Gert Schwarz

New polymer syntheses: 6. Linear and branched poly(3-hydroxy-benzoates)☆

Abstract Synthesis of poly(3-hydroxybenzoate) were conducted in three ways: (a) condensation of the novel monomer, 3-(trimethylsiloxy)benzoyl chloride in bulk and in solution, (b) bulk condensation of 3-acetoxybenzoic acid, (c) condensation of 3-hydroxybenzoic acid by means of phosphorus reagents in solution. The bulk condensation of 3(trimethylsiloxy)benzoyl chloride gave the best results with respect to both yields (89–99%) and molecular weights ( Mn = 10 000–14 000). Because amorphous poly(3-hydroxybenzoate) is soluble in various solvents the molar weights could be determined by both vapour pressure osmometry and 1 H n.m.r. endgroup analyses. Crystalline poly(3-hydroxybenzoate) was only obtainable by solvent induced crystallization; yet not by annealing. Glass transition ( Tg = 145°C) and melting point ( Tm =181°–185°C) were determined by means of differential scanning calorimetry and torsion pendulum. Branched poly(3-hydroxybenzoate) was prepared by condensation of 3-(trimethylsiloxy) benzoyl chloride and 3,5-(bistrimethylsiloxy) benzoyl chloride. Thus, for the first time a branched polycondensate was obtained which did not crosslink regardless of the conversion.

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 1 H- and 13 C-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.

LC-polyimides: 5. Poly(ester-imide)s derived from N-(4-carboxyphenyl) trimellitimide and α,ω-dihydroxyalkanes

Abstract N-(4-carboxyphenyl)trimellitimide was prepared from trimellitic anhydride and 4-aminobenzoic acid and esterified with methanol. Transesterification with α,ω-dihydroxyalkanes in the melt yielded a series of poly(ester-imide)s with varying spacer lengths. These poly(ester-imide)s were characterized by elemental analyses, inherent viscosities, differential scanning calorimetry measurements, wide angle X-ray spectroscopy powder and fibre patterns, including synchrotron radiation measurements at variable temperature, optical microscopy with polarized light, and thermogravimetric analyses. Poly(ester-imide)s with even-numbered spacers can form three different kinds of solid phase, including a smectic glass and a crystalline smectic phase. Fibre patterns of melt-spun fibres indicate a high degree of order for series of subsequent layers, even when any order inside the layers is lacking. Poly(ester-imide)s with odd-numbered spacers crystallize much more slowly and can be quenched from the isotropic melt, so that isotropic glasses can be obtained.

Phase transitions and melting of poly(4-hydroxybenzoate)

Slab-like crystals and needle-like crystals (whiskers) of poly(4-hydroxybenzoate) (poly(4-Hybe)) prepared from 4-acetoxybenzoic acid were studied by means of differential scanning calorimetry and wide-angle X-ray scattering (WAXS) measurements and by microscopy with polarized light. At a heating rate of 20°C min−1 the slab-like crystals display phase transitions at 332, 430–440, 510 and 529°C. The whiskers exhibit these transitions at 353, 430–440, 510 and 532°C. The transition of the whiskers at 353°C is not thermodynamically stable and changes upon repeated heating and cooling to the 332°C transition. The endotherm at 510°C seems to indicate the beginning of the melting process reinforced by thermal rearrangements and degradation. Infra-red spectra indicate a nearly complete change of the chemical structure upon heating above 530°C. WAXS measurements conducted with synchrotron radiation up to 500°C confirm that no melting occurs below this temperature. Yet the WAXS patterns indicate melting (at 405°C) of a 1:1 copolyester of 4-Hybe and 4′-hydroxybiphenylcarboxylic acid. Microscopic observation of the poly(4-Hybe) whiskers revealed that these crystals fade away above 500°C in air without forming a melt.

Poly(thioester)s

Syntheses and properties of aliphatic and aromatic polythioesters (PTEs) were reviewed including polythiocarbonates and polythiourethanes. The content is subdivided into the following sections: PTEs of aliphatic α‐mercapto carboxylic acid, PTEs of ω‐mercapto carboxylic acids, PTEs derived from α,ω‐dimercapto alkanes, aromatic poly(thioester)s, aliphatic poly(thiocarbonate)s, aliphatic poly(thiourethane)s and aromatic polythiocarbonates. The synthetic strategies reviewed in this article include anionic and cationic ring‐opening polymerizations, polycondensations in bulk, polycondensations in solutions, interfacial polycondensations and in vitro enzymatic polycondensations.

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.

