Liquid Crystalline Copolyester Research Articles

방향족 고리 함량이 공중합 액정 폴리에스터의 성질에 미치는 영향

방향족 고리 함량이 공중합 액정 폴리에스터의 성질에 미치는 영향

鎖長の異なるアルキル側鎖を有する液晶性コポリエステルが形成する層状構造の磁場配向と気体拡散特性

ピロメリット酸の1,4-ジアルキルエステルと4,4-ビフェノールから合成されたポリエステルは液晶状態を経て独特の層状構造を形成する．これを気体分離材料として応用するために，気体拡散性を向上させる方法を検討した．炭素数18のアルキル側鎖を主成分とし，これより短い側鎖を少量含むコポリエステルを合成し，いずれも高分子鎖が同程度の間隔で配列した層状構造を形成することを確認した．炭素数14のアルキル側鎖成分を20%含むコポリエステルは，炭素数18のアルキル側鎖成分のみから成るポリエステルと比べ，メタンの拡散係数が増大した．このコポリエステルを強磁場下で調製すれば層状構造が磁場印加方向に一軸円筒対称に配向することを確認した．配向試料のメタン拡散係数は，無磁場下で調製し層状構造をランダム配向させた試料の値より大きくなった．共重合化と磁場配向の併用により気体の拡散性は相乗的に向上することが見いだされた．

Effect of phase morphology on water diffusion in phosphorus-containing thermotropic liquid crystal copolyester film

In this paper, effect of phase morphology on water diffusion in phosphorus-containing aromatic liquid crystalline copolyester (P-TLCP) named as poly(-hydroxybenzate-co-DOPO-benzenediol dihydrodiphenyl ether terephthalate) (PHDDT) was investigated by two-dimensional correlation infrared (2DIR) spectroscopy, in order to understand well the relationship between structure and properties of P-TLCP. The phase morphologies of the PHDDT films were observed by polarized light microscope. The experimental results showed that the clear nematic texture, which was observed for PHDDT film treated at 250 °C for 3 min under a nitrogen atmosphere. However, lots of bright spots were observed for untreated PHDDT film due to weak crystallization of PHDDT molecules. Moreover, the density of the untreated PHDDT film (1.1631 ± 0.0257 g/cm−3) was lower than that of the treated one (1.2969 ± 0.0134 g/cm−3), indicating that the arrangement of the molecules in treated PHDDT film was compact in comparison with that in untreated one. Therefore, the average diffusion coefficient of water in treated PHDDT film was lower than that in untreated one. The mechanisms of water diffusion into PHDDT films with different phase morphologies can be obtained through 2DIR analysis in OH stretching and bending bands. It was found that water diffused into the treated PHDDT film by forming moderate hydrogen bonds prior to forming strong and weak hydrogen bonds, while diffused into the untreated one by forming strong and weak hydrogen bonds prior to forming moderate hydrogen bonds. It was also found that the spectral intensity of PO varied prior to that of CO during water diffusion into untreated PHDDT film, which was reversed for treated PHDDT film.

Liquid Crystalline Copolyester Made from Recycled Polyethylene Terephthalate and p-Acetoxybenzoic Acid: Synthesis, Characterization and Blending with Recycled Polyethylene Terephthalate

Liquid Crystalline Copolyester Made from Recycled Polyethylene Terephthalate and p-Acetoxybenzoic Acid: Synthesis, Characterization and Blending with Recycled Polyethylene Terephthalate

Main-chain liquid crystalline copolyesters with a phosphorus-containing non-coplanar moiety

A series of phosphorus-containing main-chain thermotropic liquid crystalline copolyesters named poly(4,4′-biphenylene decanedioate-co-4,4′-(phenylphosphoryl)dibenzoate) (PBPDP) were synthesized by random polycondensation from mesogenic diol 4,4′-biphenol (BP), decanedioic acid (DA) and phosphorus-containing non-coplanar diacid named 4,4′-(phenylphosphoryl)dibenzoic acid (PPDBA). Chemical structures and physical properties of PBPDPs were characterized by Fourier-transform infrared spectroscopy (FTIR), proton and 31P nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and X-ray diffraction (WAXD). Thermal stability of the copolyesters was determined via thermogravimetric analysis (TGA), and the liquid crystalline behaviours were observed using polarizing optical microscopy (POM). Results showed that the introduction of PPDBA into the copolyester could decrease the liquid crystalline temperature (Tlc) and the isotropic temperature (Ti) as a result of both copolymerization and the non-coplanar structure of PPDBA; furthermore, when the molar ratio of PPDBA reached 15%, the copolyester turned into a semi-crystalline polymer and lost its liquid crystallinity. Thermal stability of the copolyester increased with increasing the content of PPDBA, due to the positive contribution of the phosphorus-containing structure.

