Facile fabrication of superhydrophilic poly(styrene-co-acrylate)/SiO2 composite materials by conventional emulsion polymerization

A novel procedure for the preparation of superhydrophilic poly(styrene-co-acrylate)/SiO2 composite materials was prepared from conventional emulsion polymerization in the presence of colloidal silica. TEM photos revealed that poly(styrene-co-acrylate) latexes exhibited a clear core-shell structure, and the electrostatic repulsion and hydrogen bonds between poly(styrene-co-acrylate) latexes and SiO2 nanoparticles guaranteed the uniform dispersion of silica nanoparticles. The average diameter data indicated that the particle size of composite latexes (78 nm) was slightly smaller than that of polymer (82 nm), although the slight aggregation of SiO2 nanoparticles had increased the average diameter to 87 nm. FTIR spectra confirmed that hydrogen bonds were formed and gel reaction of -OH groups occurred during film formation. Two kinds of Si-O bonds were found in XPS spectra with a weight ratio addition of 20.0% SiO2, which one was related to the Si-OH groups of colloidal silica nanoparticles, while the other was attributed to the Si-O-Si groups obtained from the gel reaction. SEM and AFM images displayed that the formation of micro/nano structure from the gel reaction had increased the roughness of the composite films. The water contact angle (WCA) of the composite films was found to decrease from 45 to 3o (3 s) and exhibit superhydrophilicity.

Automated summary

A new method for preparing superhydrophilic poly(styrene-co-acrylate)/SiO2 composite materials was developed using conventional emulsion polymerization with colloidal silica. TEM images showed a clear core-shell structure of poly(styrene-co-acrylate) latexes, and the electrostatic repulsion and hydrogen bonds ensured the uniform dispersion of silica nanoparticles. The average diameter of the composite latexes was slightly smaller than that of the polymer, and the formation of hydrogen bonds and gel reaction resulted in enhanced roughness of the composite films. The water contact angle decreased significantly, indicating superhydrophilicity.