Mesophase behaviour in fluorocarbon-hydrocarbon polyesters

A series of liquid crystalline main chain polyesters has been synthesized in which mesogenic, linear perfluoroalkyl groups are linked to aliphatic hydrocarbon chains. The liquid crystalline phase appears to be smectic B from X-ray diffraction data. Interesting differences in the mesophase transition temperatures and enthalpies are observed along the series, as the hydrocarbon and perfluoroalkyl contents are changed. These are discussed in relation to the length of the segments. One polymer was also synthesized from biphenyl-4,4'-dicarboxyic acid for comparison with the polyesters prepared using aliphatic dicarboxylic acids.     

携带叠氮和氨侧基的脂肪族聚酯的合成和表征

通过丙交酯(LA)与环状碳酸酯单体共聚的方法制备了一种侧链带有溴原子的脂肪族聚酯, 并将溴原子用叠氮基团取代, 通过Cu(Ⅰ)催化的Click反应将其氨基化, 得到了侧链带有氨基的脂肪族聚酯.     

Crystallinity of fully aromatic thermotropic polyesters of 3,3'-bis(phenyl)-4,4'-biphenol and 1,1'-binaphthyl-4,4'-diol

The degree of crystallinity of as-made fully aromatic, thermotropic polyesters was determined for two different series of polymers, each of which contained a symmetric monomer having either pendant phenyl groups or fused aromatic rings by the WAXD technique. All of the homopolymers had a high degree of crystallinity in spite of bulky substituents attached to the mesogenic moiety. Surprisingly, the homopolymer of 2,6-naphthalenedicarboxylic acid with each of the monomers had a higher degree of crystallinity and T_m than those of the homopolymer of terephthalic acid with each of the respective monomers. As expected, on copolymerization with 30 mol % of either 4-hydroxybenzoic acid or 6-hydroxy-2-naphthoic acid, all of the resulting copolymers had a much lower degree of crystallinity and T_m/T_f values compared to those of the respective homopolymers in each series. © 1994 John Wiley & Sons, Inc.     

合成生物降解性聚酯研究的进展

对近年来采用化学法,主要是缩合聚合法及开环聚合法,合成生物降解性聚酯的研究进展作了综述。     

Main-chain side-chain liquid crystal polymer blends for improved physical properties

Previous work has demonstrated that compatible blends of main-chain liquid crystal polymers (LCP) with side-chain LCP's can be prepared. The present work was carried out to extend the scope and application of this finding to liquid crystal polyesters, similar to commercially available LCP's and to demonstrate the effect of the blend composition upon the physical and mechanical properties. A series of melt-processable main-chain polyesters was prepared as well as a series of acrylic polymers and copolymers which possess a side-chain mesogenic unit, similar to that of the main-chain LCP's. While the results of the blending studies of these high molecular weight materials were somewhat ambiguous as to compatibility, there are strong indications that the presence of the side-chain mesogen containing polymers does result in an improvement in the overall mechanical properties of the main-chain LCP.     

NMR Investigation of the Main-Chain Orientation in Liquid-Crystalline Side-Chain Polymers

The main-chain orientation in different groups of liquid-crystalline side-chain polymers was investigated using several NMR techniques. For two polyesters the average orientation of the main chain in dependence on the main-chain spacer length could be found from 2D PASS experiments. In polysiloxanes with different mesogenic side groups and different spacer lengths this information could be received from chemical shift anisotropy measurements. Additionally, application of a modified β-echo allowed the separation of the dipolar ²⁹Si-²⁹Si interaction and to characterize the transversal anisotropy of the main-chain segments. Comparison with small angle neutron scattering results gave good agreement, where the different length scale of both methods has to be taken into account.     

Synthesis and characterization of main-chain thermotropic aromatic polyazomethines with siloxane spacers

New main-chain liquid crystal copolymers have been synthesized in the polyazomethine series from two polycondensation routes (polyhydrosilylation and polyimination). The mesogenic units are separated with siloxane spacers. The obtained copolymers have been characterized by size-exclusion chromatography and NMR and FT-IR spectroscopies; their mesomorphic behavior has been investigated by polarizing microscopy, differential scanning calorimetry and RX diffraction. Moreover, when the polycondensation reactions are carried out in solution or when the copolymers are kept in a solvent, we observed the formation of macrocyclic dimers, which have been isolated and characterized.     

Synthesis and phase behaviour of liquid-crystalline side group polyesters

Several series of liquid-crystalline side group polymers with a polyester backbone structure have been synthesized using mesogenic diethylmalonate and 1,3-propanediol derivatives. The structures of the polymer backbone and the mesogenic units have been varied systematically. As shown by differential scanning calorimetry, polarizing microscopy and X-ray diffraction, the side group polyesters exhibit nematic and/or smectic mesophases. Polyesters synthesized from mesogenic diethylmalonate derivatives can tolerate long non-mesogenic segments in the polymer main chain without losing their liquid crystal properties. X-ray studies suggest that some of the smectic polymers exhibit interdigitated bilayer S_A phases.     

