Liquid crystal polymers—VI.: Synthesis and properties of main chain thermotropic polyesters with disiloxane spacers

New thermotropic, liquid crystalline polymers were synthesized, and their thermal properties and the characteristics of their mesophases were studied by differential scanning calorimetry, by use of a hot stage on a polarizing microscope, and by small-angle light scattering. The polymers had an aromatic ester triad mesogenic group and a flexible siloxane spacer in the main chain. Equimolar copolymers containing both siloxane and decamethylene spacers were also prepared and characterized. All the polymers formed nematic phases, and the thermodynamic characteristics of their nematic-to-isotropic phase transitions could be explained on the basis of their structural features.     

X-ray diffraction by thermotropic main-chain polymers with side groups. II. semiflexible polyesters

Semiflexible thermotropic aromatic polyesters with lateral groups were aligned magnetically and mechanically in monodomains after separation into high-molecular-weight (polymer) and low-molecular-weight (oligomer) fractions. Based on the x-ray intensity distributions recorded for a series of seven different substituents in the arylsulfonyl substituted group, a novel smectic structure was determined for H, F, Cl, OCH₃, and CH₃ in the para position while a normal nematic alignment prevailed when it contained Br or NO₂.     

Thermotropic polyesters with main chain isomeric naphthylene,trans-1,4-cyclohexylene,and 2,5-pyridinediyl units: The importance of the order of ester linkages in the mesogenic units

Two new series of thermotropic polyesters were prepared and their mesomorphic properties were investigated. The polymers consist of triad aromatic ester-type mesogenic units with decamethylene spacers. The mesogenic units of the first series are composed of isomeric dihydroxynaphthalene moieties as the central structure flanked by two p-oxybenzoyl groups. In the second series the mesogenic units were of reversed ester linkages: the central moieties, derived from 1,4-naphthalene dicarboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, or 2,5-pyridinedicarboxylic acid, are connected on both sides to p-phenylene structures. Two low molecular weight model compounds with 1,4-naphthylene unit at the center of the mesogenic unit were synthesized and their mesomorphic properties were compared with those of corresponding polymers. It was observed both for the model compounds and the polymers containing 1,4-naphthylene units that the linking order of the ester group in the mesogenic unit exerted a decisive influence on the capability for the formation of a mesophase. Thermal and mesomorphic properties were investigated by DSC, on a polarizing microscope equipped with a hot-stage, and by visual observation of stir-opalescence of the melts.     

Fully aromatic thermotropic liquid crystalline polyesters of substituted 4,4′-biphenols. IV. Homopolyesters with terephthalic acid and copolyesters with terephthalic acid and 4-hydroxybenzoic acid

A series of fully aromatic thermotropic polyesters based on mono-, di-, and tetra-substituted biphenols was prepared by the melt polycondensation method and examined for their thermotropic behavior by a variety of experimental techniques. The homopolyesters obtained from substituted biphenols containing either one phenyl or two phenyl groups as substituent(s) and TA formed nematic melts, but the homopolymers of the substituted biphenols containing either four sec-butyl groups or two tert-butyl groups with TA had melting transitions, T_m, above 400°C. Thus, it was not possible to determine whether they formed nematic melts. On copolymerization with 30 mol % HBA most of the resulting copolyesters had much lower T_m values, compared to those of respective homopolyesters, and the copolymers of the biphenol monomer containing the tert-butyl groups formed a nematic melt at an observable temperature. However, the copolymer of the biphenol with sec-butyl groups still had a T_m above 400°C. © 1993 John Wiley & Sons, Inc.     

Fully aromatic thermotropic liquid crystalline homopolyesters of 3,4′-benzophenone dicarboxylic acid

A series of fully aromatic, thermotropic homopolyesters, derived from 3,4′-benzophenone dicarboxylic acid and various aromatic diols, was prepared by the melt polycondensation method and examined for thermotropic behavior by a variety of experimental techniques. The aromatic diols used in the study were hydroquinone, 2,6-, 1,4-, 1,5-, 2,3-, and 2,7-naphthalenediol isomers. All of the homopolyesters of 3,4′-benzophenone dicarboxylic acid with aromatic diols (except that with 2,7-naphthalenediol) formed a nematic LC phase in the melt. They had the glass transition temperatures (T_g) in the range of 133–164°C, the melting transitions (T_m) in the range 305–360°C and the high thermal stabilities (T_d) in the range of 410–483°C. The 2,6-naphthalenediol based homopolymer had the highest T_m (360°C) and the 2,3-naphthalenediol based homopolymer had the lowest T_m (305°C) among all of the homopolymers of naphthalenediol isomers. © 1994 John Wiley & Sons, Inc.     

