Poly(phenylsilsesquioxane)s derived from acid-catalysed water–organotrimethoxysilane mixtures are hydrophilic and thermoplastic because of residual SiOH groups, disordered Si–O frameworks, and low average molar masses.

Poly(n‐alkylsilsesquioxane) [poly(R‐SQ)] liquids with R = Et, Pr, or Bu are prepared from acid‐catalyzed n‐alkyltrimethoxysilane – water binary systems through hydrolytic polycondensation followed by aging. The resultant liquids contain a lot of SiOH groups whereas the viscosities remain almost constant during storage at room temperature over a month. Heat treatment for 1 day at 200 °C in N2 yields poly(Et‐SQ) and poly(Pr‐SQ) solids whereas poly(Bu‐SQ) remains viscous. High‐energy X‐ray diffraction measurements confirm that all samples are amorphous and nonporous. The total structure factor S(Q) of poly(R‐SQ)s and amorphous silica are similar, apart from the prominent prepeak observed for poly(R‐SQ)s at Q ≈  0.5 − 0.7 Å−1. This prepeak undergoes a distinct shift to lower Q with an increase in the alkyl chain length. These observations indicate the presence of microscopic inhomogeneity consisting of silica‐rich and alkyl‐rich domains and their ordering with a periodicity of ≈9 − 12 Å both in liquid and solid forms of poly(R‐SQ). Thermal curing modifies S(Q) of poly(Et‐SQ) only slightly. The overall shapes of the total correlation function T(r) are similar between poly(R‐SQ)s and a‐SiO2, suggesting the similarity of short‐range order of Si−O network between these materials.

We describe an analytical method for investigating the signal contrast obtained in near-field scanning microscopy using a metal slit probe. The probe has a slit-like aperture at the open end of a rectangular or a parallel plate waveguide. In our method, the electromagnetic field around the metal slit aperture at the probe tip is calculated from Maxwell's equations in the Fourier domain in order to derive the electrical admittance of a sample system consisting of layered dielectrics as seen from the probe tip. A simple two-port electrical circuit terminated by this admittance is then established to calculate the complex reflection coefficient of the probe as a signal. The validity of the method is verified at millimeter wavelengths by a full-wave high frequency 3-D finite element modeler and also by experiment. The signal contrast when varying the short dimension of the slit aperture, the separation between the probe tip and the sample, and the sample thickness are successfully explained in terms of the variation in the product of the admittance and the characteristic impedance of the waveguide at the probe tip. In particular, the cause of the local minimum in the signal intensity when varying the separation is clarified.

Silsesquioxane (SQ)-based glasses with low melting temperatures were prepared by the cosolvent-free (solventless) hydrolytic polycondensation of organotrimethoxysilanes with cyclopentyl (c-Pe) and cyclohexyl (c-Hx) groups. Copolymers consisting of phenylsilsesquioxane (Ph-SQ) units and c-Pe-SQ units [poly­(Ph-co-c-Pe-SQ)] or c-Hx-SQ units [poly­(Ph-co-c-Hx-SQ)] were melted at 140 °C and formed clear glasses. The glasses prepared by this method contained many residual SiOH groups and exhibited high adhesive strength to microscope glass plates, metals, and several polymers. The glass-transition temperature of poly­(c-Hx-SQ) was lower than that of poly­(Ph-SQ) by only a small margin, whereas that of poly­(c-Pe-SQ) was much lower. The poly­(c-Hx-SQ)-based glasses were stiff at room temperature and transparent in the deep-ultraviolet spectral region (≲300 nm). They formed fragile melts with kinetic fragility parameters as high as ∼0.8. The melts of poly­(c-Hx-SQ) and poly­(c-Hx-co-Et-SQ) exhibited better resistance to thermal curing than that of poly­(Ph-SQ) and maintained thermoplasticity even after heat treatment at 200 °C for 6 h.