Layer structures. VI. Chiral sanidic polyesters derived from 2,5-bis (dodecyloxy) terephthalic acids and 4,4′-dihydroxybiphenyl

Copolycondensations of (S,S)-2,5-bis(2-methylbutyloxy) terephthaloylchloride with 2,5-bis(dodecyloxy)terephthaloylchloride and with 4,4′-bistrimethylsiloxybiphenyl yielded a series of novel chiral thermotropic copolyesters. These polyesters were characterized by elemental analyses, inherent viscosities, ¹H-NMR spectroscopy, optical rotations, optical microscopy, DSC measurements, and WAXS powder patterns recorded with synchrotron radiation under variation of the temperature. All homo- and copolyesters formed a solid sanidic layer structure with melting temperatures (T_m) ≥ 200°C. A broad enantiotropic nematic or cholesteric phase is formed above T_m with isotropization temperatures (T_is) in the range of 275–325°C. Yet, the T_m of the chiral homopolyester is so high (378°C) that the melting process is immediately followed by rapid degradation. The cholesteric phases of the copolyesters displayed unusual mobile schlieren textures, but a stable Grandjean texture was never obtained. Cholesteric domains consisting of loose bundles of more or less helical main chains are discussed as supramolecular order responsible for the observed textures and their pronounced temperature dependence. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 947–957, 1997     

LC-Polyimides. XIX. Chiral and thermotropic poly(esterimide)s based on N-(4′-caboxyphenyl)trimellitimide and novel chiral spacers

Starting from commercial S- or R-3-bromo-2-methylpropanol, several new spacer diols were prepared. These spacers were polycondensed with the acid chloride of N-(4′-carboxyphenyl)trimellitimide. The resulting poly(ester-imide)s were characterized by elemental analyses, viscosity measurements, ¹H-NMR spectroscopy, DSC- and WAXD-measurements and optical microscopy. The poly(ester-imide)s derived from chiral, aliphatic spacers form layer structures in the solid state, but no liquid crystalline phase. With nonsymmetrical, nonchiral semialiphatic spacers, poly(ester-imide)s were obtained, which form a smectic E or H phase in the solid state, a smectic-A or -C phase in the melt, and a nematic phase, when the spacer possesses an odd number of CH₂ groups. The polycondensation of a chiral semialiphatic spacer yielded thermotropic poly(ester-imide)s with either S- or R-configuration. WAXD patterns measured with synchrotron radiation at various temperatures proved that a layer structure exists in the solid state (smectic-E^* or H^*) and a chiral smectic-A^* or -C^* phase plus a cholesteric phase in the melt. A 1 : 1 blend of the S- and R-polyesters was also studied, but did not show unusual features. © 1995 John Wiley & Sons, Inc.     

New polymer synthesis. LXXXIII. Synthesis of chiral and cholesteric polyesters from silylated “sugar diols”

A series of polycondensation was conducted with the purpose to optimize the reaction conditions for the polycondensation of silylated 2,3-isopropylidene D -threitol with a dicarboxylic acid dichloride. Polycondensation in o-dichlorobenzene or 1-chloronaphthalene at 180–230°C were found to be most satisfactory. Trifluoroacetic acid/H₂O allow an easy cleavage of the isopropylidene group without hydrolysis of the polyester. Ten cholesteric copolyesters were prepared by polycondensation of mixtures of silylated methylhydroquinone and isosorbide, isomannide, or 2,3-isopropylidene threitol with the dichloride of 1,10-bis(4′-carboxyphenoxy)decane. All these copolyesters form a broad cholesteric phase above 200°C. The copolyesters containing 5 or 10 mol % of a sugar diol display a blue Grandjean texture. © 1996 John Wiley & Sons, Inc.     

Liquid-crystalline polyimides, 16. Chiral thermotropic copoly(ester-imide)s based on isosorbide and N-(4-carboxyphenyl)trimellitimide

A series of chiral copoly(ester-imide)s was prepared by polycondensation of N-(4-carboxy-phenyl)trimellitimide with mixtures of isosorbide and phenylhydroquinone. All copolyesters are non-crystalline. They form a cholesteric melt, when containing more than 50 mol-% of phenyl-hydroquinone. Containing 5 or 10 mol-% of isosorbide a “Grand-Jean” texture is detected above 300°C and 350°C, respectively.     