Soluble aromatic poly(ether amide)s containing aryl‐, alkyl‐, and chloro‐substituted phthalazinone segments

A series of novel aromatic diamines ( 2 – 4 ) containing the alkyl‐, aryl, or chloro‐substituted group of phthalazinone segments were synthesized via two synthetic steps starting from 4‐(3‐R‐4‐hydroxyphenyl)‐2,3‐phthalazinone‐1 (R = Ph, CH₃, Cl). Three series of aromatic polyamides containing phthalazinone moieties were prepared through diamines 2 – 4 reacting with different aromatic dicarboxylic acids via a direct Yamazaki–Higashi phosphorylation polycondensation reaction. The resulting aromatic polyamides had inherent viscosities in the range of 0.40–0.76 dL/g. The thermal property of the polyamides was examined with DSC and thermogravimetric analysis. The glass‐transition temperatures of these polyamides ranged from 298 to 340 °C. The 10% mass‐loss temperature was above 405 °C under nitrogen. Structures of monomers 2 – 4 and the polymers were confirmed by Fourier transform infrared spectroscopy, ¹H NMR, and mass spectrometry. Good solubility of these polymers in polar solvents such as N‐methylpyrrolidone, dimethylformamide, dimethylacetamide (DMAc), and m‐cresol was observed, and tough, flexible films were obtained from the polymer's DMAc solutions. The effect of the substituted group on the physical property of polymers was also investigated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2026–2030, 2004     

STUDIES ON THERMOTROPIC LIQUID CRYSTALLINE COPOLYESTERS——POLY (ARYLENE TEREPHTHALATE-CO-BUTYLENE TEREPHTHALATE)

A series of copolyesters based on bis(4-hydroxybutyl) terephthalate, terephthaloyl chloride andvarious aromatic diols (i.e. hydroquinone, chlorohydroquinone, bromohydroquinone or dihydroxybi-phenyl) was prepared. ~1H-NMR studies revealed that the monomer units had microstructures closeto random distribution in the chains. The copolymers showed composition-dependent liquid crystal-line properties as verified by visual observation of stir opalescence, polarizing microscope, DSC andX-ray diffration. The copolyesters with aromatic diol contents over a certain extent (for chloro-hydroquinone m≥0.33) were thermotropic with wide liquid crystalline temperature ranges. Theintroduction of chlorohydroquinone into the copolyesters could gradually destroy the crystallinityof the polymers but retain the liquid crystalline characteristics.     

STUDIES ON THERMOTROPIC LIQUID CRYSTALLINE COPOLYESTERS:POLY (ARYLENE TEREPHTHALATECO-HEXAMETHYLENE TEREFHTHALATE)

A series of copolyesters based on terephthaloyl chloride, hexamethylene glycol and hydroquinone or chlorohydroquinone were prepared. The copolymers showed composition-dependent liquid crystalline properties as verified by visual observation of stir-opalescence, polarizing microscope and DSC. The copolyesters with aromatic diol contents over a certain extent (x≥0.2) were thermotropic with wide liquid crystalline temperature ranges. Comparing with the copolyesters based on butylene glycol or ethylene glycol, the minimum fraction of aromatic diol (x value) used to get the liquid crystallinity for all these copolyesters is around 0.2 regardless of the chain lengths of aliphatic glycols. ~1H-NMP studies revealed that copolyesters have microstructure of block sequence distribution and the mesogenie segments shorter than triad with three phenyl nuclei will not provide the liquid crystallinity.     

