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Summary: A new diamine monomer containing a crown ether was made to react with commercial diacid chlorides and dianhydrides to yield new aromatic polyamides and polyimides. The crown ether moiety was introduced as a pendant group so that the polymers showed enhanced solubility in organic solvents, good thermal properties (high transition temperatures and high thermal stability), and good film-forming ability. The new aromatic polyamides and polyimides bearing a benzo-15-crown-5-pendant group synthesized here.

A novel tert-butyl-containing dianhydride was prepared from readily available reagents. It was reacted with various aromatic diamines to prepare a set of polyimides containing tert-butyl pendent groups. The resulting polyimides exhibit high molecular weights (high inherent viscosity), and a combination of desirable properties, such as good solubility in aprotic amide solvents and cresols, high glass transition temperatures (up to 320 °C), high thermal resistance, film-forming capability and good mechanical properties.

A new oxypyrone diamine, 2,6-bis(4-aminophenyl)-3,5-dimethyltetrahydro-4H-pyran-4-one (DAPP), was prepared from 4-nitrobenzaldehyde and 3-oxa-n-pentane in a two-step reaction with a high yield and a high purity. Aromatic polyamides were obtained from this novel condensation monomer and several diacid chlorides through the conventional low-temperature solution method in N,N-dimethylacetamide. Polycondensation results were consistent with a high reactivity for DAPP because high yields and high molecular weight polyamides were obtained with inherent viscosities up to 1.8 dL/g. The reactivity of DAPP was also estimated with theoretical calculations from computer programs for molecular simulation, with orbital and charge factors considered. The polymers showed improved solubility in organic solvents, relative to conventional wholly aromatic polyamides, and high glass-transition temperatures (from differential scanning calorimetry) over 270 °C. However, the thermal resistance, as estimated by thermogravimetric analysis, was lower than that of conventional aromatic polyamides; nevertheless, decomposition temperatures well beyond 300 °C were observed in nitrogen and air. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1825–1832, 2001

Aromatic polyamides based on a novel bis(ether-carboxylic acid) were synthesized by the direct phosphorylation condensation method. 1,4-Bis(4-carboxyphenoxy)-2,5-di-tert-butylbenzene was combined with various diamines containing flexible linkages and side substituents to render a set of eight novel aromatic polyamides. The polymers were produced with high yields and moderate to high inherent viscosities (0.49–1.32 dL/g) that corresponded to weight-average and number-average molecular weights (by gel permeation chromatography) of 31,000–80,000 and 19,000–50,000, respectively. Except for a single example, the polyamides were essentially amorphous and soluble in a variety of common solvents such as cyclohexanone, dioxane, and tetrahydrofuran. They showed glass-transition temperatures of 250–295 °C (by differential scanning calorimetry) and 10% weight loss temperatures above 460 °C, as revealed by thermogravimetric analysis in nitrogen. Polymer films, obtained by casting from N,N-dimethylacetamide solutions, exhibited good mechanical properties, with tensile strengths of 83–111 MPa and tensile moduli of 2.0–2.2 GPa. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 475–485, 2001

A set of new aromatic polyamides were synthesized by the direct phosphorylation condensation of 4-(1-adamantyl)-1,3-bis-(4-aminophenoxy)benzene with various diacids. The polymers were produced with high yields and moderate to high inherent viscosities (0.43–1.03 dL/g), and the weight-average molecular weights and number-average molecular weights, determined by gel permeation chromatography, were in the range of 37,000–93,000 and 12,000–59,000, respectively. The polyamides were essentially amorphous and soluble in a variety of solvents such as N,N-dimethylacetamide (DMAc), cyclohexanone, and tetrahydrofuran. They showed glass-transition temperatures in the range of 240–300 °C (differential scanning calorimetry) and 10% weight-loss temperatures over 450 °C, as revealed by thermogravimetric analysis in nitrogen. All the polymers gave strong films via casting from DMAc solutions, and these films exhibited good mechanical properties, with tensile strengths in the range of 77–92 MPa and tensile moduli between 1.5 and 2.5 GPa. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1014–1023, 2000

The thermal properties and crystal chain packing found for two series (m and p) of oligomeric compounds, with n = 5, 7, 9, and 11 phenylene units, as model compounds for aromatic polyketones are reported. While oligomers of series p contain 1–4 substituted phenylene units those of series m contain an isophthalic group (1–3 substituted phenylene) as the central aryl unit. The keto/ether mole ratio ranges from 0.5 to 0.75. It is confirmed that melting temperatures are clearly dependent on the keto/ether mole ratio as well as on the presence of the isomer defect (isophthalic ring). The keto/ether mole ratio also influences the molecar cross-section and the fusion enthalpy of crystals. Analysis of X-ray diffractograms of the powder samples reveals the presence of lamellar crystals with a thickness corresponding to the length of the linear extended molecular conformation (c axis). Molecular compounds of series p crystallize in the more stable crystal polymorph (form I), observed for aromatic polyketones, while oligomers of series m show polymorphism depending on their chain length. A partial “polymeric” character of the longest compounds (n = 11) of the two m and p series was found. Nevertheless, their inclusion in this structural study seems to be pertinent.

