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l -Lactide was polymerized by means of neat SnOct2 with variation of LA/Cat ratio, temperature and time. The resulting cyclic polylactides crystallized spontaneously at 160 °C or below, but needed nucleation via mechanical stress at 165 or 170 °C. All the crystalline polylactides obtained directly from ROP above 120 °C had melting temperatures (Tm) above 189 °C (up to 194.5 °C). SnOct2 also enabled transformation of low Tm poly( l -lactide)s (Tm

Telechelic poly(e-caprolactone)s or poly(d,l-lactide)s were prepared by SnOct2-initiated polymerization of e-caprolactone (eCL) or d,l-lactide (d,l-LA) coinitiated with 1,4-butane diol or tetra(ethylene glycol). These telechelic polyesters were in situ functionalized with 3-isocyanatopropyl trimethoxysilane (IPTMS) by SnOct2-catalized addition of the OH-endgroups. Analogously, star-shaped polyesters were synthesized and functionalized using 1,1,1-trishydroxymethyl propane or pentaerythritol as coinitiators. All functionalized polymers were characterized by 1H NMR and MALDI-TOF mass spectra. In crosslinking experiments with oligo(ethylene–glycol)s the trimethoxysilyl groups proved to be 10–30-fold more reactive than triethoxysilyl end-capped polyesters.

Dimethyladipate or dimethylsebacate were polycondensed with an excess of 1,2-ethane diol in bulk using two different temperature/time programs. Bismuth(III) n -hexanoate (BiHex 3 ), tin(II)2-ethylhexanoate (SnOct 2 ) and titanium tetrabutoxide were used as catalysts. Only the bismuth catalyst yielded clean telechelic polyesters having two ethylene glycol endgroups. With SnOct 2 cyclic oligoesters were obtained as byproducts. Ti(OBu) 4 yielded OH-terminated linear chains containing large amounts of diethylene glycol units (detectable up to three ether groups per chain). Furthermore, small amounts of cycles were also formed. Acid-catalyzed polycondensations of ethylene glycol with sebacic acid gave low yields of low oligomers, part of which contained diethylene glycol units.

Bismuth (III) subsalicylate, a commercial drug, was used as catalyst for 1,4-butanediol-initiated copolymerizations of e-caprolactone (eCL) and glycolide (GL). Telechelic copolyesters having two OH-endgroups and predominantly alternating sequences were obtained. These copolyesters are amorphous with glass transition temperatures (Tgs) below −30 °C. In a second series of polymerizations, in situ chain extension with l -lactide (LLA) was performed, whereby A-B-A triblock copolymers were obtained without significant transesterification between A- and B-blocks. Finally, these A-B-A triblock copolymers were transformed into multiblock copolymers by chain extension with 1,6-hexamethylene diisocyanate. The block copolymers were characterized by 1H and 13C NMR spectroscopy, by viscosity, SEC and DSC measurements.

Germanium, tin, titanium and zirconium tetraalkoxides were polycondensed with poly(ethylene glycol)s (PEGs) and poly(tetrahydrofuran) (PTHF) diols at temperatures between 100 and 200 °C. The lengths of the diols were varied from PEG-300 over PEG-400, PEG-600 and PEG-1000 to PEG-2000. In the case of PTHF diols number average molecular weights ( M n s) of 650, 1000 and 2000 were used. When Ge(OEt) 4 was polycondensed, all reaction products were soluble. In the case of Sn(OtBu) 4 , all products obtained from diols with M n s ≥600 Da were soluble, whereas a stiff gel was obtained from PEG-400. From Ti(OnBu) 4 and Zr(OEt) 4 soluble spirocycles were only obtained for diols with M n s≥1000, whereas the shorter diols yielded stiff networks. In the case of Ti(OnBu) 4 and PEG-1000, it was observed that at temperatures ≤120 °C initially a stiff gel was formed obviously by a kinetically controlled polycondensation. Upon heating to 140 °C this gel underwent an irreversible transformation into syrupy, soluble spirocycles due to equilibration of Ti–O–R bonds. The thermodynamic stability of the spirocycles is explained by strain-free rings and a gain in entropy. Preliminary experiments with the spirocycles of zirconium proved their usefulness as initiators for the ring-expansion polymerization of e-caprolactone.