Studies on thermotropic liquid-crystalline polymers: Part X. Synthesis and properties of crosslinkable aromatic copoly(ester)s containing conjugated double bonds

A series of aromatic copoly(ester)s containing conjugated double bonds was prepared from p-phenylene bis(acrylic acid) (PPBA) with a mixture of methylhydroquinone (MHQ) and various hydroxycarboxylic acids in the presence of diphenylchlorophosphate (DPCP) and pyridine as a catalyst and solvent. The phase behavior of these polymers was studied by differential scanning calorimetry (DSC) and thermal optical polarized microscopy. Under an optical polarized microscope all copoly(ester)s show a nematic thermotropic liquidcrystalline phase. Upon heating, these polymers undergo a photocrosslinking reaction characterized by IR and solubility analysis. This crosslinking reaction also takes place in the liquid-crystalline phase with the retention of the nematic order in the final crosslinked solid. © 1993 John Wiley & Sons, Inc.     

Fully aromatic thermotropic liquid crystalline polyesters of 3,4′-dihydroxybenzophenone

A series of fully aromatic, thermotropic polyesters, derived from 3,4′-dihydroxybenzophenone and various aromatic dicarboxylic acids, was prepared by the high-temperature solution polycondensation method and examined for thermotropic behavior by a variety of experimental techniques. The aromatic dicarboxylic acids used in this study were 2,6-naphthalenedicarboxylic acid, 4,4′-bibenzoic acid, and terephthalic acid. The two homopolymers of 3,4′-DHB with either 2,6-NDA or 4,4′-BBA formed nematic LC phases at 285°C and 255°C and also exhibited isotropization transitions (T_i) at 317°C and 339°C, respectively. The copolymer of 3,4′-DHB with 50% TA and 50% 2,6-NDA also formed a nematic LC phase and had a broader range of LC phase than that of its respective homopolymers. Two other copolymers of 3,4′-DHB, both containing 50% 4,4′-BBA, also formed nematic LC phases at low T_f values. All of the thermotropic polyesters had high thermal stabilities. © 1994 John Wiley & Sons, Inc.     

Direct polycondensation of aromatic dicarboxylic acids and bisphenols with tosyl chloride and N,N-dimethylformamide in pyridine

A Vilsmeier adduct derived from arylsulfonyl chlorides and DMF in pyridine was successfully used as a new condensating agent for the synthesis of aromatic polyesters by the direct polycondensation of aromatic dicarboxylic acids and bisphenols and also of hydroxybenzoic acids. Polymers of high molecular weights (M?_w = 78,000) with relatively narrow molecular weight distribution (M?_w/M?_n ≈ 3.0) were prepared by reacting aromatic dicarboxylic acids with the adduct in pyridine, followed by addition of bisphenols. The polycondensation was significantly affected by the amount of DMF, the nature of the arylsulfonyl chlorides, the conditions of initial reaction of the acids with the adduct, and the rate of reaction with bisphenols. The process was adaptable to the direct polycondensation of hydroxybenzoic acids, affording polymers of high molecular weight (η_inh = 1.73).     

含聚乙二醇柔性间隔段的主链型液晶聚酯的合成

分子结构与液晶行为间的关系是液晶性高分子物理问题研究的核心,通常的液晶性高分子中除液晶性基元外还引入一些相对来说很柔顺的链段,称作柔性间隔段．这是因为人们认识到高分子的液晶行为不只决定于液晶性基元的结构,也受到这些基元间以及基元和间隔段间相互作用的影...     

Liquid crystal polymers. XVIII. Comparison of the properties of aromatic polyesters with different mesogenic units and a common flexible spacer

Four closely related polyesters, with aromatic ester triads and decamethylene spacers, were prepared and characterized for their thermotropic liquid crystalline properties. Two of the polymers, which were based on linear biphenols, formed stable nematic phases, whereas one of the two based on nonlinear biphenols formed a poorly defined nematic phase; the other was not liquid crystalline. Several polymerization reactions and methods were evaluated and structure-property relationships of the polymers are discussed. The concept of “degree of liquid crystallinity” for polymers with poorly defined thermotropic behavior is considered.     

