POLYMERIC MEMBRANES FROM COLLOIDAL CRYSTAL TEMPLATES

N. CASIS, D. ESTENOZ, S. RAVAINE, M. M. FIDALGO DE CORTALEZZI, HAYDEE OLIVA, G. MEIRA

Santiago, Chile

Congreso; Congreso Internacional de Metalurgia y Materiales; 2008

CONAMET/SAM

Porous materials, in particular porous membranes, have a broad range of applications including catalytic substrates, photonic band gap materials, advanced filters, and solid electrolytes. Membranes performance depends to a great extent on the size of the internal pores, the width of the pore size distribution, and the overall membrane structure. The mechanical properties of the polymeric membranes depend on the final pore structure and polymer characteristics that are determined by the deposition process and polymerization conditions. The membrane pore morphology affects the hydraulic resistance and therefore the energy requirements for filtration. In most filtration processes, it is desirable to have an asymmetric membrane with layers of different pore size. Typically an asymmetric membrane is composed of an active thin separation layer, or skin, of small pore size that achieves the rejection of the solute. The skin is attached to a support layer of larger pore size that gives mechanical strength to the membrane with a relatively negligible hydraulic resistance. In this work, polymeric porous membranes were fabricated from templates made from silica particles. Silica particles with a narrow size distribution were synthesized by two different methods. The templates were obtained by vertical deposition of the particles on a glass substrate and by the Langmuir-Blodgett technique to create templates of different particle sizes. To produce the membrane, polystyrene (PS) and bioinspired polymers were used. They are similar to PS, except for the fact that thymine groups are chemically bonded onto the base PS structure, and their structure mimics DNA. In the presence of short-wavelength UV light, the thymine groups dimerize into non-toxic, environmentally benign, and biodegradable photo-resist materials. The porous films were characterized by SEM. Some mechanicals properties of membranes were evaluated. The membranes with pre-specified characteristics will be employed for water filtration.