Three monomers were prepared from 4,4-bis(4′-hydroxyphenyl)valeric acid (BHVA) namely its methylester (BHVAM), its bis-acetylated methylester (BAVAM) and its 4,4-bis(4′-acetoxyphenyl)valeric acid (BAVA). All three monomers were polycondensed in bulk at various temperature profiles using Ti(OBu)4, Co(OAc)2, Mn(OAc)2, Sn(OAc)2 or Bu2Sn(OAc)2 as transesterification catalysts. The structure of the resulting ‘hyperbranched’ polyesters were characterized by 1H NMR spectroscopy, MALDI-TOF mass spectroscopy and in selected cases by SEC. Regardless of the reaction conditions only low oligomers almost free of cycles were obtained from the methylesters BHVAM and BAVAM. Higher molecular weights and high contents of cycles were obtained from polycondensations of BAVA. The content of cycles increased with the conversion. Hyperbranched polyesters with cyclic core were detected up to masses around 10,000 Da. The reactivities of the three hyperbranched monomers were compared with those of bisphenol-A plus dimethyl sebacate or acetylated bisphenol-A plus sebacic acid in ‘linear polycondensations’ and close analogies were found.

Various poly(ester imide)s, PEIs, were prepared from N-(4-carboxyphenyl) trimellitimide (4-CPTI) or from N-(3-carboxyphenyl) trimellitimide (3-CPTI). Various catechols or 5-methylresorcinol served as comonomers. MALDI-TOF mass spectrometry revealed that the PEIs derived from 4-CPTI and catechols contain significantly more even than odd cycles, whereas the PEIs derived from 3-CPTI and catechols contained almost equal amounts of odd and even-numbered cycles. The predominant formation of even-numbered cycles is explained by a ‘hair pin’ conformation of the growing oligomers based on strong donor–acceptor (DA) and dipole–dipole interactions. The resulting ‘collapsed cycles’ with parallel alignment of the 4-CPTI units have the consequence that most cyclic oligomers and polymers possess mesogenic properties and form a nematic melt. The temperature range of the nematic phase depends on the substituent of the catechol units.

Et 3 GeOMe-initiated polymerizations of e-caprolactone were studied at six different temperatures, but even at 180 °C the conversion was below 50% after two days. Ge(OEt) 4 proved to be more reactive and a temperature of 120°C was found to allow for a nearly quantitative conversion after two days. All four ethoxy groups were active in the initiation process, but a broad molecular weight distribution was found and a low percentage (presumably < 1 mol%) of cyclic oligomers was formed. Ring-expansion polymerization initiated with a spirocyclic germanium alkoxide was feasible at 140 °C and yielded a molecular weight distribution quite different from that obtained with Ge(OEt) 4 . The monomer/initiator (M/I) ratio was varied, and it was found that the average degree of polymerization (DP) did not agree with the M/I ratio for M/I's above 200. Addition of 4-nitrobenzoyl chloride to the hot virgin reaction mixtures yielded poly(e-CL) chains having functional end groups but the degree of functionalization never exceeded 80%.

Starting from 1,4-diaminobutane and trimellitic anhydride a bisimide dicarboxylic acid was prepared which was transformed into its diethyl ester. This imide monomer was polycondensed with mixtures of 1,4-dihydroxybutane and poly(tetramethylene oxide) (PTMO) diols having number average molecular weights (Mns) of 650, 1000 or 2000 Da. For each PTMO diol, the weight fraction of the hard segments was varied from 30 over 40 and 50–60%. For the PTMO diols 1000 and 2000, macrophase separation was observed during polycondensation. This problem was solved in the case of PTMO-1000 by a PTMO diol of greater polydispersity. The chemical structure of the poly(ether-ester-imide)s, PEEIs, was characterized by IR and 1H NMR spectroscopy. The phase transitions were identified by DSC and DMTA measurements, which revealed that all members of this series were slowly crystallizing materials. The mechanical properties were determined by stress–strain and hysteresis measurements. Macrophase separation during the polycondensation was reflected in poorer mechanical properties.

