Series Of Polyesters Research Articles

The Förster radius for energy transfer from naphthalene to anthracene in polyesters with oxyethylene spacers

AbstractModel compounds for a series of polyesters in which 3,6,9, and 12‐rotatable CH2O and CH2CH2 bonds separate rigid units have been studied using the efficiency of nonradiative singlet energy transfer from naphthalene to anthracene. The model compounds have the structure naph‐CO(OCH2CH2)mOOC‐anth with m of 1–4, where naph and anth denote 2‐naphthyl and 9‐anthranyl groups, respectively. This series of compounds covers a larger range of potential separation of the two chromophores than was possible in an earlier study, in which the flexible spacers consisted of 2–6 methylene units. The nonradiative singlet energy transfer has an efficiency that depends on the solvent viscosity and on m. The theoretical analysis employs a rotational isomeric state model for the conformations of these molecules. The Förster radius for transfer from naphthalene to anthracene in this system is 16 ± 2 Å, and is nearly independent of whether the spacers are constructed from oxyethylene or methylene units.

Characterization of Polyester Polyurethanes by Time-of-Flight Secondary-Ion Mass Spectrometry

A series of polyesters and polyester polyurethanes were analyzed using time-of-flight secondary-ion mass spectrometry (TOF-SIMS). Analysis of poly(butylene adipate) samples produced spectra containing oligomer ions and fragments corresponding to cyclization via intramolecular ester exchange. These cyclic fragments were also observed in the spectra of polyurethane [4,4,1] samples, along with cyclic ester-urethane fragments. The mass of the diisocyanate group within the polyurethane could be determined from the mass difference between the two major fragment-ion series in the spectrum. In general, only limited fragmentation within ester or urethane repeat units was observed. The sample molecular weight for both the polyesters and polyurethanes correlated with the relative intensity of the cyclic repeat unit series ions to the linear oligomer ions. Additionally, transesterification of polyesters and polyurethanes using trifluoroacetic acid was found to selectively cleave bonds between polyester repeat units in both types of polymers.

Effect of methyl groups on the thermal properties of polyesters from methyl substituted 1,4‐butanediols and 4,4′‐biphenyldicarboxylic acid

AbstractResults are reported on the effect of lateral methyl groups on the thermal properties of a series of polyesters prepared from diethyl 4,4′‐biphenyldicarboxylate and various methyl substituted 1,4‐butanediols. The diols were 1,4‐butanediol; 2‐methyl‐1,4‐butanediol; 2,2‐dimethyl‐1,4‐butanediol; 2,3‐dimethyl‐1,4‐butanediol; 2,2,3‐trimethyl‐1,4‐butanediol; and 2,2,3,3‐tetramethyl‐1,4‐butanediol. Apart from the tetramethyl derivatve, the transition temperatures of the methyl substituted polyesters were lower with respect of the unsubstituted polyester. On the basis of polarized photomicrographs, a smectic A mesophase was found for the unsubstituted polyester, whereas a nematic mesophase was observed for the 2‐methyl substituted polyster. The 2,2‐dimethyl, 2,3‐dimethyl, and the 2,2,3‐trimethyl substituted polyesters showed no liquid crystalline behavior. The 2,2,3,3‐tetramethyl derivative displayed a birefringent melt phase although the DSC measurements were not unambiguous. A copolyester based on diethyl 4,4′‐biphenyldicarboxylate, 1,4‐butanediol, and 2,2,3,3‐tetramethyl‐1,4‐butanediol showed a broad nematic mesophase. Further evidence for the nematic mesophase of this copolyester and the 2‐methyl substituted polyester was provided by dynamic rheological experiments. Based on thermogravimetric analysis, it was concluded that the thermal stability was affected only when four methyl side groups were present in the spacer. © 1995 John Wiley & Sons, Inc.

