Terephthaloyl Unit Research Articles

Molecular Modelling of the Conformational Flexibility and Elastic Behaviour of Short Poly(ethylene terephthalate) Chains

The Monte-Carlo (MC) rotational-isomeric-state (RIS) method developed previously to model the stress–strain behaviour of poly(ethylene terephthalate) (PET) is now applied to short PET chains of between 42 and 84 skeletal bonds. The effects on the radial and probability density distribution functions of the long, flexible virtual bond used to represent the terephthaloyl unit are investigated. The distribution functions generated, based on finite samples of chains, are found to be discontinuous with subsidiary maxima in their tails. The discontinuities lead to uncertainties in the simulated network elasticity properties and, in order to reduce the uncertainty, it is necessary to truncate the distributions at the values of r where they first become discontinuous. The stress–strain properties calculated from the truncated distributions are shown to be consistent with those presented previously for longer PET chains, for which discontinuities in the sampled functions are not apparent.

Synthesis and characterization of cyclohexyl-containing poly(ether ketone sulfone)s

A series of poly(ether ketone sulfone)s were synthesized from 1,4-di(fluorobenzoyl)cyclohexane, difluorodiphenylsulfone and bisphenol A. These polymers were characterized by NMR, IR, SEC, DSC, TGA, tensile tests and DMA. The results from NMR, IR, and SEC indicated that essentially no side reactions, such as cross-linking, associated with enolate chemistry take place during the polymerizations although cis/trans stereochemistry inversion was observed. Comparison of the Tgs of the polymers with 1,4-cyclohexyl units to those of the terephthaloyl analogs suggested that the trans-1,4-cyclohexyl imparts slightly higher Tg than the terephthaloyl control. Tensile tests and DMA revealed that polymers with 1,4-cyclohexyl have essentially the same storage moduli as the corresponding aromatic analogs despite the inherent flexibility of the cyclohexyl unit. DMA also showed that the cyclohexyl unit imparts a larger magnitude of sub-Tg motion than terephthaloyl unit while maintaining high modulus.

Synthesis and Characterization of Photosensitive Phosphorus Based Polymers Containing α,β‐Unsaturated Ketones in the Main Chain

1,3‐Bis(4‐hydroxyphenyl)propenone (BHPP) and 3‐(4‐hydroxy‐3‐methoxy phenyl)‐1‐(4‐hydroxyphenyl)propenone (HMPHPP) were used as monomers for preparing photosensitive phosphorus containing polyesters. The photosensitive monomers BHPP and HMPHPP were prepared respectively by refluxing 4‐hydroxybenzaldehyde and 3‐methoxy‐4‐hydroxybenzaldehyde with 4‐hydroxy acetophenone. The polyesters were synthesized by interfacial polycondensation of photosensitive diols with N‐phenylphosphoramidic dichloride using hexadecyltrimethyl ammonium bromide (HDTMAB) as phase‐transfer catalyst. Copolymers were also prepared by incorporating terephthaloyl chloride in the polymer backbone. The synthesized monomers and polymers were characterized by UV, FT‐IR and 1H, 13C and 31P‐NMR spectroscopic techniques. The resulting polymers had inherent viscosities in the range of 0.15–0.51 dL/g and showed good solubility in polar organic solvents. The thermal properties of the polymers were studied by thermogravimetric analysis and differential scanning calorimetry under nitrogen atmosphere. The TGA data revealed that the 10% weight loss occurs at 275–320°C and all the synthesized polymers showed high char residues. DSC studies indicate that these polymers possess Tg in the range of 48 to 64°C. The photosensitive property of the polymers in film and solution state was investigated by ultraviolet spectroscopy. The effect of incorporation of terephthaloyl unit on photocrosslinking and thermal properties of the polymers was also studied.