A new monomer ( 7 ) was prepared by alkylation of N , N ,-bis(4-hydroxyphenyl)biphenyl-3,3′,4,4′-tetracarboxylic imide with 11-bromoundecanol. This imide diol ( 7 ) did not form a LC-phase, but showed two reversible first-order transitions in the solid state. It was polycondensed with various aliphatic dicarboxylic acid dichlorides in 1-chloronaphthalene. The phases and phase transitions of the resulting poly(ester-imide)s were characterized by optical microscopy, DSC measurements and X-ray measurements at variable temperature. All poly(ester-imide)s formed a crystalline smectic phase in the solid state. In the case of short spacers enantiotropic smectic-A phase were observed which vanished in the case of long spacers.

Model reactions between neat Bu 2 SnOct 2 and benzylalcohol suggest that no exchange occurs at temperatures ≤60°C. However, at 100°C a slow esterification process yielding benzyl octanoate and Sn–OH groups takes place. Bu 2 SnOct 2 is a little less reactive than SnOct 2 , but polymerizes trimethylene carbonate (TMC) at 80°C. Addition of benzylalcohol accelerates the polymerization process and allows controlling the molecular weight via the TMC/alcohol ratio. The resulting poly TMC contains the stoichiometric quantity of benzyl carbonate endgroups. Neat Bu 2 SnOct 2 reacts above 120°C with TMC by transesterification and formation of octanoate endgroups. However, a satisfactory control of M n via the M / I ratio is not possible, and the “backbiting” degradation competes with the polymerization process at high conversions.

Surface properties of two polyethers containing pyridine and pyrazine units, respectively, were compared with polysulfone. The polymers were investigated by inverse gas chromatography. The dispersive contributions of the surface free energy and the KA and KB parameters expressing the ability of the stationary phase to act as Lewis acid or Lewis base were calculated. It was shown that the polymer with pyridine units possessed extraordinarily high KB values whereas the polysulfone showed amphoteric behaviour with predominant Lewis basicity.

One non chiral homopolyester and five chiral copolyesters were prepared by polycondensations of 2,5-bis(dodecyloxy)terephthaloylchloride and 4,4′-dihydroxybiphenyl or mixtures of this diphenol and isosorbide. The resulting polyesters were characterized by viscosity measurements, elemental analyses, 1 H n.m.r. measurements, optical microscopy, DSC-measurements and X-ray measurements with synchrotron radiation at variable temperatures. If more than 20% of the 4,4′-dihydroxybiphenyl were replaced by isosorbide the copolyesters lost their thermotropic character. All polyesters with 20% or less isosorbide proved to be semicrystalline thermotropic materials showing three phase transitions: firstly a melting process ( T m1 ), secondly a transition from a sanidic LC-phase to a normal nematic or cholesteric melt ( T m2 ) and finally to the isotropisation ( T i). The copolyester containing 10% isosorbide was capable of forming a Grandjean texture.

1,12-Dihydroxydodecane and 1,22-dihydroxydocosane were prepared from diacetylene precursors in such a way that the four central methylene groups were deuterated. These deuterated spacers were polycondensed with the acid chloride of N-(4′-carboxyphenyl)trimellitimide. Analogous poly(esterimide)s were prepared from fully protonated spacers. Furthermore, copolyesters were synthesized from a 1/1 mixture of 1,12-dihydroxydodecane and 1,22-dihydroxydocosane, one of which contained a deuterated dodecane spacer, whereas in the analogous polyester the docosane spacer is deuterated. All poly(ester–imide)s were subjected to a thermal treatment yielding a smectic-E phase in the solid state. 13C nuclear magnetic resonance (n.m.r.) CP/MAS spectra revealed that spacers with ≥12 methylene groups contain trans–trans conformations even up to 100°C. 2H n.m.r. spectroscopic measurement revealed that the spacers are nearly immobile at −180°C, but gain increasing mobility upon heating. Whereas the central segments of the docosane spacer can perform crank-shaft motions at ambient temperature, the motion of the dodecane spacer is restricted to kinks. At 100°C the middle segments of the spacers partly are capable of isotropic motion in the solid smectic-E phase.