Studies on the synthesis and properties of soluble homo‐ and copolyester–imide derived from imide–diacid

AbstractA series of polyester–imides was prepared from diacid (imid–diacid [M1–M4] or a mixture of imide–diacid and terephthalic acid [TPA]) and bisphenol A in the presence of diphenyl chlorophosphate (DPCP) and pyridine as a direct condensation agent. The inherent viscosites of homo‐ and copolyester–imides were in the range of 0.39–0.58 dL/g. Almost all these homo‐ and copolyester–imides were completely soluble in N‐methyl‐2‐pyrrolidone (NMP), N,N‐dimethylacetamide (DMAC), dimethylformamide (DMF), and m‐cresol. The thermal properties of homo‐ and copolyester–imides were examined by DSC and TGA. These copolyester–imides had glass transition temperatures in the range of 95–240°C and a 5% weight loss was observed in the range of 354–465°C. © 1995 John Wiley & Sons, Inc.

Biotechnological Potentials of Anoxygenic Phototrophic Bacteria. II. Biopolyesters, Biopesticide, Biofuel, and Biofertilizer

Publisher Summary This chapter discusses the biotechnological potentials of anoxygenic phototrophic bacteria II. There is an increasing demand for the use of plasticized (polyester) materials suitable for human needs and many of them which are currently being synthesized chemically are nonbiodegradable and, hence, ecologically not ideal. There is an immediate requirement to replace the nonbiodegradable polyesters by a natural and biodegradable polyester, a waste management option for polymers in the environment, and, in many cases, the demand is driven by legislation. Studies with a number of isolates of anoxygenic phototrophic bacteria suggest that PHA formation is a common phenomenon among this group of microorganisms. In addition, Poly -β -hydroxybutyrate (PHB) is the best-known member of the PHA series of polyesters and it is known to be produced as intracellular energy and carbon reserves which are later utilized by the bacteria for cellular growth.

Structural Characterization of Polyesters by Transesterification and Time-of-Flight Secondary Ion Mass Spectrometry

The structural characterization of a series of polyesters has been done by time-of-flight secondary ion mass spectrometry (TOF-SIMS) combined with transesterification. Polymer fragments and intact oligomers composed of large numbers of repeat units were observed. Transesterification of polyesters by trifluoroacetic acid (TFA) and chlorodifluoroacetic acid (CFA) was carried out to produce TOF-SIMS spectra. The shapes and intensities of clusters in transesterification spectra showed good agreement with theoretical isotope patterns. TOF-SIMS spectra were used to monitor the progress of the transesterification reaction. Transesterification products of branched poly(1,3-butylene adipate) were identified in the TOF-SIMS spectra, providing information about polymer branching

X‐ray analysis of the structure of a wholly aromatic polyester with alkoxy sidechains

AbstractX‐ray diffraction has been used to determine the structure of the poly(p‐phenylene 2,5‐di‐hexadecyloxy‐terephthalate), which is one of a series of polyesters with stiff aromatic mainchains and flexible aliphatic sidechains currently being studied by this laboratory. The X‐ray data for oriented melt quenched films show that this polymer adopts an interesting and novel structure, in which the backbones and sidechains form separate incommensurate lattices. The backbones are fully extended, and adopt a monoclinic structure with unit cell dimensions: a=26.2Å, b=7.3Å, c=12.6Å, and α=130°C. They are in contact along the b axis, thereby forming stable sheets that are separated by intercalated, highly extended sidechains, which point along the a axis. The sidechains are packed in a columnar, approximately hexagonal structure that is similar to the hexagonal form of linear alkanes. The repeat for the sidechain lattice along the backbone direction is c=13.2Å, and thus the two lattices are incommensurate. We envisage a small disordered boundary layer between the backbone and sidechain lattices, containing some of the inital and final carbons of the sidechain, and accommodating any conformational isomerism. This allows an independent lattice to be formed by the central sections of the sidechains, but this cannot propagate indefinitely because of the different c dimension and the restrictions imposed by covalent linkage to the backbones. As a result, the sidechain crystallites are only approximately 50Å wide, compared to approximately 200Å for those formed by the backbones. Simulated X‐ray patterns for the above incommensurate structure show good qualitative agreement with the observed data.

