Liquid-crystalline poly(β-aminoester)s. Thermotropic mesomorphism and degradability in solution

Poly(β-aminoester)s 7 – 12, containing in the repeating unit ethylenebis(carbonyloxy-1,4-phenylene)carbonyloxy groups interconnected by polymethylene segments of different length and coupled by diamino spacers, were synthesized from mesomorphic diacrylates and secondary diamines. The thermal behavior and the solution properties of the polymers were investigated. Depending on the structure of the repeating unit, the polymers were found to give rise to either isotropic or anisotropic melts. The incidence and extension of the mesophase are favored in poly(β-aminoester)s based on even numbered methylene segments and 2-methylpiperazinediyl spacers. The polymer samples were found to degrade at room temperature, when dissolved in solutions containing water, an organic base or an acid. Based on a macromolecular model compound (14) a degradation process is suggested involving a selective cleavage of the benzoate ester groups assisted by the amino groups in β-position.     

Synthesis and thermal properties of liquid-crystalline polyesters with mesogenic units and siloxane spacers in the main chain

Thermotropic liquid-crystalline polyesters with either 4,4″-p-terphenylylene or p-phenylene-oxyterephthaloyloxy-p-phenylene as mesogenic units and dimethylsiloxane spacers in the main chain were synthesized. The thermal behaviour was studied by means of differential scanning calorimetry, polarizing microscopy, and X-ray diffractometry. The polymers show mainly smectic mesomorphism. The transition temperatures were found to be much lower than in the corresponding polyesters containing polymethylene or poly(oxyethylene) spacers.     

Synthesis of polyamides containing 4,4′-azodibenzamido units

Four coloured polyamides containing azo-p-phenylene units were synthesised from 4,4′-azodibenzoic acid and four aromatic diamines employing both interfacial and solution polymerization procedures. The polymers were characterized by their UV and IR spectra, by inherent viscosity measurements and by solubility data. The stability in conc. sulfuric acid and the thermal behaviour are discussed.     

Polymers of carbonic acid, 5. Nematic polyurethanes derived from 4,4′-dihydroxybiphenyl and 4,4′-bipiperidine,ethylene-4,4′-bipiperidine or trimethylene-4,4′-bipiperidine

4,4′-Bipiperidine ( 3a ), 1,2-bis(4-piperidinyl)ethane ( 3b ) and 1,3-bis(4-piperidinyl)propane ( 3c ) were condensed with the dichloroformates of p-phenylene, 2-methyl-1,4-phenylene or 2,5-biphenylylene. Furthermore, two copolyurethanes were prepared either by mixing 3a and 3c or by mixing the dichloroformates for p-phenylene and 2,5-biphenylylene. Inherent viscosities between of 0,6 and 1,7 dl/g were found for the polyurethanes of 3c , but only values below 0,86 dl/g for those of 3a and 3b . The polyurethanes derived from hydroquinone or methylhydroquinone are semicrystalline polymers with a short-term thermostability up to 310°C. The polyurethanes deriving from phenylhydroquinone are amorphous with a thermostability up to 360°C. The homo-and copolyurethanes containing 4,4′-biphenylylene units form a smectic layer structure in the solid state and a nematic melt above the melting point.     

Stabile Polykohlenstoffradikale, 2. Versuche zur Darstellung von Polyradikalen des Triphenylmethyl-Typs,verknüpft über p-Phenylen-Einheiten

As starting materials for the preparation of polyradicals of triphenylmethyl type linked by p-phenylene units bis(4-iodophenyl)phenylmethane ( 5a ) and bis(4-iodo-2,5-dimethyl-phenyl)phenylmethane ( 5b ) were synthesized by a Sandmeyer reaction from the corresponding diamino compounds and subsequently transformed into the corresponding polymeric hydrocarbons 6a and 6b by an Ullmann condensation. In the following step 6a and 6b were brominated at the tert. carbon atom by means of N-bromosuccinimide. The reaction of the resulting poly(4,4′-biphenylylen-α-bromobenzylidene)s ( 7a and 7b ) with mercury afforded the corresponding radicals, the ESR-spectra of which were recorded. From the methyl substituted polymer 7b poly[(2,2′,5,5′-tetramethyl-4,4′-bi-phenylylen)phenylmethylidyne] ( 3 ) was formed, whereas the unsubstituted product 7a was transformed into a para-quinoide polymer with radical properties.     