Optically active imidazole-containing polymers

In order to investigate the stereospecificity of enzyme-catalyzed reactions, an optically active copolymer of 4(5)-vinylimidazole and 2,5(S)-dimethyl-1-hepten-3-one was synthesized, and its effects on the solvolytic rates, in ethanol-water, of the p-nitrophenyl and 4-carboxy-2-nitrophenyl esters of 3(R)- and 3(S)-methylpentanoic acid and of the commercially available N-carbobenzoxy-(R)- and (S)-phenylalanine p-nitrophenyl esters were investigated. The optically active comonomer was prepared by thermal decomposition of solid (+)-1-piperidino-2,5(S)-dimethylheptan-3-one hydrochloride, which was obtained from the reaction of 2(S)-methylbutyllithium with 3-piperidino-2-methylpropionitrile. The 3(R)-methylpentanoic acid was prepared in 92% optical purity from L -alloisoleucine via diazotization in concentrated hydrobromic acid and subsequent reductive debromination with zinc amalgam in dilute hydrochloric acid. In the optically active copolymer-catalyzed solvolyses of the optically active esters performed at pH values of 6–8 no significant differences between the solvolytic rates of (R) and (S) isomers of substrates were observed. Poly-L -histidine was also employed as a catalyst for the solvolyses of these substrates. At pH 6.0 in ethanol–water the latter catalyst also failed to exhibit specificity towards (R) and (S) substrates.     

Synthesis and properties of novel aromatic poly(ester-imide)s bearing 1,5-bis(benzoyloxy)naphthalene units

Two series of new aromatic poly(ester-imide)s were prepared from 1,5-bis(4-aminobenzoyloxy)naphthalene (p-1) and 1,5-bis(3-aminobenzoyloxy)naphthalene (m-1), respectively, with six commercially available aromatic tetracarboxylic dianhydrides via a conventional two-stage synthesis that included ring-opening polyaddition to give poly(amic acid)s followed by chemical imidization to polyimides. The intermediate poly(amic acid)s obtained in the first stage had inherent viscosities of 0.41-0.84 and 0.66-1.37 dl/g, respectively. All the para-series and most of the meta-series poly(ester-imide)s were semicrystalline and showed less solubility. Two of the meta-series poly(ester-imide)s derived from less rigid dianhydrides were amorphous and readily soluble in polar aprotic solvents, and they could be solution-cast into transparent and tough films with good mechanical properties. The meta-series polymers derived from rigid dianhydrides were generally semicrystalline and showed less solubility. Except for one example, the meta-series poly(ester-imide)s displayed discernible T_gs in the range 239-273 °C by DSC. All of these two series poly(ester-imide)s did not show significant decomposition below 450 °C in nitrogen or in air.     

Para-ordered polybenzimidazole

A series of novel AB monomers such as 2-[p-carboxyphenyl]-5,6-diaminobenzimidazole hydrochloride have been synthesized. In addition, a new aromatic monomer, 1,3-diamino-4,6-bis(p-toluenesulfonamido)benzene has been prepared in high purity and substituted for 1,2,4,5-tetraaminobenzene in a polymerization with terephthalic acid. Homopolymerization of the AB monomers, and polycondensation of monomer with terephthalic acid in polyphosphoric acid, produced the rod-like para-oriented polymer, poly[1,7-dihydrobenzo(1,2-d: 4,5-d)diimidazole-2,6-diyl-1,4-phenylene]. The yellow polymer was completely soluble in methanesulfonic acid (MSA) and PPA, exhibiting intrinsic viscosities as high as 5 dl/g in MSA, and a blue opalescence in solution. Polymerization at temperatures above 225°C caused crystallization and subsequent precipitation to occur. Polymer thus obtained was completely insoluble in MSA and possessed a high degree of crystallinity as demonstrated by x-ray analysis.     

Synthesis and structure of novel (S)-1,6-dialkylpiperazine-2,5-diones and (3S,6S)-1,3,6-trialkylpiperazine-2,5-diones

Eleven (S)-1,6-dialkylpiperazine-2,5-diones and five (3S,6S)-1,3,6-trialkylpiperazine-2,5-diones were prepared in three steps from the corresponding (S)-α-amino acid esters comprising of reductive N-alkylation, N-acylation and cyclisation. The synthesis of (S)-1,6-dialkylpiperazine-2,5-diones has a broad scope allowing preparation of diketopiperazines with primary and secondary alkyl groups at N(1), while the synthesis of (3S,6S)-1,3,6-trialkylpiperazine-2,5-diones is limited to compounds with primary alkyl groups at N(1). Reductive alkylation of amino acid ester hydrochlorides by catalytic hydrogenation in the presence of a carbonyl compound proved to be a simple, efficient and general method for the preparation of stable (storable) α-alkylamino acid ester hydrochlorides. The structures of the novel compounds were determined by NMR and X-ray diffraction.     