Three homopolyesters were prepared by polycondensation of 4,4′-dihydroxybiphenyl and 2,5,-bis( n -octyloxy)-2,5-bis(dodecyloxy)-or 2,5-(hexadecyloxy)terephthaloylchloride. Furthermore, several copolyesters were synthesized from 4,4′-dihydroxybiphenyl and mixtures of 2.5-bis(hexadecyloxy)terephthaloylchloride and 2,5-bis(( S )isopentyloxy)terephthaloylchlotide. All polyesters were characterized by inherent viscosities, elemental analyses, 1 H n.m.r. spectroscopy, d.s.c. measurements, dynamic mechanical analyses (DMA), WAXS powder patterns at various temperatures and optical microscopy. Two liquid crystalline (LC) phases were detected for the homopolyesters and most copolyesters: a viscous sanidic (biaxial nematic) phase and, at higher temperatures, a mobile nematic phase. The chiral copolyesters displayed an unusual ‘sausage texture’, but never a Grandjean texture. A chiral nematic phase with helical main chains is discussed.

Two new dicarboxylic acids were synthesized from trimellitic anhydride anhydride and 1.5-diamino-2-methylpentane or from a mixture of isomeric 1,6-diamino-trimethyl hexanes. These dicarboxylic acids were polycondensed either with the bisacetate of 2,6-dihydroxynaphthalene or with the bisacetate of 4,4′-dihydroxybiphenyl. D.s.c. measurements, WAXD powder patterns and optical microscopy revealed that all four poly(esterimide)s derived from 1,5-diamino-2-methylpentane still form a highly ordered, quasi crystalline smectic layer structure in the solid state, but a nematic phase in the molten state. The poly(ester-imide)s derived from the trimethyl substituted spacers only form a smectic glass in the solid state. This smectic glass is a frozen smectic-A phase in the case of 4a but may be a mixture of frozen smectic-C and smectic-A phases in the case of 4b (derived from 4,4′-dihydroxybiphenyl). Upon heating above the glass-transition the layer structures gradually disappear with formation of a nematic phase. Due to this gradual change revealed by synchrotron radiation measurements no endothermic phase transition is detectable in the d.s.c. traces.

The trimethylsilylester of β-(4-acetoxyphenyl) propionic acid (APPA), which is easier to isolate than the free acid, was used as monomer for all polycondensations. Copolycondensations with small amounts of 4-tert-butylbenzoic acid or 4-tert-butylphenol acetate yielded oligo- and polyesters with two different endgroups. All oligoesters show a reversible first order phase transition between 240 and 265°C yielding a solid mesophase upon heating. The formation of an isotropic melt occurs between 340 and 380°C depending on the degree of polymerization (DP). The glasstransition temperatures increased from 48–50°C to values around 63–65°C with increasing molecular weight. Copolycondensations with acetylated bisphenol-P yielded telechelic oligoesters with two identical endgroups. Four-armed star-shaped polyesters were prepared by copolycondensation of a tetraacetoxyspirobisindan. Since the bisphenol-P and the spirobisindane units are unfavourable for the crystallization, the crystallinity depends on the DP, and the solubility depends in turn on the crystallinity. Hyperbranched copolyesters were synthesized by copolycondensation of silylated APPA with silylated or free 3,5-bisacetoxybenzoic acid with variation of the molar ratio. The hyperbranched character of these copolyesters was demonstrated by their reluctance to crystallize and by 13C n.m.r. spectroscopic sequence analyses. The Tgs of these hyperbranched copolyesters follow almost exactly the Fox equation. G.p.c. measurements revealed number average molecular weights (Mn) up to 31 000 g mol−1 (for the 1 1 copolyester) and Mw/Mn ratios in the range of 3.5–6.5.

