Polyelectrolyte multilayers on PTMSP as asymmetric membranes for gas separations: Langmuir-Blodgett versus self-assembly methods of anchoring.

Polyelectrolyte multilayers derived from poly(diallyldimethylamonium chloride) and poly(sodium 4-styrenesulfonate) have been deposited onto poly[1-(trimethylsilyl)-1-propyne] (PTMSP) with anchoring layers formed by Langmuir-Blodgett and self-assembly methods. Using gas permeation selectivity as a basis for judging the efficacy of each anchoring method, we have found that similar CO2/N2 selectivities (ranging from 110 to 140) could be achieved by both methods and that their permeances were also similar. Although LB anchors require fewer layers of polyelectrolyte to reach this level of selectivity, the greater ease associated with self-assembly and its applicability to curved, high-surface-area supports (e.g., PTMSP-coated hollow fibers) encourage its use with PTMSP in creating new membrane materials for the practical separation of gases.