Resumen de Novel polymeric membrane for artificial photosynthesis

Alireza Zare

• español

  Esta tesis se centra en la preparación de nuevas membranas poliméricas para dispositivos de fotosíntesis artificial. Preparamos y caracterizamos dos materiales diferentes,basados en Poli(epiclorhidrina-co-óxido de etileno) injertados con 3,4,5-tris[4-(n-dodecan-1-iloxi)benciloxi] benzoato, en un 20% (CP20) o 40%(CP40), respectivamente.Para alcanzar unas propiedades de transporte eficientes, se prepararon membranas orientadas homeotrópicamente mediante un tratamiento térmico controlado y posteriormente se investigaron mediante análisis térmico dinamo-mecánico (DMTA) y análisis térmico dieléctrico (DETA).DMTA y DETA confirmaron que la injerción del dendrón dificulta seriamente los movimientos del copolímero, pero no mostraron grandes diferencias entre las membranas orientadas y las no orientadas, independientemente de la cantidad de dendrones. Además, las propiedades de transporte se estudiaron mediante experimentos de permeabilidad de protones y metanol y mediante voltamperometría de barrido lineal (LSV). Los resultados demostraron que en CP20 y CP40, el transporte de cationes dependía de la presencia de canales catiónicos definidos, no afectados por la presencia de agua; la comparación entre experimentos LSV realizados con diferentes cationes alcalinos sugiere que CP40 posee canales con diámetros más grandes y estructuras internas mejor definidas. Por otro lado, intentamos mejorar el rendimiento en absorción de CO2 mediante el uso de membranas de polisulfona con dos aditivos diferentes en contactores de membrana gas-líquido. Estos aditivos están basados en una polietilenimina commercial hiperramificada (LupasolG20) parcialmente modificada con cloruro de benzoílo (mG20) o fenilisocianato (UG20). Se prepararon membranas con diferentes cantidades de aditivos por precipitación por inversión de fase y se caracterizaron mediante varias técnicas. Se encontró que la presencia del aditivo mejoró mucho las características de las membranas en cuanto a captura de CO2, especialmente la solubilidad, hidrofobicidad y resistencia química a la solución acuosa alcalina absorbente, dando los mejores resultados para 5% de aditivo. El rendimiento de las membranas en términos de permeabilidad y absorción de CO2 mejoró con ambos aditivos, mostrando UG20 un mejor rendimiento.

• català

  Aquesta tesi es centra en la preparació de noves membranes polimèriques per a fotosíntesi artificial. Hem preparat i caracteritzat dos materials diferents, basats en Poli(epicloridina-co-òxid d’etilé) (PECH-co-EO), modificada amb metil 3,4,5-tris[4-(n-dodecan-1-iloxi)benziloxi]benzoat, al 20% (CP20) o 40% (CP40), respectivament. Per assolir propietats de transport eficients, es prepararen membranes orientades homeotròpicament mitjançant un tractament tèrmic. Seguidament, es van analitzar mitjançant anàlisi tèrmic dinàmo-mecànic (DMTA) i dièlectric (DETA). DETA i DMTA van confirmar que la presència del dendró dificulta el moviment dels copolímers; tanmateix, les membranes orientades i no orientades no mostraren una gran diferència, independentment de la quantitat del dendró. A més, vam estudiar les propietats de transport mitjançant proves de permeabilitat de protó i methanol i de voltametria d’escombrat lineal (LSV). Els resultats demostraren que tant en CP20 com en CP40, el transport de cations depèn de la presència de canals de transport definits, no afectats per la presència d’aigua; els experiments LSV realitzats amb diferents cations van demostrar que CP40 posseeix canals amb diàmetres més grans, i que les seves estructures internes són millor definides. D'altra banda, vam intentar millorar el rendiment en absorció de CO2 mitjançant l'ús de membranes de polisulfona amb dos additius diferents en contactors de membrana gas-líquid. Aquests additius estan basats en una polietilenimina comercial hiperramificada (LupasolG20), parcialment modificada amb clorur de benzoil (mG20) o fenilisocianat (UG20). Es prepararen membranes amb diferents quantitats d'additius per precipitació per inversió de fase i es caracteritzaren mitjançant diverses tècniques. Vam trobar que la presència de l'additiu millora molt les característiques de les membranes quant a captura de CO2, especialment la solubilitat, hidrofobicitat i resistència química a la solució aquosa alcalina absorbent, donant els millors resultats per al 5% d'additiu. La permeabilitat i absorció de CO2 van millorar amb tots dos additius, mostrant UG20 un millor rendiment.