A new mesogene diester based on phenyltrimellitimide was synthesized and used as a condensation monomer in combination with a number of aliphatic diols to render novel poly(ester-amide-imide)s (PEAIs). The melt polycondensation method provided polymers of moderate inherent viscosity, that were characterized by elemental analyses, differential scanning calorimetry, X-ray diffractometry, including synchrotron radiation measurements at different temperatures, optical microscopy with polarized light and thermogravimetric analysis. The glass transition temperatures ( T g ) lie in the range 100–130°C, which means a substantial improvement relative to analogous poly(ester-imide)s (PEIs). All the novel PEAIs are thermotropic materials that show a mobile LC-mesophase above the melting temperature. By combining microscopic observations with X-ray diffraction diagrams, the mesophases could be identified as smectic-A phases. PEAIs with even-numbered spacers are semi-crystalline in the solid state, while those with odd-numbered spacers can form a solid smectic glass phase, i.e. a frozen smectic-A phase, upon rapid cooling from the melt.

X-ray methods have been used to investigate the solid-state structures of wholly aromatic thermotropic copolyesters prepared from equimolar amounts of p-hydroxybenzoic acid, biphenol and thiophenyl- or oxyphenyl terephthalic acid. We have also compared these structures with that of the unsubstituted copolymer. The scattering data for melt-spun fibres show that the presence of the side chains results in considerably less lateral order. Non-periodic layer lines are observed, and their positions are reproduced in simulated scattering patterns for extended chains of completely random sequence. For the unsubstituted copolymer, the chains are not fully extended but are contracted by approximately 1%, probably due to the requirements to pack random sequences with three-dimensional order. A further contraction of 1.5% occurs for the backbones of the substituted copolymers, probably in an effort to minimize the free volume. Nevertheless, the presence of the side chains results in a reduction of the density by ≈20%. The substituted copolymers adopt a distorted structure similar to that seen for poly(phenyl-p-phenylene teraphthalate), in which the side groups on adjacent chains are interdigitated. This is possible even for random sequences because there is only one side chain for every four aromatic units along the backbone. Nevertheless, this interdigitation appears to preclude any registration of adjacent random sequences, and thus there is no evidence for the three-dimensional order observed for the unsubstituted copolymer.

Cyclobis(hexamethylene carbonate), (HMC)2, was prepared from 1,6-hexane diol and diethylcarbonate by a combined polycondensation-depolymerization procedure. The recrystallized monomer was characterized by standard methods and subjected to polymerization in bulk at 140°C. Either BuSnCl3 or SnOct2 were used at initiator. When the reaction time was varied at constant monomer/initiator (M/I) ratio both initiators yielded the highest molecular weights at 20 h. Variation of the M/I ratio proved that the molecular weights do not parallel the M/I ratios. The best results were obtained with BuSnCl3 as initiator: yields up to 89% and weight average molecular weights (Mw) around 200 000 were found. In all cases the Mw/Mn ratio was of the order of 2. Differential scanning calorimetry measurements showing that polyHMC is a rapidly crystallizing polymer, which crystallizes even at a cooling rate of −40°C min−1. Thermogravimetrical analyses were conducted at a heating rate of 3°C min−1 under nitrogen, and under oxygen. The degradation begins around 250°C and reaches its maximum around 350°C. Under nitrogen, CO2, H2O and tetrahydropyran were found as low molar mass degradation products, whereas formaldehyde and the monomeric cyclocarbonate were not formed. Under an O2 atmosphere oxidation is the main degradation process above 300°C.

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.

Polyimides were prepared from α,ω-bis(4-aminophenoxy)alkanes and various aromatic tetracarboxylic anhydrides. Only the polyimides derived from biphenyl-3,3′,4,4′-tetracarboxylic anhydride form a liquid crystalline (LC) melt. In contrast, polyimides of the same dianhydride and α,ω-diamino alkanes are crystalline but not thermotropic. The mesogenic and non-mesogenic behaviour of the various poly(ester—imide)s is discussed on the basis of conformational differences calculated by a force-field program. The polyimides were characterized by elemental analyses, viscosity measurements, infra-red and nuclear magnetic resonance spectroscopies and differential scanning calorimetry measurements at variable temperatures. The formation of ‘batonet’ and ‘fan-shaped’ textures along with the wide-angle X-ray diffraction patterns suggest that the LC polyimides form a smectic A phase in addition to a smectic crystalline phase. Both melting and isotropization temperatures show an odd—even effect.