Synthesis and some reactions of naphth[1,2-d]oxazole-5-sulfonic acids

Naphth[1,2-d]oxazole-5-sulfonic acid ( 1 ) has been prepared by the fusion of 4-amino-3-hydroxynaphthalene-1-sulfonic acid with formamide. Interaction of 1 with a number of arenesulfonyl chlorides, aryloxyacetyl chlorides, 1-naphthyloxyacetyl chloride, and chloroacetyl chloride gave 2-(arylsulfonyl)-, 2-(aryloxyacetyl)-, 2-(1-naphthyloxyacetyl)- and 2-(chloroacetyl)naphth[1,2-d]oxaxole-5-sulfonic acids ( 2, 3, 4 and 5 ), respectively. The corresponding sulfonyl chloride of 2 was condensed with amines giving the expected 2-(arylsulfonyl)-naphth[1,2-d]oxazole-5-sulfonamides ( 6 ). Interaction of 5 with hydrazine gave 2-hydrazinoacetyl and disubstituted hydrazine derivatives 7 and 8 . Condensation of 7 with aromatic aldehydes yielded substituted hydrazonoacetyl derivatives 9 . Two moles of 5 react with one mole of hydroquinone in dry acetone in the presence of anhydrous potassium carbonate and potassium iodide gave 1,4-bis[5-sulfonaphth[1,2-d]oxazol-2-ylcarbonyl-methoxy]benzene ( 10 ).     

Synthesis, characterization and photolysis studies on liquid crystalline poly[4-(4′-x-biphenyl)yl-4″-(m-methacryloyloxyalkyloxy) cinnamate]’s

Three series of side chain liquid crystalline polymers containing terminally substituted biphenyl cinnamoyl esters were synthesized and characterized. The para position in the cinnamoyl group was connected with polymer backbone through various even numbers of methylene spacers. The terminal electron acceptor and donor substituted biphenyl groups were linked to cinnamoyl group through ester linkages. Polarizing microscopic and DSC studies confirm the formation of thermotropic mesophase up on heating. All the polymers exhibited nematic/grainy mesophases. The TGA and DSC studies showed that the nature of the terminal substituents have significant effect on mesophase temperatures as well as in thermal stability of these liquid crystalline polymers. UV light promoted photocrosslinking studies reveal that the clear involvement on photocrosslinking efficiency, although they are linked to the olefinic bond of cinnamoyl group through their ester linkage. It is observed that electron-donating group accelerate the photocrosslinking rate, while acceptor group retard the phase of the reaction on the other hand, the unsubstituted polymers show an intermediate rate.     

Thermotropic liquid crystalline polymers with low thermal transitions. I. Low melting thermotropic liquid crystalline homo- and co-polycarbonates

Due to the particular rheological properties of thermotropic liquid crystalline polymers (TLCP), their application for imaging technology has been investigated. The first class of polymers investigated in this study are the thermotropic liquid crystalline polycarbonates prepared from the solution polycondensation of p,p-dihydroxybiphenyl with bischloroformate as the aliphatic flexible spacer. From the variety of bischloroformates employed, smectic TLCP's were generally obtained with the possible presence of a nematic mesostate. The introduction of comonomers such as substituted hydroquinones or bisphenols were found to lower both the melting transitions and mesophasic range of the TLCP. From rheological characterization, the amount of nonmesogenic moieties present in the copolycarbonates were found to correlate with the increase in the melt viscosity of TLCP.     

Synthesis and characterization of heat resistant, pyridine-based polyimides with preformed ether and ester groups

A pyridine-based diamine as a building block for the preparation of heat resistant polyimides was prepared. Reaction of 1,5-dihydroxy naphthalene with 4-nitrobenzoyl chloride resulted in preparation of 5-hydroxy-1-naphthyl-4-nitrobenzoate (HNNB). 5-Hydroxyl-1-naphthyl-4-aminobenzoate (HNAB) was prepared via reduction of nitro group of HNNB. The diamine with built-in ether and ester groups was synthesized by nucleophilic substitution reaction of HNAB with 2,6-dichloropyridine in the presence of K₂CO₃. The obtained diamine was fully characterized and its polycondensation reaction with different aromatic dianhydrides led to preparation of novel heat resistant poly (ether ester imide)s. All the polymers were characterized and their physical and thermal properties were studied.     

