ABSTRACT:The preparation of polystyrene/MCM-41 nanocomposites was carried out by "grafting from" and "grafting through" approaches and in the presence of unmodified MCM-41, using reversible addition-fragmentation chain transfer (RAFT) polymerization. The MCM-41 was modified by attaching S-dodecyl-S -(α,α -dimethyl-α -acetic acid)trithiocarbonate (DDMAT) as the RAFT agent and methacrylate group using 3-methacryloxypropyldimethylchlorosilane. The kinetics of styrene RAFT polymerization by different approaches was compared with the model polymerization mediated by free DDMAT. The quantity of the grafted chain grown from the surface and inside of the pores of MCM-41 and free polymer chains in bulk was determined by thermogravimetric analysis. The molecular weight of the produced polymer chains increased linearly with the monomer conversion for three methods. The gel permeation chromatography showed that the molecular weight of grafted and free polymer chains in the "grafting from" approach is higher than other methods, and molecular weight distributions were relatively narrower whereas the rate of polymerization for "grafting from" was higher. C

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Diatomite platelets were employed to synthesize different polystyrene/diatomite composites. Mesoporous diatomite platelets were used for

Diatomite nanoplatelets were used for in situ random copolymerization of styrene and methyl methacrylate by reverse atom transfer radical polymerization to synthesize different well-defined nanocomposites. Inherent features of the pristine diatomite nanoplatelets were evaluated by Fourier transform infrared spectroscopy, nitrogen adsorption/desorption isotherm, scanning electron microscope, and transmission electron microscope. Gas and size exclusion chromatography was also used to determine conversion and molecular weight determinations, respectively.Considerable increment in conversion (from 81% to 97%) was achieved by adding 3 wt% diatomite nanoplatelets in the copolymer matrix. Moreover, molecular weight of random copolymer chains was increased from 12 890 to 13 960 g·mol −1 by addition of 3 wt% diatomite nanoplatelets; however, polydispersity index (PDI) values increases from 1.36 to 1.59. Proton nuclear magnetic resonance spectroscopy was used to evaluate copolymers composition. Thermal gravimetric analysis results indicate that thermal stability of the nanocomposites is improved by adding diatomite nanoplatelets. Differential scanning calorimetry shows an increase in glass transition temperature from 66°C to 71°C by adding 3 wt% of diatomite nanoplatelets. 8-10Diatoms are tiny single-celled plants that live inside a hard shell.Diatoms can be found in large quantities in both salt and sweet water.When the plants inside the shell die, the shell sinks to the bottom of lakes and, by accumulation of them over centuries, finally, the material called diatomaceous earth or the more lightweight rock called diatomite will be formed.

Hydrophilic silica aerogel nanoparticles' surface was functionalized with 3-(trimethoxysilyl)propyl methacrylate (MPS). Then, the resultant functionalized nanoparticles were used in grafting through copolymerization of styrene and butyl acrylate by simultaneous reverse and normal initiation technique for atom transfer radical copolymerization (SR&NI ATRP) to synthesize tailor-made random poly (styrene-co-butyl acrylate) nanocomposites with twofold chains. Successful surface modification of hydrophilic silica aerogel nanoparticles with MPS is demonstrated by Fourier transform infrared spectroscopy and thermogravimetric analysis (TG). Nitrogen adsorption/desorption isotherm is applied to examine surface area and structural characteristics of the synthesized silica aerogel nanoparticles. Evaluation of size distribution and morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography, respectively. Addition of MPS-functionalized nanoparticles by 3 mass% results in a decrease in conversion from 71 to 46 %. Molecular weight (M n ) of the free poly (styrene-cobutyl acrylate) chains decreases by adding 3 mass% MPSfunctionalized silica aerogel nanoparticles; however, polydispersity index (PDI) value increases from 1.17 to 1.48. Although PDI values of the attached poly (styrene-cobutyl acrylate) chains are increased from 1.54 to 1.76, M n values reveal an increment by adding silica aerogel nanoparticles. 1 H NMR spectroscopy results indicate that the molar ration of each monomer in the copolymer chains is approximately similar to the initial selected mole ratio of the monomers. Increasing thermal stability of the nanocomposites is demonstrated by TG. Differential scanning calorimetry also shows a decrease in glass transition temperature by increasing modified silica aerogel nanoparticles.