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Polyurethanes and polyureas from renewable castor oil-derived 10-undecenoic acid were synthesized using the AB-type self-condensation approach. ω-Hydroxy- or ω-amino methyl carbamate ester precursor monomers were prepared under mild conditions from cysteamine methyl carbamate by thiol-ene addition. Synthesis of cysteamine carbamate and the self-condensable monomers derived of 10-undecenol or 10-undecenylamine was studied by using different synthetic conditions. Two different polymers, a polyurethane and a polyurea, were prepared using conventional catalysts thus following a non-isocyanate route. The proposed synthetic approach constitutes a general route that allows for the easy preparation of methyl carbamate monomers not only from renewable (limonene, myrcene, geraniol, etc.), but also from petroleum-derived unsaturated substrates. [ABSTRACT FROM AUTHOR]

This work reports a series of versatile post-polymerization modifications of an aliphatic functional polyester obtained by enzymatic polycondensation of dimethyl 2,9-dibromosebacate and 1,10-decanediol, both derived from castor oil. The alkyl halide functionality has shown to react with thiols, amines and carboxylic acids under mild conditions obtaining high modification degrees. Moreover, functionalization using NIPAAm-COOH terminated polymer has been carried out. [ABSTRACT FROM AUTHOR]

Abstract: A nucleophilic monomer (3,3′-diamino-4,4′-dihydroxybiphenyl, mHAB), isomer of the commercial 3,3′-dihydroxybenzidine (pHAB), has been synthesized in good yield and high purity by a two-step synthesis. This monomer was polymerized with 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA) to form a new ortho-hydroxy polyimide (mHAB-6FDA) followed by thermal rearrangement to polybenzoxazole in solid state. mHAB-6FDA polyimide film showed excellent film-forming ability and good mechanical properties, which were similar to those found for the isomeric polymer pHAB-6FDA. A detailed thermal study was carried out for both polymers (mHAB-6FDA and pHAB-6FDA) to discover the relationship between the thermal treatment employed and the degree of conversion to polybenzoxazole (PBO). Thermal rearrangement (TR) to PBO for the polymer derived from mHAB started from a lower temperature than for the polymer pHAB-6FDA. Final TR conversion was higher for pHAB-6FDA when the employed temperature and residence time were high enough; also, for any treatment temperature, fractional free volume (FFV) was higher for the polymer derived from mHAB. Gas separation properties were measured and it was found that gas permeability (and particularly CO2 permeability) was much better for the material made from mHAB. The high gas permeability along with good selectivity qualifies mHAB-6FDA as a good candidate in carbon capture applications. [Copyright &y& Elsevier]

Abstract: The effect of bulky side groups on the molecular mobility and chain packing of three polyimides derived from dianhydrides with m-terphenyl moieties and 2,4,6-trimethyl-m-phenylenediamine has been studied. Moreover, structure–properties relationships in terms of gas transport have been established. One of the polyimides has no side groups, while the other two have a t-butyl group in 5′ (meta) position on the central ring of the m-terphenyl moiety and one of them has also a pivaloylimino group placed in the 2′ (ortho) position. The changes in chain packing of the membranes were evidenced by wide angle X-ray diffraction (WAXS), whilst the molecular mobility was evaluated from the dielectric sub-ambient secondary relaxation, γ relaxation. The WAXS pattern of the polyimide containing both t-butyl and pivaloylimino side groups evidenced a greater degree of packing regularity than in the other two polyimides. Moreover, the additional pivaloylimino group strongly restricted the local molecular mobility associated with the phenylene-imide ring flips. On the other hand, the gas permeability of the polyimides strongly increased with the introduction of side groups. This increase was mainly related to the increase in the gas diffusivity, which could not be explained by an increase in fractional free volume (FFV). The results presented in this work indicate that the difference in gas diffusivity of the substituted polyimides is consistent with a difference in size distribution of free volume elements. [Copyright &y& Elsevier]

Abstract: This study demonstrates that thermal treatment of ortho-hydroxy containing polyimides (HPIs) in the solid state certainly leads to the formation of polybenzoxazoles (PBOs). Thermal conversion protocol, including temperature and dwell time, and the form of the sample (film or powder) determine the rearrangement reaction rate of HPI into PBO. Thermal rearrangement kinetics seems to be faster for film samples rather than for powder ones. Also, mild thermal treatment conditions (i.e., low temperatures and short times) seem to result in negligible or low degrees of conversion to PBO. Moreover, synthetic routes of HPI do not alter in any way the thermal conversion pathway. These findings validate the widely reported imide-to-benzoxazole thermal rearrangement mechanism, and contradict the alternative rearrangement pathway, proposed recently, of HPI into poly(biphenylene bisimide) polymers. [Copyright &y& Elsevier]

