Molecular Weight Dependence of Domain Structure in Silica-Siloxane Molecular Composites

Abstract

A detailed investigation of the molecular weight dependence of silica growth in in situ filled polydimethylsiloxane/tetraethylorthosilicate (PDMS/TEOS) materials was conducted using small angle neutron scattering (SANS). Composite materials were produced by using TEOS to simultaneously produce the glassy filler phase and to crosslink linear, hydroxyl terminated PDMS of variable molecular weight, M. Correlated domains of glassy filler were produced. The morphology of the in situ filled material showed a definite dependence on the molecular weight of the precursor polymer. The scale, R, of the glassy domains follows de Gennes' description of phase separation in a crosslinked system (R ∝ M1/2).

PDMS-SiO2-TiO2-CaO hybrid materials – Cytocompatibility and nanoscale surface features

“…The same was also obtained for the Guinier crossover of sample K at high q. This value has been reported as the distance between metal-oxo domains embedded in the siloxane network [62][63][64], which is in agreement with the results of 29 Si MAS NMR, that indicated the maintenance of the full coordinated Q 4 signal in cross-polarization mode. …”

Dependence of silica particle sizes on network chain lengths, silica contents, and catalyst concentrations inin situ-reinforced polysiloxane elastomers

“…In this case, the phase separation of the hydrolyzed TEOS (which is driven by the extent of the hydrolysis and condensation) occurs in a multicomponent, partially crosslinked system, leading to a complicated interplay of chemical growth and phase separation. 27 Scattering measurements on these composites indicated that particle sizes increased with increase in network mesh size. The simplest interpretation of this constraining effect would be that entropy decreases from the network chains being stretched out as the in situ-generated particles grow larger.…”

“…Thus, the relationship between particle or domain size and constraints provided by the polymer environment becomes very important. Some studies have been carried out in this area, 27,31,41 but additional results would be highly desirable.…”

“…Ulibarri et al 27 studied the particle size dependence on mesh size of a network, as gauged by the molecular weight M c between crosslinks. They used a one-step process of simultaneously filling and curing poly(dimethylsiloxane) (PDMS) [Si(CH 3 ) 2 OO], with TEOS simultaneously acting as both end-linking agent and source of the silica particles.…”

A biocompatible hybrid material with simultaneous calcium and strontium release capability for bone tissue repair

“…According to the literature [43], the peak height is related to the number of coordinated neighbors at a characteristic distance a defined by a = 2π/q. As explained in authors previous works [16,23] this characteristic distance is the distance between metal-oxo domains (main silica primary particles) embedded in the siloxane network [44][45][46]. For both samples this characteristic distance is ca.…”