Synthesis, characterization and thermal properties of soluble aromatic poly(amide imide)s

Novel diamines such as N, N′-bis(aminoaryl)terephthalamido-2-carboxylic acids (BATCA), which contain primary amine, amide and carboxylic acid groups and are soluble in dilute aqueous NaOH solution, were synthesized by reacting aromatic diamines with trimellitic anhydride chloride in dimethylformamide. Poly(amide imide)s containing 3:1 ratio of amide:imide groups in the polymer chain were prepared by low temperature solution polymerization of BATCAs with isophthaloyl chloride or terephthaloyl chloride in dimethylformamide at 5–10 °C to form poly(amide amic acid)s, and followed by treating with a mixture of triethylamine and acetic anhydride. The PAIs were soluble in polar aprotic solvents like dimethylformamide, dimethylacetamide, dimethylsulphoxide and N-methylpyrrolidone, and have inherent viscosities in the range of 0.30–0.66 dL/g. The PAIs were characterized by IR, 1H NMR and 13C NMR techniques. Thermogravimetric analysis (TGA) has shown that the initial decomposition temperatures of the polymers are in the range of 250–440 °C, depending upon the structures of diamine and diacid chloride. The glass transition temperatures of the PAIs are in the range of 128–320 °C. The IDT and T g values of the polymers containing terephthaloyl unit are higher by about 20–40 °C than those of the polymers with isophthaloyl unit. BATCA could be utilized for the preparation of thin film composite membranes having PAA/PAI barrier layer on PES by in situ interfacial polymerization with IPC/TPC/TMC.

Influence of hydrogen bonding on the generation and stabilization of liquid crystalline polyesters, poly(esteramide)s and polyacrylates

Induction and stabilization of liquid crystallinity through hydrogen bonding (HB) are now well-established. Interesting observations made on the influence of HB on LC behaviour of amido diol-based poly(esteramide)s, poly(esteramide)s containing nitro groups and azobenzene mesogen-based polyacrylates will be discussed. The use of amido diol as an important precursor for the synthesis of novel PEAs containing inbuilt di-amide linkage enabled generation of extensive hydrogen bondings between the amide-amide and amide-ester groups which stabilized the mesophase structures of the PEAs. The contributions of hydrogen bonding to the generation and stabilization of mesophase structures were plainly evident from the observation of liquid crystallinity even in PEAs prepared from fully aliphatic amido diols. Replacement of terephthaloyl units by isophthaloyl moiety totally vanquished liquid crystalline phases while biphenylene and naphthalene units did only reduce the transition temperatures as expected. The occurrence of the smectic phases in some of the polymers indicated possibly self-assembly through the formation of hetero intermolecular hydrogen bonded networks. A smectic polymorphism and in addition, a smectic-to-nematic transition, were observed in the monomers and polymers based on 1,4-phenylene[bis-(3-nitroanthranilidic acid)] containing nitro groups. A smectic polymorphism was also observed as a combined effect of hydrogen bonded carboxyl groups and laterally substituted alkyl side chains in the case of azobenzene mesogen containing side chain polyacrylates. It was further shown that the presence of the mesophase enhances the non-linear optical (NLO) response of these polymers.

PET versus PEN: what difference can a ring make?

Poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalate) (PEN) are structurally related polyesters. In each polymer, the ethylene glycol diesters are separated by rigid rings and are attached to the 1,4-positions of the phenyl and the 2,6-positions of the naphthyl rings in PET and PEN, respectively. Because neighboring ethylene glycol units of each polyester are separated by phenyl or naphthyl rings, their conformations are independent of each other. As a consequence, their RIS conformational models should be identical, with the same populations of trans, gauche +, and gauche− conformations about the –O–CH2–, –CH2–CH2–, and –CH2–O– bonds. This means that PET and PEN are equally flexible as judged by their conformational partition functions. However, because they differ geometrically, properties such as the mean-square end-to-end distance (〈r2〉0) or characteristic ratio (Cr=〈r2〉0/n〈l2〉), though averaged over identical conformations, are not expected to be coincident. The terephthaloyl portion of PET can be considered to consist of the ▪, the –C1⋯C4–, and ▪ bonds, which are collinear and only the conformations about the carbonyl carbon to phenyl ring carbon bonds may be altered. This results in the terephthaloyl unit acting as a freely rotating link in both the statistical and dynamic senses. In the naphthaloyl residue, on the other hand, the carbonyl carbon to C2 and C6 to carbonyl carbon bonds are connected to a collinear, non-rotatable virtual bond between C2 and C5 and to the non-collinear, non-rotatable real bond between C5 and C6, respectively. These geometrical differences between PET and PEN result in distinctly different values for properties like 〈r2〉0 and Cr, even though they are averaged over the same conformational populations. Additionally, volumes occupied by their segments when confined to extended conformations and interconversions between these extended conformers were found to be particularly sensitive to the geometrical distinctions between PET and PEN and several differences in their physical properties are discussed in this context.