Abstract: An attempt was made to elucidate the relationship between chemical structure, in terms of glass transition temperature (T g), and conversion temperature (T TR ) of thermally rearranged polybenzoxazole membranes, by analyzing DSC and TGA data for a total of 15 sets of o-hydroxypolyimides and copolyimides, derived from two experimental and four commercial structurally different diamines, as well as four different dianhydride monomers. Our research revealed that T TR was influenced by chain ridigity of o-hydroxypolyimides, and exhibited a linear relationship with T g. Therefore, structure and thermal property of o-hydroxypolyimide should be considered when studying TR polymers to determine thermal conversion to polybenzoxazole. [Copyright &y& Elsevier]

Abstract: Mixed matrix membranes of H-ZSM-5 incorporated poly(vinyl alcohol) (PVA) membranes were prepared by solution casting method and crosslinked with glutaraldehyde. The prepared membranes were characterized by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy, differential scanning calorimeter and thermogravimetric analysis. Resulting membranes were tested for pervaporation (PV) separation of methanol–benzene mixture. Pervaporation separation characteristics of the zeolite incorporated membranes were tested at varying methanol feed compositions at different temperatures. It was observed that the mixed matrix membrane containing 5wt.% of zeolite showed the highest selectivity value of 47 with 71.03g/m2 h of flux at 20wt.% methanol in feed mixture at 30°C temperature. In comparison with higher (5wt.%) zeolite content membrane, the less zeolite (1wt.%) incorporated membrane shown the less selectivity along with moderate flux. The experimental studies explain that there is an increase in membrane performance such as swelling, permeation flux and methanol selectivity with H-ZSM-5 content in the membrane. In addition membrane swelling experiments with feed components were performed to understand the PV results. [Copyright &y& Elsevier]

Abstract: A series of polyimides has been obtained from the experimental diamine 1,4-bis(4-aminophenoxy)2,5-di-tert-butylbenzene (TBAPB) and three commercial dianhydrides, i.e. pyromellitic dianhydride (PMDA), 3,3′,4,4′-byphenyltetracarboxylic dyanhidride (BPDA) and 4,4′-hexafluoroisopropyliden diphthalic anhydride (6FDA), following classical polyimidation methods. Analogous polyimides with diamines 2,2-bis(4-aminophenyl)hexafluoropropane (6FpDA) and 1,4-bis(4-aminophenoxy)benzene (APB) have been also prepared for comparative purposes. All polyimides showed high thermal stability, with decomposition temperatures above 490°C, and glass transition temperatures higher than 270°C. The rigid, rod-like structure of PMDA, combined with bulky diamines TBAPB and 6FpDA, yielded polyimides with high fractional free volume (FFV), close to that of 6FDA–6FpDA. The high FFV of PMDA–TBAPB contrasts with its structure that has fairly large degree of short range order as evidenced by X-ray diffraction. The gas permeation properties were greatly dependent on the dianhydride moiety and, as a rule, they compared well with those of polyimides used for gas separation. The polymers from PMDA, PMDA–TBAPB and PMDA–6FpDA, showed the best gas productivity values. By means of molecular modelling calculations, it has been observed that monomer TBAPB preferably adopts a contorted, rotation-restricted conformation, what can explain the special characteristics observed in the reported polyimides. [ABSTRACT FROM AUTHOR]

Abstract: Differently silylated 3- or 4-isoxazolines and 3-pyrazolines, bearing versatile vinyl- or allylsilane moieties in various positions of the heterocyclic system, have been synthesized starting from new silylazolium salts by reduction with metal complex hydrides or alkylation with organolithium reagents. On the other hand, the reductive ring-opening of silylated isoxazolium salts with lithium dimethylcuprate led to interesting β-enamino acylsilanes and α′-silylmethyl-β-enaminoketones. These polysynthetic equivalents are useful building blocks in organic synthesis. [Copyright &y& Elsevier]

Abstract: Silicon and tin 3-, 3,5-, and 3,4,5-metalated pyrazoles have been synthesized by 1,3-dipolar cycloadditions of silyl-, disilyl-, and silylstannylacetylenes with N-phenylsydnone or trimethylsilyldiazomethane. On the other hand, 1- and 2-pyrazolines monometalated and dimetalated in different positions of the heterocycle have been prepared by reaction of vinylsilanes and vinylstannanes with the same 1,3-dipolar reagents. Other interesting products resulting from homologation were obtained by cycloaddition of trimethylsilyldiazomethane with β-silyl enones and esters. Moreover, for the first time a 3-silylpyrazole has been converted into a 3-cyanopyrazole. [Copyright &y& Elsevier]

Abstract: Silyl β-enaminones have been synthesized by reductive cleavage of 5-silyl, 3-, 4- and 5-silylmethylisoxazoles.These versatile synthons bearing different silyl groups in various positions of the enaminoketonic system are of great interest in the regioselective synthesis of 3- or 5-silylpyrazoles and 3-, 4- or 5-silylmethylpyrazoles, which can serve as building blocks in heterocyclic chemistry. [Copyright &y& Elsevier]