The polymerization of L-lactide was catalysed with Sn(II)2-ethylhexanoate (SnOct 2 ) in the presence or absence of benzyl alcohol. The molecular weights parallel the lactide/benzyl alcohol ratio, but never the lactide/Sn ratio. 1 H n.m.r. spectroscopy revealed the existence of benzylester and −CH(CH 3 )OH end-groups. Polymerizations conducted at low lactide/catalyst ratios in the absence of an alcohol yield polylactide with a low content of 2-ethylhexanoate end-groups. 1 H and 119 Sn n.m.r. spectroscopy of CHCl 3 solutions also demonstrated that SnOct 2 forms strong complexes with both benzyl alcohol and ethyl lactate and weaker complexes with lactide. A similar but weaker complexation was also detected for Bu 2 SnOct 2 in combination with either benzyl alcohol or lactide. A new polymerization mechanism is discussed, assuming the reaction between lactide and OH end-groups bound to a Sn atom via two sp 3 d 2 orbitals.

The dibutylmagnesium (Bu2Mg)-initiated polymerizations of l-lactide at 120°C in bulk yielded poly(l-lactide) of low molecular weights (ηinh ⩽ 0.4 dlg−1 in CH2Cl2), regardless of reaction time and initiator concentration. Higher molecular weights were obtained in solution when carried out in the presence of ethers. The addition of crown ethers to polymerizations conducted in toluene at 0°C gave the best results, with ηinh values up to 3.0 dlg−1 (in Ch2Cl2), corresponding to number-average molecular weights (Mns) the order of 3 × 105g mol−1. These high-molecular-weight poly(l-lactide)s possess almost complete optical purity and show melting temperatures of ∼170°C. Relatively high-molecular-weight poly(d,l-lactide)s were also obtained by the Bu2Mg-initiated polymerizations of racemic- or meso-d,d-lactides, with ηinh values up to 1.4 dl g−1 (in CH2Cl2), corresponding to Mn = 105, being found. The Grignard reagent, BuMgCl, gave somewhat better results than Bu2Mg when used as an initiator for l-lactide in bulk. However, BuMgCl is not reactive enough to initiate satisfactory polymerizations in solution at temperatures ⩽25°C.

Polymerizations of cyclotrimethylenecarbonate (TMC) with SnCl 4 , SnBr 4 were and SnI 4 were conducted in bulk. The reaction time, the temperature and the monomer/initiator (M/I) ratio were varied, and the influence of these parameters on yields and molecular weights was investigated. Yields above 90% were obtained with all these initiators, but the highest molecular weights ( M w ≈ 1.5 × 10 5 ) resulted from SnI 4 -initiated polymerizations. SnI 4 has the additional advantage that the polycarbonates were free of ether groups when prepared at moderate temperatures (e.g. 60°C). In contrast, SnCl 4 and SnBr 4 cause partial decarboxylation even at 60°C, and at higher temperatures up to 20 mol% of the carbonate groups may be replaced by ether linkages. Furthermore, mechanistic studies were conducted. SnCl 4 and SnBr 4 form solid 1:2 complexes with TMC at 20–25°C. Infra-red, 1 H and 13 C nuclear magnetic resonance (n.m.r.) spectroscopies indicate complexation at the carbonyl oxygen. Kinetic measurements of polymerizations in solvents of different polarity suggest cationic polymerization mechanisms. In addition to CH 2 OH, CH 2 Cl and CH 2 Br end groups were detected by 1 H n.m.r. spectroscopy. The endgroup analyses of reaction mixtures and isolated poly(TMC) support the assumption of a cationic polymerization mechanism.

