Dielectric and thermal studies of the segmental dynamics of poly(methyl methacrylate)/silica nanocomposites prepared by the sol–gel method

Abstract

ABSTRACT:Poly(methyl methacrylate)/silica (PMMA/SiO x ) nanocomposites were synthesized via sol-gel method and studied by various techniques. The dispersion of the silica particles (10-100 nm) in the matrix was probed by transmission electron microscopy (TEM), while solid-state NMR and Raman spectroscopy detected the formation of an inorganic network with high degree of crosslinking. To elucidate the impact of the filler on the molecular dynamics of the PMMA, different methods were used; namely differential scanning calorimetry, thermally stimulated depolarization current and broadband dielectric relaxation spectroscopy. All three methods observed a significant impact of the nanoparticles on the segmental dynamics of the matrix, which was expressed as an increase of the glass transition temperature (T g ) in terms of calorimetry and as a shift of the a (segmental) relaxation to lower frequencies in terms of dielectric spectroscopy.

Physics and Chemistry of Sol-Gel Nanocomposites Formation

“…At high content of inorganic phase mechanical and thermal properties deteriorate, which is caused by aggregation of silica gel particles in the hybrid. These polyamides are promising candidates for usage in microelectronics [168], other types of sol-gel products of similar composition are promising for production of membranes with high gas transporting properties [169], ceramics [170], nonflammable nanocomposites [171], materials with low dielectric permeability [172,173] and with stable optical properties for non-linear optics, [174], etc. Also widely used are polyamide-silica gel hybrid coatings (0-20 wt% SiO 2 ), which are obtained, for example, from PI, TEOS, glycidyloxypropyl trimethoxysilane and polyamic acid (synthesized from 3, 3, 4 benzophenone tetracarboxylic dianhydride (BTDA) and 3,3 0 -Diaminodiphenyl sulfone)(DDS) [143]), combination of sol-gel technique with Scheme 4.7 Covalent binding of nanoparticles with a polymer chain by 3-glycidiloxytrimethoxy silane thermal imidization.…”

Controlling dielectrical properties of polymer blends through defined PEDOT nanostructures

“…[26][27][28][29][30][31][32][33][34] However, considering the different results obtained for several nanocomposite systems, a high number of challenging questions remain unsolved.…”

Influence of drying procedure on glass transition temperature of PMMA based nanocomposites

“…For the determination of the solvent content after drying, the samples were heated to 150uC at a rate of 10uC min 21 and thereafter kept isothermally for 90 min. Thereafter, the samples were heated up to 450uC.…”

“…For the determination of the glass transition temperature via DSC measurements, a Q1000 DSC from TA Instruments was used. The samples were heated from room temperature to 200uC at a rate of 10uC min 21 and held at that temperature for 5 min. Thereafter, they were cooled to room temperature, also at a rate of 10uC min 21 .…”

“…The samples were heated from room temperature to 200uC at a rate of 10uC min 21 and held at that temperature for 5 min. Thereafter, they were cooled to room temperature, also at a rate of 10uC min 21 . The cycle was repeated once.…”