{"id":{"repo_id":"buffalo","oai_identifier":"oai:ubir.buffalo.edu:10477/86746"},"canonical_url":"https://search.dev.ndltd.org/etd/buffalo/oai:ubir.buffalo.edu:10477/86746","repository":{"repo_id":"buffalo","name":"Buffalo","base_url":"https://ubir.buffalo.edu/oai/request"},"display":{"title":"Understanding the Effect of Polymer Morphology on Gas Transport Characteristics","abstract":"Ph.D.","abstract_html":"Ph.D.","abstract_has_math":false,"creators":["Nguyen, Hien; 0000-0002-5275-7449"],"institution":"State University of New York at Buffalo","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Lin, Haiqing","Chemical and Biological Engineering"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-02-21T21:44:40Z","date_published":"2025-02-21T21:44:40Z","updated_at":"2026-07-27T19:05:37Z","subjects":["chemical engineering"],"languages":["eng"],"rights":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/10477/86746","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Lin, Haiqing","Chemical and Biological Engineering"]},{"key":"dc:creator","label":"Author","values":["Nguyen, Hien; 0000-0002-5275-7449"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2025-02-21T21:44:40Z","2020"]},{"key":"dc:publisher","label":"Institution","values":["State University of New York at Buffalo"]},{"key":"dc:type","label":"Dc Type","values":["Text","Dissertation"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["chemical engineering"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/10477/86746"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Ph.D.","Polymeric gas separation membranes represent an attractive approach to separate carbon dioxide (CO2) from fuel gas (natural gas, syngas, etc.) due to their simplicity, compactness, and energy-efficiency. The thrust of this dissertation consists of critically examining the morphology of polymers practiced for commercial membranes, identifying the fundamental contributions of gas sorption and diffusivity towards permeability, and tailoring morphology appropriately to maximize separation performance. To achieve these objectives, semi-crystalline cellulose acetates (CAs) and amorphous polybenzimidazoles (PBI) were studied individually for CO2/CH4 separation and H2/CO2 separation, respectively. In the CAs study, we demonstrate that bulk crystallinity can be suppressed by reducing film thickness (confinement) or blending CAs optimally, which contributes to higher CO2 permeability via higher diffusivity and solubility. The first part of our study focuses on cellulose diacetate (CDA), and the effect of confinement on crystallinity/gas transport properties. The second part centers around the effect of blending CDA with cellulose triacetate (CTA) in conjunction with the effect of confinement on crystallinity/gas transport properties. The findings in both studies shed light on a long-standing puzzle regarding the discrepancy in gas transport properties between bulk CA films (20 µm) and commercial CA membranes comprised of a thin selective layer (50-200 nm). In the PBI study, the combined effects of phosphoric acid (H3PO4) doping and carbonization on the morphology and H2/CO2 separation characteristics of PBI-derived carbon molecular sieves (CMS) are systematically studied. We demonstrate that harnessing the power of acid doping can significantly increase the CMS size-sieving abilities by tightening the precursory PBI polymer chains prior to carbonization, while carbonization can greatly increase both H2 permeability and H2/CO2 selectivity by rearranging the PBI morphology to favor H2 permeation. This approach shows that doping and carbonization can synergistically enhance the CMS H2 permeability and H2/CO2 selectivity, and overcomes the fundamental permeability/selectivity tradeoff. Overall, the CMS were optimized by fine-tuning the doping level and the carbonization temperature, and exhibit performance well-beyond the Robeson upper bound.","**To request an accessible version of the file(s) associated with this item, contact library@buffalo.edu. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.**"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Understanding the Effect of Polymer Morphology on Gas Transport Characteristics"]}]}],"canonical_facts":{"dc:contributor":["Lin, Haiqing","Chemical and Biological Engineering"],"dc:creator":["Nguyen, Hien; 0000-0002-5275-7449"],"dc:date":["2025-02-21T21:44:40Z","2020"],"dc:description":["Ph.D.","Polymeric gas separation membranes represent an attractive approach to separate carbon dioxide (CO2) from fuel gas (natural gas, syngas, etc.) due to their simplicity, compactness, and energy-efficiency. The thrust of this dissertation consists of critically examining the morphology of polymers practiced for commercial membranes, identifying the fundamental contributions of gas sorption and diffusivity towards permeability, and tailoring morphology appropriately to maximize separation performance. To achieve these objectives, semi-crystalline cellulose acetates (CAs) and amorphous polybenzimidazoles (PBI) were studied individually for CO2/CH4 separation and H2/CO2 separation, respectively. In the CAs study, we demonstrate that bulk crystallinity can be suppressed by reducing film thickness (confinement) or blending CAs optimally, which contributes to higher CO2 permeability via higher diffusivity and solubility. The first part of our study focuses on cellulose diacetate (CDA), and the effect of confinement on crystallinity/gas transport properties. The second part centers around the effect of blending CDA with cellulose triacetate (CTA) in conjunction with the effect of confinement on crystallinity/gas transport properties. The findings in both studies shed light on a long-standing puzzle regarding the discrepancy in gas transport properties between bulk CA films (20 µm) and commercial CA membranes comprised of a thin selective layer (50-200 nm). In the PBI study, the combined effects of phosphoric acid (H3PO4) doping and carbonization on the morphology and H2/CO2 separation characteristics of PBI-derived carbon molecular sieves (CMS) are systematically studied. We demonstrate that harnessing the power of acid doping can significantly increase the CMS size-sieving abilities by tightening the precursory PBI polymer chains prior to carbonization, while carbonization can greatly increase both H2 permeability and H2/CO2 selectivity by rearranging the PBI morphology to favor H2 permeation. This approach shows that doping and carbonization can synergistically enhance the CMS H2 permeability and H2/CO2 selectivity, and overcomes the fundamental permeability/selectivity tradeoff. Overall, the CMS were optimized by fine-tuning the doping level and the carbonization temperature, and exhibit performance well-beyond the Robeson upper bound.","**To request an accessible version of the file(s) associated with this item, contact library@buffalo.edu. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.**"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/10477/86746"],"dc:language":["eng"],"dc:publisher":["State University of New York at Buffalo"],"dc:rights":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."],"dc:subject":["chemical engineering"],"dc:title":["Understanding the Effect of Polymer Morphology on Gas Transport Characteristics"],"dc:type":["Text","Dissertation"]},"updated_at":"2026-07-27T19:05:37Z"}