Aliphatic Diacids Research Articles

Trap characteristics study of photorefractive polymer materials by thermal stimulated current spectroscopy

A thermal stimulated current (TSC) spectrometer was used to study the trap characteristics of photorefractive polymeric materials in this article. In addition to normal positive peaks due to segmental disorientation induced depolarization, there were negative peaks, even after a prior annealing treatment above Tg without electrical field to release the intrinsically trapped carriers in the film. The negative peaks of the photorefractive polymer containing the hole transport material probably resulted from the release of the trapped field-induced positive carriers during polarization. The negative peak enables trap characteristics to be distinguished from the segmental disorientation behavior. It also makes TSC a useful tool to study the trap characteristics of photorefractive polymers containing organic conducting materials with hole carrier domination in transportation. Incorporating different components into the film caused the change of trap behaviors. The charge transport material (CTM) incorporating in the nonlinear optical (NLO) material PMDA-DR19 reduced the trap depth and transformed the NLO material from nonphotoconductive to photoconductive. Adding charge generating material (CGM) generated an additional shallow trap by which the photogenerated electron-hole pairs were separated and the trapped holes were released more easily. The photorefractive composites with aromatic polyester hosts PMDA-DR19 and IPA-DR19 exhibited deeper trap depth and higher trap density than that with AA-DR19 host from aliphatic diacid. IPA-DR19/PVB/CTM, containing no carboxyl acid groups, possessed the same total trap density as PMDA-DR19/PVB/CTM, but the former exhibited a larger part of low energy traps than the latter did.

Electro-Optical Properties of Waveguides Based on a Main-Chain Nonlinear Optical Polyamide

Polyamides based on 2',5'-diamino-4-(dimethylamino)-4'-nitrostilbene (DDANS) and linear aliphatic diacids represent a class of polymers with large and stable second-order nonlinear optical properties, where the nonlinear optical units are fixed in the polymer backbone with their dipole moments oriented transversely to the main chain. Such NLO polymers were processed by spin-coating into planar waveguides ranging from 500 to 1500 nm in thickness. Subsequently, a macroscopic noncentrosymmetric orientation of the NLO-phores was induced by a corona-discharge poling process. The refractive indices, n TM and n TE , and the electro-optic coefficients, r 33 and r 13 , were determined by measurement of the waveguiding modes of such devices at a wavelength of 785 nm. The electro-optic coefficient r 33 of 12 pm/V compares favorably with state-of-the-art polymeric electro-optic materials. It also equals approximately the electronic contribution to the electro-optic effect which can be calculated from the nonlinear optical susceptibility d 33 . The ratio of electro-optic coefficients r 33 /r 31 was found to be 3, independent of the magnitude of the NLO-phore orientation. This behavior is in perfect agreement with the predictions from the isotropic model.

Lipase-Catalyzed Polyester Synthesis

Abstract The use of lipase as biocatalyst in polyesterification of aliphatic diacids or their derivatives, and diols in an organic solvent has been discussed. We have demonstrated that bis(2-chloroethyl) esters of succinic, fumaric, and maleic acid, and bis(2,2,2-trifluoroethyl) sebacate and -dodecanedioate can be polymerized by lipase-catalyzed polytransesterification. Maleate was isomerized to fumarate even under mild reaction conditions, resulting in poly(1,4-butyl fumarate). In order to obtain a high mass-average molar mass of the polyester, solid Mucor miehei lipase was found to be the best lipase and diphenyl ether the best solvent of several investigated. There was no clear relationship with the log P value of the solvent and the polyesterification activity of lipase. The highest degree of polymerization (DP = 184) of poly(1,4-butyl sebacate) with a mass-average molar mass of 46,600 g·mol−1 was obtained in polytransesterification of bis(2,2,2-trifluoroethyl) sebacate and 1,4-butanediol using a prog...

Incorporation of diacids into the polyglycine II structure: model studies.

