Collaborative Research: Design a New Polymer Platform for Engineering Fast and Selective Molecular Transport in Membranes

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Polymer-based separation membranes play central roles in many technological innovations, such as clean energy (e.g., H2 purification) and environmental remediation (e.g., carbon capture). However, one major barrier to advancement in membrane field is the lack of feasible synthetic methods that can produce high-molecular-weight polymers with desirable function and composition. In this project, the investigators aim to develop a highly adaptive polymer platform that targets specific macromolecular designs for fast and selective molecular transport in polymeric membranes. By applying a new polymerization tool and targeting specific structure motifs for maximizing molecular transport while readily achieving high molecular weights, this research will open a new intellectual area for thinking about how to design polymer membrane materials for a variety of applications. In addition, the proposed research is dedicated to educating and training students at all levels in this interdisciplinary field with particular emphasis to attract underrepresented students into polymer materials research. By using the Friedel-Crafts hydroxyalkylation polymerization technique recently developed in the principal investigator's group, the project aims to synthesize a series of triphenylmethane-backboned polymers that have high molecular weight, a wide range of tunability on both substituent groups, and chain architectures. The polymerization technique provides an opportunity to explore the respective effect of polymer structures (e.g., polar, steric and morphological) at multiple length scales on gas transport properties without cross-influence from molecular weight. The investigators hypothesize that gas transport properties can be correlated with variations in the substituent groups and will vary with geometric size (physical effects on free volume) or polarity (interactive chemical effects). Three major research tasks are planned: 1) to synthesize triphenylmethane-based polymers with various substituent groups to investigate the respective chemical and physical effects of functional groups on gas transport; 2) to synthesize graft triphenylmethane-based polymers with target side chains to interrogate the mesoscale morphological effect on gas transport; 3) to investigate fundamental gas transport properties (i.e., permeation, diffusion, and sorption) and evaluate membrane performance under both ideal and realistic conditions. The ultimate goal of this membrane materials research project is to engineer fast and selective gas transport in polymers based on the rigorous structure-property relationship determination enabled by the proposed new polymer synthesis tool and polymer platform. The synthetic derivatives proposed here will allow the investigators to decouple chemical and physical effects and study them independently. The project is supported by both the Interfacial Engineering program (Chemical, Bioengineering, Environmental, and Transport Systems Division of the Engineering Directorate) and the Polymers program (Division of Materials Research in the Mathematical and Physical Sciences Directorate).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.