High-Performance Segmented Liquid Crystalline Copolyesters

Abstract

The ability of a multiphase copolymer to exhibit both the physical properties of liquid crystalline and elastomeric polymers enables a variety of emerging applications. Traditional synthetic methods often require many steps to achieve such diversity in a copolymer. This work describes the synthesis and characterization of biphenyl‐containing segmented copolyesters in a single step. A fundamental investigation of the thermal and thermomechanical properties as a function of methylene spacer length demonstrates a relationship between melting temperature and even/odd spacer lengths. DSC and SAXS analysis reveal microphase separation in these randomly segmented copolyesters. The copolymers retain a liquid crystalline morphology despite the incorporation of a flexible oligomeric polyether, and melting and isotropic temperatures ranged from 77 to 167 °C and 117 to 217 °C, respectively. Wide angle X‐ray diffraction provides further insight into the effect of the soft segment on the highly crystalline nature of the segmented copolyesters. Thermomechanical analysis and tensile testing elucidate the effect of hard segment (HS) content and structure. Plateau moduli range from ≈5 to 150 MPa and increasing from 50 to 75 wt% HS doubled tensile strain. This synergy will enable superior fabrication and processing of intricate electronic devices that require high‐thermal properties and mechanical durability.

Annealing effect of thermotropic liquid crystalline copolyester fibers on thermo- mechanical properties and morphology

“…In addition, there is an advantage in synthesizing a thermotropic liquid crystalline copolyester (Co-TLCP) using various monomers because a copolymer with the necessary physical properties can be synthesized using the respective properties of the monomers. 1,6,10,11 Because of these advantages, Co-TLCPs of varying compositions have been extensively developed, some representative Co-TLCPs include Xydar, Vectra, and X7G.1,12 Melt polymerization is a widely used technique, in which the monomer is melted at a high temperature inside an extruder to enable polymerization. Because polymerization rapidly occurs in a single process, it is cost-effective and time-saving, yielding polymers with a higher molecular weight than those obtained from solution polymerization.…”

Annealing effect of thermotropic liquid crystalline copolyester fibers on thermo-mechanical properties and morphology

“…A copolymer TLCP synthesized using a well-designed monomer is easy to process and has excellent physical properties, which can greatly expand its applicability. In addition, a thermotropic liquid crystalline copolyester (Co-TLCP) synthesized using various monomers will possess the necessary physical properties of the respective monomers 3 , 8 , 12 , 13 . Hence, Co-TLCPs of varying compositions, such as Xydar, Vectra, and X7G, have been extensively developed 3 , 14 .…”

Influence of hydroquinone content on thermotropic liquid crystalline copolymers and nanocomposites: thermo-mechanical properties and morphology

“…[7][8][9][10] However, TLCPs containing straight aromatic and aliphatic units can form mesogenic groups arranged in a regular manner by employing exible aliphatic segments of different lengths. 11,12 By the introduction of a exible alkyl group into the rigid main chain, the melting point can be lowered, the solubility of the polymer can be increased, and the compatibility between the matrix polymer and the additive can be increased when used as a composite material. [13][14][15] Therefore, despite the slightly inferior physicochemical properties, improvements in the applicability in several areas may be achieved by increasing the compatibility by using the intermolecular attraction of the chain by employing the alkyl group.…”

“…7–10 However, TLCPs containing straight aromatic and aliphatic units can form mesogenic groups arranged in a regular manner by employing flexible aliphatic segments of different lengths. 11,12…”