New polymers of carbonic acid. XXV. Photoreactive cholesteric polycarbonates derived from 2,5‐bis(4′‐hydroxybenzylidene)cyclopentanone and isosorbide

Several binary copolycarbonates were prepared by polycondensation of 2,5‐bis(4‐hydroxybenzylidene)cyclopentanone, BHBC, with methylhydroquinone, MHQ, hydroquinone 4‐hydroxybenzoate, HQHB, or isosorbide. Furthermore, five ternary copolycarbonates were prepared based on the aforementioned monomers. All polycondensations were conducted in pyridine with trichloromethyl chloroformate as condensing agent. All polycarbonates were characterized by elemental analyses, viscosity and DSC measurements, IR and ¹H‐ and ¹³C‐NMR spectroscopy, optical microscopy, and the WAXS powder pattern. All isosorbides containing binary and ternary copolycarbonates were found to form a cholesteric melt, but only three of them were capable to form a stable Grandjean texture upon shearing. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1125–1133, 1999     

Aromatic rigid chain copolymers. I. Synthesis,structure, and solubility of phenyl-substituted para-linked aromatic random copolyamides

Four 2,5-biphenylene based difunctional condensation monomers, such as 2,5-diphenyldicar-boxylic acid or phenylterephthalic acid (PTA), 2,5-bis(carbonylimino-4-benzoic acid)biphenyl (2,5-BCIBABP), 2,5-diaminobiphenyl hydrochloride (2,5-DABP.HCl) and 2,5-bis(iminocarbonyl-4-benzoic acid)biphenyl (2,5-BICBABP), have been synthesized and characterized. These monomers were polymerized in combination with terephthalic acid (TA) and p-phenylenediamine (PPD) via the phosphorylation reaction to prepare a series of phenyl-substituted random copolyamides having all amide groups attached to para-positions of the benzene rings. All the copolyamides have been characterized by solubility, solution viscosity, and by differential scanning calorimetry (DSC). Some of these copolyamides have unusual solubility in organic solvents such as N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidinone (NMP) containing dissolved lithium chloride. A few copolyamides were tested for lyotropic behavior and found to form anisotropic solutions at critical concentrations in organic solvents. A randomly distributed unsymmetrical phenyl substituent on the benzene ring of para-oriented wholly aromatic polyamides dramatically changes the solubility and melting point. The phenyl substituent on a terephthalic acid unit is more efficient in decreasing melting point and increasing solubility in organic solvents of aromatic polyamides than the one on a p-phenylenediamine unit. However, the former also introduces a more flexible link in the extended polyamide chain.     

Thermotropic liquid‐crystalline poly(oxadiazole)s with poly(methylene) spacers: Preparation and extraordinary odd–even effect

A novel synthetic procedure for the preparation of poly(oxadiazole)s was developed with nucleophilic substitution of α,ω-alkanediols with oxadiazole-activated bisfluoride. Seven poly(oxadiazole)s were successfully prepared by the solution polymerization of 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and various α,ω-alkanediols [HO (CH₂)_n OH, n = 5–10 or 12] in diphenyl sulfone at temperature greater than 230 °C with K₂CO₃ as a catalyst. The reduced viscosities of the poly(oxadiazole)s were 0.14–0.51 dL/g, and the decomposition temperatures were greater than 350 °C and decreased from 436 to 379 °C with increasing spacer length (n). Corresponding model compounds, consisting of two terminal mesogenic 2,5-bisphenyl-1,3,4-oxadiazole units and central poly(methylene) spacers, were also prepared for comparison. Both the polymers and model compounds exhibited an extraordinary odd–even effect: odd ones showed higher transition temperatures (melting and clearing temperatures). With differential scanning calorimetry, polarized optical microscopy (POM), and X-ray diffraction, we found that the nematic mesophase was the only texture in the melts except for the polymers with longer methylene units (n = 9), in which smectic mesophases were observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 293–301, 2002     

New polymer syntheses. LXXV. 2,5-biaryloxyterephthalic acids and rigid-rod polyaramides derived from them

Several 2,5-bisaryloxyterephthalic acids were prepared by a new method, namely arylation of diethyl-2,5-bistrimethylsiloxyterephthalate. Rigid-rod polyaramides were prepared by polycondensation of silylated diamines with a terephthaloylchloride with two diphenylsulfone side chains. Another polyamide was prepared from 2,5-bis(4′-cyanophenoxy) terephthalic acid and 1,4-diaminobenzene. None of these polyaramides is meltable and their solubilities differ largely. A copolymer of 1,4-diaminobenzene and 3,3′-dimethoxybenzidine is soluble in various organic solvents including polar vinyl monomers. © 1994 John Wiley & Sons, Inc.     

