2026-04-30T04:59:16Zhttps://uvadoc.uva.es/oai/request

oai:uvadoc.uva.es:10324/709262025-03-26T19:10:04Zcom_10324_1186com_10324_931com_10324_894col_10324_1404

Rojas Rodríguez, Mario Rico Martínez, Sandra Prádanos del Pico, Pedro Lourdes Álvarez, Cristina Alexandrova, Larissa Moo Lee, Young Lozano, Ángel E. Aguilar Lugo, Carla 2024-10-25T08:12:44Z 2024-10-25T08:12:44Z 2024 Macromolecules, Agosto 2024, vol. 57, n. 16. p. 8187–8201 0024-9297 https://uvadoc.uva.es/handle/10324/70926 10.1021/acs.macromol.4c00169 A series of polyimides (PIs) was synthesized from 6FDA and two o-OH substituted diamines having bulky pendant phenyl, Ph, and trifluoromethyl, CF3, groups as precursors for thermally rearranged polybenzoxazole, TR-PBO, membranes. One diamine had two pendant Ph substituents; in the other, the substituents were Ph and CF3. Applying azeotropic and chemical cyclizations allowed the obtention of four o-hydroxy (o-OH) or/and o-acetoxy (o-OAc) substituted PIs depending on the imidization method. The PIs were labeled as 3Ph-OH, 4Ph-OH, or 3Ph-OAc and 4PH-OAc, respectively. Thermal rearrangements of all four precursors were investigated in the interval from 350 to 450 °C. The conversions to TR-PBO increased with temperature, and almost quantitative conversions were obtained at temperatures close to 450 °C, although o-OH substituted PIs reached conversions slightly higher than those of o-OAc PIs at a given temperature. The TR-polymers’ fractional free volume (FFV) also increased with conversion but was higher for the o-OAc substituted precursors. Despite the high TR-PBO conversions, self-supported uniform TR membranes with reasonable mechanical properties were obtained, except for 4Ph-OH. Gas separation behavior of the membranes significantly improved after the thermal treatment, and the final CO2/CH4 permselectivities lay between the 1991 and 2008 Robeson upper bounds. Particularly, TR-membranes derived from o-OAc precursors and with pendant CF3 group demonstrated better gas transport properties with values of P(CO2) = 1121 barrer and αCO2/CH4 = 29 for 3Ph-OAc derived membrane, which positioned it beyond the 2008 upper limit. eng info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/4.0/ © The Authors Attribution 4.0 Internacional Poliimidas Thermally rearranged (TR) polybenzoxazoles from o‑substituted prTecursor polyimides with phenyl pendant groups: synthesis, properties, and thermal rearrangement conditions info:eu-repo/semantics/article