Synthesis and characterization of thermotropic liquid crystalline copolyester/multi-walled carbon nanotubes composites via in situ polymerization

We present a novel approach for the preparation of thermotropic liquid crystalline copolyester (TLCP)/multi-walled carbon nanotubes (MWCNTs) composites via in situ polymerization. A two-stage polycondensation procedure was employed in our process, where carboxylic acid modified MWCNTs were dispersed in acetic anhydride via ultrasonication prior to being charged to a prepolymerization reactor together with monomers and catalysts for esterification reaction at 130 °C–200 °C. The esterified mixture was then fed into a polycondensation reactor at 280 °C‒320 °C. In this way, fully exfoliated MWCNTs were dispersed in the TLCP matrix at concentrations up to 0.3 wt%. Systematic studies show that well dispersed MWCNTs acted as “pseudo nucleation sites” for the nematic ordering in the adjacent TLCP melt. Thus the extrudates show a smaller core region and higher overall orientational order. Consequently, the addition of MWCNTs is not only effective in improving the mechanical stiffness but also toughness of the composites. For example, the 0.3 wt% TLCP/MWCNT composite shows a 62%, 135% and 145% increase in Young's modulus, tensile strength and toughness, respectively, in comparison with the pure TLCP.

PET in situ composites improved both flame retardancy and mechanical properties by phosphorus-containing thermotropic liquid crystalline copolyester with aromatic ether moiety

A novel phosphorus-containing thermotropic liquid crystalline copolyester with aromatic ether moiety (TLCP-AE) was used to prepare the in situ composites of poly(ethylene terephthalate) (PET)/liquid crystalline polymer. The morphological structure and properties of PET/TLCP-AE in situ composites were investigated using scanning electron microscopy (SEM), capillary rheometer, tensile tests, limiting oxygen index tests (LOI), cone calorimeter and thermogravimetric analysis (TGA). The rheological measurements show that the viscosity ratio of TLCP-AE to PET at 260°C is less than 1, which meets a precondition for TLCP-AE to form fibrils in PET matrix during processing. The mechanical, LOI and cone tests prove that TLCP-AE can improve the mechanical properties and flame retardancy of PET synchronously. Moreover, TGA results exhibit that the initial decomposition temperatures and the final residues of PET/TLCP-AE composites increase with increasing TLCP-AE content.

Erratum: A novel thermotropic liquid crystalline copolyester containing phosphorus and aromatic ether moity toward high flame retardancy and low mesophase temperature

A series of thermotropic liquid crystalline polyesters containing phosphorus and aromatic ether groups (TLCP-AEs) were synthesized from p-acetoxybenzoic acid (p-ABA), terephthalic acid (TPA), 4,4′-oxybis(benzoic acid) (OBBA), and acetylated 2-(6-oxid-6H-dibenz(c,e) (1,2) oxaphosphorin 6-yl) 1,4-benzenediol (DOPO-AHQ). The chemical structure and the properties of TLCP-AEs were characterized by Fourier-transform spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electronic microscopy (SEM), polarizing optical microscopy (POM), limiting oxygen index, and UL-94 tests, respectively. The results showed that TLCP-AEs had low and broad mesophase temperatures (230–400 °C). TLCP-AEs also showed excellent thermal stability; their 5%-weight-loss temperatures were above 440 °C and the char yields at 700 °C were higher than 45 wt %. All TLCP-AE polyesters exhibited high flame retardancy with a LOI value of higher than 70 and UL-94 V-0 rating. The SEM observation revealed that TLCP-AEs had good fibrillation ability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1182–1189, 2010

In situ reinforced and flame-retarded polycarbonate by a novel phosphorus-containing thermotropic liquid crystalline copolyester