Polymers containing formamidine groups, 4. Copolyformamidines prepared from triethyl orthoformate,benzidine and various diamines

Fully aromatic and aromatic-aliphatic polyformamidines were prepared by high-temperature solution polycondensation of the appropriate diamines with triethyl orthoformate (TEOF). Copolyformamidines of benzidine (4,4′-biphenyldiamine) with p-phenylene and trans-1,4-cyclohexylene units, respectively, showed liquid-crystalline behaviour. Both series of copolyformamidines differ distinctly in crystallinity. This has been discussed with respect to sequence distribution, which was determined by ¹³ C NMR spectroscopy.     

Poly(amide-imide)s prepared from 4,4′-[1,4(or 1,3)- phenylenebis(isopropylidene-1,4-phenyleneoxy)]dianiline,trimellitic anhydride,and various aromatic diamines

Two imide ring-bearing dicarboxylic acids, N,N′-[1,4(or 1,3)-phenylenebis(isopropylidene-1,4-phenyleneoxy-1,4-phenylene)]diphthalimide-4-carboxylic acid (p-4 and m-4), were prepared via condensation of 4,4′-[1,4(or 1,3)-phenylenebis(isopropylidene-1,4-phenyleneoxy)]dianiline (p-3 and m-3) with trimellitic anhydride. Two series of novel poly(amideimide)s were synthesized by the direct polycondensation of the diimide-diacids p-4 and m-4, respectively, with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents. The inherent viscosities of the resultant poly(amide-imide)s were in the range of 0,43–1,68 dL/g, and most of these polymers were amorphous, as revealed by wideangle X-ray diffractograms. Almost all the poly(amide-imide)s were readily soluble in polar aprotic solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF), and could be solution-cast into transparent, flexible, and tough films. These polymers had glass transition temperatures in the range of 200-267°C and showed no significant decomposition below 450°C, with 10% weight loss being recorded above 485°C in nitrogen or air.     

Preparation and properties of poly(p-phenylene) and polynaphthylene

Poly(p-phenylene), poly(2,6-naphthylene), poly(2,7-naphthylene), poly(1,5-naphthylene), and poly(1,4-naphthylene) were prepared by nickel-catalyzed polycondensation of Grignard reagents from the corresponding dibromides. The polymers were annealed in vacuo. Doping with SbF₅ markedly increase the conductivity of the polymers. Annealed poly(2,6-naphthylene) is the most conductive among the four isomers after SbF₅ doping. The conductivity of doped poly(2,6-naphthylene) and poly(p-phenylene) is about 10^?1 S · cm^?1. Annealed poly(p-phenylene) shows a broad single line ESR signal which changes to a narrow single line upon doping. Superposition of the two signals is observed at the initial stage of doping. Simultaneous conductivity and ESR measurements indicate that the narrow signal is closely related to conductivity.     

Synthesis and 1H NMR study of aromatic poly(amide-thioether)s

The synthesis of aromatic poly(amide-thioether)s by reaction between 4,4′-thiodianiline, 4,4′-thiodibenzoic acid and 4-(4-aminophenylthio)benzoic acid is studied. Depending on the initial monomer ratio, polymers with head-to-head, head-to-tail or statistical distribution of amido groups along the polymer chains were obtained. Corresponding triads effects were observed in the ¹H NMR spectra and assigned. The synthesis of the same aromatic poly(amidethioether)s by reaction between dichlorobenzanilides and Na₂S is also studied. Only the Cl substituents in para position to a carbonyl groups are reactive and a head-to-head poly(amidethioether) was obtained by reaction of N,N′-thiobis(1,4-phenylene)-di-4-chlorobenzamide (2f) with Na₂S.     

Combined liquid-crystalline polymers: Rigid-rod type main-chain polyester with lateral mesogenic groups

