Visible Light Induced Living/Controlled Radical Polymerization of Acrylates Catalyzed by Cobalt Porphyrins

Visible light induced living radical polymerization of a wide scope of acrylates mediated by organocobalt porphyrins was developed. The photocleavage of the Co–C bond of organocobalt porphyrin produced carbon centered radicals, which initiated polymerization, and porphyrin cobalt­(II), a persistent metal-centered radical. The organocobalt porphyrins were highly sensitive to external visible light irradiation so that photostimulus was used to control the initiation steps and regulate chain growth by reversibly activating the Co–C bond. Polymerization occurred spontaneously under irradiation and stopped promptly once shutting down light source. The scope of monomers was successfully extended from acrylamides to various hydrophobic and hydrophilic acrylates via the control of the light intensity. The structure of polyacrylate obtained was confirmed by ²D NMR, ¹³C NMR, GPC, and MALDI-TOF-MS. One of the unique features of this neat visible light induced polymerization process is that organocobalt porphyrins played dual roles of photoinitiators and mediators without addition of any dyes, photosensitizers, or sacrificial reagents

Visible-Light-Induced Living Radical Polymerization (LRP) Mediated by (salen)Co(II)/TPO at Ambient Temperature

Visible-light-induced living radical polymerization of acrylates (MA, <i>n</i>BA, <i>t</i>BA), acrylamides (DMA, AMO), and vinyl acetate (VAc) at ambient temperature mediated by (salen)­Co­(II)/TPO was described. Effects of light intensity, feeding ratio of monomer and equivalent of TPO for the polymerization of MA were investigated. Well-defined homopolymers and block polymers with predetermined molecular weight and narrow polydispersity were obtained under mild conditions. The mechanism of the polymerization was proposed based on polymerization behavior and polymer structure analysis. The (salen)­Co­(II)/TPO system was suitable for both conjugated and unconjugated monomers under mild conditions

Multilevel Manipulation of Supramolecular Structures of Giant Molecules via Macromolecular Composition and Sequence

We have successfully synthesized a series of monodispersed chain-like giant molecules with precisely controlled macromolecular composition and sequence based on polyhedral oligomeric silsesquioxane (POSS) nanoparticles using an orthogonal “click” strategy. Their nonspherical supramolecular structures, such as lamellae, double gyroids, and hexagonal packed cylinders, are mainly determined by the composition (namely, the number of incorporated amphiphilic nanoparticles). In addition, by precisely alternating the sequence of arranged nanoparticles in the giant molecules with identical chemical compositions, the domain sizes of their supramolecular structures could be fine-tuned. This is attributed to the macromolecular conformational differences caused by collective hydrogen bonding interactions in each set of sequence isomeric giant molecules. This work has demonstrated multilevel manipulation of supramolecular structures of giant molecules: coarse tuning by composition and fine-tuning by sequence

Modularly Constructed Polyhedral Oligomeric Silsesquioxane-Based Giant Molecules for Unconventional Nanostructure Fabrication

Controlled assembly of nanoscale building blocks is a promising approach to obtain functional materials with unique properties. Here, we report a way to manipulate the supramolecular structures of giant molecules based on discotic triangle cores and isobutyl polyhedral oligomeric silsesquioxanes (BPOSS) nanoparticles (NPs). It is found that depending upon the number of BPOSS at the periphery of the discotic cores, the packing of these nanoscale components (discotic core and POSS) could be manipulated into either cylindrical or Frank–Kasper (F–K) A15 (Pm3̅n) phases. The formation of these supramolecular nanostructures is mandated by the balance between the stacking of the discotic cores and the steric hindrance effect of the BPOSS NPs. This strategy to manipulate the packing of nanoscale building blocks for different supramolecular nanostructures including the fabrication of cylindrical structures and A15 (Pm3̅n) phases may be extended to other nanoscale building blocks for future development of materials with complex structures as well as tailored functionalities and properties