Water-soluble polystyrene latexes as photoredox media. 2. Excited-state electron transfer from anthracene covalently bound poly(methacrylic acid)

Abstract

Poly(methacrylic acid)-co-2-(9-anthryl)ethylmethacrylate, abbreviated as PMA-A hereafter, has been adsorbed at the interface of water-soluble latexes, referred to as microspheres (abbreviated as [mu]S). Two distinct stages of the adsorption processes of the polymer at [mu]S interfaces are observed that depend on pH. The initial association stage is quickly achieved (<3 min) after mixing the polymer and [mu]S in aqueous solution. The final equilibration of the polymer at the interface requires about 2 days to reach equilibrium. Excited-state quenching of PMA-A via electron transfer at interfaces of [mu]S has been measured using a zwitterionic viologen SPV (4,4[prime]-bipyridinyl-l,l[prime]-bis(propanesulfonate)). The [mu]S interface provides a unique environment for the anthracene moiety of PMA-A. Charge separation was found in all cases with the largest yield at high pH for the triplet state and at low pH for the singlet state. There is little sensitivity to the environment for triplet-state electron transfer because the dominant factor is the spin-forbidden recombination of the reactive charge pair. The efficiency of triplet-state charge separation at the [mu]S interface was found to be comparable to homogeneous solution. 17 refs., 14 figs., 4 tabs.