Aliphatic diacids are often incorporated into polypeptide structures in order to obtain model compounds for hormones, protein turns, etc. They are also fundamental components of many commercial polyamides. On the other hand glycine, the simplest amino acid, shows unique conformational features. In order to better understand the structure of such compounds, we have synthetized and determined the molecular structure of three models represented by the general formula CH3-CH2-CH2-NH-CO-CH2-NH-CO-(CH2)n-2-CO-NH-CH2-CO-NH-CH2-CH2-CH3, with n = 3, 4, or 6. Conformational differences have been found in the dicarboxylic moiety, whereas glycine always has the polyglycine II conformation. The -CO-(CH2)n-2-CO-segment adopts a folded conformation: SS, TGT, and SGTGS for n = 3, 4, and 6, respectively. Molecular packing is always pseudohexagonal and a network of hydrogen bonds oriented in three directions at 120 degrees is formed. The results are of interest in order to provide information about polyamides in which glycine residues are incorporated. Our results confirm the tendency of glycine residues to adopt the polyglycine II conformation in its copolymers with aliphatic compounds.

In vivo and in vitro elimination of aliphatic polyanhydrides

The hydrolysis and elimination processes of biopolyanhydrides has been studied using a polymer series of linear aliphatic diacids. This polymer series degrade into their monomer counterparts at about the same rate but differ in the water solubility of their degradation products. Polymers based on natural diacids of the general structure -[OOC-(CH 2) xCO] n- where x is between 4 and 12 were implanted subcutaneously in rats and the elimination of the polymers from the implantation site was observed. The in vitro hydrolysis of this polymer series was studied by monitoring the weight loss, release of monomer degradation products and the content of anhydride bonds in the polymer as a function of time. A dependence was found between the monomer solubility and the rate of polymer elimination in both in vivo and in vitro. The elimination time for polymers based on soluble monomers (x = 4–8) was 7–14 days, while the polymers based on low monomer solubility (x = 10–12) were eliminated only after 8 weeks. The in vitro degradation of polyanhydrides in the presence of several common hydrolytic enzymes found around implants did not affect polymer degradation. All polymers were biocompatible and found to be useful as carriers for drug delivery.

Orientational Relaxation in Electric-Field-Poled Films from Main-Chain Nonlinear Optical Polyamides

The orientational relaxation of the NLO-phores in polyamides based on 2',5'-diamino-4-(dimethylamino)-4'-nitrostilbene (DDANS) and linear aliphatic diacid chlorides was investigated at different temperatures below the glass transition by the decay of the nonlinear optical susceptibilities of corona-poled thin films. The time dependence of the decay was found to be well represented by the Kohlrausch-Williams-Watts stretched exponential function. The temperature dependence of the decay could be correlated with the glass transition temperature T g using a normalized relaxation low with (T g - T)/T as the relevant scaling parameter. For one of the polyamides, showing a T g of 176 °C, no decay of the NLO coefficient was observed at 25 °C within 8 months. For the purely orientational relaxation at 80 °C a relaxation time of significantly over 10 years could be estimated. As shown by UV-vis spectroscopy, the long-term stability of the new polyamides is restricted by the limited thermal stability of the NLO-phore. The polyamides investigated exhibit an enhanced orientational stability, as can be seen from the aging data. They represent a new approach to the design of polymers with large and stable second-order nonlinear optical properties, where the nonlinear optical units are fixed in the polymer backbone with their dipole moments oriented transversely to the main chain.

Curing of a rigid rod epoxy resin with an aliphatic diacid: an example of a lightly crosslinked liquid crystalline thermoset

AbstractBy reacting a rigid rod epoxy terminated molecule (p‐bis(2,3‐epoxypropoxy)‐α‐methylstilbene) with an aliphatic carboxylic acid (decanedioic acid), a lightly crosslinked liquid crystalline network is obtained. This network exhibits a smectic‐like phase. While the mesophasic structure resulted “frozen” by the crosslinks in the case of higly crosslinked liquid crystalline epoxy resins, in this case a reversible transition from the liquid crystalline to the isotropic phase is observed. Moreover, while curing the same rigid rod epoxy molecule with amines resulted in a thermoset with a nematic structure, in this case a more ordered mesophase can be obtained. Preliminary results show that it is possible to orient macroscopically the mesogenic chains by stretching thin films above the glass transition temperature (Tg) and then quickly cooling down to the glassy state. This makes this material very attractive in the field of optical applications.

Synthesis and activity of some antimalarial bisquinolines.

A new type of bisquinoline antimalarial, in which the basic side chain of chloroquine is retained, has been evaluated. Nine bisamides were prepared from aliphatic diacids with 6-amino- and 8-amino-((4-(diethylamino)-1-methylbutyl)amino)quinoline, and screened against chloroquine-sensitive and -resistant strains of Plasmodium falciparum in vitro. The resistance indices for all compounds were lower than for chloroquine. The position of attachment and length of the linker chain markedly affected activity. The most active (IC50 = 120 nM against the chloroquine-resistant FAC8 strain) was the -(O)C(CH2)4C(O)- linked 8-amino compound.