A series of combined main-chain side-group liquid-crystalline polymers was synthesized by melt polycondensation from trans-1,4-cyclohexanedicarboxylic acid, chloro-1,4-phenylene diacetate and 6-(4-methoxy-4′-biphenylyloxy)hexyl-1,4-phenylene diacetate. These polyesters combine the features of rigid-rod main-chain LC-polymers and of side-group LC-polymers. Polymers with small fractions of mesogenic side-groups (5 and 10 mol-%) have lower melting points than the parent polymer poly(chloro-1,4-phenylene 1,4-cyclohexanedicarboxylate) but are still liquid crystalline up to their decomposition at T ≥ 400°C. In polymers with larger fractions of mesogenic side-groups (50 and 100 mol-%) partial isomerization of the trans-1,4-cyclohexanedicarboxylate units to the cis-form occurs. The cis units represent kinks which disrupt the rigid-rod main-chain structure, leading to non-crystalline polymers with clearing temperatures below 350°C. The clearing temperatures of a series of polyesters with 100 mol-% mesogenic side-groups and trans contents ranging from 23 to 97% suggest that some interaction between mesogenic side-groups and residual mesogenic segments in the main chain is required for the formation of a liquid-crystalline phase. X-ray diffraction patterns obtained from melt-spun fibers show that the polymers with 5 and 10 mol-% mesogenic side-groups are highly crystalline and have a triclinic unit cell. The mechanical properties of the combined polymers were studied by means of dynamic mechanical thermal analysis (DMTA). Three different mechanical loss processes were observed. The glass relaxation was found to be more pronounced in the polymers with larger fractions of mesogenic side-groups, suggesting that the latter have a plasticizing effect.     

New poly(amide-imide)s syntheses, 6. Preparation and properties of poly(amide-imide)s derived from 2,7-bis(4-aminophenoxy)naphthalene,trimellitic anhydride and various aromatic diamines

An imide ring-containing dicarboxylic acid, 2,7-bis[4-(N-trimellitoyl)phenoxy]naphthalene (1,1′,3,3′-tetraoxo-2,2′-[2,7-naphthylenedioxybis(1,4-phenylene)]di-1H, 3H-isoindole-5-carboxylic acid ( 3 )), was prepared by condensation of 2,7-bis(4-aminophenoxy)naphthalene (4,4′-(2,7-naphthylenedioxy)dianiline) and trimellitic anhydride (1,2,4-benzenetricarboxylic acid 1,2-anhydride). A series of new aromatic poly(amide-imide)s 5 containing bis(phenoxy)naphthalene moieties having inherent viscosities of 0,8–1,57 dL/g were prepared by direct polycondensation of this diimide-diacid 3 with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents in 1-methyl-2-pyrrolidone (NMP) in the presence of calcium dichloride. Polymers 5 show excellent solubility in polar solvents such as NMP, and most of them could be cast into transparent and tough films. Measurements of wide-angle X-ray diffraction revealed that those polymer containing p-phenylene or oxyphenylene groups are partially crystalline. Amorphous members exhibit glass transition temperature in the range of 250–311°C. Thermal analyses indicated that these polymers are fairly stable, and the 10% weight loss temperature were recorded in the ranges of 526–575°C in nitrogen and 481–556°C in air.     

Synthesis and properties of polyamides and poly(amideimide)s based on 4,4′-[1,4(or 1,3)-phenylenebis(isopropylidene-1,4-phenyleneoxy)]dianiline

The diamines 4,4′-[1,4(or 1,3)-phenylenebis(isopropylidene-1,4-phenyleneoxy)]dianiline (p- 3 and m- 3 ) were synthesized in two steps from the condensation of 4,4′-[1,4(or 1,3)-phenylenediisopropylidene]diphenol (p- 1 and m- 1 ) and p-chloronitrobenzene in the presence of K₂CO₃ in N,N-dimethylformamide (DMF), giving the corresponding bis(4-nitrophenoxy) compounds, followed by reduction with the hydrazine/Pd-C system. A series of aromatic polyamides, aliphatic-aromatic polyamides, and poly(amide-imide)s were prepared by the direct polycondensation of the diamines with aromatic or aliphatic dicarboxylic acids and phthalimide unit-bearing dicarboxylic acids in N-methyl-2-pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. In addition, two series of polyamides were prepared from terephthalic acid or isophthalic acid and aromatic diamines with isopropylidene and/or ether linking groups between the phenylene units, and the structure-property relationships of these polyamides were studied. Almost all the resultant polymers were amorphous in nature and could be solution-cast into transparent, tough, and flexible films. Most of the polymers exhibited moderately high thermal stability. Thus, they are considered as new candidates for processable high-performance polymeric materials.     

