Nanoporous Membranes by Solventless Melt Processing and Post-Treatments

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Conventional fabrication methods for nanoporous polymeric filtration membranes employ organic solvents resulting in membranes having a wide pore size distribution and limited organic solvent resistance. Large volumes of solvent-contaminated aqueous wastes are produced. Preliminary studies have described a novel and generally applicable solventless technique for making nanoporous membranes from a multicomponent polymer system containing a matrix phase and an immiscible minor phase with/without a compatibilizing block copolymer. The method involves melt extrusion of the multicomponent polymer system into a film and subjecting it to post-extrusion treatments involving stretching steps leading to continuous microcracks in the matrix and pores at the phase interface via debonding. A general investigation of such a technique for making flat nanoporous membranes is proposed. The specific research objectives and the corresponding methods are as follows: (1) Broaden the range of immiscible polymer blends to a variety of systems from two broad classes of polymer combinations: semicrystalline/amorphous, and semicrystalline/semicrystalline with different melting temperatures. System selection will consider their polarity, hydrophilicity, degree of crystallinity, melting temperature, melt viscosity and elasticity and molecular weight and distribution. (2) Established the detailed processing/structure/property correlations between film extrusion and post-treatment conditions, the precursor solid film morphology and the nanoporous membrane structure developed. (3) Investigate the separation characteristics of such membranes in ultrafiltration, nanofiltration, microfiltration, supported liquid membrane permeation as a skin-barrier analog and battery separator applications. (4) Analyze the drastically reduced overall environmental impact of the proposed solventless membrane manufacturing method vis-a-vis existing solvent-based membrane making process.Successful achievement of these research objectives will establish an environmentally friendly general solventless technique of making flat nanoporous polymeric membranes having a variety of commercially-useful separation and transport capabilities for mixtures of molecules/proteins/nanoparticles. The manufacturing methodology will have immediate potential for extension to hollow fiber membranes. Understanding the science of this membrane-making technology and its potential will facilitate development of novel nanoporous membranes. A graduate student and a post-doctoral fellow will be educated in membrane fabrication, membrane characterization and membrane processes. Collaboration between Polymer Processing Institute and the Center for Membrane Technologies at NJIT will advance existing cooperation to a higher level.