipyridyl) photosensitizer on the formation of honeycomb-patterned film

Photoactive, porous honeycomb films prepared from Rose Bengal-grafted polystyrene

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.

Aggregation behaviour of peptide-polymer conjugates containing linear peptide backbones and multiple polymer side chains prepared by nitroxide-mediated radical polymerization

A series of peptides with an alternating sequence of alkoxyamine conjugated lysine and glycine residues were synthesized by classical solution phase peptide coupling. The resulting peptides containing up to eight alkoxyamine moieties were used as initiators in nitroxide-mediated polymerization (NMP) to obtain peptide-polymer conjugates with well defined linear peptide backbones and a defined number of polymeric side chains. Polymerization of styrene and N-isopropylacrylamide (NIPAM) occurred in a highly controlled fashion. Molecular weight and polydispersity index (PDI) were determined by gel permeation chromatography (GPC). Aggregation behaviour of these hybrid materials was investigated by dynamic light scattering (DLS) and atomic force microscopy (AFM). Depending on composition, number and length of the polymer side chains, the conjugates aggregate to different topologies. Whereas peptide-polystyrene conjugates may aggregate to so called honeycomb structures, peptide-poly-N-isopropylacrylamide conjugates show differentiated aggregation behaviour.