Synthesis and Properties of Stereoregular Polyamides Derived from L-Tartaric Acid: Poly[(2S,3S)-2,3-Dimethoxybutylene alkanamide

The synthesis of (2S,3S)-(-)-2,3-dimethoxy-1,4-butanediamine to be employed in the preparation of stereoregular polyamides 4,n containing two chiral carbons in the diamine repeating unit has been carried out by using L-tartaric acid as a raw material. Polycondensation in a chloroform solution of this diamine activated as the N,N'-bis(trimethylsilyl) derivative with pentachlorophenyl esters of even aliphatic diacids ranging from 4 to 12 carbons afforded the title polyamides with DP n in the range 20-100 depending upon the value of n. These highly crystalline polyamides melted in the range 150-190°C, had a pronounced affinity to water and exhibited moderate optical activity

Homogeneous and Heterogeneous Hydrogenation of Nitriles in a Liquid Phase: Chemical, Mechanistic, and Catalytic Aspects

Abstract Primary or alkylated amines are important chemicals and intermedi-ates. N-Alkylamines are used without further transformation as surface-active agents. Aliphatic primary diamines polymerize with aliphatic diacids to give linear polyamides which have conquered a large place in textile and mechanical industry [11. Mono- and polyamines are produced by catalytic hydrogenation of the corresponding nitriles [2]. In particular this pathway to hexamethylenediamine has been made easier since the synthesis of adi-ponitrile by hydrocyanation of butadiene was made possible [3]. The spec-ifications for production of amines are often very drastic from the point of view of purity, in particular for the diamines used in the textile industry. Thus the stress is put on selectivity of the reaction and most of industrial processes have a yield approaching stoichiometry. It exists few reviews on reduction of nitriles [4, 51, the literature dealing with this type of reaction being mostly published in patents [6–91, and practical knowledge is at the state of “know-how” [lo]. Up to now, two types of processes have been used industrially for the

Preparation and Properties of Aliphatic Polybenzoxazoles from 4,4′-Diamino-3,3′-Dihydroxybiphenyl and Aliphatic Dicarboxylic Acid Chlorides by the Silylation Method

Abstract A series of aliphatic polybenzoxazoles of high molecular weights was prepared in three steps by the low-temperature solution polycondensation of tetrakis(trimethylsilyl)-substituted 4,4′-diamino-3,3′-dihydroxy-biphenyl with aliphatic diacid chlorides with 7 to 12 methylene units yielding trimethylsilyl-substituted poly(o-hydroxysamide) precursor polymers, which were subjected to desilylation with methanol giving the poly(o-hydroxyamide)s, followed by thermal cyclodehydration. The aliphatic polybenzoxazoles had melting points in the 172 to 246 °C range with glass transition temperatures of 55-97°C. They were stable in the melt state up to 400 °C in nitrogen. These polybenzoxazoles and the corresponding bisbenzoxazole model compounds exhibited no liquid crystallinity.

Thermoplastic polyheterocycles. I: Polyalkylene‐benzoxazoles

AbstractPolyalkylenebenzoxazoles of high molecular weight (inherent viscosity values from 0.76 to 2.95) were prepared from 4,6‐diaminoresorcinol dihydrochloride and aliphatic diacids in polyphosphoric acid by heating at 180 to 200°C for 3–5 h. Melting points of the polymers ranged from 148 to 423°C, depending on the length of the alkylene chain. Glass transition temperatures were relatively low, ranging from 50 to 100°C and did not show the pronounced odd/even effect noted for melting points. In all cases, rapid weight loss occurred above 400°C. No evidence for the formation of a molecular composite was observed in an attempt to prepare in situ a rod‐like polybenzoxazole in a polyalkylenebenzoxazole.

