We found both nucleation-growth-type and spinodal-decomposition-type transformation from one liquid state to another in a "molecular liquid," triphenyl phosphite (TPP). Binodal and spinodal temperatures of this transition at ambient pressure were determined by the characteristics of morphological evolution, domain-growth kinetics, and rheological evolution. Furthermore, a distinct thermal signature of the glass transition of a second liquid was also detected in addition to that of an ordinary liquid. These findings strongly suggest the existence of a liquid-liquid transition; more precisely, a transformation of one supercooled liquid to a glassy state of another liquid, in TPP.

It has been found that nanostructured organic/inorganic composites, in which nanometer-sized inorganic inclusions are uniformly dispersed in and fixed to a matrix polymer, can modify the property of the matrix polymer while suppressing Rayleigh scattering to exhibit preferable transparency. Rather, when compared with the transparency of a matrix polymer alone, the composite could exhibit better transparency as the content of inorganic inclusions increases. Furthermore, because the refractive index of the composite agrees well with the Maxwell-Garnett model, it is suggested that synergetic effects obtained by the bulk properties of both the matrix polymer and inorganic inclusions can be exhibited. Such a potential has been verified by applying the composites to optical waveguides and optically athermal materials.

The authors have demonstrated stimulated emission from polymer-based planar waveguide doped with Eu–Al nanoclusters under continuous-wave optical pumping. For the waveguide sample with a nanocluster concentration of 5.0wt%, amplified spontaneous emission was observed in the spectra of the light decoupled from the waveguide edge under a pumping density of 0.16–1.55W∕cm2. The optical gain coefficient was 0.92mm−1 when pumped at 1.55W∕cm2. The well-suppressed concentration quenching and multiphonon quenching may cause the high-gain and low-threshold optical amplification. These results show that the Eu–Al nanocluster is a promising material for polymer-based solid-state lasers and waveguide-type optical amplifiers.

We have fabricated a planar poly(methyl methacrylate) (PMMA) optical waveguide doped with 10 wt % Eu-Al nanoclusters, and have successfully demonstrated optical amplification at 610 nm excited by a N 2 laser ( ¼ 337 nm). The gain of the optical amplification was found to be as high as 5.57 dB/mm, which, to the best of our knowledge, is the highest observed for various rare-earth (RE)-doped planar optical waveguides. An Er-Al-nanocluster-doped PMMA optical waveguide has also been successfully fabricated, and guided emission at around 1.55 mm has been observed in spite of the large absorption loss induced by PMMA. The RE-metal nanoclusters can therefore be regarded as promising candidates as the active materials for polymer-based waveguide-type optical amplification devices.