Gas transport properties of thermally rearranged (TR) polybenzoxazole –silica hybrid membranes

• Published in: Polymer (Guilford) Vol. 214; p. 123274
• Main Author: Suzuki, Tomoyuki
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.02.2021; Elsevier BV
• Subjects: Carbon dioxide; Gas separation membrane; Gas transport; Hybridization; Hybrids; Inorganic hybrid; Membranes; Methane; Organic; Permeability; Polybenzoxazole; Polymers; Prepolymers; Selectivity; Separation; Silica; Silicon dioxide; Sol-gel processes; Synergistic effect; Transport properties; Upper bounds; Inorganic hybrid; Gas separation membrane; Polybenzoxazole; Organic
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2020.123274

Novel thermally rearranged polybenzoxazole (TR-PBO) -based silica hybrid membranes were prepared via thermal rearrangement and sol – gel processes, and their gas transport properties were investigated. The pristine TR-PBOs rearranged at different temperatures showed higher fractional free volume (FFV) and d-spacing values than the poly(ortho-hydroxy imide) as a precursor polymer. Gas permeability of TR-PBO – silica hybrids increased with increasing silica content. The increased gas permeability was mainly attributed to increased gas diffusivity, suggesting the formation of free volume holes at polymer/silica interfacial region. The TR-PBO – silica hybrids possessed an outstanding CO2/CH4 selectivity, exceeding the upper bound trade-off line for CO2/CH4 separation. The notable CO2/CH4 selectivity was achieved by synergistic effects of (1) enlarged FFV and d-spacing by the thermal rearrangement towards PBO and (2) the additional formation of characteristic free volume holes with a size-selective CO2/CH4 separation ability at polymer/silica interfacial region by the hybridization with silica. [Display omitted] •Novel TR-PBO – silica hybrid membranes for gas separation were prepared.•The TR-PBO – silica hybrids possess high gas permeability and CO2/CH4 selectivity.•The CO2/CH4 selectivity is enhanced with increasing silica content.•Free volumes created at polymer/silica interfaces contribute to CO2/CH4 separation.