Structurally isomeric monomers Directed copolymerization of polybenzimidazoles and their properties

Three different series of pyridine based polybenzimidazole (PyPBI) random copolymers consisting of meta-para pyridine linkages were synthesized from various stoichiometric mixtures of meta (2,4; 2,6 and 3,5) and para (2, 5) structure pyridine dicarboxylic acids (PDA) with 3, 3’, 4, 4’- tetra-aminobiphenyl (TAB) by solution polycondensation in polyphosphoric acid (PPA). The influences of the structural isomers of PDA on the PyPBI copolymerization and properties were elucidated by characterizing the resulting copolymers. The solubility of PDA monomers in PPA and the overall monomer concentration in the polymerization were found to be the deciding factors. The higher molecular weight PyPBI were obtained for higher para content copolymers due to the low solubility of para PDA in PPA. The introduction of para structure had enhanced the conjugation along the polymer chain. NMR study showed that the reactivity ratio of para PDA was not identical for all the three sets of PyPBI copolymers, it varied upon the positions of the dicarboxylic acids in the pyridine ring of meta PDAs (structural isomeric effect) with which 2,5 PDA is forming the copolymer. Introduction of para structure and meta PDAs structural isomers affected the thermal stability, flexibility and the photophysical properties of the PyPBI copolymers.     

Determination of the structural configuration of cresol–novolak resins by 13C NMR spectroscopy

¹³C NMR spectroscopy was used to investigate the structures of a series of pure isomeric cresylic novolak resins. Chemical shifts were measured and assigned, and end groups were distinguished from the central repeat units of the chains. Based on these measurements, the number average molecular weight of the para-cresylic oligomer was determined. A comparison of the ¹³C decoupled and coupled spectra of the three isomeric resins indicates that the para isomer has a linear, ordered structure in which the aromatic rings are linked only by ortho–ortho′ methylene-bridging groups. The structures of the ortho and meta isomers are more complex and contain ortho–ortho′, ortho–para′, and para–para′ methylene bridges.     

Processable heat-resistant polymers. XIII. Structure–property relationship in polyamideimides

Novel isomeric polyamideimides were synthesized by reacting the diacid chloride of 2-(4-carboxy phenyl)-1,3-dioxoisoindoline-5-carboxylic acid and o-, m-, and p-phenylenediamine at 30–70°C using polar solvents. The reactivity of the isomeric amines in the polycondensation reaction was studied. The isomeric effects on the physical, chemical, thermal, and electrical properties of the polymers were also studied. The polymers were found to be soluble in highly polar solvents such as DMF, DMAC, NMP, DMSO, m-cresol, etc. Thermal analysis indicated that polymers were thermostable and that their thermal stability follows the order para > meta > ortho. X-ray diffraction data revealed that para polymer is crystalline in nature. Dielectric properties with the variation of frequency at room temperature indicated that the dielectric constant and dielectric loss of the polymers follow the order ortho > meta > para.     

Thermal decomposition kinetics of thermotropic liquid crystalline polyesterimides

We investigated the thermal decomposition behavior of three groups of polyesterimides that had been synthesized from different compositions of monomers that were added in different. We characterized these polymers with thermogravimetric analysis (TGA) and calculated the apparent activation energy (E_a) associated with the thermal decomposition process by the Ozawa method. The results showed that the E_a of the polyesterimides was correlated with the length of the methylene spacer and the content of the 4,4′‐dihydroxybenzophenone monomer. The polyesterimide with four methylene spacers in the main chain had a higher E_a than that with six methylene spacers. The polyesterimide with a higher 4,4′‐dihydroxybenzophenone content provided better thermal stability. The E_a of the polyesterimides also depended on the sequence in which the monomers were added during the copolycondensation process. The E_a of these polyesterimides followed the order: p‐hydroxybenzoic acid added first > p‐hydroxybenzoic acid mixed 4,4′‐dihydroxybenzophenone adding > 4,4′‐dihydroxybenzophenone added first. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2467–2472, 2005     

Synthesis of biphenylated cyanate esters: Thermomechanical resin comparisons within two isomeric series

