Photoinduced Reversible Addition-fragmentation Chain Transfer Research Articles

Photo-induced reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylonitrile at ambient temperature: A simple system to obtain high-molecular-weight polyacrylonitrile

Photo-induced reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylonitrile was performed in a two-component system using 2-cyano-2-propyl dodecyl trithiocarbonate as the initiation-regulator dual-functional agent. The polymerization was carried out under mild conditions, e.g. under irradiation of blue light-emitting diode light at ambient temperature. Well-controlled polymers with high molecular weight and narrow molecular weight distribution were obtained. The light on and off experiments showed photosensitivity of this polymerization system. The structure of the obtained polymers was characterized by GPC and NMR. Polymers with molecular weight as high as Mn=286,300g/mol could be obtained in optimized conditions.

Metallocene-Containing Homopolymers and Heterobimetallic Block Copolymers via Photoinduced RAFT Polymerization.

We report the synthesis of cationic cobaltocenium and neutral ferrocene containing homopolymers mediated by photoinduced reversible addition-fragmentation chain transfer (RAFT) polymerization with a photocatalyst fac-[Ir(ppy)3]. The homopolymers were further used as macromolecular chain transfer agents to synthesize diblock copolymers via chain extension. Controlled/"living" feature of photoinduced RAFT polymerization was confirmed by kinetic studies even without prior deoxygenation. A light switch between ON and OFF provided a spatiotemporal control of polymerization.

Polypropylene membrane surface modification by RAFT grafting polymerization and TiO 2 photocatalysts immobilization for phenol decomposition in a photocatalytic membrane reactor

The main technical barriers that impede photocatalytic membrane reactor (PMR) commercialization remain on the post-recovery of the catalyst particles after water treatment. To overcome this problem, surface modification of polypropylene macroporous membrane was performed with the technique of photoinduced reversible addition-fragmentation chain transfer grafting polymerization of acrylic acid. Titanium oxide photocatalysts were introduced to the acrylic acid grafted membrane surface. Phenol decomposition was carried out under UV irradiation in a recycle batch photocatalytic membrane reactor. The normalized membrane flux reached 1.7 times that of the unmodified membrane for the PAAc modified membrane. Introducing TiO 2 photocatalysts to the membrane surface reduced the normalized membrane flux slightly. For the PMR with a grafting degree of 12.9% (wt) of PAAc on the membrane surface, the corresponding decomposition percentage was 32.5% after 6 h UV light irradiation.

Thermo- and pH-responsive polypropylene microporous membrane prepared by the photoinduced RAFT-mediated graft copolymerization

Thermo- and pH-responsive polypropylene microporous membrane prepared by photoinduced reversible addition–fragmentation chain transfer (RAFT) graft copolymerization of acrylic acid and N-isopropyl acrylamide by using dibenzyltrithiocarbonate as a RAFT agent. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM) were used to characterize the structural and morphological changes on the membrane surface. Results of ATR/FT-IR and XPS clearly indicated that poly(acrylic acid) (PAAc) and poly(N-isopropyl acrylamide) (PNIPAAm) were successfully grafted onto the membrane surface. The grafting chain length of PAAc on the membrane surface increased with the increase of UV irradiation time, and decreased with the increase of the concentration of chain transfer agent. The PAAc grafted membranes containing macro-chain transfer agents, or the living membrane surfaces were further functionalized via surface-initiated block copolymerization with N-isopropyl acrylamide in the presence of free radical initiator, 2,2′-azobisisobutyronitrile. It was found that PNIPAAm can be grafted onto the PAAc grafted membrane surface. The results demonstrated that polymerization of AAc and NIPAAm by the RAFT method could be accomplished under UV irradiation and the process possessing the living character. The PPMMs with PAAc and PNIPAAm grafting chains exhibited both pH- and temperature-dependent permeability to aqueous media.