Synthesis and Thermotropic Liquid Crystalline Behavior of Novel Main-Chain Poly(aryl ether ketones) Copolymer Containing Phthalazinone Moiety and Biphenyl Mesogen

Abstract

A novel thermotropic liquid crystalline poly(aryl ether ketones) copolymer containing phthalazinone moiety and biphenyl mesogen named P-5050 was developed by a mild solution polycondensation reaction. The thermotropic liquid crystalline properties were characterized by the means of differential scanning calorimetry (DSC), polarized light microscopy (PLM) and wide-angel X-ray diffraction (WAXD). A thread-like texture was achieved when P-5050 was annealed at 320 C for 1 h, and a typical schlieren texture was observed when shear forces were induced at that temperature. The crystalline-to-liquid crystalline transition (T m ) and the liquid crystalline-to-isotropic phase transition (T i ) appeared in both the first cooling and second heating DSC thermograms. The glass transition temperature (T g ) was 160C and the value for 5% weight loss temperature was 510 C in nitrogen from DSC and TGA determinations, respectively. 2-13It is well-known that liquid crystalline properties are particularly valuable in the applications of high performance engineering materials. For example, the melt viscosities of thermotropic liquid crystalline polymers (LCPs) possessing an isotropic melt state were significantly lower than structurally similar polymers. [14][15][16] In addition, LCPs were also attached importance to their high modulus and a very low thermal expansion in their direction of the macroscopic orientation.A series of thermotropic liquid crystalline poly(aryl ether ketones) copolymers have been prepared since Bennett and Farris firstly reported a kind of thermotropic liquid crystalline poly(aryl ether ketones) copolymers based on 4, 4 0 -biphenol, bulky substituted hydroquinone and 4, 4 0 -difluorobenzophenone in 1994.

Synthesis and characterization of poly(phthalazinone ether ketone ketone) copolymers with 4,4′-dihydroxybiphenyls

“…On the other hand, amorphous PAEKs with diazaphthalene still have the problem of high processing temperature. Sun et al 21 synthesized poly(phthalazinone biphenyl ether ketone ketone) (PPBEKK) with BP, DHPZ and 1,4-bis(4-fluorobenzoyl)benzene (DFKK). PPBEKK has thermotropic liquid crystal phase with reduced melt viscosity.…”