Effect of flexible spacers in liquid crystalline copolyesters containing a non-linear biphenol moiety

A series of copolyesters 2 containing both linear mesogenic and non-linear non-mesogenic aromatic ester units was prepared and characterized for the ability of the latter to either modify or destabilize the liquid-crystalline (LC) properties of the former. The mesogenic units were formed from the reaction of 1,4-phenylene diacetate ( 3 ) with 4,4′-decamethylenedioxydibenzoic acid ( 5 ), whereas the non-mesogenic units were formed from reaction of the latter monomer with the diacetate of the non-linear biphenol, sulfonylbis(1,4′-phenylene) diacetate ( 4 ). The presence of the flexible spacer in each unit allows the copolyesters to form a nematic phase even at a content of non-mesogenic units as high as approximately 80 mole-%. Copolyester compositions with mesogenic unit contents approaching this limit for LC behavior appear to form melts which contain both nematic and isotropic phases below the isotropization transitions.     

Synthesis and properties of thermotropic polyesters modified with a non-mesogenic rigid group

Four series of copolyesters, namely BB6-DMT, BB5-DMT, BB6-DMI and BB5-DMI series, were prepared by melt polycondensation of dimethyl 4,4′-bibenzoate (BB) with a dimethyl phthalate (DMT: dimethyl terephthalate or DMI: dimethyl isophthalate) and an alkanediol (1,6-hexanediol or 1,5-pentanediol). The homopolyesters poly(hexamethylene 4,4′-bibenzoate) (BB6) and poly(pentamethylene 4,4′-bibenzoate) (BB5) exhibit a smectic phase. The thermotropic liquid crystalline and crystalline properties of the copolyesters are significantly influenced by the presence of the non-mesogenic rigid phthalate unit. All BB6-DMT copolyesters remain crystalline. As x, the molar fraction of the phthalate units in the diacid units, ≧ 0.7 the mesophase of the BB6-DMT copolyesters is destroyed completely. For BB5-DMT copolyesters, the mesophase disappears as x ≧ 0.4, and the copolyesters become amorphous as 0.5 ≦ x ≦ 0.8. The mesophase and the crystallinity of the BB6-DMI copolyesters are destroyed completely as x > 0.5. The BB5-DMI copolyesters lose the mesophase as x ≧ 0.3, and become amorphous as x ≧ 0.4. The results indicate that the non-linear isophthalate unit destroys mesophase and crystallinity of the copolyesters to a greater extent than the para-linked terephthalate unit.     

Reactive poly(2-vinyl-4,4-dimethyl-5-oxazoione) and poly[(2-vinyl-4,4-dimethyl-5-oxazolone)-co-(methyl methacrylate)]s. Synthesis,characterization and chemical modification with 4-methoxy-4′-(β-aminoethoxy)biphenyl

Poly(2-vinyl-4,4-dimethyl-5-oxazolone) ( P₀ ) and poly[(2-vinyl-4,4-dimethyl-5-oxazolone)-co-(methyl methacrylate)]s with increasing content of methyl methacrylate units ( P₁–P₄ ) were synthesized and characterized. NMR spectra were discussed in terms of monomer sequence distribution and tacticity effects. The reaction of 4-methoxy-4′-hydroxybiphenyl ( 1 ) with 2-ethyl-2-oxazoline was utilized to prepare 4-methoxy-4′-(β-aminoethoxy)biphenyl ( 3 ) through the intermediate 4-methoxy-4′-[(N-propanoyl)-β-aminoethoxy]biphenyl ( 2 ). The homopolymer P ₀ and two copolymers P ₂ and P ₃ were functionalized with 4-methoxybiphenyl side groups by reaction with 3 via a ring-opening process in N,N-dimethylformamide (DMF) or 1,2-dichloroethane. The resulting copolymers P₅–P₈ were characterized by ¹H and ¹³C NMR. The highest degree of functionalized units was obtained in DMF at 80°C.     

Aromatic polybenzoxazoles bearing ether and isopropylidene or hexafluoroisopropylidene units in the main chain

A series of poly(o-hydroxyamide)s having high molecular weights were synthesized by means of low-temperature solution polycondensation of 4,4′-[isopropylidenebis(1,4-phenylene)dioxy]dibenzoyl chloride ( 1 ) and 4,4′-[hexafluoroisopropylidenebis(1,4-phenylene)dioxy]dibenzoyl chloride ( 2 ) with three bis(o-aminophenol)s. Subsequent thermal cyclodehydration of the poly(o-hydroxyamide)s afforded polybenzoxazoles. All poly(o-hydroxyamide)s are readily soluble in a variety of solvents, whereas the polybenzoxazoles are insoluble with one exception. The polybenzoxazoles exhibit glass transition temperatures in the range of 218–231°C and are stable up to 500°C in air or nitrogen, with the 10% weight loss temperatures being recorded between 553–607°C in nitrogen.     

