Molecular Design of an Interfacially Active POSS-Bottlebrush Block Copolymer for the Fabrication of Three-Dimensional Porous Films with Unimodal Pore Size Distributions through the Breath-Figure Self-Assembly

摘要

We compared the interfacial activity of two classes of POSS-bottlebrush block copolymers (POSSBBCPs) in the breath-figure (BF) self-assembly. Poly[3-(5-norbornene-exo-2,3-dicarboximido)propyl-heptaisobutyl POSS]-block-poly(exo-5-norbornene-2-carbonylate-graft-benzyl methacrylate) (P1-b-P(NB-g-BzMA)) and poly[3-(2-(5-norbornene-exo-2,3-dicarboximido)ethylamino)propyl-heptaisobutyl POSS]-block-poly(exo-5-norbornene-2-carbonylate-graft-benzyl methacrylate) (P2-b-P(NB-g-BzMA)), which contain nonfunctionalized and secondary-amino-functionalized POSS-based blocks, respectively, were prepared by sequential ring-opening metathesis polymerization of norbornenyl monomers (P1-b-P(NB-g-BzMA) with f(P1) = 50 wt % (1-50): M-n = 213 kDa, D = 1.12; P2-b-P(NB-g-BzMA)s with f(P2) = 5/11/20/50 wt % (2-5/11/20/50): M-n = 2464/1043/581/268 kDa, D = 1.46/1.26/1.24/1.20). Of 1-50 and 2-50, only 2-50 afforded the three-dimensional porous films with unimodal pore size distributions. At high wet thickness, the efficient encapsulation of water droplets through the adsorption of water by the secondary amino groups allowed the 2-50 chains to stabilize the solvent-water interfaces, thus preventing the formation of giant pores. The interfacial activity of P2-b-P(NB-g-BzMA) was enhanced by increasing the weight fraction of the P2 block from 5 to 50 wt %.