Gas separation or absorption technology via porous membranes has become increasingly recognized as a promising approach to combat issues related to global warming and air pollution. Carbon dioxide (CO2) is the most common greenhouse gas emitted from industry, power plants, and vehicle transportation. Cryogenic separation and pressure swing adsorption (PSA) are conventional methods to separate CO2. However, their practical use is limited due to high power consumption and high operating costs. Membrane technology represents a competitive tool for gas absorption and separation over conventional technologies. In this regime, polymer membranes have shown numerous advantages due to the distinct bulk properties of polymer materials, such as low cost, chemical stability, and low density. Porous membranes with controllable size, quantity, and morphology of pores, which enables selective gas permeation and allows for tuning gas absorption capacity, are attractive materials for gas separation technology. In this approach, we envision that the formation of pores can be achieved by removal of bottlebrush polymer templates from a matrix. The pore sizes and morphologies can be controlled by the predetermined architectures of the extractable bottlebrushes, while the porosities can be modulated by precise control over the volume fraction of the extracted domain. We exploit the concept of contrary development processes of positive- and negative-tone photoresists to selectively remove the extractable domain while maintaining the matrix domain. The extractable bottlebrush polymers consist of positive-tone photoresist functionalities and covalently-bonded photoacid generator (PAG) moieties, whereas the matrix polymers consist of negative-tone photoresist functionalities. Upon UV exposure of the cast mixture of bottlebrush copolymers, matrix polymers, and cross-linkers, the generated photoacids modulate the solubility of positive-tone bottlebrush templates and induce cross-linking of the negative-tone matrix. The pores are then generated by a development process through the dissolution of bottlebrush copolymers into the aqueous base developer.

Nanoporous films with controllable porosity and pore morphologies

2019 Fall National Meeting

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