Chiral 1,4-bis-diphosphine ligands from optically active (Z)-olefines

The catalytic asymmetric hydrogenation of prochiral ketones was carried out with Ru(II) complexes prepared from new chiral diphosphine ligands, cis-(R,R)-2,5-bis[(diarylphosphino)]-3-hexenes. These new ligands were prepared from enantiomerically pure (R,R) or (S,S)-(Z)-3-hexene-2,5 diol and enantiomeric excesses up to 85% were obtained in the reduction of 2-benzamidomethyl-3-oxobutanoate, starting material for the synthesis of 4-acetoxy-2-azetidinone.     

A chiral poly(para-phenyleneethynylene) (PPE) derivative

We have investigated the chiroptical properties of novel PPEs containing chiral side chains. The synthesis of poly(2,5-bis[2-(S)-methylbutoxy]-1,4-phenyleneethynylene) (BMB-PPE) was achieved in a Heck-type aryl-aryl cross coupling (M _n = 10 000, D_p = 40). The very good solubility of BMB-PPE allows for a detailed study of its chiroptical properties. Our studies demonstrate that the bisignated CD spectra of BMB-PPE are associated with an intermolecular aggregation phenomena.     

Side chain cholesteric liquid crystalline elastomers: synthesis and phase behaviour

A series of new side chain cholesteric liquid crystalline elastomers (P-2–P-6) containing the nematic crosslinking monomer 4-(10-undecen-1-yloyloxy)benzoyl-4′-allyloxybenzoyl-p-benzenediol bisate (M-1) and the cholesteric monomer 4-cholesteryl 4-(10-undecen-1-yloyloxy)benzoate (M-2) were synthesized. The chemical structures of the monomers and elastomers obtained were confirmed by FTIR and ¹H NMR spectroscopy. Their liquid crystalline properties and phase behaviour were investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction. The effect of the crosslinking units on phase behaviour is discussed. Elastomers containing less than 20?mol?% of the crosslinking units showed elasticity, reversible phase transitions and cholesteric Grandjean texture. The experimental results demonstrated that the glass transition and isotropization temperatures of P-2–P-6 increased with the increasing concentration of crosslinking unit M-1.     

Pyrido[2,3-g]quinolines

The heretofore unknown sym-octahydro-4,9-dioxopyrido[2,3-g]quinoline was synthesized by carboxyethylation of dimethyl 2,5-diaminoterephthalate with -propiolactone with subsequent hydrolysis of the resulting 2,5-bis(-carboxyethylamino)terephthalic acid ester and cyclization of 2,5-bis(-carboxyethylamino)terephthalic acid. The structure of the product was confirmed by the UV and IR spectra and also by reduction to the known sym-octahydropyrido [2,3-g]quinoline.See [7] for preliminary communication.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1535–1537, November, 1970.     

Polymers of carbonic acid. XXIV. Photoreactive,nematic or cholesteric polycarbonates derived from hydroquinone-4-hydroxybenzoate 4,4′-dihydroxychalcone and isosorbide

Numerous polycarbonates were prepared by means of “diphosgene” in pyridine using hydroquinone 4-hydroxybenzoate (HQHB) as mesogenic diphenol. In addition to the homopolycarbonate, binary copolycarbonates of HQHB and 4,4′-dihydroxychalcone (DHC) with varying molar composition were prepared. A series of ternary copolycarbonates were obtained by incorporation of isosorbide. Furthermore, an alternating copolycarbonate of HQHB and isosorbide was synthesized. All polycarbonates were characterized by inherent viscosities, elemental analyses, IR-, ¹H-NMR, and ¹³C NMR spectroscopy, by WAXS powder patterns DSC measurements, and optical microscopy with crossed polarizers. The homopolycarbonate of HQHB and most binary copolycarbonates were semicrystalline materials forming an enantiotropic nematic melt. Particularly noteworthy is the finding that the alternating copolycarbonate of HQHB and isosorbide forms a broad cholesteric phase despite the unfavorable stereochemistry of isosorbide. The ternary copolycarbonates containing isosorbide formed a cholesteric melt and a Grandjean texture upon shearing. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1611–1619, 1997     