Polycarbonate (PC) was blended with various loadings of novel phosphorus-containing thermotropic liquid crystalline copolyester named PHDDT to form the in situ reinforced composites (PC/PHDDT) by flake extrusion. The morphology, thermal behaviors, tensile properties and flame-retardant performances of PC/PHDDT composites were investigated. Results suggested that fine deformation and microfibrillation of PHDDT in PC matrix could be formed during flake extrusion, which was confirmed by both the SEM observation and rheological analysis. With the increase of PHDDT content, the limiting oxygen index (LOI), tensile strength and storage modulus of the composites were enhanced simultaneously, along with the gradually decreased values of the peak heat release rate (PHRR) and the total heat released (THR), indicating the in situ reinforced and flame-retardant PC/PHDDT composites could be obtained.

Fabrication and Thermal Characteristics of Liquid Crystalline Copolyester/OMMT Nanocomposite Films

Liquid crystalline copolyester (LCC)/organically modified-montmorillonite (OMMT) nanocomposite films were prepared by a solvent casting method with different OMMT contents, using p-chlorophenol as a solvent. Both LCC and LCC/OMMT were heat treated to obtain the smectic structure. To examine their internal structure and morphology, the prepared LCC/OMMT nanocomposite films were characterized by an X-ray diffraction method and TEM (transmission electron microscopy). The d-spacing of the silicate layers for each LCC/OMMT nanocomposite film was shifted, indicating that the OMMT particles were dispersed in the LCC matrix and formed intercalated structures. Thermal characteristics of the LCC/OMMT nanocomposite films were investigated by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and thermo-mechanical analysis (TMA). The gel-to-liquid crystal transition (Tc-lc) and degradation temperatures (Td) of both LCC and LCC/OMMT nanocomposite films with different heat treatment time were examined. The Tc-lc and Td of the LCC/OMMT were found to be enhanced compared with those of the LCC film, exhibiting their improved thermal characteristics.

2,3-butanediol based liquid crystalline random copolyester, synthesis and characterisation

A copolyester was synthesized using 2,3-butanediol as one of the diols with phthaloyl chloride as Diacid chloride. 2,5-ditertiary butyl quinol, was used as another diols for the synthesis of random copolymer. A formation of copolyester was confirmed using Ultraviolet (UV), Fourier Transform Spectroscopy Infrared (FTIR), Nuclear Magnetic Resonance(NMR) spectral techniques. Thermal studies were carried out using Differential Scanning Calorimetry (DSC) and Thermo Gravimetric Analysis (TGA). Hot Stage Optical Polarising Microscope (HOPM) was studied to confirm the existences of mesophase. Elemental analysis further confirms the formations for the copolymer. Morphology of the copolyesters was also characterized using Scanning Electron Microscope (SEM). Results of the investigation confirms a relatively new entry copolymer in the family of liquid crystalline copolymers. Key words: Copolyester, thermo gravimetric analysis, differential scanning calorimetry, infrared spectroscopy, nuclear magnetic resonance, scanning electron microscope, characterization.

ChemInform Abstract: Advanced Materials: Trends and Possibilities in Liquid Crystalline Polymers

During the past ten years there has been a sharp increase in interest in the opportunities afforded by R & D in the field of specialty polymers. Interest is mainly being shown in two distinct categories of polymers, namely, (a) polymers which are used in very small quantities to fulfill critical needs as a part of device system, and (b) high-performance engineering polymers which significantly extend their mechanical and thermal properties for structural applications. The first category ranges from advanced resists and insulating layers for microelectronic devices to membranes for filtration systems. The second category encompasses improved matrices for advanced composites as well as liquid crystalline polymers. In the present paper an overview is first given of the emerging opportunities for advanced materials and particularly specialty polymers. The status of work on liquid crystalline copolyesters is then discussed with special emphasis on one of the major problems confronting this field, namely interpreting the microstructure of the copolyesters.

