2026-05-05T21:28:44Zhttps://uvadoc.uva.es/oai/request

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

00925njm 22002777a 4500 dc Rojas Rodríguez, Mario author Rico Martínez, Sandra author Prádanos del Pico, Pedro Lourdes author Álvarez, Cristina author Alexandrova, Larissa author Moo Lee, Young author Lozano, Ángel E. author Aguilar Lugo, Carla author 2024 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. Macromolecules, Agosto 2024, vol. 57, n. 16. p. 8187–8201 0024-9297 https://uvadoc.uva.es/handle/10324/70926 10.1021/acs.macromol.4c00169 Poliimidas Thermally rearranged (TR) polybenzoxazoles from o‑substituted prTecursor polyimides with phenyl pendant groups: synthesis, properties, and thermal rearrangement conditions