Design, synthesis, and pr eliminary characterization of tyrosine-containing polyarylates: New biomaterials for medical applications

Five structurally related, aliphatic polyarylates were synthesized from tyrosine-derived diphenols and diacids. The diphenols were a homologous series of three desaminotyrosyl-tyrosine alkyl esters (ethyl, hexyl, octyl) which had previously been used in the synthesis of mechanically strong and tissue-compatible polycarbonates. The diacids (succinic acid, adipic acid, sebacic acid) were selected among compounds that were known to be of low systemic toxicity. By using different diacids as comonomers, the flexibility of the polymer backbone could be varied while the desaminotyrosyl-tyrosine alkyl esters provided pendent chains of various length. Some of the thermal and mechanical properties of the five polymers could be correlated to their chemical structure: the glass transition temperature decreased from 53 to 13 degrees C, and the tensile modulus (measured at room temperature) decreased from 1500 to about 3 MPa when the length of the aliphatic diacid in the polymer backbone and/or the length of the alkyl ester pendent chain was increased. The presence of an arylate bond in the polymer backbone introduced a hydrolytically labile linkage into the polymer structure. Under physiological conditions in vitro all polymers degraded: thin films retained only about 30-40% of their initial molecular weight (Mw) after 26 weeks of storage in phosphate buffer solutions (pH 7.4) at 37 degrees C. Release studies with p-nitroaniline as a model drug indicated that a diffusion controlled release process occurred. The rate of p-nitroaniline release could be correlated with the glass transition temperature of the polymer.

Melt spinning and mechanical properties of semirigid liquid‐crystal copolyesters

AbstractMelt‐spinning and mechanical properties of fibers of a new class of semirigid thermotropic liquid‐crystal polymers are presented. These copolyesters are synthesized from 4‐4′‐dihydroxybiphenyl (B), 4‐hydroxybenzoic acid (H), and flexible units provided by aliphatic diacids. The flexible units depress the melting temperature without strongly depressing the mechanical properties. These liquid‐crystal polymers can be easily spun at high draw ratios. Indeed, unlike rigid liquid‐crystal polymers, relatively high draw ratios are needed to attain high mechanical strength. Tensile moduli of about 28 GPa and tensile strengths of about 350 MPa are obtained. © 1993 John Wiley & Sons, Inc.

Coagulation-floculation par le chlorure ferrique de quelques acides organiques et phenols en solution aqueuse

Some studies on the role and behaviour of organic matter during coagulation of raw waters or solutions have been reported in the literature. As far as coagulation of dissolved humic substances is concerned, some general conclusions could be made from the studies. The best removal of these substances was obtained at pH 4–5 with ferric iron and between pH 5 and 6 with alum (Hall and Packham, 1965; Van Breemen et al., 1979; Jekel, 1985; Lefebvre and Legube, 1990). Fulvic acids were found to be less easy to remove than humic acids (Babcock and Singer, 1979; Jekel, 1985). A relationship between initial concentration of humics and optimal coagulant dosage was often shown (Narkis and Rebhun, 1977; Edzwald et al., 1977, 1979; Kim et al., 1989; Lefebvre and Legube, 1990). The aim of our study was to optimize the removal of organic matter by iron(III) coagulation. A first set of experiments on aquatic humic substances allowed some results to be obtained (Lefebvre and Legube, 1990) such as an optimum of pH between 4.5 and 5.5 and the presence of the stoichiometric relationship of 2 mg Fe per mg of DOC, to obtain the best removal at pH 5.5. The objective of this paper was to try to define the role of the acidic function of organic matter on its removal by iron(III). Some simple aromatics and aliphatic acids were studied in weakly mineralized solution. Experiments were carried out with laboratory apparatus including coagulation-flocculation sedimentation and flocculation treatment steps (Lefebvre and Legube, 1990). The removal of organic compounds was followed by TOC and u.v.-absorbance analysis. Residual iron was determined by atomic adsorption spectrometry. The optimal pH of coagulation was found to be about 5.8 for the salicylic acid and 5.5 for gallic acid. Figure 1 shows data obtained with gallic acid. Hence, the following studies were performed at pH 5.5. Furthermore, choice of this pH allowed comparison with results obtained from coagulation of fulvic acids in similar conditions (Lefebvre and Legube, 1990). Table 2 collects average values of results obtained with 17 aromatic compounds (2.5–15 mg l −1 TOC) coagulated at pH = 5.5 and 20°C, with 15, 30 or 40 mg l −1 Fe. Examination of Table 2 allows us to define four classes of aromatic compounds regarding their behaviour during iron coagulation. Aromatics bringing only one acidic group (COOH and OH) or more (two or three) non-adjacent acidic groups, were not removed under our experimental conditions (benzoic acid, p-hydroxybenzoic acid, m-hydroxybenzoic acid, 3-methoxybenzoic acid, o-aminobenzoic acid, phenol, resorcinol, phoroglucinol, o-cresol). Aromatics bringing at least two adjacent acidic groups were more or less removed. The type of acid group seemed to play a significant role on the removal yield. Two different groups in the ortho position led to a small removal not depending on the coagulant/influent TOC ratio, as shown by Fig. 2 for salicylic acid. Two identical groups in the ortho position induced an increasing removal when the coagulant/TOC i ratio increased. Figure 3 illustrates this in the case of phthalic acid. Finally, two adjacent acidic groups on an aromatic compound led to a similar behaviour for humic substances (Lefebvre and Legube, 1990), that is the presence of optimum removal when the coagulant/TOC i ratio varied (gallic acid, pyromellitic acid and pyrogallol). Figure 4 shows an example of gallic acid. Figure 5 summarizes general shapes of curves in terms of remaining compound (TOC effluent/TOC influent) versus coagulant dose (mole/mole). Table 3 gives the values of the results obtained for some aliphatic diacids, coagulated under similar conditions (pH = 5.5, 20°C, TOC i = 2–16 mg l −1, Fe = 30 mg l −1). Figure 6 presents the synthesis. In the case of the saturated aliphatic, removal depended on the number ( n) of CH 2 groups between the two acidic functions. The smaller n was, the better the removal of diacid. Discussion about the possible mechanisms concludes on two main pathways. The first is an exchange of ligand to the surface of amorphous FeOOH. The second is a complexation or ligand exchange between soluble monomers, dimers or oligomers of iron hydroxide and organic matter to lead (directly or after hydrolysis) to a precipitate.