A comparative study of thermotropic LCP and organoclay as fillers in high molecular mass polyethylene with different blending sequences

AbstractThe influences of thermotropic liquid crystalline copolyester (TLCP) on viscosity reduction in high molecular mass polyethylene (HMMPE) filled with organoclay were investigated by controlling the blending sequence. The interactions between organoclay and TLCP in HMMPE create different morphologies and influence rheological properties of the clay/TLCP/HMMPE blends. When the organoclay was blended with TLCP first, large amounts of organoclay formed partially intercalated structures in TLCP, with phase separation occurring at the temperature when TLCP was in the nematic phase, corresponding an antagonistic effect which weakens viscosity reduction ability of TLCP for HMMPE. However, with first blending of TLCP with HMMPE and then adding organoclay into the blend, most of the organoclay enriched on TLCP surfaces in the blend. Such interaction prevents TLCP droplets from coalescing at high shear stresses, enlarging the processing window. A phenomenological model, originally for HMMPE/TLCP systems, was successfully adopted to predict the flow behaviors of clay/HMMPE/TLCP blends. POLYM. ENG. SCI., 50:1679–1688, 2010. © 2010 Society of Plastics Engineers

A novel thermotropic liquid crystalline copolyester containing phosphorus and aromatic ether moity toward high flame retardancy and low mesophase temperature

AbstractA series of thermotropic liquid crystalline polyesters containing phosphorus and aromatic ether groups (TLCP‐AEs) were synthesized from p‐acetoxybenzoic acid (p‐ABA), terephthalic acid (TPA), 4,4′‐oxybis(benzoic acid) (OBBA), and acetylated 2‐(6‐oxid‐6H‐dibenz(c,e) (1,2) oxaphosphorin 6‐yl) 1,4‐benzenediol (DOPO‐AHQ). The chemical structure and the properties of TLCP‐AEs were characterized by Fourier‐transform spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electronic microscopy (SEM), polarizing optical microscopy (POM), limiting oxygen index, and UL‐94 tests, respectively. The results showed that TLCP‐AEs had low and broad mesophase temperatures (230–400 °C). TLCP‐AEs also showed excellent thermal stability; their 5%‐weight‐loss temperatures were above 440 °C and the char yields at 700 °C were higher than 45 wt %. All TLCP‐AE polyesters exhibited high flame retardancy with a LOI value of higher than 70 and UL‐94 V‐0 rating. The SEM observation revealed that TLCP‐AEs had good fibrillation ability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1182–1189, 2010

Synthesis and eutectic behavior of liquid crystalline copolyesters

AbstractA series of liquid crystalline copolyesters, derived from 1,4‐hydroxy‐benzoic acid (HBA), 6‐hydroxy‐2‐naphthoic acid (HNA), terephthalic acid (TA), and hydroquinone (HQ), were prepared; crystallization, melting and solid‐state structure of the copolyesters were studied by using differential scanning calorimetry (DSC) and wide‐angle x‐ray diffraction (WAXD). It was found that the variation of melting point of the copolyesters with increasing HBA mol % exhibits eutectic melting behavior at a constant mole ratio of HNA, and the extrapolated eutectic temperature decreases linearly with increasing HNA mol %. WAXD analysis of the copolyesters indicates that the d‐spacing related to three‐dimensional order increases first and then decreases with increasing HBA mol %. The increase of the d‐spacing, consistent with looser packing of chains, leads to the reduction of melting point and most likely accounts for the eutectic behavior observed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2171–2177, 2009

Synthesis and characterization of main-chain liquid crystalline copolyesters containing phosphaphenanthrene side-groups

Abstract A series of thermotropic main-chain liquid crystalline copolyesters P1–P5 containing 2-(6-oxide-6H-dibenz〈c,e〉〈1,2〉oxaphosphorin-6-yl)-1,4-dihydroxyphenylene (ODOPB) as non-mesogenic unit and 4,4′-dihydroxybiphenyl (DB) as mesogenic unit were prepared by polycondensation with sebacoyl chloride. The thermal and mesogenic properties were characterized by differential scanning calorimetry (DSC), polarizing optical micrography (POM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). It was found that introducing of ODOPB into polyester decreased the melting temperature (Tm) and the isotropic temperature (Ti). The copolyesters P1–P5 exhibited mesomorphic properties even when the molar ratio of the non-mesogenic monomer ODOPB to mesogenic monomer DB reached 6:4 in feed. For explaining the effect of DOPO group on the mesomorphic properties, the X-ray diffraction analysis of a low molecular weight modal compound containing ODOPB was carried out and the results show that the DOPO side-group is parallel with the most-adjacent benzene ring in the main-chain, which reveals the small effect of ODOPB on the mesogenic structure of polyesters. The thermal analysis showed that the incorporation of phosphorus-containing moieties increase the residual char of the formed liquid crystalline polymers. The thermal stability, however, decreases because the O P–O bond is less stable than the common C–C bond.