Fluorescing wholly aromatic polyesters containing diphenylanthracene fluorophores

New, wholly aromatic polyesters carrying 9,10-diphenylanthracene fluorophores along the main chain or both in the pendent and main chain were prepared and their properties were studied by differential scanning calorimetry, wide-angle X-ray diffractometry and fluorometry in solution as well as in thin solid films. The diphenylanthracene pendent groups are attached to the terephthaloyl unit of the aromatic polyester main chains through the oxyhexamethyleneoxy spacer. Two of the polymers were found to be thermotropic and all of the polymers exhibited relatively strong photoluminescence in solution as well as in thin films. Their fluorescence behavior is discussed in relation to their structures. When the diphenylanthracene fluorophores exist either both in the main chain and the side chain or only in the side chain, the polyesters reveal photoluminescence over a broad range of wavelength from 400 to about 700 nm with the maximum emitting intensity at about 450 nm. The polymer that contains the same fluorophore only in the main chain, however, shows a rather sharp luminescence from about 420 to 550 nm, although its maximum emitting intensity is observed at the same wavelength (ca. 450 nm) as for other polyesters.

H-shaped dimeric LC compounds: synthesis and thermotropic properties of alpha, omega -bis\\[2,5-bis(4-ethoxyphenoxycarbonyl)phenoxy]alkanes

A series of new dimeric liquid crystalline compounds were synthesized and their thermotropic properties studied by differential scanning calorimetry and observation of their melts by polarizing microscopy. These compounds consist of two bis (p-ethoxyphenoxy)terephthalate units interconnected through an oxypolymethyleneoxy spacer on the central terephthaloyl units resulting in a structure of 'H-shaped' dimeric twin compounds. The length of spacers was varied from oxytetramethyleneoxy (n4) to oxyoctamethyleneoxy (n8). The compound containing the oxydodecamethyleneoxy (n12) was also included in this study. With the exception only of the dodecamethylene compound, all of the present compounds are monotropically nematic. In contrast, the compound with the oxydodecamethyleneoxy spacer is enantiotropically nematic. It was found that the heats (DeltaHm) of melting of the monotropic compounds are exceptionally high, 70 100kJ mol1.The DeltaHm value of the compound having the oxydodecamethyleneoxy spacer, however, is much less, about 17 kJ mol1. It is concluded that 'H-shaped' compounds possess less tendency to be thermotropic and also that they tend to vitrify when the spacer length exceeds 6.

Modification of bismaleimide resin by poly(phthaloyl diphenyl ether) and the related copolymers

Poly(ether ketone ketone)s were prepared and used to improve the brittleness of the bismaleimide resin. The bismaleimide resin was composed of 4,4′-bismaleimidediphenyl methane (BMI) and o,o′-diallyl bisphenol A (DBA). Poly(ether ketone ketone)s include poly(phthaloyl diphenyl ether) (PPDE), poly(phthaloyl diphenyl ether-co-isophthaloyl diphenyl ether) (PPIDE), and poly(phthaloyl diphenyl ether-co-terephthaloyl diphenyl ether) (PPTDE). PPIDE (50 mol % isophthaloyl unit) was more effective as a modifier for the bismaleimide resin than were PPDE and PPTDE (50 mol % terephthaloyl unit). Morphologies of the modified resins changed from particulate to cocontinuous and to phase-inverted structures, depending on the modifier structure and content. The most effective modification for the cured resins could be attained because of the cocontinuous phase or phase-inverted structure of the modified resins. For example, when using 10 wt % of PPIDE (50 mol % IP unit, MW 349,000), the modified resin had a phase-inverted morphology and the fracture toughness (KIC) for the modified resins increased 75% with retention in flexural properties and the glass transition temperature, compared to those of the unmodified cured bismaleimide resin. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:769–780, 1998

