Siloxane‐containing liquid‐crystalline supramolecular polymers: Preparation and study of thermotropic behavior

Abstract

New hydrogen-bonding supramolecular polymers were obtained from 4,4 0 -bipyridine and different silicon-containing diacids. The formation and thermal stability of these complexes were verified with Fourier transform infrared spectroscopy following the specific absorption bands at 1950 and 2450 cm À1 . Their thermotropic behavior was investigated with polarizing optical microscopy and differential scanning calorimetry. All the obtained supramolecular compounds were liquid crystals within mesophase ranges that depended on the structure of the starting siloxane/silane diacid.

PTC effect in HDPE filled with carbon blacks modified by Ni and Au metallic particles

“…It is well known that bifunctional monomeric units with complementary groups (proton donor and proton acceptor) can be incorporated into the polymer backbone by self‐assembling. The self‐assembly of carboxylic acids as proton donors with pyridyl fragments as proton acceptors is most frequently used in the formation of hydrogen‐bonded structures 11, 12, 25, 28. We choose three commercially available pyridine derivatives, 4,4′‐bipyridyl, 1,2‐bis(4‐pyridyl)ethylene, and 4,4′‐azopyridine, to build supramolecular polymers, SP1 , SP2 , and SP3 , respectively, with above‐synthesized dicarboxylic acid, 2 (Scheme ).…”

“…The presence of the pyridyl ring that is an electron‐deficient aromatic heterocycle with a localized lone pair of electrons in the sp 2 orbital on nitrogen atom improves the electron transporting properties 29. Different from similar compounds reported in literature by us25 and others,12, 30 having liquid crystal behavior, this time we obtained polymers in the form of single crystals, which are also desirable in electronics. The structures of the derived supramolecular polymers were investigated by Fourier transform infrared (FTIR) and proton magnetic resonance ( 1 H NMR) spectroscopy and X‐ray single‐crystal diffraction.…”

“…In the recent past, we tried to modify a PI by alternating its segment, 1,3‐bis(3‐trimellitylimidopropyl)tetramethyldisiloxane, with organic one, 4,4′‐bipyridyl, by noncovalent interactions 25. The resulted compound showed liquid crystal behavior and proved to be effective in gas sensing (CO 2 and NO x ) 26…”

From Amorphous Silicones to Si-Containing Highly Ordered Polymers: Some Romanian Contributions in the Field

“…Several general characteristics of the resulted LC materials are due to these specific behaviors of (poly)siloxanes: lower transition temperatures, larger mesophase range, tendency for formation of smectic mesophases and suppression of the nematic mesophase. In our group a large variety of siloxane-containing LCs has been reported, mainly of azomethine type, but also polyethers, polyesters and H-bond supramolecular polymers [ 119 , 121 , 122 , 123 ]. By varying the siloxane segment lengths and the structure of the adjacent organic flexible groups, tuning of the mesophase range and type, as well as large solubility domains can be achieved.…”

Inorganic and organometallic polymers

“…41 A number of studies have reported the synthesis and study of siloxane polymers bearing rigid mesogens in the side chain structure to impart liquid crystalline properties. [42][43][44][45][46][47][48] Two studies reporting an exciting application for boron-containing polysiloxanes and poly(borosiloxane) as precursors to ceramic materials have been reported. 49,50 A stabilizing matrix for palladium nanoparticles for use in catalysis was obtained by the self-catalyzed hydrosilylation of poly(methylhydrosiloxane)-poly(dimethylsiloxane) copolymers with poly(methylvinylsiloxane)-poly(dimethylsiloxane) copolymers.…”