Synthesis and characterization of random semi-flexible thermotropic liquid crystalline poly(ester-imide)s

A series of novel poly(ester-imide)s were prepared by the reaction of meta- and para-substituted trimellitimide dicarboxylic diacid chlorides with various diols containing four, five, six, seven, eight, nine, 10, and 12 methylene groups by a solution polymerization technique utilizing refluxing 1,2,4-trichlorobenzene as a solvent. The poly(ester-imide)s were characterized by dilute solution viscosity, infrared spectroscopy, differential scanning calorimetry, and polarized light microscopy. The inherent viscosities of the meta-substituted poly(ester-imide)s ranged from 0.06 to 0.25 dL/g while those of the para-substituted poly(ester-imide)s ranged from 0.10 to 0.65 dL/g and were obviously of higher molecular weight. The meta series were amorphous and showed no mesophase formation. All para-substituted poly(ester-imide)s exhibited monotropic mesophase identified as smectic A order. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterisation of chiral liquid crystalline elastomers containing four-arm crosslinking agent

A new series of side-chain chiral liquid crystalline elastomers derived from M₁ (cholest-5-3-ol(3β)-4-(2-propen-yloxy)]benzoate) and M_C(2,5-[3,5-bis(4-(3-(4-(allyloxy)phenyl)propanoyloxy)benzoyloxy)benzoic acid]isosorbide diester). The structures of monomers and elastomers measured by using Proton Nuclear Magnetic Resonance Spectra (¹H-NMR) and Fourier transform infrared spectroscopy (FTIR) separately are consistent with our design. IIP~VIP all appeared blue Grandjean (GJ) texture on the heating cycle or cooling cycle. The glass sheets of IIP~VIP were made under 150°C and measured its ultraviolet–visible spectrophotometry by PerkinElmer Lambda 950 instrument (Shelton, CT, USA). IIP~VIP all have absorptions at about 481~483 and 561~562 nm. The optical activities were measured at different temperatures on heating and cooling cycles. And the blue selective reflection of IIP~VIP on the round glass sheet can be seen. The elastomers containing less than 6 mol% of the crosslinking units displayed elasticity, reversible phase transition and high thermal stability. The glass transition temperatures reduced first and then increased, the isotropisation temperatures and the mesophase temperature ranges increased first and then decreased with increasing content of crosslinking unit. The thermogravimetric analysis (TGA) results showed that the temperatures at which 5% weight loss occurred (T_d) were greater than 310°C for all the polymers.     

New poly(amide-imide)s syntheses. I. Soluble high-temperature poly(amide-imide)s derived from 2,5-bis(4-trimellitimidophenyl)-3,4-diphenylthiophene and various aromatic diamines

Novel aromatic poly(amide-imide)s with high inherent viscosities were prepared by direct polycondensation reaction of 2,5-bis(4-trimellitimidophenyl)-3,4-diphenylthiophene ( IV ) and aromatic diamines using triphenyl phosphite in the N-methyl–2-pyrrolidone (NMP)/pyridine solution containing dissolved CaCl₂. The diimide-diacid IV was readily obtained by the condensation reaction of 2,5-bis(4-aminophenyl)-3,4-diphenylthiophene ( III ₁) with trimellitic anhydride. The obtained poly(amide-imide)s showed high thermostability. Their decomposition temperatures at 10% weight loss in nitrogen atmospheres were above 550°C and the anaerobic char yield at 800°C ranged from 48 to 68%. Almost all the poly(amide-imide)s showed high glass transition temperatures above 300°C by differential scanning calorimetry (DSC) measurements. These polymers were readily soluble in various organic solvents and could be cast into transparent, tough, and flexible films. Their casting films showed obvious yield points in the stress-strain curves and had strength at break up to 74.2 MPa, elongation to break up to 70.1%, and initial modulus up to 4.56 GPa. The factors affecting the reaction of diimide-diacid IV and 4,4′-oxydianiline in view of monomer concentration, reaction temperature, and amount of CaCl₂ were also investigated. © 1992 John Wiley & Sons, Inc.