Molecular Recognition of Aqueous Dipeptides by Noncovalently Aligned Oligoglycine Units at the Air/Water Interface

Abstract: Binding of aqueous dipeptides, GlyX and X'Gly (X = Leu, Phe, Pro, and Ala; X' = Leu and Phe), onto monolayers of dialkyl oligoglycyl amphiphiles has been investigated by n-A isotherm measurement, FT-IR spectroscopy, and XPS elemental analysis. Dipeptides with the N-terminal glycine residue (GlyX) were selectively bound onto monolayers of an amphiphile in which dioctadecylamine moiety was connected with the glycylglycinamide head group via the terephthaloyl unit. When the dipeptide (GlyLeu) concentration in the subphase was varied, the Langmuir-type saturation behavior was observed with the equimolar binding and the binding constant of 35 M-I. The binding efficiency increased in the order of GlyPhe > GlyLeu > GlyPro > GlyAla, implying that the binding is promoted by hydrophobic interaction. The binding was not detected when either of the terephthaloyl and glycylglycinamide units were absent in the monolayer component. Dipeptides with the C-terminal glycine residue (X'Gly) were not bound at all. These results are satisfied by a molecular model in which guest peptides were inserted into the monolayer from the C-terminal. The observed binding selectivity is explained by hydrophobic interaction between the side chain of the C-terminal residue and the hydrophobic cavity in the monolayer and formation of stable antiparallel hydrogen bonding between guest dipeptides and host diglycine chains. The formation of a specific binding site by noncovalent self-assembly leads to a new thinking in the monolayer research.

Thermotropic polyesters: synthesis and properties of modified poly(4-oxybenzoate- co-1,4-phenylene isophthalate)s

The constitution of poly(4-oxybenzoate- co-1,4-phenylene isophthalate)s, consisting of rod-like 4-oxybenzoyl and 1,4-phenylenedioxy units and angular isophthaloyl units, is modified by gradually replacing (i) the 1,4-phenylenedioxy units with chloro-1,4-phenylenedioxy units, and (ii) the angular isophthaloyl units with rod-like terephthaloyl units. The former modification results in a gradual decrease of the melting temperature, while the latter one has the opposite effect. When both modifications are employed simultaneously, their effects essentially compensate each other. Thus, a fully aromatic nematogenic copolyester consisting of equimolar quantities of rod-like 4-oxybenzoyl, chloro-1,4-phenylenedioxy and terephthaloyl units melts at 313°C, more than 100°C below its thermal stability limit. Although the melting behaviour of the materials investigated is strongly affected by annealing, the changes can be reversed by remelting.

Alkoxy substituted liquid‐crystalline aromatic copolyesters

AbstractThe increasing exchange of 2,5‐dipentyloxyterephthaloyl units by terephthaloyl units, studied up to 60 mole‐%, influences the chemical and physical behaviour of the corresponding copolyesters. The copolyesters with an exchange of 30 mole‐% and more become insoluble in chloroform and dichloromethane. The decomposition temperatures increase and the copolyesters show a better long‐time thermal stability. The melting and clearing intervals shift to higher temperatures. The low temperature liquid‐crystalline (LC) phase, which can be seen very well in the HT05‐100 samples, disappears continuously with the increase of the terephthaloyl content. The solid to LC (high temperature phase) transition enthalpies decrease linearly with increasing terephthaloyl content.

The rheological characterization of a series of thermotropic liquid crystalline polymers

AbstractDynamic rheological experiments were performed on a series of two copolymers and a homopolymer based on units of terephthaloyl chloride and isophthaloyl chloride at 90/10 and 75/25 mole ratios combined with 1,10‐bis(4‐hydroxyphenyl)‐decane. Optical microscopy and wide angle X‐ray diffraction (WAXD) confirmed that all of the polyesters in the present series formed nematic liquid crystals with nematic‐to‐isotropic temperatures in the range of 270 to 320°C with increasing terephthaloyl unit content. Broad nematic‐to‐isotropic transitions observed by differential scanning calorimetry (DSC) were indicative of biphasic regions where the nematic and isotropic phases coexist. The rheological behavior of each polymer was more complex in the nematic phase than in the isotropic phase with shear thinning occurring in the former but Newtonian behavior in the latter. There were also some indications that nematic flow behavior could be induced in these polymers by dynamic oscillatory shear flow above the nematic‐to‐isotropic transition, Ti. A form of hysteresis was observed with the homopolymer in that measurements of the dynamic viscosity, η*, taken with ascending frequency sweeps were higher than those taken with descending frequency sweeps.