Synthesis,thermal, rheological characteristics,and enzymatic degradation of aliphatic polyesters with lignin‐based aromatic pendant groups

This research aims to produce lignin‐based biodegradable polyesters with improved thermal quality. A series of aliphatic polyesters with lignin‐based aromatic side groups were synthesized by conventional melt‐polycondensation. Decent molecular weight (21–64 kg mol^?1) was achieved for the polymerizations. The molecular structures and thermal and mechanical properties of the obtained polyesters were characterized. As a result, the obtained polyesters are all amorphous, and their glass‐transition temperature (T_g) depends on the size of the pendant aromatic group (31–51 °C). Furthermore, according to the TGA results, the thermal decomposition temperatures of the polyesters are all above 390 °C, which make them superior compared with commercial biodegradable polyesters like polylactic acid or polyhydroxyalkanoates. Finally, rheological characteristics and enzymatic degradation of the obtained polyesters were also measured. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2314–2323     

The influence of substituents on the orientational behaviour of novel azobenzene side-chain polyesters

A series of new mesogenic azobenzene propanediols with nitro, methoxy, cyano and no substituent have been synthesized and their mesomorphic behaviour mapped. The diols are employed in a melt transesterification with diphenyl tetradecanedioate to produce side-chain polyesters with high molar masses. Diols and polyesters have similar UV-visible spectra reflecting the acceptor character of the substituent. Polarization FTIR spectroscopy has been used to determine the mesogenic order parameter for the polyesters with different substituents at four laser irradiation wavelengths (413, 458, 488 and 515 nm). Diffraction gratings in thin polyester films have been recorded through polarization holography. Cyano and unsubstituted azobenzene polyesters are shown to exhibit the highest diffraction efficiencies on the order of 13%.     

Alternative synthetic strategies for Schiff base derived liquid crystal polymers: A comparative study

Semiflexible liquid crystalline polymers based on Schiff bases as mesogenic cores have been synthesized through different synthetic strategies. The mesogenic cores are derived from 1,5-naphthalenediamine linked to a polymethylenic spacer by means of ether or ester groups. The synthetic strategies differ in the disconnection of the molecules to design the synthesis of the repeating units. Polymers were synthesized either as polyazomethines, where imine bonds are formed in the polymer synthesis, or as polyethers or polyesters, where the ether or ester groups are formed at the polymer-forming stage. The influence of the synthetic method and the linking groups between mesogenic core and flexible spacer on the thermal and mesogenic properties has been analyzed by DSC, thermogravimetry, and optical microscopy. The possibility of obtaining hydroxy-functionalized polymers by different synthetic strategies has been studied as well as the influence of these groups on the thermal and mesogenic properties. © 1996 John Wiley & Sons, Inc.     

Polyethylene like polymers. Aliphatic polyesters of dodecanedioic acid: 1. Synthesis and properties

A series of aliphatic polyesters has been synthesized starting from 1,12-dodecanedioic acid and aliphatic diols, bearing from 2 to 12 carbon atoms. These polymers, which were fully characterized in terms of chemical structure, molecular weight and thermal behaviour, were obtained as crystalline materials with melting points ranging from 70 to 90 °C and with a relatively high molecular weight. All the monomers used can be obtained from biomasses, as a consequence these materials can be an interesting alternative to synthetic polymers produced from petrochemical processes based on nonrenewable resources.     

Synthesis and properties of two new series of isomeric liquid crystalline polyesters with conjugated double bonds

Two homologous series of flexible main chain liquid crystalline polyesters with isomeric mesogenic groups containing conjugated double bonds, were synthesized and studied by differential scanning calorimetry and optical microscopy. One series (S1) has the p-phenylene-diacryloyloxydibenzoyl moiety as a mesogenic unit. The other (S2) has the terephtaloyl dioxydicinnamoyl moiety as a mesogenic unit. The reactivity of the conjugated double bonds of the p-phenylenediacryloxy unit, at the temperature of mesophase formation, impedes the stability of liquid crystalline mesophases of polymers of series (S1). Two low molecular weight analogues of polymers were also prepared and their properties compared with those of polymers of similar structure. The two model compounds form stable smectic mesophases over a wide range of temperatures, which shows the high mesomorphogenic ability of both mesogenic units.     

Dimeric liquid‐crystalline epoxyimine monomers: Influence of dipolar moments on mesomorphic behavior and the formation of liquid‐crystalline thermosets

We examine some of the structural aspects that influence the mesomorphic behavior of liquid‐crystalline dimeric epoxy resins with imine groups in the mesogens. We synthesized two new series of monomers and compared them with previously synthesized monomers. Compared with previously studied series, the imine group in the new monomers is oriented differently with respect to the ether and ester groups linked to the end of the mesogenic unit. Our results confirmed the importance of polarization of the mesogenic groups and the presence of an ester group in the inner position in the formation of smectic mesophases. By curing with primary and tertiary amines, we demonstrate that these two requirements are necessary if liquid‐crystalline thermosets are to be obtained with different degrees of order. These studies were carried out with differential scanning calorimetry, polarized optical microscopy, and X‐ray diffraction. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1465–1477, 2003     

Side chain liquid crystalline diethanolamine‐based polyesters with methoxy and/or nitroazobenzene mesogenic moieties

Side‐chain polyesters based on diethanolamine and 5‐hydroxyisophthalic acid with mesogenic methoxyazobenzene and nitroazobenzene groups were synthesized and their liquid crystalline properties were examined.

