Enhanced Dispersibility of Graphitic Carbon Nitride Particles in Aqueous and Organic Media via a One-Pot Grafting Approach

A facile route to synthesize hydrophilically or hydrophobically grafted graphitic carbon nitride (g-CN) is reported. For this purpose, functionalized olefinic molecules with a low polymerization tendency are utilized for grafting onto the surface to preserve the features of g-CN while improving its dispersibility. One-pot, visible light-induced grafting yields highly dispersible g-CNs either in aqueous or organic media. Moreover, functional groups such as amines can be introduced, which yields pH-dependent dispersibility in aqueous media. Compared with unfunctionalized g-CN, low sonication times are sufficient to redisperse g-CN. In addition, because of increased dispersion stability, higher amounts of functionalized g-CN can be dispersed (up to 10% in aqueous dispersion and 2% in organic dispersion) when compared to unfunctionalized g-CN

Morphogenesis of Metal–Organic Mesocrystals Mediated by Double Hydrophilic Block Copolymers

Mesocrystalssuperstructures of crystalline nanoparticles that are aligned in a crystallographic fashionare of increasing interest for formation of inorganic materials with complex and sophisticated morphologies to tailor properties without changing chemical composition. Here we report morphogenesis of a novel mesocrystal consisting of nanoscale metal–organic frameworks (MOF) by using double hydrophilic block copolymer (DHBC) as a crystal modulator. DHBC selectively prefers the metastable hexagonal kinetic polymorph and promotes anisotropic crystal growth to generate hexagonal rod mesocrystals via oriented attachment and mesoscale assembly. The metastable nature of hexagonal mesocrystals enables further hierarchical morphogenesis by a solvent-mediated polymorphic transformation toward stable tetragonal mesocrystals that retain the outer hexagonal particle morphology. Furthermore, synthesis of hybrid MOFs, where hexagonal mesocrystals are vertically aligned on specific surfaces of cubic MOFs, is demonstrated. The present strategy opens a new avenue to create MOF mesocrystals and their hybrids with controlled size and morphology that can be designed for various potential applications

Organized Polymeric Submicron Particles via Self-Assembly and Cross-Linking of Double Hydrophilic Poly(ethylene oxide)‑<i>b</i>‑poly(<i>N</i>‑vinylpyrrolidone) in Aqueous Solution

The formation of submicron particles consisting of double hydrophilic diblock copolymers of poly­(ethylene oxide) and poly­(<i>N</i>-vinylpyrrolidone) (PEO-<i>b</i>-PVP) in aqueous solution is described. Block copolymers were synthesized via reversible deactivation radical polymerization using a PEO-xanthate as macro RAFT/MADIX chain transfer agent. Increasing polymer concentrations in aqueous solutions, the block copolymer is able to self-assemble into spherical structures with apparent hydrodynamic diameters in the range between 200 nm and 2 μm. The self-assembly was further improved by copolymerization with a more hydrophilic monomer, <i>N-</i>vinylimidazole (VIm). Submicron particles from PEO-<i>b</i>-P­(VP-<i>co</i>-VIm) were preserved via cross-linking utilizing imidazolium formation with a dihalogenide. Thus, submicron double hydrophilic particles were obtained that are stable in organic solvents and under high dilution. Almost quantitative formation of submicron particles with an average diameter of 200 nm can be afforded by the self-assembly in the polar organic solvent DMF and subsequent crosslinking as well. Furthermore, the obtained particles show a promising ability to incorporate various molecules for delivery and release, here exemplified with simple dyes

Organized Polymeric Submicron Particles via Self-Assembly and Cross-Linking of Double Hydrophilic Poly(ethylene oxide)‑<i>b</i>‑poly(<i>N</i>‑vinylpyrrolidone) in Aqueous Solution

The formation of submicron particles consisting of double hydrophilic diblock copolymers of poly­(ethylene oxide) and poly­(<i>N</i>-vinylpyrrolidone) (PEO-<i>b</i>-PVP) in aqueous solution is described. Block copolymers were synthesized via reversible deactivation radical polymerization using a PEO-xanthate as macro RAFT/MADIX chain transfer agent. Increasing polymer concentrations in aqueous solutions, the block copolymer is able to self-assemble into spherical structures with apparent hydrodynamic diameters in the range between 200 nm and 2 μm. The self-assembly was further improved by copolymerization with a more hydrophilic monomer, <i>N-</i>vinylimidazole (VIm). Submicron particles from PEO-<i>b</i>-P­(VP-<i>co</i>-VIm) were preserved via cross-linking utilizing imidazolium formation with a dihalogenide. Thus, submicron double hydrophilic particles were obtained that are stable in organic solvents and under high dilution. Almost quantitative formation of submicron particles with an average diameter of 200 nm can be afforded by the self-assembly in the polar organic solvent DMF and subsequent crosslinking as well. Furthermore, the obtained particles show a promising ability to incorporate various molecules for delivery and release, here exemplified with simple dyes

