Mechanically and Thermally Robust Ordered Nanoporous Monoliths Using Norbornene-Functional Block Polymers

A norbornene-functional styrene was synthesized and copolymerized with styrene, and monomer reactivity ratios were calculated in a controlled radical copolymerization. Polylactide-b-poly (norbornenylethylstyrene-s-styrene) (PLA-b-P(N-S)) block polymers were produced by a reversible addition-fragmentation chain transfer polymerization technique using a PLA-based macro chain transfer agent and fully characterized using conventional techniques. Blends composed of this block copolymer, dicyclopentadiene (DCPD), and a metathesis catalyst were waxy materials that formed ordered structures containing cylindrical PLA nanodomains in a composite DCPD/P(N-S) matrix. These composite materials were pressed in a channel die to align the cylindrical domains and were cured by a ring-opening metathesis mechanism at elevated temperatures. Removal of the PLA from the resulting monoliths by mild basic etching resulted in nanoporous monoliths with cylindrical channels. The nanoporous materials were characterized by small-angle X-ray scattering, scanning electron microscopy, and N-2 adsorption experiments. The nanoporous monoliths were thermally stable up to about 130 degrees C and exhibited remarkable mechanical strength that was comparable to pure polyDCPD.