The Synthesis and Properties of Liquid Crystalline Polyurethanes, Chemically Modified by Polyhedral Oligomericsilsesquioxanes

Abstract

In this work, we report for the first time on the influence of polyhedral oligomericsilsesquioxanes (POSS) on the structure and properties of liquid crystalline polyurethane (LCPU). LCPU/POSS hybrids were synthesized via a two-step method. In the first step, 4,4′-methylenephenyl diisocyanate (MDI) and polytetramethylene ether glycol (PTMG) reacted with functionalized trisilanolphenyl POSS (TSP-POSS) bearing three hydroxyl groups. In the second step, the growing chain was extended with 4,4′-bis(hydroxyhexoxy)biphenyl (BHHBP). FTIR measurements confirmed the chemical bonding between the POSS and LCPU matrix and showed the influence of the silsesquioxane modification on the intensity of hydrogen bonds. The DSC and POM techniques confirmed the formation of liquid crystalline phases. The incorporation of silsesquixanes into the LC matrix leads to higher melting and isotropization temperatures along with the broadening phase transition effect. Scanning electron microscopy showed a good distribution of POSS moieties, both in the bulk and on the surface of the liquid crystalline PU matrix, whereby wide-angle X-ray diffraction (WAXD) patterns revealed halos from both the liquid crystalline and unmodified polyurethane matrix. The stress at the breaking points for LCPU/POSS hybrids containing 50% and 60% of elastic segments is greater than the stress at the breaking point of the reference material (LCPU), what is due to good dispersion of POSS in less elastic matrix. Thermal properties of the LCPU/POSS materials obtained, determined by TGA, revealed that the char residue increased with the amount of POSS for 40% of elastic segments materials.

Fabrication of Liquid Crystalline Polyurethane/Polyhedral Oligomeric Silsesquioxane Nanofibers via Electrospinning

“…The pattern of the matrix is mainly amorphous, with the main halo at 22°. Aro θ of 25°, a sharper peak can be observed, which corresponds to the crystalline str form of a mesogenic unit, which was discussed in our previous works [52,53]. T fluence of POSS on this pattern is minimal.…”

“…The synthesis of liquid crystalline polyurethanes with POSS has already been described in [52,53], along with a detailed chemical characterization. In brief, a series of liquid crystalline polyurethanes containing two types of nanofiller were prepared.…”

“…The synthesis and characterization of this mesogenic unit were reported in Ref. [52]. The reaction was conducted in an inert atmosphere.…”

Environmentally friendly polyurethanes based on non-isocyanate synthesis

“…In other words, the hard and soft segments were completely miscible. The highest T g values were for NIPUs containing DMDPA and PXD diamine, indicating decelerated chain mobility, most likely due to rigid aromatic rings and nitrogen-containing functional groups in the polymer backbone as well as strong hydrogen bonding between the polymer chains, restricting the chains' mobility [59]. Likewise, the NIPU-FADA demonstrated the lowest T g , which could be attributed to long flexible arms that resulted in a significant decrease in the regularity and symmetry of the chain segments as well as a reduction in the density of hydrogen bonding between polymer chains [60].…”

Progress in the Synthesis of Bifunctionalized Polyhedral Oligomeric Silsesquioxane

“…The applications have been extended to the biomedical field due to the biocompatibility of PUs [107]. Even the liquid crystalline PU (LCPU) field, when LCPU was incorporated into POSS, the LCPU/POSS hybrids could show high melting and isotropization temperatures along with the broadening phase transition effect due to the incorporation of POSS [108]. Although PUs have been used in many fields, they still have many limitations, such as poor thermal and moisture stability originating from urethane groups and low mechanical resistance due to the intrinsic hardness of the hard segments.…”