2024-03-29T12:08:51Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/1319932022-06-15T10:02:52Zcom_10261_56com_10261_3col_10261_309
Effect of polymer structure on gas transport properties of selected aromatic polyimides, polyamides and TR polymers
Smith, Z. P.
Hernández, Guiomar
Gleason, K. L.
Anand, A.
Doherty, C. M.
Konstas, K.
Álvarez, Cristina
Hill, A. J.
Lozano López, Ángel Emilio
Paul, D. R.
Freeman, Benny D.
Oak Ridge National Laboratory (US)
Thermally rearrangedpolymers
Polybenzoxazoles
CO2 separations
Olefin/paraffin separations
Plasticization
Thermally rearranged (TR) polymers are formed through a thermally induced solid-state reaction of polyimides or polyamides that contain nucleophilic reactive groups ortho-positioned to their diamine. Naturally, the transport properties of TR polymers are intimately related to the chemical structure and reactivity of their precursors. Herein, we report characterization and transport properties for three poly(hydroxyimide) precursors prepared via thermal imidization in solution and for their corresponding TR polymers. Structural modifications to the polymer backbone can be used to control thermal rearrangement reaction kinetics. In regards to TR polymer formation, samples prepared from diamines with biphenyl functionality reacted more efficiently than those prepared from diamines with hexafluoroisopropylidene-linked aromatic units. However, hexafluoroisopropylidene functional units provided the highest combinations of permeability and selectivity for separations involving H<inf>2</inf>, N<inf>2</inf>, O<inf>2</inf>, CH<inf>4</inf>, and CO<inf>2</inf>. Differences in permeability between samples correlated well with changes in free volume, and 3 poly(hydroxyimide)s showed unusually high selectivities for their given free volume. The effect of synthesis route was also investigated for a specific TR polymer derived from 3,3'-dihydroxy-4,4'-diamino-biphenyl (HAB) and 2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA). Poly(hydroxyimide) precursors prepared via thermal imidization in solution and thermal imidization in the solid-state showed nearly identical permeabilities and selectivities regardless of synthesis route. However, after thermal rearrangement, the TR polymers prepared from polyimides synthesized via solid-state imidization have higher gas permeabilities than their solution-imidized analogs. In addition to light gas permeabilities, plasticization effects were investigated with CO<inf>2</inf> hysteresis loops for all samples, and pure-gas olefin/paraffin permeabilities were determined for a TR polymer derived from 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane (APAF) and 6FDA. With the exception of HAB-6FDA polyimides, pure-gas CO<inf>2</inf> feed pressures up to approximately 50bar do not reveal a plasticization pressure point, but conditioning effects are observed for most samples. APAF-6FDA TR polymers have pure-gas permeabilities and selectivities beyond the propylene/propane upper bound.
2015
2016-05-11T10:16:10Z
artículo
Journal of Membrane Science 493: 766-781 (2015)
http://hdl.handle.net/10261/131993
10.1016/j.memsci.2015.06.032
http://dx.doi.org/10.13039/100006228
eng
http://dx.doi.org/10.1016/j.memsci.2015.06.032
Sí
closedAccess
Elsevier