Synthesis of polyester and copolyesters having amino acid moieties in the main chain

AbstractN, N‐di (2‐hydroxyethyl)‐3‐aminopropionic acid (M3) was synthesized and used for the preparation of a series of polyesters having amino acid moieties in the main chain and carboxyl groups as the side group. Polycondensation of M3, diols, bisphenol A, and isophthaloyl dichloride were performed in the presence of tertiary amine by solution and interfacial methods. Molecular weights of the polymers obtained by the solution method were not high, because oligomers produced at the early stage of reaction are ionized by H+ ions from the by‐product, and become nonreactive triethylamine hydrochloride. Polymers with high M̄w (1–10 × 104) were obtained in a high yield by organic/organic two‐phase interfacial polycondensation using DMAc and n‐heptane as solvents. The combined nucleophilic and basic complex catalytic action of N, N, N′, N′‐tetramethyl ethyiene diamine (TEMED) is suggested for the present organic phase/organic phase interfacial polycondensation. This method can be applied for the preparation of novel functional polyesters. © 1994 John Wiley & Sons, Inc.

Thermogravimetric Analysis of Polyesters Derived from 2,2-bis(4-chloroformyl-phenyl)-propane and 4,4′-Biphenyl-Dicarboxyl Chloride

Abstract The thermal stability and the kinetic parameters of a series of polyesters were studied by non-isothermal thermogravimetry. The thermal decomposition temperatures (TDT) depend principally on the nature of the diphenols, in the sense that when the bulk of the diphenol is increased, the TDT values decrease. The kinetic parameters, determined using the Arrhenius relationship, show that these polyesters degrade by a complex mechanism or possibly two or more superimposed processes, probably due to the complex structure of both diacids and diphenols.

Synthesis and characterization of aromatic polyesters with dicyanovinyl substituents

AbstractThe synthesis, characterization, and structure—property relations of aromatic polyesters with dicyanovinyl substituents is presented. Two comparable series of polyesters based on 3,4‐dihydroxybenzylidenemalononitrile and 3,4‐dihydroxy‐5‐methoxybenzylidenemalononitrile were prepared. As aromatic diacid components, terephthalic acid, phenylterephthalic acid, isophthalic acid, and 2‐phenylisophthalic acid were used. The polyesters were prepared by solution polycondensation. GPC investigations revealed the existence of substantial amounts of defined cyclic products. These cycles could be isolated by preparative GPC. The polyesters are soluble in common low boiling organic solvents, particularly the phenyl‐substituted ones. The polyesters are amorphous and have glass transition temperatures between 140 and 170°C. The absorption maxima are in the 306–322 nm range. The cut‐off wavelength is between 400 and 428 nm. The polyesters with methoxy substitutent have generally the absorptions at longer wavelength. The refractive index of thin films of these polyesters were between 1.61 and 1.63 at 632.8 nm. © 1993 John Wiley & Sons, Inc.

Synthesis and properties of polyesters derived from 2′,5′‐dialkyl‐p‐terphenyl‐4,4″‐diol

AbstractA series of polyesters based on 2′,5′‐dihexyl‐p‐terphenyl‐4,4″‐diol as one component and various aliphatic or aromatic diacids as the second component have been synthesized. The polyesters are soluble and film forming. Materials based on the terphenyldiol and terephthalic acid or the terphenyldiol and 2′,5′‐dihexyl‐p‐terphenyl‐4,4″‐dicarboxylic acid show a temperature dependence of the elastic modulus between 100 and 300°C resembling the behavior of hard elastic polymers, Glass transition phenomena in the conventional sense were not observed. The materials exhibit good mechanical properties up to temperatures well above 300°C.

Synthesis and mesogenic properties of four series of polyesters derived from dicarboxylic and dihydroxylic aromatic monomers

AbstractSome members of four series of polyesters were synthesized by the direct polycondensation of two types of dicarboxylic acids (4,4′‐dicarboxy‐α,ω‐diphenoxyalkanes and 4,4′‐dicarboxy‐α,ω‐dibenzoyloxyalkanes) with two types of bisphenols (4,4′‐dihydroxy‐α,ω‐diphenoxyalkanes and 4,4′‐dihydroxy‐α,ω‐dibenzoyloxyalkanes) using tosyl chloride in pyridine in the presence of N, N‐dimethylformamide. The 1H‐NMR spectra of the polymers synthesized showed that these polymers have an ordenated structure. The mesogenic properties of these polymers were studied by optical microscopy and differential scanning calorimetry. Many of the polymers show nematic mesomorphism.

