Surface-dependent effect of functional silica fillers on photocuring kinetics of hydrogel materials

Abstract

Two types of silica: precipitated (P, prepared in non-polar media, a new type, submicrometer sized) and fumed (F, nanosized), both unmodified and surface modified are investigated as functional fillers for potential applications in nanocomposites with poly(2-hydroxyethyl methacrylate) matrix. Special attention is paid to the kinetics of composite formation in an in situ photopolymerization process. Silicacontaining formulations polymerize faster; this effect is much stronger for silica P having much larger particle size than silica F. Surface treatment leads to further acceleration of the polymerization in case of silica P but to retardation in case of silica F; the effect of modification of the filler surface on properties of composites is different for each of the silicas. The obtained results are discussed in terms of effects of curvature of silica particles, surface properties, solvation cell, interphase region, viscosity changes, and morphology of the resulting composites.

Photocurable polymethacrylate-silica nanocomposites: correlation between dispersion stability, curing kinetics, morphology and properties

“…[13] by an increase in the propagation rate coefficient k p (no reason was proposed) and a slight decrease in the termination rate coefficient k t (associated with the increase in viscosity of the formulation); moreover, slightly higher k p values showed compositions containing Aerosil R7200 than those with Aerosil R711. The increase in the polymerization rate does not result simply from the enhanced total concentration of the polymerizing groups after addition of methacryloxygrafted silica, because a similar effect is observed also in the presence of non-modified silicas [8]. Our considerations concerning the influence of dispersion stability prove that the polymerization is faster in case of formulations showing higher absolute Zeta potential values, both resulting from the silica content as well as silica type.…”

“…3a). This type of the accelerating behavior of silica has been also reported earlier [8,13,29] and many possible explanation were proposed but only our earlier reports took into account a possible influence of dispersion stability on curing kinetics [13,30]. Inspection of Figs.…”

“…Ours previous papers [8,13,14] analyzed kinetics more deeply (in the considered cases a maximum on the dependence of the polymerization rate on the silica content was observed). On the other hand, mechanical properties of this type of composites were often investigated (e.g.…”

“…Recently, photocurable hybrids based on silica have been applied in medicine to create polymer networks for use in applications such as bone and dental restorations [6], coatings [7], for artificial implants and functional hydrogel materials [8].…”

Recent Advances in Photo-Induced Free-Radical Polymerization

“…19,20 Recent works indicate that the kinetics depends to a high degree on the stability of the monomer/filler dispersion 21,22 or particle size. 23 A decreased photopolymerization rate of an acrylate monomer was observed in the presence of nano-TiO 2 , which was associated with the light absorption by this filler in the range of photoinitiator absorption. 24 Recently a lot of attention has been devoted to carbon nanotubes, due to improved mechanical properties of the derived nanocomposites and their electrical conductivity.…”