Cosolvent-free synthesis and characterisation of poly(phenyl-co-n-alkylsilsesquioxane) and poly(phenyl-co-vinylsilsesquioxane) glasses with low melting temperatures

Abstract

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(cyclohexylsilsesquioxane)-Based Hydrophilic Thermoset-Resistant Deep-Ultraviolet-Transparent Glasses with Low Melting Temperatures

“…The absence of cracks in the poly(c-Hx-SQ) and poly(c-Hx-co-Et-SQ) glasses that melted on glass plates (Figure 4b and Table 1) is attributed to the relatively low T g (Figure 6a) and the resulting ability of the structural relaxation to mitigate the mismatch in the thermal expansion coefficients between the samples and glass plates. 28 Figure 7 shows the T g -scaled Arrhenius plots of the viscosity, η, of selected samples and their least-squares fits to the following Vogel−Fulcher−Tammann (VFT) equation 37−40…”

“…Polysilsesquioxanes [poly­(R-SQ)­s] with small alkyl groups (e.g., methyl and ethyl groups) typically form solids that irreversibly cure and do not melt upon heating. − Poly­(R-SQ)­s with longer alkyl groups, such as n -propyl ( n -Pr) and n -butyl ( n -Bu) groups, are viscous or soft at room temperature and difficult to solidify. ,− In contrast, poly­(R-SQ)­s containing aryl groups (e.g., phenyl and benzyl groups) often exhibit thermoplasticity and form stiff clear glasses after melting at ca. 100–200 °C ,,,− because the weak π bonds between the aryl groups readily dissociate upon heating and are reversibly restored after cooling. However, aryl groups exhibit strong optical absorption at wavelengths shorter than ∼300 nm, impairing DUV transparency .…”

Low-Refractive-Index Deep-Ultraviolet Transparent Poly(fluoroalkyl-co-methylsilsesquioxane) Resins Synthesized by Cosolvent-Free Hydrolytic Polycondensation of Organotrimethoxysilanes

“…Silsesquioxanes (SQs) with the general chemical formula of RSiO 3/2 are important components of organic–inorganic hybrid silicates. − Because of their high transparency, chemical stability, and wide variety of organic functional groups, R, SQ polymers (poly­(R-SQ)­s) are desired as transparent optical materials. Poly­(R-SQ)­s with phenyl groups, such as poly­(Ph-SQ)­s and poly­(Bn-SQ)­s, have been studied as thermoplastic materials, ,− whose properties arise from weak π interactions between phenyl groups that readily dissociate upon heating. The refractive index of poly­(Ph-SQ)­s is n D ≃ 1.55.…”

“…In this article we report on the development of transparent, low-refractive-index ( n D < 1.4), and dense (nonporous) amorphous poly­(R-SQ) thermosetting resins that contain linear fluoroalkyl groups as R groups. They were synthesized through a cosolvent-free hydrolytic polycondensation of fluorinated alkyl­trimethoxysilanes and methyl­trimethoxysilane with a dilute acid; this is an environmentally friendly process that does not require the use of cosolvents, such as alcohols and other organic solvents. ,,− …”

Cosolvent-free sol–gel dip-coating of silica films from tetraalkoxysilane–water binary systems: precursor solutions of long pot life and their characterization by nuclear magnetic resonance spectroscopy

“…53)55), 60) This method causes macroscopic phase separation in parallel with gelation, and the resultant macroporous gels are suitable as precursors of silica glasses. This cosolvent-free method has also been applied to organotrialkoxysilanes, and unique silsesquioxanebased materials, including deep-ultraviolet-transparent hybrids, 61) photocurable hybrids, 62) polysilsesquioxane liquids, 63)65) and low-temperature-melting glasses, 66) have been synthesized.…”