Abstract
Carboxylated polystyrene (PS) microspheres were synthesized by the two-step dispersion polymerization of styrene in hydrocarbon alcohols (CnH2n+1OH,n=1–5) in the presence of acrylic acid (AA) as a functional comonomer, 2,2′-azobis-(2-methylbutyronitrile) (AMBN) as the initiator and polyvinylpyrrolidone (PVP55) as the dispersant. The effects of solvent type, AA concentration, and first reaction time on the carboxyl content on the microsphere surfaces were investigated. The PS microspheres were characterized by scanning electron microscopy, infrared spectroscopy, nuclear magnetic resonance, and gel permeation chromatography. The results showed that the first reaction time of the two-stage dispersion polymerization had a great influence on the nucleation process, and appropriately prolonging the first-step reaction time had a great influence on the surface carboxyl content. The effect of the solvent on the surface carboxyl content of PS microspheres was significant. With n-butanol as the solvent, the carboxyl group content on the surface of the microspheres reached 57.05 mg/g.
Highlights
In recent years, as the emphasis on health has increased, the technical requirements for the detection of various indicators in serum have become increasingly high
A dry chemical in vitro diagnostic reagent usually consists of a diffusion layer, reagent layer, indicator layer, and substrate layer
It can be seen that the peak of 11 ppm which is a characteristic peak of the hydrogen atom on the carboxyl group from the Figure 1 indicating that the carboxyl group is successfully modified to the surface of polystyrene
Summary
As the emphasis on health has increased, the technical requirements for the detection of various indicators in serum have become increasingly high. The selection of materials with high surface reactivity and uniform diffusivity is necessary for the preparation of dry chemical in vitro diagnostic reagents. Lee and Ha et al [17] used dispersion polymerization to prepare PS microspheres using fluorinated alcohol as the solvent; the synthesized microspheres had high carboxyl contents but small particle sizes. Many problems remain in dispersion polymerization, restricting the applications of carboxyl microspheres in the biomedical and diagnostic fields; these problems include low surface carboxyl content, nonuniform particle sizes, and irregular sphericity. A two-step dispersion polymerization method was used to prepare carboxylated PS microspheres with controllable surface carboxyl groups by adjusting the solvent, the concentration of acrylic acid (AA) added, and the reaction time of the first step. The influence of the above preparation conditions on the surface carboxyl content of the microspheres was analyzed
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