N,O -Bistrimethylsilyl-4-aminobenzoic acid was selectively acylated at the amino group with 4-acetoxy-3-methoxybenzoyl chloride. The resulting dimer with silylated carboxyl group was polycondensed in situ at 300 or 350°C using Marlotherm-S as an inert reaction medium. In an alternative approach the silylester group of the dimer was hydrolysed and the resulting N -(4′-acetoxy-3-methoxybenzoyl)-4-aminobenzoic acid was polycondensed at 300 or 350°C. Furthermore, copolyesters rich in vanillic acid units were prepared by co-condensations with 4-acetoxy-3-methoxybenzoic acid or its trimethylsilylester. Elemental analyses and 1 H nuclear magnetic resonance spectra indicate that the vanillic acid units partially decompose at 350°C, whereas at 300°C the composition of the copolyesters agrees well with the feed ratio. Infra-red spectra support this conclusion. Wide-angle X-ray diffraction powder patterns indicate that the crystallinity increases with higher molar fractions of vanillic acid. The 1:1 copolymers are nearly amorphous. The copoly(ester—amide)s obtained from the monomers with free carboxyl groups form globular aggregates regardless of composition. In contrast, the silylated monomers yield columnar particles with lengths of 10–15 μm and aspect ratios ⩾ 10 for copoly(ester—imide)s with a 6:4 and 5:5 composition. Transmission electron microscopy revealed ordered structures in these columnar particles, but the ‘crystal growth’ cannot yet be interpreted.

The polymerization of l -lactide with triethylaluminium and alkylaluminium alkoxides was studied in detail. It was found that commercial triethylaluminium is often contaminated with aluminium ethoxide groups resulting from the rapid oxidation of triethylaluminium. The ethoxide group is a far more reactive initiator than the aluminium-carbon bond. Therefore reactive initiators can be prepared in situ by the reaction of pure triethylaluminium with vitamins, hormones or drugs containing hydroxyl groups. Polymerization of l -lactide with these in situ prepared initiators yields oligo- or poly( l -lactide) with covalently bound vitamins, hormones or drugs. The bioactive co-initiators used in this study were geraniol, stigmasterol, tocopherol, testosterone, pregnenolone, ergocalciferol, cortisone and quinine. It is demonstrated by 13 C n.m.r. spectroscopy that the keto groups of steroids do not undergo redox reactions during the polymerization process.

Two symmetrical imide diacids were prepared from trimellitic anhydride and two α,ω -diamines containing ether linkages, namely 1,8-diamino-3,6-dioxaoctane and 1,12-diamino-4,9-dioxadodecane. Polycondensations in the melt of the imide diacids and diacetyl bisphenols yielded the corresponding series of poly(ester imide)s (PEIs), characterized by an alternating sequence of stiff, aromatic imide units and ether-containing aliphatic spacers. The presence of -O- linkages within the flexible spacers greatly affected the thermal transitions and the thermotropic behaviour of the PEIs. Comparison with homologous PEIs without ether linkages revealed lower glass transition temperatures and a weaker tendency to form liquid crystal mesophases. Only the PEIs from 4,4′-dihydroxybiphenyl showed a regular thermotropic behaviour, as could be proved by optical microscopy with crossed polarizers, by d.s.c. and by synchrotron radiation measurements at variable temperature. These PEIs form layer structures in the solid and liquid state. The textures suggest the formation of a smectic-A phase.

Substituted poly(benzobisoxazole)s and poly(biphenylbisoxazole)s were synthesized by polycondensation of silylated diaminohydroquinone or 3,3′-dihydroxybenzidine with substituted terephthaloyl chlorides. Hexadecylthio-, 2,5-bis(hexadecylthio)- and 2,5-bis(hexadecyloxy)terephthaloyl chloride were used as reaction partners. A reaction temperature of 300°C was required for the final cyclization step of the reaction sequence. At this high temperature partial crosslinking occurred in most cases. The poly(biphenylbisoxazole)s melt in the temperature range of 310–350°C, but the characterization of the melt was affected by rapid thermal degradation. By means of wide-angle X-ray scattering powder patterns and 13 C nuclear magnetic resonance cross-polarization/magic-angle spinning spectroscopy, two kinds of sanidic layer structures were found for the solid state. The hexadecyl side chains form reversibly melting quasicrystalline paraffin domains between the layers of the main chain. The molar fraction of these ordered paraffin domains is significantly higher for bis(hexadecylthio)-substituted chains than for bis(hexadecyloxy)-substituted ones.

