Functional poly(methylstyrene) latex particles: Synthesis, characterization and applications

In this study, the functional poly(methylstyrene) (PMS) latex particles bearing aldehyde and carboxylic acid groups with various particle size are prepared and characterized and some applications in binding specific DNA sequences are also studied.;Highly monodisperse emulsifier-free PMS latex particles were prepared via an emulsifier-free emulsion polymerization, using 2,2'-azobis-(2-amidineopropane) dihydrochloride (V-50) as an initiator. Effects of initiator concentration, ionic strength in the aqueous phase, and polymerization temperature on the polymerization reaction are examined. The polymerization followed the micellization nucleation mechanism. The appropriate initiator concentration was necessary in order to obtain monodisperse and stable latex particles. The size of PMS particles decreased with the increase of initiator concentration and reaction temperature at a constant ionic strength, and the conversion of latexes increased significantly with increasing initiator concentration. On the other hand, the size increased as the ionic strength of aqueous phase increased, but the change of ionic strength had little effect on the particle size distribution. The SEM micrograph showed that an agitation rate of 350 rpm or higher was a necessity for the preparation of highly monodisperse poly(methylstyrene) latex particles.;Purification of the latexes by dialysis was followed in order to remove residual monomer, initiator and electrolytes. The kinetics of oxidation of PMS latexes at different oxidant concentration was studied, and the effects of catalyst concentration, pH value and reaction temperature on oxidation were also investigated. The degree of oxidation increased with reaction time, but the emulsions of highly oxidized PMS latexes were found to be unstable. An increase of oxidant concentration enhanced the rate of oxidation, while the catalyst concentration had little influence on it. The addition of base and acid to latexes inhibited the oxidation reaction and the oxidation degree increased with increasing reaction temperature.;The amount of aldehyde groups on the particle surface was determined using the 2.5 pH method, and the amount of carboxylic acid groups on the particle surface were measured by conductometric and potentiometric titration methods. Surface morphology of latex particles was observed by the SEM. Control of aldehyde content on the particle surface could be easily achieved by manipulating the reaction conditions.;A convenient method to prepare ultrafine PMS latex particles with aldehyde groups on the surface was developed. (PMS) latexes with well-defined sizes 26--81 nm in diameter were first prepared via microemulsion polymerizations, using cetyltrimethylammonium bromide as surfactant. The surface oxidation of (PMS) microlatexes were then carried out in the presence t-butyl hydroperoxide catalyzed by copper (II) chloride. Aldehyde group was found to be the major functional group on the particle surface.;Binding of DNAs to the functional PMS latex particles was carried out. The functional PMS latex particles had a good binding efficiency at normal condition. The addition of salt inhibited the binding reaction. (Abstract shortened by UMI.)...