Three isomeric tetraaryl cyanate esters containing biphenyl moieties {bis‐[4‐(4′‐cyanatophenyl)phenyl]propane, 2,2‐bis‐[4‐(3′‐cyanatophenyl)phenyl]propane, and 2,2‐bis‐[4‐(2′‐cyanatophenyl)phenyl]propane} and three isomeric triaryl cyanate esters {2‐(4′‐hydroxyphenyl)‐2‐[4′‐(4‐hydroxyphenyl)phenyl]propane, 2‐(4′‐hydroxyphenyl)‐2‐[4′‐(3‐hydroxyphenyl)phenyl]propane, and 2‐(4′‐hydroxyphenyl)‐2‐[4′‐(2‐hydroxyphenyl)phenyl]propane} were synthesized from their corresponding bisphenols. The structures of the monomers were confirmed with IR and ¹H‐NMR spectroscopy. The curing behavior was investigated with differential scanning calorimetry. Cyanate esters were cured thermally in the absence of a catalyst and were characterized by dynamic mechanical analysis. The results were compared to the properties of commercial bisphenol A polycyanurate. Of the three tetraaryl isomers, 2,2‐bis‐[4‐(2′‐cyanatophenyl)phenyl]propane had the highest melting point, and its corresponding resin had the lowest glass‐transition temperature (T_g). The para isomer displayed the highest T_g value of the three novel tetraaryl resins. The triaryl dicyanate isomers were low‐melting solids, with the ortho and meta isomers existing as liquids at room temperature. The T_g value of the para‐triaryl isomer was the highest of the three triaryl isomers and was about the same as that of bisphenol A polycyanurate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

同分异构双酚F型苯并噁嗪的研究

分别以同分异构体混合型双酚F和对位双酚F为原料,通过溶液法制备出双酚F型苯并噁嗪。利用傅里叶变换红外光谱(FTIR)、核磁共振氢谱(1H NMR)、凝胶渗透色谱法(GPC)、示差扫描量热法(DSC)、动态热力学分析(DMA)和热重分析(TGA)对2种双酚F型苯并噁嗪中间体的结构、固化行为及其固化物的性能进行了研究。结果表明双酚F中的同分异构体对苯并噁嗪的性能存在影响。对位双酚F型苯并噁嗪的成环率、固化物耐热性和热稳定性均高于同分异构混合双酚F型苯并噁嗪。     

Preparation and characterization of polymethoxymethylstyrenes1H-13C NMR studies

Summary To study the influence of dipolar moments on the permittivity of polymers, three isomeric polymers ortho, meta and para polymethoxystyrenes have been synthesized. Physical properties and NMR studies¹H and¹³C are described.     

Nonlethal rodent repellents: Differences in chemical structure and efficacy from nonlethal bird repellent

At least some anthranilates (e.g., methyl anthranilate), and acetophenones (e.g., orthoaminoacetophenone) are aversive to mice as well as to birds. Here we systematically examined nine acetophenone isomers (ortho, meta, para) and moieties (amino, hydroxy, methoxy) previously tested as drinking and feeding repellents for European starlings (Sturnus vulgaris). All nine substances reduced intake by mice in single-bottle tests. When molecular characteristics were examined, amino group reactivity and, to a lesser extent, isomeric position (i.e., resonance), were related to the strength of the avoidance response. Unlike effective avian repellents, the presence of intramolecular hydrogen bonds did not appear to affect avoidance responding.     

Synthesis of a novel polyesterimide

A new polyesterimide has been synthesized from trimellitic acid anhydride, diaminodiphenylsulfone, and bisphenol-A following three different routes. Solubility behavior in different solvents, solution viscosity, density, crystallinity, and thermal and electrical properties of the polyesterimide have been discussed. Results indicate that the polyesterimide thus prepared has medium thermal stability.     

Isolation of the 9- and 10-isomers of carboxystearic acid and their polyamidation with hexamethylenediamine

Physical properties of the two isomers in 9(10)-carboxystearic acid were found to be sufficiently different to permit isolation by recrystallization. Fractions containing carboxystearic acid of high isomeric purity but containing such impurities as stearic and hydroxystearic acids were purified through the nylon salts formed with hexamethylenediamine to obtain each isomer in high functional and isomeric purity. Physical properties were determined for each isomer, its nylon salt, and its polyamide. The different physical properties suggest for substituted dicarboxylic acids the alternating effect in melting points and solubilities shown by the unsubstituted α,ω-alkanedioic acids.     

Synthesis and Structures of Substrates for Investigation of Intramolecular Electronic Energy Transfer

A series of cyclic α-diketones incorporating a benzene ring (ortho, meta or para substituted) have been synthesized for studies of intramolecular energy transfer (intra-ET). The synthetic method involved acyloin cyclization of the corresponding dicarboxylic acid diesters followed by oxidation with DMSO-acetic anhydride reagent. All compounds were sufficiently flexible so that, even at temperatures in the range of −120°, only broadened lines were observed in their NMR spectra, consistent with observations on temperature dependence of the intra-ET process. The structure of one compound (P-4,4) was established by X-ray crystallographic analysis and of the remaining compounds by a combination of spectroscopic data and molecular mechanics calculations. The calculated structure of P-4,4 is essentially identical to the X-ray structure. In all compounds the methylene chains assume staggered conformations, the dicarbonyl torsion angle aproached 180°, and the molecule folds in such a way that, with one exception, the dicarbonyl moiety lies above (or below) the plane of the benzene ring. Distances between chromophores range from about 3.3 to 5.8 Å.     

