Visible Light-Induced Cationic Polymerization Using Fullerenes

A novel visible light sensitive photoinitiator system for the cationic polymerization of typical monomers, for example, of oxiranes, such as cyclohexene oxide, vinyl ethers, such as iso-butyl vinyl ether, and other vinyl monomers, such as <i>N</i>-vinylcarbazole, using fullerene derivatives is described. The cationic polymerization of these monomers was initiated at room temperature upon irradiation in the visible region (λ_inc > 400 nm) in bulk or chlorobenzene solutions with polystyrene-C₆₀ (PS-C₆₀) adduct or bare C₆₀, respectively, in the presence of oxidizing salts such as silver hexafluorophosphate (AgPF₆) and diphenyliodonium hexafluorophosphate (Ph₂I⁺PF₆^–). A feasible mechanism, as correlated with optical absorption measurements, free energy changes (Δ<i>G</i>), and proton scavenging studies, involves formation of exciplex by the absorption of light in the first step. Subsequent electron transfer from excited C₆₀ or PS-C₆₀ to oxidizing salt yields radical cations of the fullerene derivatives. Both radical cations and a strong Brønsted acid derived by hydrogen abstraction initiate the cationic polymerization of a variety of monomers

Photoinduced Free Radical Promoted Copper(I)-Catalyzed Click Chemistry for Macromolecular Syntheses

Photoinduced copper­(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC) via photoinduced electron transfer using free radical photoinitiators has been developed as a new platform to serve as orthogonal click system. Photoinitiators acting at near UV and visible range, namely 2, 2-dimethoxy-2-phenyl acetophenone, 2-benzyl-2-dimethylamino-4′-morpholino butyrophenone, 2,4,6-trimethylbenzoyl)­diphenylphosphine oxide, dicyclopentadienyl bis­[2,6-difluoro-3-(1-pyrrolyl)­phenyl] titanium) and camphorquinone/benzyl alcohol were tested with copper­(II) chloride/<i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>″,<i>N</i>″-pentamethyldiethylenetriamine complex to catalyze the CuAAC via photoinduced electron transfer reaction. This strategy has been applied in construction of various macromolecular architectures including telechelic polymers and block copolymers. Spectroscopic and chromatographic investigations revealed that successful macromolecular syntheses have been achieved by this technique