Abstract
Hyperbranched polyimide–silica hybrids (HBPI–silica HBDs) and hyperbranched polyimide–silica composites (HBPI–silica CPTs) were prepared, and their general and gas transport properties were investigated to clarify the effect of silica sources and preparation methods. HBPI–silica HBDs and HBPI–silica CPTs were synthesized by two-step polymerization of A2 + B3 monomer system via polyamic acid as precursor, followed by hybridizing or blending silica sources. Silica components were incorporated by the sol-gel reaction with tetramethoxysilane (TMOS) or the addition of colloidal silica. In HBPI-silica HBDs, the aggregation of silica components is controlled because of the high affinity of HBPI and silica caused by the formation of covalent bonds between HBPI and silica. Consequently, HBPI-silica HBDs had good film formability, transparency, and mechanical properties compared with HBPI-silica CPTs. HBPI-silica HBD and CPT membranes prepared via the sol-gel reaction with TMOS showed specific gas permeabilities and permselectivities for CO2/CH4 separation, that is, both CO2 permeability and CO2/CH4 selectivity increased with increasing silica content. This result suggests that gas transport can occur through a molecular sieving effect of the porous silica network derived from the sol-gel reaction and/or through the narrow interfacial region between the silica networks and the organic matrix.
Highlights
In order to build a sustainable society, it is necessary to develop alternative energy sources to fossil fuel, as well as renewable energy, and low environmental impact processes
The increased solubilities of the HBPI–silica HBD and CPT membranes prepared via the sol-gel reaction with TMOS suggest that the Langmuir-type sorption site is formed by the incorporation of silica domains
There are so many sorption sites in the HBPI–silica HBD and CPT membranes prepared via the sol-gel reaction with TMOS because the silica domain prepared via the sol-gel reaction is porous and its specific surface area is large [35]
Summary
In order to build a sustainable society, it is necessary to develop alternative energy sources to fossil fuel, as well as renewable energy, and low environmental impact processes. Hybrids and composites can be obtained by use of polyimide with and without terminal modification, respectively Another effective method to improve the dispersibility is to use dendrimers or hyperbranched polymers with a highly branched structure. We studied the syntheses and gas transport properties of hyperbranched polyimide–silica hybrid membranes prepared with commercially available dianhydride monomers and several kinds of triamine monomers, and found that these membranes showed characteristics quite different from the conventional linear type polyimide membranes. The gas permeability and the CO2/CH4 selectivity of hyperbranched polyimide–silica hybrid membranes prepared via the sol-gel reaction using tetramethoxysilane (TMOS) increased with increasing silica content without any dependence on the molecular structure, suggesting the characteristic distribution and interconnectivity of free volume holes created by the incorporation of silica [10,11,12,13,14,15]. The physical and gas transport properties of hyperbranched polyimide–silica hybrid (HBPI–silica HBD) and hyperbranched polyimide–silica composite (HBPI–silica CPT) membranes prepared with silicon alkoxide (TMOS) or colloidal silica were investigated to clarify the differences as well as the gas transport mechanism in the HBPI–silica HBD and CPT membranes
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
