Intergallery living polymerization using silicate-anchored photoiniferter. A versatile preparatory method for exfoliated silicate nanocomposites

Living free radical polymerization of a variety of monomers using dithiocarbarmate photoiniferter modified silicate gave dispersed polymer/silicate nanocomposites, even for nanocomposites with very high silicate contents (7-63 wt%). Thus, nanocomposites containing polystyrene, poly(methyl methacrylate), poly(tert-butyl methacrylate), and poly(methyl methacrylate-b-styrene) of controlled molecular weight, architecture, and polydispersity were prepared. Dispersion and random orientation of the silicate layers in the polymer matrix were confirmed by both wide-angle X-ray diffraction and transmission (TEM) and scanning transmission electron microscopy (STEM). One principal finding is that exfoliated nanocomposites with very high silicate contents (above 20 wt%) could be used as nanoadditives or masterbatches to prepare all kinds of nanocomposites by simple blending without always having to begin from scratch. The exfoliation remained stable to subsequent thermal processing. The storage modulus of PMMA/silicate nanocomposite at only 3.2 wt% silicate loading was 30-40% higher than that of neat PMMA at all temperatures in the glassy region below the T-g of PMMA. The method is versatile, simple, and applicable to many monomers and requires no additional catalyst.