[Poly(ethylene terephthalate) ionomer]/silicate hybrid materials via polymer–in situ sol‐gel reactions

Abstract

A scheme was developed for producing poly(ethylene terephthalate (PET) ionomer)/silicate hybrid materials via polymer-in situ sol-gel reactions for tetraethylorthosilicate (TEOS) using different solvents. Scanning electron microscopy/EDAX studies revealed that silicate structures existed deep within PET ionomer films that were melt pressed from silicate-incorporated resin pellets.29 Si solid-state NMR spectroscopy revealed considerable Si-O-Si bond formation, but also a significant fraction of SiOH groups.23 Na solid-state NMR spectra suggested the presence of ionic aggregates within the unfilled PET ionomer, and that these aggregates do not suffer major structural rearrangements by silicate incorporation. For an ionomer treated with TEOS using MeCl 2 , Na ϩ ions are less associated with each other than in the unfilled control, suggesting silicate intrusion between PET-SO 3 Ϫ Na ϩ ion pair associations. The ionomer treated with TEOS ϩ tetrachloroethane had more poorly formed ionic aggregates, which illustrates the influence of solvent type on ionic aggregation. First-scan DSC thermograms for the ionomers demonstrate an increase in crystallinity after the incorporation of silicates, but solvent-induced crystallization also appears to be operative. Second-scan DSC thermograms also suggest that the addition of silicate particles is not the only factor implicated in recrystallization, and that solvent type is important even in second-scan behavior. Silicate incorporation does not profoundly affect the second scan T g vs. solvent type, i.e., chain mobility in the amorphous regions is not severely restricted by silicate incorporation. Recrystallization and melting in these hybrids appears to be due to an interplay between a solvent-induced crystallization that strongly depends on solvent type and interactions between PET chains and in situgrown, sol-gel-derived silicate particles.

Chemical, Structural and Thermal Changes in PET Caused by Solvent Induced Polymer Crystallisation

“…It has been established 10,14,15 that highly interacting solvents, after diffusion into the polymer, promote crystallisation and recrystallisation of the molecules and increase their segmental mobility so that ultimately structural rearrangements take place. As a result of this process of solvent induced crystallisation the structural, mechanical and dyeing properties of the polymeric materials are modifi ed and a number of studies have highlighted these effects 13,[16][17][18][19] .…”

Nonisocyanate polyurethane/silica hybrid coatings via a sol–gel route

“…Perhaps this is due to a plasticization of the amorphous regions by a solvent that is a residue of the in situ sol-gel process. 29,30 On the other hand, the addition of different amounts of phosphine oxide resin increased the T g values from −28.5 to 1.5 • C for the formulation without sol-gel and from −24.2 to 2.2 • C for the formulation with the 20% sol-gel ratio. The T g is an important intrinsic characteristic that influences the properties of a polymer and its potential applications.…”

“…These results indicate that the inorganic network does not restrict the mobility of the polymer chain segments. Perhaps this is due to a plasticization of the amorphous regions by a solvent that is a residue of the in situ sol–gel process 29,30…”