Preparation and properties of transparent bulk polymer nanocomposites with high nanophase contents

Transparent bulk polymer nanocomposites with high contents of ZnS nanoparticles (NPs) were prepared by free radical initiated in-situ bulk polymerization of N, N-dimethylacrylamide (DMAA), styrene (St) and divinylbenzene (DVB) using 2,2'-azobisisobutyronitrile (AIBN) as initiator in the presence of 2-mercaptoethanol (ME) capped ZnS NPs. The structure and properties of the nanocomposites were studied. Sphalerite ZnS NPs with average size of about 3nm were dispersed homogeneously in polymer matrices. The ME capped ZnS nanophase reached 30 wt%, while the bulk nanocomposites still exhibited good transparency in the visible light range. TGA study showed that the nanocomposite materials had excellent thermal stability below 245 degrees C. Dynamic mechanical analysis and pencil hardness studies showed that the materials had good mechanical properties. However, with the increase of the ME capped ZnS content, the glass transition temperature of the nanocomposites decreased probably due to the plasticizing effect of the ME capped ZnS NPs. Refractive indices of the nanocomposite materials increased from 1.536 for the matrix to 1.584 upon increasing the weight fraction of the ME capped ZnS NPs to 30 wt%.