Synthesis of multifunctional liquid crystalline epoxy resin embedded cyclic-siloxane chain with Tg-less behavior and enhanced toughness

A novel tetrafunctional mesogenic epoxy monomer with a cyclic-siloxane chain as a central part was successfully synthesized and characterized by proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, differential scanning calorimetry, and polarized optical microscopy. The transition temperature and liquid crystallinity of cyclic-siloxane type mesogenic epoxy were compared with those of linear-siloxane type mesogenic epoxy. Moreover, epoxy thermosets were prepared based on the cyclic- and linear-siloxane type mesogenic epoxy monomers and 4,4′-diaminodiphenylethane. The effects of epoxy backbone moiety on thermal and mechanical properties were investigated in detail. As a result, the cyclic-siloxane type mesogenic epoxy thermoset shows glass transition temperature-less behavior and low coefficient of linear thermal expansion without a decrease in toughness.

Strong hydrophobizer: laterally chemisorbed low-molecular-weight polydimethylsiloxane

We introduce a siloxane chain-based hydrophobizer that exhibits superior thermal and chemical stability compared to the conventional hydrophobizing silane agent under conditions of over 300 °C and pH 2–13.

Chain mobility in bulky carbosilane modified polymeric siloxane systems

Hydrosilylation of bulky carbosilanes [CH2=CHRC(SiMe2R')3, R=CH2, (CH2)3 or SiMe2; R'=Me or Ph] with oligosiloxane precursors [M(D2DH)7D2M, M(D2DH 2)11D2M, PDMSx%-PMHS100-x% (x=85, 50, 30, 0)] was carried out. The relationship between the mobility of siloxane chain and the type of carbosilane moiety, as well as the type of distribution of carbosilane group along the polymer chain, was consecutively studied. Carbosilane substituents, due to their exceptional steric requirements, have been shown to strongly affect thermal properties of siloxane oligomers, implying a substantial change of the chain flexibility and free volume of modified oligomers.