Synthesis and Characterization of New Liquid Crystalline Thermoplastic Elastomers Containing Mesogen-Jacketed Liquid Crystalline Polymers

Abstract

In order to improve the high-temperature performance of thermoplastic elastomers (TPEs), we designed and synthesized a new kind of ABA triblock copolymer containing a mesogen-jacketed liquid crystalline polymer (MJLCP), poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS), as the hard blocks and polybutadiene (PB) as the soft block. The triblock copolymer, PMPCS-b-PB-b-PMPCS (M-B-M), was synthesized by ring-opening metathesis polymerization in the presence of a chain transfer agent and atom transfer radical polymerization. The glass transition temperature (T g ) of the PMPCS hard block is 110−118 °C in the triblock copolymers. In addition, the liquid crystalline (LC) phase of PMPCS is stable before thermal decomposition. All the triblock copolymers form lamellar microphase-separated structures, as demonstrated by small-angle X-ray scattering and transmission electron microscopy results. The triblock copolymer (M-B-M-55) with a mass fraction of 55% of PMPCS exhibits typical properties of an LC thermoplastic elastomer (LCTPE). The maximum elongation at break and the tensile strength of M-B-M-55 are 736% and 10.6 MPa, respectively, and the stretching strength at 300% is 6.9 MPa. Above the T g of PMPCS, the LC phase of PMPCS provides new physical cross-linking points in the LCTPEs, and the triblock copolymer M-B-M-55 still shows a relatively high modulus.

SET-LRP from Programmed Difunctional Initiators Encoded with Double Single-Cleavage and Double Dual-Cleavage Groups

“…Noteworthy examples are disulfide-containing initiators, − which cleave upon exposure to a highly reducible environment and therefore can serve to prepare redox-responsive nanoplatforms for cellular delivery applications by means of glutathione. , Interestingly, von Delius and co-workers demonstrated that disulfide-centered polyacrylates can also split into two equally sized fragments when exposed to ultrasound activation or dynamic covalent disulfide exchange . Other difunctional initiators containing cleavage entities such as hemiacetal esters (cleavable by harsh acid conditions or temperature), , Diels–Alder adduct (temperature), 2-nitrobenzyl esters , and ethers (UV light), 2-(pyridine-2-yl)­ethyl carboxylate esters (temperature), and olefin (ozone) , have been reported. As can be seen from Figure b, most of these initiators contain a single-type labile linkage.…”

Liquid crystalline epoxy resin with improved thermal conductivity by intermolecular dipole–dipole interactions

“…To maximize the MFP of phonon in polymers, or to minimize the phonon scattering, it is necessary to enhance the crystallinity and the orientation of the polymers . Therefore, epoxy resins bearing liquid crystalline (LC) mesogen were suggested as matrix with enhanced thermal conductivity …”

Functional liquid crystalline epoxy networks and composites: from materials design to applications

“…However, they show low values of thermal conductivity (<0.3 W mK −1 ). In this frame, LCENs have the potential to efficiently act as heat-dissipating materials as they exhibit thermal conductivity values as high as 0.89 W mK −1 [101,102] This is due to their anisotropic, highly oriented LC domains that promote heat transfer through a phonon vibration mechanism. By compounding with suitable fillers, further improvements of thermal conductivity of LCENs can be realised [103].…”