Synthesis and characterization of novel polyesterimides

A series of soluble novel polyesterimides was synthesized from diamines [a mixture of 2,2‐bis(4‐(4‐aminophenoxy)phenyl)propane (BAPP) with amine‐terminated polysiloxane (ATPS) in various mole ratios] and the ester‐group‐containing dianhydrides. The ester group containing dianhydrides in turn was synthesized by the transesterification reaction of trimellitic anhydride (TMA) with diacetate ester of hydroquinone (HQ), 4,4′‐dihydrophenyl (BP), 1,6‐hexanediol, or ethylene glycol. The resulted polyesterimides were characterized by using Fourier‐transform infrared spectroscopy, inherent viscosity, solubility, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The polyesterimides of BP and HQ had relatively high glass transition temperatures in the range of 214.7–227.2 and 195.7–210.5°C, respectively. The glass transitions decreased rather slowly with the increase in polysiloxane content. Thermal stability and the weight‐loss behavior of polyesterimides were studied by TGA. All polyesterimides of BP and HQ (BPI and HQI) showed no significant weight loss below 500°C in a N₂ environment, and the decomposition temperatures (T_d5%) of BPI and HQI were >520°C. Most polyesterimides were soluble in polar aprotic solvents and m‐cresol. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 730–738, 2004     

邻、间、对苯二甲酰氯的合成工艺

介绍了以邻苯二甲酸酐为原料,采用光气法、氯化亚砜法或氯代烃法等制备邻苯二甲酰氯的工艺和以间／对苯二甲酸为原料,采用光气法、氯化亚砜法、金属氧化物法、羧酸／酉自法等制备间／对苯二甲酰氯的工艺,对各合成方法的优缺点进行了评价。通过工艺对比可知,以邻苯二甲酸酐或间屑寸苯二甲酸为原料,采用光气法和氯化亚砜法制备邻苯二甲酰氯或间／对苯二甲酰氯的工艺应用广泛;以间／对二甲苯为原料,先生成间／对六氯二甲苯,再与对应的苯二甲酸或者酯反应制备间履寸二甲酰氯的方法最经济。     

Synthesis and fluorescence in solution of polybenzimidazolylphenylenephthalamides

Six polybenzimidazolylphenylenephthalamides (PBIPPA), two meta/para isomers, and four meta/para isomers that had different distances between a benzimidazolyl and the adjacent benzimidazolyl in a polymer chain were synthesized. They were soluble in N,N‐dimethylacetamide. In addition to the fluorescence from the π → π* transition of isolated phenylbenzimidazole, a fluorescence from a chromophore complex in the grand state appeared in the fluorescence spectra, which was observed at higher concentrations. The concentration dependence of the intensity of the fluorescence was investigated in order to learn whether the chromophore complex was intermolecular or intramolecular. It was concluded that the chromophore complex is intramolecular, a conclusion supported by the viscometric results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1412–1416, 2003     

Self‐healing imidazolium‐based ionene‐polyamide membranes: an experimental study on physical and gas transport properties

A new series of six imidazolium‐based ionenes containing aromatic amide linkages has been developed. These ionene‐polyamides are all constitutional isomers varying in the regiochemistry of the amide linkages (para, meta) and xylyl linkages (ortho, meta, para) along the polymer backbone. The physical properties as well as the gas separation behaviors of the corresponding membranes have been extensively studied. These ionene‐polyamide membranes show excellent thermal and mechanical stabilities, together with self‐healing and shape memory characteristics. Most importantly, [TC‐API(p)‐Xy][Tf₂N] and [IC‐API(m)‐Xy][Tf₂N] membranes (TC, terephthaloyl chloride; API, 1‐(3‐aminopropyl)imidazole; Xy, xylyl; Tf₂N, bis(trifluoromethylsulfonyl) imide; IC, isophthaloyl chloride), where the amide and xylyl linkages are attached at para and meta positions, exhibit superior selectivity for CO₂/CH₄ and CO₂/N₂ gas pairs. We also demonstrate the transport properties and diverse applicability of our newly developed ionene‐polyamides, particularly [TC‐API(p)‐Xy][Tf₂N], for various industrial applications. © 2019 Society of Chemical Industry     

