(383n) Discovery of Pervaporation Membranes for Ethanol Dehydration Using a Reactive Polymer Framework

Conventional thermal separations of aqueous solvent mixtures are energy-intensive and costly. Aqueous polar solvent mixtures often form azeotropes, increasing the difficulty of the separation and necessitating additional operations for separation. Membrane-based separations have emerged as an energy- and cost-efficient alternative separation method, with pervaporation as the prime candidate for separating such mixtures. Current polymeric pervaporation membranes are limited to a few commodity polymers that are often not molecularly designed for the intended separation, leading to low fluxes and mild selectivities. In addition, synthesizing and fabricating these polymeric membranes requires several liters of volatile organic solvent per gram of polymer deposited. This project utilizes the spin coating ring-opening metathesis polymerization (scROMP) method reported by our group to generate thin film composite membranes (TFC) of poly(norbornene diacyl chloride) (pNBDAC). The pendant acyl chloride groups of pNBDAC readily react with amines and alcohols to form amide and ester products respectively. As such, pNBDAC TFC can be immersed into solutions of amines or alcohols following scROMP to generate polymers with novel compositions. Reacting pNBDAC with substituted phenyl amines (aniline derivatives) and substituted phenyl alcohols (phenol derivatives) has resulted in polymers that possess compelling properties as membranes. Coupling the modifiable side chains of pNBDAC films with molecular simulations enables rapid polymeric material discovery. Specifically, this project aims to discover, synthesize, and evaluate novel polymeric membranes that excel at separating water from ethanol through membrane pervaporation. Following side chain identification through molecular simulations, pNBDAC films were synthesized and modified post-polymerization. Conversion of the acyl chloride side chain into the desired amide or ester side chain was confirmed through ATR-FTIR. Additionally, polymer properties such as contact angles, glass transition temperatures, and molecular weights were determined. Following this, pNBDAC TFC were formed, modified with the desired molecule, and evaluated in a membrane pervaporation testing cell for their ability to dehydrate an ethanol/water mixture. Performance markers such as flux and selectivity were calculated to identify high-performing polymers.