Porous polyurea network showing aggregation induced white light emission, applications as biosensor and scaffold for drug delivery

We have designed a urea functionalized novel nanoporous material, POP-PU, which showsaggregation induced white light emission in the presence of suitable polar solvents. This nanomaterial has been explored as a pseudowhite light emitter where the polymeric luminogen moiety can interact with the suitable polar solvent, leading to charge transfer. Thus, solvent assisted rotational freezing of nonrigid polymeric nanoparticles gives radiative emission and the whole solution emits white light with color temperature of 8533 K. This nanoporous material also holds the pockets (donor-donor-acceptor array) for specific biomolecular interaction. Among three pyrimidine based nucleotide bases, only cytosine can amplify the PL emission intensity of POP-PU and the other two bases cannot, suggesting its future potential as a biosensor. Further, this urea functionalized porous organic nanomaterial can be utilized as an efficient drug-delivery vehicle for liver cancer diagnostics and therapy based on the specific biomolecular interaction at its surface.

Facile Synthesis of Robust and Pore-Size-Tunable Nanoporous Covalent Framework Membrane by Simultaneous Gelation and Phase Separation of Covalent Network/Poly(methyl methacrylate) Mixture

We report a facile route toward the preparation of organic-solvent-resistant and three-dimensionally continuous nanoporous covalent framework membrane. The membrane was prepared from the blend of linear poly(methyl methacrylate) and the cross-linked polyurea-based organic network, followed by selective removal of the linear polymer part. The pore morphologies, porosity, and solvent permeation properties of the membrane could be simply modified by the initial composition of the poly(methyl methacrylate) added to a sol of the organic network. The pore was three-dimensionally continuous with pore size ranging from 5 nm to tens of nanometers. Despite the broad pore size distribution, ultrafiltration of sub-10 nm solutes was realized with a molecular size cutoff near 5 nm thanks to the bicontinuous pore structure of the membrane. The nanoporous structure exhibited long-term resistance to organic solvents as well as thermal stability and mechanical strength. The separation performance remained unchanged in organic-rich medium for a prolonged time. Our strategy provides a synthetic route to a structurally robust, three-dimensionally continuous nanoporous polymeric membrane for potential application that necessitates the use of organic solvent.

Template-Free Preparation of a Mesopore-Rich Hierarchically Porous Carbon Monolith from a Thermally Rearrangeable Polyurea Network

A mesopore-rich, hierarchically porous carbon monolith was prepared by carbonizing a polyisocyanurate network derived by thermal rearrangement of a polyurea network. The initial polyurea network was synthesized by the cross-linking polymerization of tetrakis(4-aminophenyl)methane (TAPM) and hexamethylene diisocyanate (HDI) in the sol-forming condition, followed by precipitation into nanoparticulate solids in a nonsolvent. The powder was molded into a shape and then heated at 200–400 °C to obtain the porous carbon precursor composed of the rearranged network. The thermolysis of urea bonds to amine and isocyanate groups, the subsequent cyclization of isocyanates to isocyanurates, and the vaporization of volatiles caused sintering of the nanoparticles into a monolithic network with micro-, meso-, and macropores. The rearranged network was carbonized to obtain a carbon monolith. It was found that the rearranged network, with a high isocyanurate ratio, led to a porous carbon with a high mesopore ratio. The electrical conductivity of the resulting carbon monoliths exhibited a rapid response to carbon dioxide adsorption, indicating efficient gas transport through the hierarchical pore structure.