Confinement effect of mesoporous silica reactors on electron transfer atom transfer radical polymerization of styrene

Controlled/living free radical polymerization in confined space is expected to produce new materials with predetermined structures and special properties. In this work, various morphologies of mesoporous silicas were synthesized and used as a nanoreactor for bulk activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) of styrene. The resulting mesoporous silica/polystyrene (MS/PS) nanocomposites and PS within the pore channels were characterized by scanning electron microscope, transmission electron microscope, nitrogen adsorption–desorption measurements, fourier transform infrared spectrometer, thermogravimetry analysis, gel permeation chromatography, differential scanning calorimetry, and proton nuclear magnetic resonance (¹H-NMR) spectra. In comparison to conventional bulk ARGET ATRP of styrene (without MS), the pore channels of the MS show an evident confinement effect on bulk ARGET ATRP of styrene. The morphology, molecular weight and polydispersity, glass transition temperature (T_g), and spatial configuration of PS are strongly related to the morphology and internal pore channels of the MS. The bulk ARGET ATRP of styrene in 3D cubic bicontinuous structure MCM-48 shows a high potential for isospecific polymerization. The PS obtained in rod-like SBA-15 (2D), spherical SBA-15, and MCM-41 (1D) exhibit a higher molecular weight, polydispersity index and T_g. The PS obtained in 3D MCM-48 exhibits enhanced molecular weight along with decreased the polydispersity. Moreover, the morphologies of the polymers obtained in mesoporous silica are consistent with that of the corresponding mesoporous silicas.