Reinforced Hydrogels via Carbon Nitride Initiated Polymerization

The utilization of graphitic carbon nitride (g-CN) as photoinitiator for hydrogel formation is reported. On top of the photochemical activity, g-CN entails the role of a reinforcing agent. Hydrogels formed via g-CN (0.6 wt % g-CN and 11 wt % solid content in total) possess significantly increased mechanical strength, around 32 times stronger storage moduli (from 250 Pa for the reference sample up to 8300 Pa for g-CN derived hydrogels) than the ones initiated with common radical initiators. In addition, the g-CN derived hydrogels show mechanical properties that are pH dependent. Therefore, g-CN acts as a photoinitiator for hydrogel formation and as reinforcer at the same time

Toward Ultimate Control of Radical Polymerization: Functionalized Metal–Organic Frameworks as a Robust Environment for Metal-Catalyzed Polymerizations

Herein, an approach via combination of confined porous textures and reversible deactivation radical polymerization techniques is proposed to advance synthetic polymer chemistry, i.e., a connection of metal–organic frameworks (MOFs) and activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Zn₂(benzene-1,4-dicarboxylate)₂(1,4-diazabicyclo­[2.2.2]­octane) [Zn₂(bdc)₂(dabco)] is utilized as a reaction environment for polymerization of various methacrylate monomers (methyl, ethyl, benzyl, and isobornyl methacrylate) in a confined nanochannel, resulting in polymers with control over dispersity, end functionalities, and tacticity with respect to distinct molecular size. To refine and reconsolidate the compartmentation effect on polymer regularity, initiator-functionalized Zn MOF was synthesized via cocrystallization with an initiator-functionalized ligand, 2-(2-bromo-2-methylpropanamido)-1,4-benzenedicarboxylate (Brbdc), in different ratios (10%, 20%, and 50%). Through the embedded initiator, surface-initiated ARGET ATRP was directly initiated from the walls of the nanochannels. The obtained polymers had a high molecular weight up to 392 000. Moreover, a significant improvement in end-group functionality and stereocontrol was observed, entailing polymers with obvious increments in isotacticity. The results highlight a combination of MOFs and ATRP that is a promising and universal methodology to prepare various polymers with high molecular weight exhibiting well-defined uniformity in chain length and microstructure as well as the preserved chain-end functionality

Toward Ultimate Control of Radical Polymerization: Functionalized Metal–Organic Frameworks as a Robust Environment for Metal-Catalyzed Polymerizations

Herein, an approach via combination of confined porous textures and reversible deactivation radical polymerization techniques is proposed to advance synthetic polymer chemistry, i.e., a connection of metal–organic frameworks (MOFs) and activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Zn₂(benzene-1,4-dicarboxylate)₂(1,4-diazabicyclo­[2.2.2]­octane) [Zn₂(bdc)₂(dabco)] is utilized as a reaction environment for polymerization of various methacrylate monomers (methyl, ethyl, benzyl, and isobornyl methacrylate) in a confined nanochannel, resulting in polymers with control over dispersity, end functionalities, and tacticity with respect to distinct molecular size. To refine and reconsolidate the compartmentation effect on polymer regularity, initiator-functionalized Zn MOF was synthesized via cocrystallization with an initiator-functionalized ligand, 2-(2-bromo-2-methylpropanamido)-1,4-benzenedicarboxylate (Brbdc), in different ratios (10%, 20%, and 50%). Through the embedded initiator, surface-initiated ARGET ATRP was directly initiated from the walls of the nanochannels. The obtained polymers had a high molecular weight up to 392 000. Moreover, a significant improvement in end-group functionality and stereocontrol was observed, entailing polymers with obvious increments in isotacticity. The results highlight a combination of MOFs and ATRP that is a promising and universal methodology to prepare various polymers with high molecular weight exhibiting well-defined uniformity in chain length and microstructure as well as the preserved chain-end functionality

A Versatile and Scalable Strategy to Discrete Oligomers

A versatile strategy is reported for the multigram synthesis of discrete oligomers from commercially available monomer families, e.g., acrylates, styrenics, and siloxanes. Central to this strategy is the identification of reproducible procedures for the separation of oligomer mixtures using automated flash chromatography systems with the effectiveness of this approach demonstrated through the multigram preparation of discrete oligomer libraries (<i><i>Đ</i></i> = 1.0). Synthetic availability, coupled with accurate structural control, allows these functional building blocks to be harnessed for both fundamental studies as well as targeted technological applications