Tunable
Ultrathin Membranes with Nonvolatile Pore Shape Memory
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Abstract
The
concept of a responsive nanoporous thin-film gel membranes whose pores
could be tuned to a desired size by a specific “molecular signal”
and whose pore geometry becomes “memorized” by the gel
is reported. The ∼100 nm thick membranes were prepared by dip-coating
from a solution mixture of a random copolymer comprising responsive
and photo-cross-linkable units and monodisperse latex nanoparticles
used as a sacrificial colloidal template. After stabilization of the
films by photo-cross-linking the latex template was removed, yielding
nanoporous structures with a narrow pore size distribution and a high
porosity. The thin-film membranes could be transferred onto porous
supports to serve as tunable size-selective barriers in various colloids
separation applications. The pore dimensions and hence the membrane’s
colloidal-particle-size cutoff were reversibly regulated by swelling–shrinking
of the polymer network with a specially selected low-molar-mass compound.
The attained pore shape was “memorized” in aqueous media
and “erased” by treatment in special solvents reverting
the membrane to the original state