Effects of linking groups in fluorinated aromatic polyamides

AbstractBased on dynamic thermogravimetric analysis (TGA) of fluorinated aromatic polyamides, we found that substituting terephthaloyl units for isophthaloyl units usually increased the thermal stability of the polymers. In contrast, the first steps of thermal degradation of poly(5,5′‐sulfonyl‐2,2′‐difluoro‐diphenyl terephthalamide) (2,2′‐DIF‐PSDPT) and poly(5,5′‐sulfonyl‐2,2′‐difluorodphenyl isophthalamide)(2,2′‐DIF‐PSDPI) followed almost the same curve. This was attributed to the relative flexibility of the SO2 group, and also to the activating effect on the dehydrofluorination reaction, which was believed to be the first step of the degradation of the ortho‐fluorinated aromatic polyamides, , resulting in the formation of benzoxazole groups, , on the polymer backbone. With fluorinated aromatic polyamides having ortho fluorine to the amide nitrogen, the electron releasing CH2 group deactivated the nucleophilic substitution of the dehydrofluorination reaction and the electron withdrawing group SO2 activated the reaction, so that the onset degradation temperatures of the fluorinated aromatic units R in followed the order:

Synthesis and Study of New Fluorescent Copolyamides

New fluorescent aromatic copolyamides were synthesized by condensing (i) a mixture of 4,4′-[1,4-phenylenebis(methylidyne nitrilo)]-di(benzoyl chloride) (I) and terephthaloyl chloride (II) with 4,4′-diaminodiphenyl ether and 4,4′-diaminobibenzyl and (ii) a mixture of monomer (III) and monomer (II) with 4,4′-diaminodiphenyl methane by a low temperature solution polycondensation method.1 The copolyamides were characterized by solubility tests, viscosity measurements, UV, IR, emission spectroscopy, TGA, and DSC data. The spectral and thermal properties of the copolyamides are correlated to their structure and the effect of the new fluorescent diacid monomer unit and terephthaloyl unit on the thermal degradation of the copolymer was also studied.

ChemInform Abstract: POTENTIAL ANTITUMOR AGENTS. 18. BISQUATERNARY AMMONIUM HETEROCYCLES

AbstractZur Untersuchung auf tumorhemmende Wirkung werden bisquaternäre Ammoniumsalze der allgemeinen Struktur (I) untersucht.

Donor acceptor interactions in polymeric systems, 2. Polyesters from N‐[5,5‐bis(hydroxymethyl)hexyl]carbazole

AbstractPolyesters with a pendant 9‐carbazolyl group were prepared by polycondensation of 9‐[5,5‐bis(hydroxymethyl)hexyl]carbazole (1a) with diethyl malonate, dimethyl terephthalate, and adipoyl chloride. Charge transfer complex formation of these polyesters and their monomeric model compound with 2,4,7‐trinitrofluorenone (TNF) was investigated by means of absorption spectroscopy in 1,2‐dichloroethane.Stability constants (K) of the polymeric systems were always larger than that of the monomeric system in the following order: polymer 3c (with the terephthaloyl unit) > polymer 3a (with the malonyl unit) ≈ polymer 3b (with the adipoyl unit) > 9‐[5,5‐bis‐(acetoxymethyl)hexyl]carbazole (2b).From the measurements of monomer and excimer emission in dilute solutions, interactions between the 9‐carbazolyl groups are discussed for the polymers and the monomeric model compound. For the polymer 3c (containing the terephthaloyl unit), exciplex formation between the 9‐carbazolyl group and the terephthaloyl group was demonstrated. Polymer effects on K are discussed based on the structural information obtained from fluorescence measurements.