We report the reversible addition–fragmentation chain transfer (RAFT) solution copolymerization of methyl methacrylate (MMA) with a cleavable divinyl comonomer, bis(2-methacryloyl)oxyethyl disulfide (BMAODS). 2-Cyano-2-propyldodecyl trithiocarbonate was used as a RAFT chain transfer agent and 2,2′-azobis(2-methylpropionitrile) as an initiator. The selective cleavage of BMAODS disulfide bonds was used to collect primary chains for the determination of the branching density (BD). The effects of initial monomer concentration, vinyl/divinyl ratio, and primary chain length on the branching and cyclization reactions were thoroughly investigated. It was found that more than 50% pendent double bonds from BMAODS were consumed in cyclization rather than in branching. The BD increased linearly with the conversion up to approximately 60% conversion. The monomer concentration was found to be the most efficient parameter in promoting branching. Increasing divinyl monomer ratio and primary chain length favored cyclization over branching. The work provides experimental evidence to support the random branching mechanism in RAFT copolymerization of vinyl and divinyl monomers.
Feng He,Dan Wang,Anyang Wu,Baiyu Jiang,Zhen Zhang,Zhenmei Cheng,Zhisheng Fu,Qisheng Zhang,Zhiqiang Fan
An α-diimine nickel catalyst (Cat-1) with highly conjugated acenaphthylene backbone was synthesized and used in ethylene polymerization. Compared with typical Brookhart catalyst B-Cat, Cat-1 could produce polyethylene with both higher molecular weight (up to 5.1 × 10 5 g mol −1 ) and branching density (up to 135 branches per 1000 carbons) in good polymerization activity. The polyethylene prepared using Cat-1 with higher molecular weight and branching density possessed exceptional mechanical properties (ultimate tensile strength and elongation at break could reach 12.08 MPa and 1148%) and outstanding elastomeric recovery as compared with the polymer prepared using B-Cat. Cat-1 was synthesized using a simple reaction route and the polymerization conditions were suitable for the industrial polymerization process. The novel nickel catalyst Cat-1 is promising for producing highly resilient polyethylene elastomers industrially.
This work reported branching studies in reversible addition-fragmentation chain transfer (RAFT) miniemulsion copolymerization of styrene and triethylene glycol dimethacrylate (TEGDMA), and control of branching density distribution using a model-based computer-programed monomer feeding strategy. Highly branched polystyrenes (PS) were produced with small amount of TEGDMA. The branching density experienced drifting in a batch operation. A semi-batch kinetic model by combining the kinetic model for RAFT miniemulsion copolymerization with a semi-batch reactor model was used to design the monomer feeding rate profiles for targeted branching density distributions. A series of hyperbranched PSs with the designed branching density distributions were synthesized.
危险品化学品经营许可证（带存储）