Vinyl‐terminated liquid‐crystalline dendrimers based on dendritic polyols and their siloxane‐based elastomers

Abstract

A new series of side-chain liquid-crystalline dendrimers (LCDs) by grafting vinyl-terminated phenyl benzoatebased promesogens to a novel polypropyleneimine-derived dendritic polyols are reported. Polarized optical microscopy and X-ray diffraction studies show that both the compounds display a smectic-A (SmA) mesophase. The second-generation dendrimer bearing eight-branched promesogens exhibits a more stable SmA mesophase with a wide mesomorphic temperature range. It is demonstrated that ''promoting groups'' in the structure of LCD for the enhancement of mesomorphic stability are unnecessary in the case of strong anisotropic interactions. In contrast to conventional LCDs, these two compounds possess reactive vinyl terminals that endow them with the potential for the preparation of polymeric materials. For the first time, a type of thermoset elastomers is explored from LCDs via hydrosilylation crosslinking reaction of vinyl terminals and siloxane crosslinker. Two-dimensional X-ray diffraction study indicates that the lamellar structures of original dendrimers are reserved in the elastomer networks. Stress-strain curves reveal that these elastomers exhibit excellent elasticity under successive uniaxial compression. The combination of anisotropic structures of rigid units and elasticity of flexible networks in this novel series of elastomers makes them promising candidates for the application in artificial muscles or cartilages.

Stabilization of Bicontinuous Cubic Phase and Its Two‐Sided Nature Produced by Use of Siloxane Tails and Introduction of Molecular Nonsymmetry

“…After 153 days (Figure S3e in the Supporting Information), the POM observation barely detected the presence of optically anisotropic domains after changing the brightness and contrast of the image. Nevertheless, the liquid crystallinity of those samples was still maintained because the wide-angle XRD patterns (Figure S4 in the Supporting Information) only showed two diffuse maxima at around 2θ = 13°and 18°, which originate from the interchain packing of siloxane and hydrocarbon chain segments, respectively, [41][42][43] suggesting no presence of long-range ordering in the direction perpendicular to the molecular long axis.…”

A Highly Versatile Polymer Network Based on Liquid Crystalline Dendrimers

“…J. Sun [30] reported the preparation of vinyl-terminated liquid crystalline dendrimers based on dendritic polyols and their siloxane-based elastomers. This is quite an unexplored topic of research up to now, and therefore, the properties found for these materials open a broad field of possibilities for further investigation.…”