Transitions and morphology of a thermotropic liquid-crystalline polyester with a flexible spacer

The mesomorphic transitions, crystallization from the mesophase, and the influence of the specimen preparation method on the solid-state structure of an aromatic polyester containing a triad aromatic ester mesogenic group and a decamethylene flexible spacer in the main chain were studied by DSC, SALS, WAXS, polarizing microscopy, torsional braid analysis, and depolarizing transmittance techniques. The specimens obtained from solution were semicrystalline and exhibited nematic mesophase formation above the melting point T_m, whereas the melt-cast specimens were mesomorphic as cast. A transition from the nematic phase to another mesophase, designated M_x, is proposed to occur below T_m, so this transition is monotropic. It appears that the transition to the M_x mesophase occurs before, and may even be a prerequisite for, crystallization of the melt-cast specimens. The thermal expansion coefficient of the anisotropic melt is close to that of the isotropic melt, and the T_g of the supercooled solid mesophase is close to that of the amorphous phase.     

Linear and A2+B3‐type hyperbranched polyesters comprising phenylbenzothiazole unit: Preparation,liquid crystalline,and optical properties

Novel liquid crystalline (LC) hyperbranched (HB) polyesters comprising phenylbenzothiazole (PBT) unit as mesogen in the interiors were prepared at various feed mole ratios (A₂/B₃) by solution polycondensation of a dioxydiundecanol derivative of PBT (A₂ monomer) with trimesic acid trimethyl ester (B₃ monomer) via A₂+B₃ approach and their LC and optical properties were investigated. Analogous linear polyesters containing the PBT unit in the main chains were also prepared by the solution polycondensation of A₂ monomer with aromatic or aliphatic dimethyl esters. FTIR and ¹H‐NMR spectroscopies indicated that the HB polyesters are produced without gelation during the polycondensation and have degree of branching (DB) of 7–46%. The structures of HB polymers changed depending on the feed mole ratios and the polymer prepared in the mole ratio of A₂/B₃ = 3/2 had the highest inherent viscosity and DB. Acetylation of terminal OH group‐having HB polyesters prepared in excess mole ratios of A₂/B₃ afforded ones bearing acetoxy groups in the terminals. DSC measurements, polarizing microscope observations of textures, and X‐ray analyses suggested that only the terminal OH group‐having HB polymer prepared in the mole ratio of A₂/B₃ = 3/1 form smectic C phase. In the linear polymers, the polymers derived by using the aromatic dimethyl esters had no LC melt, but those from the aliphatic dimethyl esters formed LC smectic C phase. The acetoxy group‐bearing HB polymers showed more stable smectic A or C phase than those with the OH terminals. Solution UV‐vis and photoluminescent (PL) spectra indicated that the linear and the HB polymers have analogous optical properties and display maximum absorbances and blue‐light emission on the basis of the PBT unit, where the Stokes shifts were observed because of intermolecular aggregation effects, but there is a large difference between the optical behaviors of the linear and the HB polymers in film, whose E_g values of the linear polymers decreased and those of the HB polymers vice versa. Quantum efficiencies (Φ) had a tendency of increase in the linear polymers and the HB polymers forming LC phases. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6688–6702, 2008     

Sulfone/ester polymers containing pendent ethynyl groups

Sulfone/ester polymers containing pendent ethynyl groups were prepared by multistep and direct routes. Hydroxy-terminated sulfone oligomers(M _n = 2650 and 8890 g/mol) were reacted with diacid chlorides to yield high-molecular-weight polymers. In the multistep route, a pendent bromo group on the polymer was converted to an ethynyl group. In the direct route, the hydroxy-terminated sulfone oligomers were reacted with a stoichiometric amount of 5-(4-ethynylphenoxy)isophthaloyl chloride to yield high polymers. The pendent ethynyl groups on the sulfone/ester polymers were reacted in the 200 to 300°C range to provide branching and crosslinking. The resultant polymers exhibited higher T_gs and better resistance to chloroform than comparable polymers void of ethynyl groups. Films of the cured polymers displayed good mechanical properties. The synthesis and characterization of the monomer, oligomers, and polymers are discussed.