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Comesana-Gandara B.,CSIC - Institute of Polymer Science and Technology | Comesana-Gandara B.,Hanyang University | Comesana-Gandara B.,UVA CSIC Research Unit | Calle M.,CSIC - Institute of Polymer Science and Technology | And 10 more authors.
Journal of Membrane Science | Year: 2014

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. © 2013 Elsevier B.V.

Molina S.,CSIC - Institute of Polymer Science and Technology | Carretero P.,CSIC - Institute of Polymer Science and Technology | Teli S.B.,University of Alcala | De la Campa J.G.,CSIC - Institute of Polymer Science and Technology | And 3 more authors.
Journal of Membrane Science | Year: 2014

A series of experimental aramid-g-PEO copolymers was employed to fabricate ultrafiltration (UF) membranes by the conventional method of phase inversion, using N,N-dimethylformamide as the solvent and water as the coagulating medium. By adjusting the dope concentration for each polymer, porous membranes were attained which were suitable for UF operations and were tested using a laboratory-scale cross-flow test unit. The water flux of the membranes showed a strong dependency on the chemical composition, with water permeability increasing with increasing PEO content in the copolymer. Their separation potentials were investigated using standard solutions of poly(ethylene oxide) (PEO) as the feed, and the performance of the membranes in UF operations was systematically compared. A relationship between the dope concentration and the molecular weight cut-off (MWCO) could be observed, with higher concentrations resulting in a lower MWCO. In contrast, it was observed that the higher the content of PEO in the copolymer the greater the MWCO. In fouling tests performed using a bovine serum albumin (BSA) solution, aramid-g-PEO UF membranes exhibited very good antifouling properties compared to a commercially sourced polysulfone membrane and to polyamide UF membranes. The results of this work indicate that aramid-g-PEO copolymers are promising materials for the fabrication of fouling resistant membranes for biomacromolecules' separations. © 2013 Elsevier B.V.

Garcia C.,CSIC - Institute of Polymer Science and Technology | Lozano A.E.,CSIC - Institute of Polymer Science and Technology | Lozano A.E.,UVA CSIC Research Unit | Lozano A.E.,University of Valladolid | And 7 more authors.
Macromolecules | Year: 2015

The synthesis of three aromatic polymers containing phthalide cardo groups having high inherent viscosities is described. Polyimides PIC-6F and PIC-TB were prepared from a cardo diamine and two different dianhydrides, and poly(phthalidylidenearylene) (PPDAr) was prepared by a precipitative Friedel-Crafts homopolycondensation of 3-(4-biphenylyl)-3-chlorophthalide. All polymers presented high glass transition temperatures varying between 600 and 690 K. Dense membranes prepared by casting from N,N-dimethylacetamide solutions exhibited good mechanical properties and decomposition temperatures over 770 K under a N2 atmosphere. Results of gas transport measurements of O2, N2, and CO2 were comparatively analyzed based on the chemical structure of the polymers. Additionally, the solubility, diffusion, and permeability coefficients of [13C]O2 in these membranes were determined by 13C NMR spectroscopy and pulsed-field gradient NMR measurements, and the results were in good agreement with those determined with pressure-driven measurements. It was found that membranes of PPDAr exhibited the highest permeability and CO2/N2 and CO2/O2 permselectivities. © 2015 American Chemical Society.

Comesana-Gandara B.,CSIC - Institute of Polymer Science and Technology | Comesana-Gandara B.,Hanyang University | Comesana-Gandara B.,UVA CSIC Research Unit | Comesana-Gandara B.,University of Valladolid | And 8 more authors.
Journal of Membrane Science | Year: 2015

Ortho-hydroxypolyimides (HPIs) undergo thermal rearrangement processes in a solid state at high temperatures to produce thermally rearranged polybenzoxazoles (TR-PBOs), which are promising materials for gas separation membranes due to their exceptional permeability-selectivity performance. The strong dependence between the structure of HPIs and the final properties of the TR-PBOs and the high cost of the HPI precursors are considered excellent reasons for their continued study. In this work, a set of low-cost HPIs were synthetized via the reaction of 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) with 2,4-diaminophenol dihydrochloride (DAP-Cl) and 4,6-diaminoresorcinol dihydrochloride (DAR-Cl). The polyimide made from 6FDA and m-phenylene diamine (MPD) was also obtained for comparison purposes. The polyimide precursors and the corresponding TR-PBOs, which were tested as films, were thoroughly characterized. The glass transition temperature of these precursor polyimides was shown to be a function of the number of hydroxyl groups such that the lowest value corresponded to the polyimide from MPD and the highest value corresponded to that derived from DAR. The conversion rate of HPIs to PBO at different processing temperatures was determined, and the highest conversion rate matched the DAP derived polyimide. With respect to their gas separation properties after thermal treatment at 450. °C, these HPIs gave rise to TR-PBOs with very high permeability and satisfactory permselectivity values for several gas pairs. © 2015 Elsevier B.V.

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