A polymer mesogen that self-assembles into a stable cubic nanoporous liquid crystal, for use in filtration, catalysis, and ion transport.
Cubic nanoporous liquid crystals (CNLCs) are ordered materials with nanoscale holes created using polymers called mesogens. CNLCs hold extraordinary promise in nanoscale filtration, with obvious applications in filtering salt or organic solvents from water. CNLCs also have catalytic applications, such as hosting Bronsted acid sites in petroleum hydrocracking. Further, CNLCs offer highly selective, temperature-independent lithium ion conductivity in liquid electrolyte batteries. Unfortunately, CNLCs require complicated mesogens and are often unstable. This severely limits their commercial and industrial applicability. Achieving robust molecular selectivity in harsh operating environments holds the key to unlocking the next generation of these wide-ranging technologies.
The authors created a simple single-head/single-tail polymer mesogen that can assemble into stable CNLCs. This mesogen is easy to manufacture, cross-links itself upon UV light exposure, and creates CNLCs that is stable when exposed to heat, water, acids, and bases. This requires no co-monomers or cross-linkers, unlike prior single-head/single-tail monomer systems.
Previous CNLC mesogen designs incorporated a single-head/single-tail structure which was straightforward to produce but required complicated chemical stabilizers and crosslinkers to form a CNLC. This technology leverages a polymerizable methacrylamide group near the single ionic headgroup and a polymerizable diene group in the single hydrophobic tail. This mesogen can self-crosslink with a simple photoinitiator and UV light and remains stable to elevated temperatures and submersion in water, acids, and bases for extended periods.
- Mesogen assembles stable CNLC with nanoscale gaps of size 1.5 nm
- A simple single-head, single-tail design takes just 3 hours to crosslink – significantly shorter than other CNLC methods which process overnight
- Pressure-driven filtration of vitamin B12 attains 98% solute rejection, indicating strong potential in organic solvent filtration
- Captures 90% of negatively charged molecules with size 0.7 nm but 0% of negatively charged molecules with size 1.9 nm, exhibiting robust size selectivity for ion transportation
- Stable up to temperatures of at least 210°C and upon exposure to 1N NaOH or 1N HCl for 96 hours
Stage of Development:
- Proof of Concept
The mesogen designed by the authors includes a polymerizable methacrylamide group near an ionic headgroup and a polymerizable diene group in a hydrophobic tail. The structure cross-links and self-assembles into a cubic nanoporous liquid crystal (CNLC). This CNLC contains a gyroid structure with nanometer-scale gaps created by the hydrophilic and hydrophobic portions of the mesogens.
Imran et al., Chem Comm, 2021, 57 (83): 10931.
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