Thermogravimetric analysis of polyesters derived from terephthalic, tetrachloroterephthalic and related diacids with bisphenol A

The thermogravimetric behaviour of polyesters derived from terephthalic, tetrachloroterephthalic and related diacids, with -CH 2- and -OCH 2- as spacer groups with bisphenol A as diphenol, was studied by dynamic thermogravimetry. Polyesters derived from a diacid with an entirely aromatic structure degrade at higher temperatures than those derived from aliphatic diacids owing to the flexibility of the polymeric chain. Polyesters derived from tetrachloroterephthalic acid showed a higher thermal stability than that derived from terephthalic acid, but for the aliphatic polyesters, the chlorinated form showed a lower stability than those without chlorine atoms, probably because the influence of the aliphatic character is greater. The kinetics parameters of the thermal decomposition were determined by the Arrhenius relationship; in the range considered, all the studied polyesters degrade in a single stage, but probably via complex reactions.

Copolycarbonates derived from bisphenol A phthalates

Blocked copolymers from aliphatic diacids and diol-terminated aromatic polyester blocks have been prepared and studied. The preparations of such block copolymers with good molecular weights proved difficult, but a final carbonation reaction enabled the preparation of materials with values of [η] above 1.0. The mechanical and thermal properties of these have been studied and reported.

Configurational properties of polyesters derived from aliphatic diacids and 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane

Configurational properties of polyesters derived from aliphatic diacids and 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane

Synthesis and physical properties of liquid-crystalline polyesters derived from 4,4'-dihydroxybicyclohexyl

Polyesters are prepared by polycondensation with linear aliphatic diacids. They exhibit the following thermotropic transition sequences: crystal-smectic G-isotropic. The spacer is found to be in an extended chain conformation. The polymers follow the usual pattern displayed by mesogenic core-flexible spacer polymers

Polyanhydrides. IV. Unsaturated and crosslinked polyanhydrides

AbstractUnsaturated polyanhydrides of the structure [(COCHCHCOO)x(CORCOO)y]n, were synthesized. The polymers were prepared by either melt or solution polycondensation. Weight average molecular weights of up to 30,000 were obtained. The double bonds remain intact throughout the polymerization process and were available for a secondary reaction to form a crosslinked matrix. Poly(fumaric acid) is crystalline and insoluble in common organic solvents. Copolymers of fumaric acid with aliphatic diacids are less crystalline and soluble in chlorinated hydrocarbons. These copolymers displayed nearly constant degradation rates and drug release rates under physiological conditions. The time for complete degradation of 14 × 1.5 mm discs of poly(fumaric anhydride) and poly(sebacic anhydride) occurred in 2 and 15 days, respectively, while their copolymers degraded within this range. Further crosslinking of the polyanhydrids is demonstrated.