Synthesis and characterization of new segmented polyurethanes with side‐chain, liquid‐crystalline chain extenders

Abstract

Liquid‐crystalline, segmented polyurethanes with methoxy–biphenyl mesogens pendant on the chain extender were synthesized by the conventional prepolymer technique and esterification reaction. Two, side‐chain, liquid‐crystalline (SCLC) polyurethanes with mesogens having spacers of six and eight methylene units were prepared. The structures of the mesogenic units and SCLC polyurethanes were confirmed by Fourier transform infrared spectroscopy and 1H NMR. Polymer properties were also examined by solubility tests, water uptakes, and inherent viscosity measurements. Differential scanning calorimetry studies indicated that the transition temperature of the isotropic to the liquid‐crystalline phase decreased with increasing spacer length. Wide‐angle X‐ray diffraction (WAXD) studies revealed the existence of liquid‐crystalline phases for both SCLC polyurethanes. Polarized optical microscopic investigations further confirmed the thermotropic liquid‐crystalline behaviors and nematic mesophases of both samples. Thermogravimetric analysis displayed better thermal stabilities for both SCLC polymers and indicated that the presence of mesogenic side chains may increase the thermal stability of segmented polyurethanes. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 290–302, 2004

Liquid crystalline and photoactive poly[4,4′-stilbeneoxy]alkylbiphenylphosphates

“…The decomposition of all the polymers was completed at 600 C and no further weight loss was observed. The thermal stability decreases with increasing methylene chain length in the polymers [27]:…”

Liquid crystalline and photocrosslinkable poly(4,4′‐stilbeneoxy) alkylarylphosphates

“…The decomposition was completed at 600°C, and no further weight loss was observed. The TGA data suggested that thermal stability and char yield of the polymers decreases with increasing number of methylene units in the following order [42–44]:…”

Polymeric carbon nanocomposites from multiwalled carbon nanotubes functionalized with segmented polyurethane

“…35 M n and polydispersity determined by gel permeation chromatography are 90,400, and 1.68, respectively. The reaction is given in Scheme 1.…”

“…Since characterization of PUD has been published elsewhere, 35 this part will only concern about the characterization of MWNT-PUD. The molecular composition of the resulting MWNT-polyurethane nanohybrids was confirmed by FTIR and WAXD measurements.…”