The development of anhydrous high-temperature proton-exchange membranes (HT-PEMs) combining durable high proton conductivity and modest mechanical properties is a huge challenge to the macromolecular design and engineering system. HT-PEMs with...
The
design of functionalized porous materials is an important research
direction in material science, especially for fluorine-containing
materials with enhanced thermal/oxidative stability, lower dielectric
constants, and better gas-selective permeation. In this work, a series
of poly(phenyl-alkane)s of intrinsic microporosity (PIM-xR) were synthesized by the methanesulfonic acid-catalyzed Friedel–Crafts
hydroxyalkylation polycondensation of contorted and rigid multibenzene
and benzaldehyde derivatives. The PIM-xR exhibited
good thermal stability, excellent solution processability, and high
Brunauer–Emmett–Teller (BET) surface areas (400–1200
m2 g–1). The physicochemical properties
and applications of PIM-xR could be tuned by the
type, quantity, distribution, and postmodification of substituents
on the benzaldehyde derivatives. Unlike other contorted and rigid
multibenzene derivatives, only electron-rich spirobiindane derivatives
directly produced soluble, linear, high-molecular-weight polymers
without cross-linking because spirobiindane possesses three t-butyl-like structural units that provide large steric
hindrance at potential reactive sites. Subsequently, a series of fluorinated
PIMs (PIM-xF) with different fluorine contents and
distributions were explored, and the relationship between the microporosity
of PIM-xR and degrees of rotational freedom of the
polymer chains was analyzed using these PIM-xF. Flexible
and transparent PIM-xF membranes were easily obtained
by solution processing and exhibited high gas permeabilities and moderate
permeability selectivity. In particular, the CO2/N2 separation performance of the PIM-5F membrane exceeded the
2008 Robeson’s upper bound (P
CO2
= 3240 barrer and α(CO2/N2) = 27.9). This work provides a facile method for the precise
design and preparation of fluorinated or other functionalized porous
materials for environmental and energy applications.
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