Supramolecular chemistry with macromolecules: Macromolecular knitting,reversible formation of branched polyrotaxanes by self-assembly

Mechanically linked branched polymer 10 was prepared via rotaxane formation by self assembly (“knitting”) of poly[bis(5-methylene-1,3-phenylene)-32-crown-10 sebacate] ( 4 ) and preformed polyurethane 9 containing N,N′-bis(β-oxyethyl)-4,4′-bipyridinium 2PF₆⁻ (“paraquat”) moieties in tetrahydrofuran (THF). The interpenetrating structure resulting from “knitting” the bipyridinium units of the polyurethane through the crown ether cavities of the polyester structure was proved by its color, NMR studies and gel permeation chromatography (GPC) measurements. In accord with its equilibrium nature, the branching process (rotaxane formation) was reversible depending on the solvent and temperature. The branched material was soluble because the two polymeric components were designed to have relativley low molecular weights and the polyurethane to contain only about two paraquat units, so as to be able to carry out solution characterization. However, extension of this concept to higher molecular weight and/or more highly functionalized systems provides interesting possibilities for reversible processing of thermoset-like materials and production of new types of polymeric supermolecules with potentially interesting and controllable properties.     

Syntheses of polymers having imidazolidinone rings

4,4′-Diaminodiphenylmethane and 1-(p-chlorophenyloxycarbonyl)aziridine gave 1,1′-(methylene-di-p-phenylene)-bis-(1,3-imidazolidine-2-one). The bis-imidazolidinone reacted with formaldehyde or acrylonitrile to give 1,1′-(methylene-di-p-phenylene)-bis-(3-hydroxymethyl-1,3-imidazolidine-2-one) or 1,1′-(methylene-p-phenylene)-bis-[3-(2-cyanoethyl)-1,3-imidazolidine-2-one] respectively. The bis-methylol derivative gave a polycondensation product on standing in dichloroacetic acid. The dicarboxylic acid which was obtained by treating the bis-cyanoethyl derivative with concentrated hydrochlorie acid gave high molecular polyamides having imidazolidinone rings in the polymer chain by the reaction with hexamethylene diamine or m-xylylene diamine.     

Synthese neuer pseudoleiterpolymere mit 7H-benzimidazo[2,1-a]benzo[d,e]isochinolin-7-on-3,11-diyl-einheiten in der hauptkette

A series of novel semi-ladder polymers containing 7H-benzimidazo[2,1-a]benzo[d,e]isoquinolin-7-on-3,11-diyl units in the chain was prepared by one-step high temperature solution polycondensation of 4,4′-oxy-,4,4′-carbonyl-, and 4,4′-sulfonyldi-1,8-naphthalenedicarboxylic anhydride ( 1a - c ) with 2,2′-diamino-4,4′-oxydianiline ( 2 ) or 2,2′-diamino-4,4′-hexafluoroisopropylidenedianiline ( 4 ). The similarity of the IR and UV spectra of the polymers and the model compounds 7 a- c confirms the presence of the benzimidazobenzoisoquinolinone rings in the polymer chain. All the resulting polymers have excellent thermal stability both in argon and in air. The polymers prepared from 4 are soluble in 1-methyl-2-pyrrolidone and phenol/1,1,2,2-tetrachloroethane.     

Poly(2,5-dialkoxy-p-phenylene)s—synthesis and properties

The synthesis of poly(2,5-dialkoxy-p-phenylene)s (PPP) by palladium-catalyzed polycondensation of 2,5-dialkoxy-4-bromophenylboronic acids is described. Number-average degrees of polymerization of ca. 30 have been reached at best. The characterization of the polymers by NMR, IR, UV-VIS and fluorescence spectra, data on the bulk structure obtained by X-ray methods, melting behavior and thermal stability are reported. PPP's with long alkoxy side chains exhibit a layered phase structure, those with short or branched alkoxy side chains, cylindrical packing. Poly(2,5-dibutoxy-p-phenylene) was prepared with chain lengths 7 ≤ P_n ≤ 30. The polymer with P_n of 30 shows thermal transitions in the bulk phase at 182°C and 227°C. It forms an anisotropic melt above 227°C which only starts decomposing if heated above 300°C. The polymers of shorter chain length show isotropic melts, with the melting point strongly depending on chain length.