Hydrophilic, crosslinked polymer membranes such as crosslinked poly(vinyl alcohol) are promising low-energy substitutes for distillation in polar solvent dehydration. Unfortunately, the crosslinked, insoluble nature of these thick membranes makes correlating film composition to membrane performance in polar solvent dehydration particularly challenging. As a potential approach to both (1) fundamentally examine hydrophilic composition and crosslinking and (2) molecularly design new hydrophilic polymer films for polar solvent dehydration, we use a rapid (< 2 min) and low solvent (< 1 mL) polymer film synthesis technique called spin coating ring-opening metathesis polymerization (scROMP) to synthesize layered, block-like copolymer films of the form poly(dicyclopentadiene)-b-poly(trans-5-norbornene-2,3-dicarbonyl chloride), the latter surface block of which can be easily modified with a hydroxyl-terminated amine to produce a variety of hydrophilic, crosslinked films. The thickness of the outer hydrophilic selective layer can be controlled at the sub-micron level by varying spin speed to affect flux and selectivity of the water-rich permeate. Free -OH and -NH2- functional groups within these polymer membranes are quantified using absorbance peak shifts in transmission IR after modification with trichloroacetyl chloride and compared to standard reference polymers that contain fixed amounts of -OH and -NH2- groups per repeat unit. The results of this study pinpoint the optimal levels of hydrophilic groups and crosslinking within polar solvent dehydration membranes and can act as a guide for the future development of membranes that aim to selectively permeate water over less polar liquids.