Morphology and dynamical mechanical properties of poly ether ketone ketone (PEKK) with meta phenyl links

Poly ether ketone ketone (PEKK) with different proportion of meta phenyl links were investigated by combining differential scanning calorimetry and dynamic mechanical analysis. The influence of the Terephthalyl/Isophthalyl isomers (T/I) ratio on the vitreous phase is mild, the shift of the glass transition is limited to a few degrees and the vitreous G′ is only sensitive to the content of the crystalline phase. Contrarily, the increase of meta isomers is responsible for a significant decrease of the melting temperature (T_m) by 60 °C, which considerably facilitates processing. The modification of interchain interactions in the crystalline phase might be implied. A series of thermal protocols evidenced that the difference of crystallization behavior is also dependent upon the T/I isomer ratio. A time and temperature dependence of annealing on the double melting behavior of PEKK was observed. Regarding the mechanical behavior, the observed reinforcing effect due to the crystalline phase was more prominent in the rubbery state than in the glassy state. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43396.     

The nucleation effect of linear polyethylene lamellae over the crystallization of branched polyethylene

Summary The polyamides with aromatic rings in the main chain were synthesized by the solution polymerization of 4,4-diphenylmethane diisocyanate and aliphatic dicarboxylic acid in the presence of catalyst. The thermal properties and the miscibility behaviours with polyamide-6,6 of these aromatic polyamides were studied. The aromatic polyamides synthesized with one kind of dicarboxylic acid had typical thermal properties of crystalline polymers, whereas those synthesized with the mixtures of dicarboxylic acids were not easily crystallized. The observed miscibility behaviours showed some differences from those predicted by binary interaction model.     

Cyclopinolenic acids: Synthesis,derivatives and thermal properties

The two isomeric cyclopinolenic acids (CP-1 and CP-2), components of distilled tall oil, have been synthesized by means of an intramolecular Diels-Alder reaction of isomers of 5,10,12-octadecatrienoic esters, themselves synthesized in a stereocontrolled manner. The 5cis,10-trans,12trans isomer cyclizes at 200°C to a 1:3 mixture of esters of CP-1 and CP-2. At 200°C, the 5cis,10trans,12cis isomer is unreactive, but at 240°C it gives the same CP-1 + CP-2 ester mixture, presumably by way of prior isomerization to the 5cis,10trans,12trans isomer. A subambient thermal study of CP-1 and CP-2 and their derivatives shows that the compounds, excluding CP-1, lack crystalline structures or melting points, and display glass transitions only, below −80°C for esters and below −50°C for the carboxylic acids.     

Synthesis and curing of new epoxycycloaliphatic polyesterimides with dianhydrides and diisocyanates as hardeners

New epoxy resins obtained from a series of bis(4,5-epoxytetrahydrophthalimides) and three different dicarboxylic diacids were prepared and characterized by spectroscopic techniques and thermal analyses. Homopolymerization of epoxy groups was observed as a parallel process to the polycondensation reaction. Using Epiclon B with a tertiary amine and hexamethylene diisocyanate as hardeners, we studied the reaction of epoxy groups and hydroxylic groups attached to the cycloaliphatic moiety in the main chain. No exotherms were clearly detected by DSC, and during the curing process, only increases in the T_g, values were observed. These cycloaliphatic epoxy polyesters have similar thermal characteristics to related aromatic epoxy polyesterimides, but have better processability. © 1996 John Wiley & Sons, Inc.     

Cross-linking agents for the protection of lyocell against fibrillation: stability of benzeneacrylamido compounds to high temperature acidic environments

A number of benzeneacrylamido compounds, each with at least one sulphonic acid or carboxylic acid group, have been synthesised and converted to the corresponding methyl ethers. The derivatives were then subjected to high temperature polyester dyeing conditions (130 °C) in pH 4.0 buffer solution for 1 h. Derivatives with sulphonic acid groups meta or para to the amide links proved to be hydrolytically stable to the high temperature treatment, whereas derivatives with either an ortho sulphonic acid or carboxylic acid substituent underwent significant amide hydrolysis. This is consistent with previous findings and with a neighbouring group participation mechanism. Accordingly, benzeneacrylamido cross-linking agents for lyocell fibres, designed to be hydrolytically stable to a range of high temperature polyester dyeing conditions appropriate for polyester/lyocell blends, should be devoid of ortho sulphonic acid or carboxylic acid substituents.