• English

  This doctoral thesis focuses on the synthesis and preparation of novel polymeric membranes to be used in artificial photosynthesis. In this regard, this thesis is conducted based on two types of membrane; biomimetic ion conductive membranes and polymeric membranes as contactors in a gas/liquid system for CO2 capture from air.

  We investigated the synthesis and preparation of biomimetic membranes as ion conductive membranes. Biomimetic membranes are interesting artificial materials based on a biomimicking approach. The chemical modification of a linear copolymer, (Poly (epichlorohydrin-co-ethylene oxide) (PECH-co-EO)) was performed with the Potassium 3,4,5-tris[4-(n-dodecan-1-yloxy)bezyloxy]benzoate (Tap) with different degrees of modification, i.e. 20% (CP20) and 40% (CP40). The modified copolymers were characterized by nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and optical microscopy (POM). Membranes were prepared by immersion precipitation method. Additionally, to achieve efficient transport properties, homeotropically oriented membranes were obtained by means of optimized thermal annealing treatment. This technique was optimized, and the results showed that the cooling rate at which the material cooled and the temperature at which the material was annealed were two critical parameters in achieving the maximum homeotropic orientation. Dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA) were used to study the mobility of copolymers in both unoriented and oriented membranes. According to mechanical test results, modification with the dendron strongly hindered copolymer motions. Mechanical tests proved that the main chain required more thermal energy to become mobile and dissipate energy as the modification degree increased. DETA analysis exhibited four molecular relaxations in unmodified and modified copolymers, while some of them had different origin. DMTA and DETA showed no significant changes between unoriented and oriented membranes regardless of the degree of modification; however, due to restrictions imposed by the orientation process, the same molecular mobility and slight shifts towards higher temperatures were detected as projected. Membranes were characterized in terms of morphology, wettability, water uptake, methanol permeability, and transport properties. According to the findings of Atomic Force Microscopy (AFM), membrane orientation results in a significant reduction in roughness for CP20 and an increase for CP40. For both samples hydrophobicity increased with membrane orientation. Water uptake was significantly less than seen for the unmodified copolymer, being furtherly reduced on orientation. No methanol permeability was detected for both samples. The cross-section of the oriented CP40 sample was analyzed by Field emission scanning electron microscopy (FESEM) and exhibited bundles with diameters of about 50 nm. The permeability test for oriented CP20 and CP40 revealed an evident tendency related to the present of defined cationic channels unaffected by water presence. The higher modified copolymer CP40 showed better permeability, probably due to a larger number of Tap groups supporting the column, which improved the inner structure of channels throughout the structure. The linear sweep voltammetry (LSV) technique proved proton transport through membranes. Proton had the highest cationic performance, followed by sodium/potassium and lithium cations. Besides, the higher modified copolymer CP40 demonstrated better proton transport properties. Therefore, membranes based on (PECH-co-EO)) grafted with Tap, homeotropically oriented, can be employed in proton transfer devices such as artificial photosynthesis.

  Polysulfone based membranes were employed as gas-liquid membrane contactors. We focused on improving CO2 absorption performance by using two different types of additives in neat polysulfone (PSf). These additives are amine additives based on hyperbranched Lupasol G20 partially grafted with benzoyl chloride (mG20) or phenyl isocyanate (UG20). Membranes with different amounts of additives were prepared by phase inversion precipitation. Membranes were characterized in terms of morphology, porosity, wettability, thermal and mechanical properties, CO2 solubility permeability, and absorption, especially solubility, hydrophobicity and chemical resistance to the aqueous alkaline absorbent solution. Incorporating the modified polymeric additives into neat polysulfone determined a change in water uptake, KOH uptake, contact angle (CA), porosity, roughness, morphology, solubility, permeability, and CO2 absorption flux. Finger-like macropores, meso- and micropores, and a thin dense layer were observed in all samples. Water uptake and KOH uptake increased in the presence of hydrophilic additives for all samples, as expected. Furthermore, the addition of additives (mG20 and UG20) into neat PSf demonstrated enhanced features in terms of mass transfer coefficient and CO2 absorption depending on the amount and structure of the additives; however, a reverse impact was observed when higher additive amounts (more than 5%) were used. In conclusion, the performance of blend membranes in terms of CO2 permeability and absorption was improved by both additives, while UG20 demonstrates better performance compared to mG20. Interestingly , urea linkages in the modified Polyethylenimine Lupasol G20 is shown to be a successful strategy for the design of additives for facilitated CO2 direct air capture using polymeric membranes.