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

AbstractA 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.

Dynamic mechanical relaxations of polyterephthalates based on trimethylene glycols

AbstractThe dynamic mechanical relaxations of poly(trimethylene glycol terephthalate) (PTMT), poly(ditrimethylene glycol terephthalate) (PDTMT) and two copolymers obtained from them have been studied between − 150 and 200°C with a dynamic viscoelastometer. The four polymers show three relaxations that are designated α, β, and γ in order of decreasing temperature. The α relaxation is considered to be the glass transition of the polymers. The β relaxation is wider and weaker than the α, as normally occurs in the polyester series. The γ relaxation takes place at temperatures below − 100°C and is usually overlapped by the β relaxation. The influence of thermal and mechanical histories on the nature, location, and intensity of the three relaxations is studied and discussed.

Molecular Mass and Structure Dependence of Liquid Crystalline Properties for a Homologous Series of Polyesters

Abstract Mesomorphic properties of higher homologues of flexible main chain thermotropic polyesters based on regularly alternating p-dioxy,2,2′dimethylazoxybenzene mesogen and (α,αω)-alkanedicarboxylic acid were investigated. Attention was given to changes from cybotactic nematic to smectic C (Nc—Sc) mesophases. On the basis of SAX data, rheology and miscibility diagrams with low M compounds displaying both a Sc and Nc mesophase it was shown that the polyester with n=18 and M > 3,000 displays a Sc monotropic mesophase. The data suggest that while polyesters of odd spacer parity in the nematic quiescent state do not display any tendency toward formation of layered order, polyesters with n even exhibit a pronounced tendency toward the formation of layered order, This tendency increasing with n and M is favored by a decrease of temperature. It may be argued that the observed passage Nc—Sc is continuous. The formation of layered (Nc) order was also observed for large n and M for a spacer of odd parity but onl...

Structure and Liquid Crystalline Properties of Poly(azomethine-ester)s

A series of polyesters having azomethine groups in the main chain was synthesized and ability of the polymers to formation of thermotropic mesophase was investigated.

Measurement of the Three Elastic Constants and the Shear Viscosity γ1 in a Main-Chain Nematic Polymer

Abstract K 1, K 2, K 3 and [mgrave]1 have been measured for the first time in a typical main-chain polymer belonging to a polyester series. K 1 is very large compared to conventional nematics, while K 2 and K 3 have more conventional values. K 1 have been measured by two methods, one of them consisting in the measurement of the characteristic rise time of regular striped domains.

Improved Comfort Polyester

A series of polyester, cotton, rayon, polypropylene, polybenzimidazole, and polyester/cotton blend fabrics were evaluated in two subjective wearer trials. Subjective trial data were correlated with results of in-house laboratory tests. Important findings were that both geometric modifications and surface treatments play an important role in perceived comfort; however, objective testing can only predict general trends in comfort or pick out extremely poor candidates. These are supplemental but are no substitutes for a well planned and well run subjective wear trial analysis.

Improved Comfort Polyester

A series of polyester, cotton, and polyester/cotton blends and a few miscellaneous types were evaluated in a number of subjective wearer trials by the Gillette Research Institute. The modifications, which were shown most substantially to improve the comfort of polyester, included certain engineering modifications, cross-section variations, and pressure jet treatments. Some modification combinations increased the perceived comfort level of polyesters to a point equal to or exceeding that of a 50/50 PET/ cotton blend and close to all cotton.

Improved Comfort Polyester

Thermal transport properties of a series of polyester, cotton, and polyester/cotton blend fabrics were determined in an effort to understand physical basis of clothing comfort. The results indicate that both the fabric construction and the constituent fiber properties affect thermal transport. In general, thermal insulation, air permeability, and water vapor transmission rate are dependent mainly on the fabric geometrical parameters, namely, thickness and porosity. Conversely, liquid water transport is strongly dependent on the constituent fibers, with cotton generally showing advantages over polyester. Geometrical factors do, however, play a major role in this mechanism, and a 50/50 polyester/cotton blend was nearly identical to cotton in liquid water transport behavior. Further, the perceived superior comfort performance of cotton seems largely due to the packing behavior in the yam.