A kinked unit‐containing thermotropic liquid crystalline copolyester with low glass transition temperature and broad phase transition temperature

Abstract

A novel phosphorus-containing thermotropic liquid crystalline copolyester with kinked unit named as poly(hydroxybenzate-co-DOPO-benzenediol dihydrodipheyl ether terephthalate) (PHDDT) was synthesized successfully by melting transesterification from terephthalic acid (TPA), p-hydroxybenzoic acid (p-ABH), 2-(6-oxid-6H-dibenz(c, e) (1,2) oxaphosphorin 6-yl)1,4-benzenediol (DOPO-HQ), and 4,4 0 -dihydroxydiphenyl ether (DOP). The chemical structure, the mesophase behavior, and the thermal properties of the copolyesters were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy ( 1 H, 13 C, and 31 P NMR), wide-angle X-ray diffraction, polarizing light microscopy (PLM), differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. Results suggested that PHDDTs exhibited the typical nematic mesophase that occurred at low temperatures and maintained in a broad temperature range from 230 C to higher than 400 C, and had low glass transition temperature ranging from 154.5 to 166.9 C. The novel phosphorus-containing thermotropic liquid crystalline copolyester will have a potential application in preparing various in situ reinforced polymer materials with excellent mechanical properties and flame retardancy.

Rheological, thermal, and mechanical properties of phosphorus‐containing wholly aromatic thermotropic liquid crystalline polymer‐filled poly(butylene terephthalate) composites

“…It is known that the thermal stability is generally related to the mobility of macromolecular chains, which is mainly dependent on the structure of each component. As reported by Huang et al [13], more rigid groups in TLCP bring its higher modulus. Figure 4 illustrates the storage modulus of neat PBT and PBT/TLCP composites as a function of temperature, measured through DMA.…”

“…As the temperature approaches to 700°C, the content of the residue char is 10.3 wt% for PT30, while in neat PBT 1.7 wt% residues are left. According to the study of Huang et al [13], the T 5wt% and residues of neat TLCP are 443°C and 43.5 wt%, respectively. Hence, the char residues of PT30 would be 11.3 wt% in theoretical, which is close to the experimental result.…”

Aromatic liquid crystalline copolyesters with low Tm and high Tg: Synthesis, characterization, and properties

“…According to the Gibbs free energy equation T m = Δ H /Δ S , when the chemical reaction is at equilibrium state, the methods whatever can decrease Δ H or increase Δ S can be adopted to decrease the melting temperature. Based on this principle, several effective ways have been developed by researchers via incorporating asymmetrically substituted monomer, kinked or nonlinear comonomer, flexible spacers to synthesize desirable TLCP. Most of these ways were investigated extensively except by utilizing a kinked monomer.…”

Improved antiplatelet therapy? There's a generic thought

“…The concept of achieving thermal stability, flame retardancy, and liquid crystalline behavior through combination of phosphorus‐containing monomers and aliphatic moieties into aromatic mesogenic moieties was successfully applied for the control of thermal stability, phase transitions, and crystallinity degree of aromatic–aliphatic phosphorus‐containing copolyesters 29, 31–33. Recently, Wang and coworkers have paid attention to the use of phosphorus‐containing TLC polymers for flame retardation on other thermoplastic polymers 34–36. Thermal stability and flame retardancy of these polymers were excellent, but the mesophase and melting temperatures need to be more decreased.…”