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

AbstractA 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′‐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 (1H, 13C, and 31P 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. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4703–4709, 2009

Isothermal crystallization kinetics of poly(phenylene sulfide)/TLCP composites

AbstractThe isothermal crystallization kinetics, the morphology, and the melting behavior of melt‐processed composites of poly(phenylene sulfide) (PPS) with a thermotropic liquid crystalline copolyester, Vectra A950, (TLCP) were studied by differential scanning calorimetry (DSC) and optical microscopy. The crystallization behavior of PPS in PPS/TLCP composites is observed to be highly sensitive to Tc and immiscible TLCP content in the composites. The spherulite growth rate, the overall crystallization rate, and the activation energy of PPS in PPS/TLCP composites are markedly depressed by the presence of TLCP. The analysis of the Avrami kinetic parameters (n and k) indicates that blending of TLCP with PPS causes heterogeneous growth process and nucleation mechanisms. At low Tcs, the PPS crystallization rate is faster than that neat PPS with ≤30 wt% TLCP loading whereas at high Tcs it remains almost unchanged. The analysis of the melting behavior of these composites indicates that the stability of PPS crystals and their reorganization is influenced both by the Tcs and the composite compositions. The sizes and the number of spherulites change a great extent with composite composition with a drop of spherulite rapid growth rate, at constant Tc, with increasing content of TLCP in composites. The analysis based on the Lauritzen‐Hoffmann secondary nucleation theory, using present DSC data, indicates that present data predominantly follow a linear growth trend over a present range of Tcs and PPS crystallization in composites still occurs according to regime II kinetics, whereby multiple surface nuclei form on the substrate with multiple nucleation acts commencing before initially formed growth layer is completed. The fold surface free energy of PPS chains in composites is found higher than that of neat PPS, leading to an average higher work of chain folding and is ascribed to a general development of the PPS chain mobility in the composite melt. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers

Effects of phosphorus-containing thermotropic liquid crystal copolyester on pyrolysis of PET and its flame retardant mechanism

In order to compare their inherent flame retardancy and thermal stability, two phosphorus-containing thermotropic liquid crystalline copolyesters (P-TLCP) were synthesized by melting transesterification. Additionally based on the facts that the P-TLCP can work as a functional additive to enhance the flame retardancy and mechanical property of PET, we further studied the flame retardant mechanism. Scanning Electronic Microscope (SEM) observations show that the char from PET/P-TLCP is more compact, therefore more efficiently resists fire and heat attack than pure PET. Moreover, Fourier Transform Infrared Spectroscopy (FTIR) measurements of evolved gas, indicate that P-TLCP decomposes to produce phosphorus-containing small molecular compounds during the pyrolysis process, such that P-TLCP could play a flame retardant role in vapour phase. Furthermore, P-TLCP strongly inhibits the generation of combustible compounds in the pyrolysis of PET, which also helps to resist fire propagation.

A phosphorus‐containing thermotropic liquid crystalline copolyester with low mesophase temperature and high flame retardance

AbstractA novel phosphorus‐containing thermotropic liquid crystalline copolyester with flexible spacers (P‐TLCP‐FS) was synthesized by melt transesterification from p‐acetoxybenzoic acid (p‐ABA), terephthalic acid (TPA), ethylene glycol, and acetylated 2‐(6‐oxid‐6H‐dibenz(c,e) (1,2) oxaphosphorin 6‐yl) 1,4‐benzenediol (AODOPB). The chemical structure and properties of the obtained P‐TLCP‐FS were characterized by Fourier‐transform infrared spectroscopy (FT‐IR), proton nuclear magnetic resonance spectroscopy (1H‐NMR), inherent viscosity measurements, differential scanning calorimetry (DSC), thermogravimetry (TGA), polarizing light microscopy (PLM), and X‐ray diffraction (XRD) analysis. P‐TLCP‐FS had inherent viscosities of 0.92–1.12 dL/g and exhibited low and wide mesophase temperatures, ranging from 185 to 330 °C, which can match with the processing temperatures of most conventional polymers and high flame retardancy with a limiting oxygen index value of 70% and UL‐94 V‐0 rating. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5752–5759, 2008