Loading and release mechanisms of a biocide in polystyrene-block-poly(acrylic acid) block copolymer micelles.
The kinetics of loading of polystyrene197-block-poly(acrylic acid)47 (PS197-b-PAA47) micelles, suspended in water, with thiocyanomethylthiobenzothiazole biocide and its subsequent release were investigated. Loading of the micelles was found to be a two-step process. First, the surface of the PS core of the micelles is saturated with biocide, with a rate determined by the transfer of solid biocide to micelles during transient micelle-biocide contacts. Next, the biocide penetrates as a front into the micelles, lowering the Tg in the process (non-Fickian case II diffusion). The slow rate of release is governed by the height of the energy barrier that a biocide molecule must overcome to pass from PS into water, resulting in a uniform biocide concentration within the micelle, until Tg is increased to the point that diffusion inside the micelles becomes very slow. Maximum loading of biocide into micelles is approximately 30% (w/w) and is achieved in 1 h. From partition experiments, it can be concluded that the biocide has a similar preference for polystyrene as for ethylbenzene over water, implying that the maximum loading is governed by thermodynamics.
Vyhnalkova
Renata
R
Pulp and Paper Research Centre, McGill University, 3420 University Street, Montreal, Quebec, H3A 2A7, Canada.
Eisenberg
Adi
A
van de Ven
Theo G M
TG
D000180:Acrylic Resins / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D004202:Disinfectants / Q000008:administration & dosage*; D004337:Drug Carriers; D016503:Drug Delivery Systems; D008823:Micelles; D011137:Polystyrenes / Q000737:chemistry*; D012995:Solubility; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D000180:Acrylic Resins; D004202:Disinfectants; D004337:Drug Carriers; D008823:Micelles; D011137:Polystyrenes; D014867:Water