Poly(methyl methacrylate) (PMMA)/silicate interpenetrating networks (IPNs) have been synthesized in formic acid solutions. The fast gelation times observed in these solutions reduced the phase separation of the polymer, and the 50% by weight PMMA/silicate hybrid showed virtually no evidence of a glass transition (Tg) from thermomechanical data. 2H NMR showed that the PMMA is extremely mobile in the wet gels, and liquid-like 2H NMR spectra are observed even after prolonged aging of the samples. A 2H static NMR lineshape, indicative of the rigid polymer, does not occur until polymer to solvent ratios of approximately 0.2 (weight basis) are attained. Motional narrowing of the 2H resonances is not observed in the vacuum-dried IPNs below 180 °C. In contrast, pure PMMA shows motional narrowing between 150 and 180 °C. There was little evidence of isotropic motion of the polymer chains, for low polymer concentrations, up to the highest temperature studied (200 °C). The percentage of polymer undergoing isotropic motion increased with polymer content, and as a function of the aging time before solvent stripping.