In this article a new synthesis of 3,3'-diaminobiphenyl (3,3'-DABP) is described, along with the preparation and characterization of polyamides and polyimides based on it. Reactivity of this monomer was calculated by a molecular simulation study, using ab initio quantum-mechanical methods. Terephthaloyl and isophthaloyl chloride were used for the synthesis of polyamides, while 3,3',4,4'-biphenylenetetracarboxylic acid dianhydride and 4,4'-(hexafluoroisopropylidene) diphthalic anhydride were used for the synthesis of polyimides. Medium to high molecular weight polymers were attained, with inherent viscosities near or higher than 1.0 dL/g, the solubility of the 3,3'-DABP polymers was much better than that of the homologous polymers from benzidine (4,4'-DABP), the glass-transition temperatures were lower, by about 40°C, and the thermal resistance, as measured by thermogravimetry, was virtually the same. Amorphous films, made from cast polymer solutions, showed excellent mechanical properties, comparable to conventional aromatic polyamides and polyimides. Theoretical calculations demonstrated that the radius of giration, end-to-end distance and density of poly(3,3'-DABP-isophthalamide) were lower than those of poly(4,4'-DABP-isophthalamide), as a consequence of the chain folding induced in the backbone by the m-substitution in 3,3'-DABP. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4646–4655, 1999

Polyimides derived from a new dianhydride with p-nitrophenyl pendant groups have been synthesized and their properties compared with those of a reference series, without side groups. The polymers were obtained by combination of the novel monomer with aromatic diamines, in a two-step procedure that involved the synthesis of poly(amic acid) or poly(amic silyl ester) intermediates and the cyclization of them to polyimides by thermal treatment. The introduction of the polar nitro groups caused significant increase of the Tgs. On the contrary, the thermal stability was reduced because of the breakdown of CAr—NO2 linkages around 400^oC. A slight decrease in mechanical properties was observed, due to the bulkiness of the side groups, that also produced an important decrease in the strength of the β relaxation, as determined by dynamic mechanical analysis. The solubility of the current polyimides in organic solvents was as poor as that of the parent unsubstituted polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3377–3384, 1999

New dianhydrides containing t-butyl and phenyl pendant groups have been synthesized and used as monomers, together with commercial diamines, to prepare novel polyimides. The influence of the chemical structure of the monomers on their reactivity has been studied by quantum semiempirical methods. The polyimides have been characterized by FTIR and by NMR in the case of soluble polymers. The presence of pendant groups and the method used to imidize polyimide precursors greatly affected polymer properties such as solubility, glass transition temperature, thermal stability, and mechanical properties. As a rule, the novel polyimides showed better solubility in organic solvents than the parent polyimides. Glass transition temperatures in the range 250–270°C and decomposition temperatures over 520°C were observed for the set of current polymers. Tensile strengths up to 135 MPa and mechanical moduli up to 3.0 GPa were measured on films of the current polyimides. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 805–814, 1999

Dielectric relaxation spectroscopy (DRS) is presented for a family of four aromatic polyamides trying to relate the structure of the lateral groups to the molecular mobility. A prominent sub-Tg absorption is always seen followed in some cases by remanent dielectric activity at room temperature and a subsequent increase of the loss permittivity. The low temperature relaxation is analyzed in terms of a Fuoss-Kirkwood equation to obtain the broadness and the strength of these relaxations as well as the activation energy (ranging from 10 to 11 Kcal/mol). The low frequency conductive peak shows in each case a half-width higher (1.30) than those corresponding to a single relaxation time peak (1.144). These values of the half-width are an indication of the complex character of these phenomena. A final discussion of the rotational barriers of the lateral chains rules out that such motions are the only molecular origin for the gamma relaxation. Instead, some kind of motion involving the main chain and where the interchain interactions play a significant role should be considered as responsible for that relaxation. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 919–927, 1997

Two different series of poly(ester imide)s, which are distinguished from each other in the orientation of the ester linkages and show well-differentiated thermotropic behavior, are investigated by means of model calculations and dielectric relaxation spectroscopy. Model calculations show that the orientation of the ester linkages has a strong influence on the rotational energy barriers. The dielectric relaxation spectra of both series shows three relaxation regions in the temperature range between 100 and 400 K that have been identified as the α-, β- and γ-relaxation processes. A difference of about two orders of magnitude between the characteristic rates of the γ-relaxation is the main feature observed in the dielectric response. However, the β-relaxation shows very similar behavior for both series. The differences in the relaxation behavior in the solid state are interpreted on the basis of the rotational barriers deduced from the model calculation results. © 1997 John Wiley & Sons, Inc.

Linear polyaryl(ether ketones) containing tert-butyl pendent groups were prepared from aromatic hydrocarbons and aromatic diacid chlorides, both classes of monomers containing tert-butyl pendent groups. The polymers were prepared in high yield and high molecular weight by low-temperature precipitation polycondensation in 1,2-dichloroethane. The presence of meta-oriented moieties and bulky pendent groups played a beneficial role with regard to solubility, while the thermal transitions and thermal resistance were not greatly impaired relative to conventional all para-oriented polyaryl(ether–ketones). The current polyaryl(ether–ketones) showed glass transition temperatures in the range 170–240°C and decomposition temperatures, as measured by TGA, of about 500°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1251–1256, 1998

The reasons for the reactivity increase toward acyl chlorides caused in aromatic amines by silylation are studied by quantum semiempirical and ab initio methods. Silylated amino groups adopt an sp² planar geometry, in contrast to that observed in the unsilylated series, where a partially pyramidal structure intermediate between sp³ and sp² geometry was obtained. Silylation also causes a strong increase of electronic density on the amine nitrogen and an increase of the Highest Occupied Molecular Orbital (HOMO) energy, both effects favoring the higher reactivity of these silylated amines. In addition to that, silylation produces a decrease of the activation energy in the reaction with an acyl chloride, relative to the unsilylated amines, thus increasing reaction rate.