Four different types of polyesters were prepared by using various combinations of monomers differing in the mesogen group and the length of the spacer. The thermal and structural properties depend on the type of polyester as well as on the side chain length. The glass transition and isotropization temperatures increase when the methoxyazobenzene group is bound to a diol and decrease when it is bound to an isophthalic acid. Most of the polyesters are thermotropic liquid crystals and form a nematic phase on heating. Some polyesters exhibit shear induced isotropisation to nematic transition up to 25°C above the isotropization temperature.     

Synthetic Approaches to Combine the Versatility of the Thiol Chemistry with the Degradability of Aliphatic Polyesters

Abstract

Thiol chemistry is an efficient tool to manipulate the microstructure of aliphatic polyesters and open the way to different applications. Synthetic strategies that aim to synthesize thiol-functionalized aliphatic polyesters are reviewed herein. The introduction of thiol-editable groups on aliphatic polyesters can occur both at chain ends and along the chains, enabling diverse modifications of the polymeric chains and imparting new properties and functions. The use of thiol chemistry for postpolymerization modification of this class of polymers and the (co)polymerizations of monomers bearing thiol groups has also been described herein.     

L-glutamic acid as a versatile platform for rapid synthesis of functional polyesters via facile Passerini multicomponent polymerization

In this work, a series of polyesters with different functional side groups were successfully prepared by Passerini three-component polymerization (P-3CP) in “one-pot” from biorenewable l -glutamic acid (l -GA)-based monomers. First, the polymerization conditions including monomer feed ratios, solvents and comonomer were systematically studied using Boc-protected l -GA with adipaldehyde and tert-butyl isocyanide. Under the optimal polymerization conditions, a variety of N-substituted l -GA-based monomers as well as functional isocyanides were attempted in the P-3CP to produce polyesters with different functionalities. Moreover, it was found that after removal of pendant protecting groups, the obtained l -GA-based polyester degraded spontaneously into small molecules via 1,5-intramolecular cyclization between the pendant amine groups and the ester groups in polymer backbone. The structures and thermal properties of obtained polymers were determined by ¹H NMR, IR, SEC, MALDI-ToF-MS, DSC, and TGA measurements. Starting from biorenewable l -GA, this approach will provide a facile and straightforward route to produce functional and biodegradable polyesters, thus effectively expanding the range of biodegradable polymers.     

Side chain liquid crystalline diethanolamine-based polyesters with methoxy and/or nitroazobenzene mesogenic moieties

Side-chain polyesters based on diethanolamine and 5-hydroxyisophthalic acid with mesogenic methoxyazobenzene and nitroazobenzene groups were synthesized and their liquid crystalline properties were examined.

Four different types of polyesters were prepared by using various combinations of monomers differing in the mesogen group and the length of the spacer. The thermal and structural properties depend on the type of polyester as well as on the side chain length. The glass transition and isotropization temperatures increase when the methoxyazobenzene group is bound to a diol and decrease when it is bound to an isophthalic acid. Most of the polyesters are thermotropic liquid crystals and form a nematic phase on heating. Some polyesters exhibit shear induced isotropisation to nematic transition up to 25°C above the isotropization temperature.     

官能团化聚己内酯的合成与表征

通过分子结构设计合成了新型含有侧基官能团的聚己内酯材料.首先,通过亲核加成反应,由溴乙酸乙酯与烯胺合成2-乙氧甲酰甲基环己酮;然后以间氯过氧化苯甲酸为氧化剂,通过Baeyer-Villiger氧化反应,得到带有官能团的己内酯单体,6-乙氧甲酰甲基-ε-己内酯;该单体在异辛酸亚锡(Sn(Oct)2)的催化下,本体开环聚合得到相应的均聚物及其与ε-己内酯的共聚物.采用1H-NMR、13C-NMR、GPC和DSC表征了聚合物的结构和热力学性能.随着6-乙氧甲酰甲基-ε-己内酯在共聚物中的含量增加,共聚物的分子量降低,同时熔点和熔融焓也随之降低.     

Synthesis of Polyamides and Polyesters Having Various Functional Groups

Polyamides and polyesters having various functional groups have been synthesized either by the polycondensation of functional monomers having a high reactivity or by the modification of unsaturated polymers by means of suitable polymer reactions. Polyamides or polyesters having hydrophilic groups such as hydroxyl group have a high affinity for moisture adsorption and are applicable to membrane uses. Photosensitive polyamides or polyesters were also prepared.