Structure and Dynamics of a Colloidal Silica−Poly(methyl methacrylate) Composite by ¹³C and ²⁹Si MAS NMR Spectroscopy

Abstract

A silica-poly(methy1 methacrylate) (PMMA) composite was prepared by condensation polymerization of a 2 nm shell of the silane coupling agent 3-(trimethoxysilyl)propyl methacrylate (TPM) on the surface of 10.5 nm diameter sol-gel colloidal silica particles followed by free-radical Folymerization of a 50 wt % dispersion of the TPM-silica in methyl methacrylate. Cross-polarization combined with magic angle spinning and high-power decoupling (CPIMAS) and single-pulse 29Si NMR s p x t r a together with quasi-adiabatic cross-polarization (QACP) 13C NMR spectra provided quantitative analyses of the structural components of the parent silica, the TPM-silica, and the composite. The parent silica contained one ethoxy group and eleven hydroxy groups per ten silicon atoms. The TPM-silica containcd one residual methoxy group per TPM group and no residual hydroxy groups. Polymerization with M.MA consumed 85% of the methacrylate groups of the TPM. Time constants T l p~ for proton spin-lattice, relaxation in the rotating frame detected via 13C and 29Si CPMAS spectra showed rapid spin diffusion bstween all CH protons in the samples, but not between the CH protons and the OH protons that cross-polarize 29Si atoms in the parent silica. Time constants Tlpc for carbon spin-lattice relaxation in the rotating frame showed that the TPM-silica has substantial motion at kilohertz frequencies leading to fast relaxation, whereas the PMMA composite is more rigid and the ethoxy groups in the parent silica arc more mobile.Measurements of lH-lH dipolar transverse relaxation times via 13C and 29Si detection showed decreasing strengths of homonuclear dipolar interactions due to increasing molecular motion in the order composite > TPM-silica > OH groups in parent silica.

Synthesis, characterization and thermal properties of inorganic-organic hybrid

“…The chemical shifts from the 29 Si NMR spectra of Q 2 , Q 3 , and Q 4 were -87, -102, -116 ppm, respectively, and were similar to those reported in the lit- erature [17]. The chemical shifts of T 2 and T 3 were -54 and -68 ppm, respectively, and also in good agreement with the literature values [18]. Results revealed that Q 3 , Q 4 and T 3 were the major microstructures forming a network structure.…”

Poly(methyl methacrylate) (PMMA)-based hybrid materials with reactive zirconium oxide nanocrystals

“…22,23 In studies of PMMA/inorganic oxide materials, the inorganic network in hybrid materials is generally prepared from metal alkoxides [24][25][26] or colloidal inorganic nanoparticles. [27][28][29][30] There are many reports that base the preparation of PMMA/SiO 2 hybrid materials on unfunctionalized and trialkoxysilyl-functionalized acrylic polymers using an in situ sol-gel process in the presence of tetraethoxysilane (TEOS) or Ti(OBu) 4 . In this case, the polymerization of monomers and the hydrolysis and condensation of TEOS occur simultaneously.…”

Hybrid thin films derived from UV-curable acrylate-modified waterborne polyurethane and monodispersed colloidal silica

“…These spectra show a weak absorption peak at 106 ppm. The band might be due to the carbon atom of the Si-OCH 3 group [29]. The result indicates that the Si-OCH 3 residue exists in MSMA-SiO 2 , 5% MSMA-SiO 2 /WPU-AC and 20% MSMA-SiO 2 / WPU-AC hybrids.…”

“…The 13 C and 29 Si NMR spectra of the solid-state hybrids were determined (Bruker, AVANCE-400, USA) with cross polarization combined with the magic angle spinning (CP/ MAS) technique using 200-300 mg samples. The 13 C measured conditions of pulse width, recycle delay, contact time and number of scans are 5.5 µs, 5 s, 1000 µs, and 1486 cycles, respectively, at 100.6 MHz.…”

“…The 13 C measured conditions of pulse width, recycle delay, contact time and number of scans are 5.5 µs, 5 s, 1000 µs, and 1486 cycles, respectively, at 100.6 MHz. These conditions corresponding to 29 Si are 3 µs, 200 s, 1000 µs, and 294 cycles, respectively, at 79.4 MHz. MSMA-SiO 2 particle size was measured on the transmittance electron microscope (120 kV, TEM, JOEL JEM-1230, Japan).…”