Numerous phosphorus-containing aromatic polyesters were prepared by polycondensation of silylated diphenols with dicarboxylic or phosphoric acid dichlorides. Phenyl phosphate and naphthyl phosphate, phenyl- or methylphosphonate groups were incorporated into poly (phenylhydroquinone terephthalate). Regardless of the substituent attached to the phosphorus atom the nematic phase disappeared when more than 20mol% of the terephthalic acid was replaced by phosphoric or phosphonic acid units. Furthermore, phenylphosphonic acid was incorporated into various thermotropic copolyesters. It was found in all cases that the stability of the mesophase depends on the percentage of phosphorus and on the length of the repeating unit.

Crystalline poly(3-phenyl-4-hydroxybenzoic acid) was prepared by polycondensation of 4-acetoxy-3-phenylbenzoic acid in solution at 320°C. Differential scanning calorimetry (d.s.c.) and wide angle X-ray scattering (WAXS) measurements indicate that this homopolyester forms a nematic melt between 345°C and 465°C. Five copolyesters of 4-hydroxybenzoic acid (HBA) and 4-hydroxy-3-phenylbenzoic acid (3-PhHBA) with varying molar composition were prepared by polycondensation in solution. One additional copolyester was prepared by polycondensation in bulk. 1 H n.m.r. spectroscopy revealed a significantly lower reactivity of the phenyl-substituted acetoxybenzoic acid. The influence of the molar composition on crystallinity, phase transitions and stability of the nematic mesophase was studied by d.s.c. and WAXS measurements and by optical microscopy. Heat distortion temperatures were determined by the penetration method. It was found that the copolyesters prepared in bulk and in solution possess quite different properties. Only the copolyester prepared in bulk forms a nematic melt above its melting point at 205 ± 3°C.

The homopolyester of 4-(4′-hydroxyphenoxy)benzoic acid (poly(4-HPBA)), was prepared under two different reaction conditions and compared with a sample provided by another research group. Depending on the synthetic route, different melting points, d.s.c. traces and crystal lattices were found. However, after repeated heating and cooling, one thermodynamically stable modification with a melting point of 370–375°C can be obtained. Copolyesters of 4-hydroxybenzoic acid and 4-(4′-hydroxyphenoxy)benzoic acid were prepared with various molar ratios either in the melt (condensation in bulk) or in solution. These copolyesters were characterized by elemental analyses, 1 H n.m.r. spectroscopy, d.s.c. measurements, wide-angle X-ray scattering measurements at various temperatures, and optical microscopy. Whereas copolyesters prepared in solution do not melt below 500°C, those prepared by polycondensation in bulk show melting points down to approximately 260°C and form a nematic melt.

Racemic and meso d,l -lactide were polymerized at 90 or 120°C in xylylene or at 120, 150 and 180°C in bulk. Furthermore, copolymerizations of racemic d,l -lactide and l,l -lactide were conducted at 180°C in bulk. Tributyltin methoxide (Bu3SnOMe), dibutyltin dimethoxide (Bu2Sn(OMe)2) and Sn(II) octoate were used as initiators. Despite high yields only low molecular weights were obtained with both tin methoxides. Sn(II) octoate gave significantly higher molecular weights. The stereosequences were analysed by 1H and 13C n.m.r. spectroscopy on the basis of tetrad effects. The signal assignments are discussed. Bu3SnOMe and Bu2Sn(OMe)2 are effective transesterification catalysts and cause ‘back-biting’ degradation even at 90°C. In all series of polymerizations initiated with tin methoxides two tendencies are detectable: increasing randomization of the stereosequence with increasing reaction time and with higher reaction temperatures. In contrast, Sn(II) octoate does not cause transesterification at ≤ 120°C and even at 180°C randomization of the stereosequences is slow.

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.