Heterogeneous Photocatalysis as a Means for Improving Recyclability of Organocatalyst in “Living” Radical Polymerization

Abstract

A novel heterogeneous catalytic system consisting of Eosin Y conjugated to silica nanoparticle (EY-SNP) is explored in this work to promote visible light photoinduced electron/energy transfer–reversible addition–fragmentation chain transfer (PET-RAFT) polymerization. In contrast to unconjugated Eosin Y (EY) that has been extensively studied and employed in free radical and controlled/“living” radical polymerization, EY-SNP was found to be tolerant to photodegradation during the polymerization. In addition, ultralow concentration of EY-SNP (less than 10 ppm) was found to efficiently catalyze polymerization of hydrophobic and hydrophilic monomers to reach high monomer conversions with narrow molecular weight distributions in a range of different solvents, including water, dimethyl sulfoxide, and N-methyl-2-pyrrolidone. Finally, the EY-SNP was also recovered via centrifugation and was reused to perform multiple cycles of polymerization.

A Versatile 3D and 4D Printing System through Photocontrolled RAFT Polymerization

“…Based on our previous experience with organic dyes as photocatalysts (PCs) for PET-RAFT polymerization, we initially tested two xanthene based dyes,n amely eosin Y (EY) and erythrosin B(EB), for their ability to mediate rapid polymerization under green light in the presence of air. [14][15] EY is frequently used as ab iological stain, and has also previously been used to initiate free-radical polymerization in the presence of tertiary amines as co-catalysts via at ype II photoinitiation mechanism, as well as other organic synthetic transformations. [16] Thestructurally similar EB has been used by our group for PET-RAFT polymerization, where it was determined to be am ore effective PC compared to EY and similar halogenated xanthene dyes,s uch as phloxine Ba nd rose bengal, due to its favorable photophysical and electrochemical properties,including ahigher triplet quantum yield (F T ), decreased fluorescence quantum yield (F F ), and ahigher excited state reduction potential (E 0 (PCC + / 3 PC*)).…”

Organic/Inorganic Heterogeneous Silica‐Based Photoredox Catalyst for Aza‐Henry Reactions

“…To do so, switching from homogeneous to heterogeneous catalysis by the immobilization of well‐defined photocatalysts onto insoluble solid‐state materials is very attractive. Recently some related approaches have been reported but mainly involving organic polymers or MOF (Metal‐Organic Frameworks) supports, known for their moderate chemical, thermal and mechanical stability . Because these stabilities are mandatory for the development of environmentally compatible and robust catalytic systems, we selected zeolites and ordered mesoporous silica materials as heterogeneous supports.…”

Precise growth of polymer brushes on silica-based nanocomposites via visible-light-regulated controlled radical polymerization

“…[15][16][17][18][19][20][21][22][23][24] Arising from its highly advantageous characteristics including low cost, user-friendly operation, fast initiation efficiency and convenient spatiotemporal polymerization modulation, photoinduced electron/energy transfer reversible addition fragmentation chain transfer (PET-RAFT) polymerization enables a versatile toolkit for controlled polymerizations of diverse functional monomers from nanomaterials and is universal in its specificity to satisfy the energetic criteria for conducting such polymerization, which would be otherwise inaccessible by thermal counterparts. [25][26][27][28][29] To the best of our knowledge, the current work is the first example to illustrate a systematic method to propagate well-defined polymer brushes directly from the surface of various silica-assisted nanomaterials using a PET-RAFT approach. The effects of photocatalyst concentration and light irradiation time on the polymerization kinetics, monomer conversion, molecular weight distribution, grafting density, and shell thickness of the surface-linked polymer brushes were investigated.…”