New polymer syntheses: 10. Syntheses of high molecular weight poly(4-hydroxybenzoate)s by bulk condensations of 4-hydroxybenzoic acids

Abstract The condensation of 4-hydroxybenzoic acid by means of various carboxylic acid anhydrides, acid chlorides and diphenylcarbonate has been investigated. All condensations were conducted in ‘one-pot procedures’. The average degrees of polymerization ( DP ) were determined by means of 1H nuclear magnetic resonance (n.m.r.) spectroscopic end-group analyses. The bulk condensation of 4-hydroxybenzoic acid by means of acetic anhydride at temperatures between 320° and 350°C was found to be the simplest and least expensive procedure. Yields between 97 and 99% and DP up to 300 were obtained in this way. Bulk condensations of purified acetoxybenzoic acid or condensations of 4-hydroxybenzoic acid with acetic anhydride in an inert solvent gave similar yields and DP . Also, the bulk condensations of 3,5-dimethyl-4-hydroxybenzoic acid, 3-methoxy-4-hydroxybenzoic acid, 3-chloro-4-hydroxybenzoic acid, 3,5-dichloro-4-hydroxybenzoic acid and 3,5-dibromo-4-hydroxybenzoic acid by means of acetic anhydride gave yields above 90%. However, the DP s varied greatly with the nature of the substituents. ‘One-pot procedures’ using a variety of phosphorus derivatives as condensing reagents did not yield pure polyesters. The differential scanning calorimetry (d.s.c.) curves of the substituted poly(4-hydroxybenzoate)s do not show any endotherm, although X-ray diffraction measurements indicate a high degree of crystallinity. The thermogravimetric analyses demonstrate that the thermal stability depends largely on the synthetic procedure.

Polymers of carbonic acid, 31: Cyclic polycarbonates by hydrolytic polycondensation of bisphenol-A bischloroformate

The hydrolytic polycondensation of bisphenol-A bischloroformate in NaOH/CH 2 Cl 2 was studied using triethylamine as the catalyst. Reaction conditions were optimized towards high molar masses. The isolated polycarbonates were characterized by means of SEC and MALDI-TOF mass spectrometry. The fraction of cyclic polycarbonates strongly increased with higher molecular weights and in the best sample only cycles were detectable (up to 50000 Da). The largest cycles can compete with cyclic DNS of microorganisms.

Thermotropic Aromatic Poly(amide-ether)s

Novel poly(amide ether)s were synthesized from aminophenyl-terminated oxyethylene oligomers and terephthaloyl chloride or 4,4′-biphenyldicarboxylic acid dichloride. The polymers were produced in high yield and high molecular weight (ηinh = 0.8–1.9 dl/g), and were characterized by elemental analyses, NMR spectroscopy and viscosity measurements. They showed low solubility in organic solvents, and a remarkable ability to develop high crystallinity, with melting temperatures in the range 300–370°C. Polymers containing biphenylene units formed stable mesophases (smectic) upon melting, as revealed by calorimetry, optical microscopy and X-ray diffraction.

Whiskers: 13. Polyesters based on 4,4′-biphenyldiol and biphenyl-4,4′-dicar☐ylic acid

Abstract Acetylated 4,4′-biphenydiol (ABD) and biphenyl-4,4′-dicar☐ylic acid (BDCA) were polycondensed in inert aromatic reaction media at various temperatures and monomer concentrations. At temperatures ≤300°C oligoesters were obtained, which according to infra-red and 13 C nuclear magnetic resonance cross-polarization/magic-angle spinning spectroscopic characterization preferentially possess two car☐yl end-groups. Furthermore, polycondensations were conducted at 400°C whereby high-molecular-weight polyesters were obtained. Electron microscopy revealed the formation of lengthy crystallites, but true needle-like whiskers were never formed. Analogous polycondensations were conducted with acetylated hydroquinone and BDCA or with ABD in combination with terephthalic acid. Furthermore, all three polyesters were prepared by polycondensation of the free diphenols with terephthaloyl chloride or biphenyl-4,4′-dicar☐ylic acid dichloride in Marlotherm-S at 400°C. Highly crystalline polyesters were obtained whenever the polycondensations were conducted at 400°C in Marlotherm-S, but in all cases the morphology was that of irregular particles. Wide-angle X-ray diffraction powder patterns measured with synchrotron radiation up to 440°C revealed that all three polyesters undergo a gradual transition from an orthorhombic crystal lattice to pseudo-hexagonal and finally to hexagonal chain packing with increasing temperature. These transitions cover a temperature range of more than 400°C. Only in the case of the polyester derived from hydroquinone and BDCA was a reversible first-order phase transition observed around 506°C.