Novel polymeric membrane for artificial photosynthesis

Identifier:  TDX:4182

Handle: https://hdl.handle.net/20.500.11797/TDX4182

Authors:  Zare, Alireza

Abstract:
This doctoral thesis focuses on preparing novel polymeric membranes to be used in artificial photosynthesis devices. In particular, we are interested in membranes for both ion conductive and CO2 capture. We prepared and characterized two different materials, based on Poly(epichlorohydrin-co-ethylene oxide) (PECH-co-EO) grafted with potassium 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy] benzoate, containing 20% (CP20) or 40% (CP40) modified units, respectively. In order to reach efficient transport properties, homeotropically oriented membranes were prepared by a fine-tuned thermal annealing treatment and were subsequently investigated by dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA). DMTA and DETA confirmed that grafting with the dendron strongly hinders copolymer motions, but did not show great differences between unoriented and oriented membranes, regardless of the amount of dendrons. Moreover, transport properties were studied by methanol and proton conductivity experiment and by linear sweep voltammetry (LSV). Results demonstrated that in CP20 and CP40, cation transport depends on the presence of defined cationic channels, not affected by water presence; the comparison between LSV experiments performed with different alkaline cations suggests that CP40 possesses channels with larger diameters and better-defined inner structures. We focused on improving CO2 absorption performance by using two different additives in neat polysulfone as gas-liquid membrane contactors. These additives are amine additives based on hyperbranched Lupasol G20 partially grafted with benzoyl chloride (mG20) or phenyl isocyanate (UG20). Membranes with different amount of additives were prepared by phase inversion precipitation and characterized by several techniques. In general, it was found that the presence of the additive greatly improved the characteristics of the membranes as regards the CO2 capture, especially solubility, hydrophobicity and chemical resistance to the aqueous alkaline absorbent solution, giving the better results for 5% additive content. In summary, 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.