Transfer agent

About: Transfer agent is a research topic. Over the lifetime, 894 publications have been published within this topic receiving 9799 citations.

Coordinative Chain Transfer Copolymerization and Terpolymerization of Conjugated Dienes

Abstract: The coordinative chain transfer co- and ter-polymerizations of myrcene, isoprene and styrene have been achieved using Cp*La(BH4)2(THF)2 (Cp* = pentamethylcyclopentadienyl) combined with magnesium dialkyl and aluminum dialkyl. New highly stereoregular poly(myrcene-co-styrene), poly(myrcene-co-isoprene), and poly(myrcene-co-isoprene-co-styrene) copolymers have been obtained with good yields and a wide range of compositions. The concept of coordinative chain transfer polymerization (CCTP) induced control of the microstructure of statistical copolymers could be successfully extended to 1,4-conjugated dienes statistical copolymerization and terpolymerization and to a renewable monomer. In addition to significant transmetalation in the course of the polymerization, a modification of the apparent comonomers reactivity ratio was observed in the presence of a chain transfer agent. This could be combined, depending on the nature of the chain transfer agent, with either a stereospecific polymerization of both conjug...

Emulsifier-Free Controlled Free-Radical Emulsion Polymerization of Styrene via RAFT Using Dibenzyltrithiocarbonate as a Chain Transfer Agent and Acrylic Acid as an Ionogenic Comonomer: Batch and Spontaneous Phase Inversion Processes

Abstract: Surfactant-free, batch emulsion polymerization of styrene was carried out in the presence of sodium acrylate as a comonomer and dibenzyltrithiocarbonate (DBTTC) as a reversible addition−fragmentation chain transfer (RAFT) agent Very stable latex was recovered with narrow particle size distribution Because of the low water-solubility of DBTTC, diffusion of the RAFT agent from the monomer droplets toward the polymer particles was slow, which did not allow a linear increase of molar mass with monomer conversion However, Mn eventually reached the expected value and the final polymer chains could be extended, when the latex was used as a seed for a second polymerization step To overcome the slow diffusion of the RAFT agent, a new process was proposed, based on a spontaneous phase inversion mechanism The method relies upon a first bulk copolymerization of styrene and acrylic acid, followed by neutralization of the carboxylic acid moieties by the addition of a sodium hydroxide solution under gentle stirring

Synthesis of dual-sensitive nanocrystalline cellulose-grafted block copolymers of N -isopropylacrylamide and acrylic acid by reversible addition-fragmentation chain transfer polymerization

Abstract: A core–shell structure of crosslinked poly(2-hydroxyethylmethacrylate) as corona and nanocrystalline cellulose (NCC) as core was synthesized by distillation precipitation polymerization. Then, it was reacted with a chain transfer agent of S-(thiobenzoylthioglycolic) acid to obtain NCC-RA. Homopolymers of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) as temperature- and pH-sensitive materials, as well as their dual-sensitive block copolymers, were grafted at the surface of NCC-RA by an in situ reversible addition-fragmentation chain transfer polymerization method via R-group approach. Grafting of chain transfer agent and polymer chains at the surface of nanocrystals was studied by X-ray photoelectron (XPS), Fourier transform infrared, and Raman spectroscopies. Thermogravimetric analysis and XPS were also used to study the graft content of chain transfer agent and polymers. Sensitivity of the polymer-grafted NCCs to temperature and pH were studied by UV–visible spectroscopy. By the addition of poly(N-isopropylacrylamide) block to the poly(acrylic acid)-grafted nanocrystals, phase transition is observed at 32 °C. When the poly(acrylic acid) block is the outer layer, phase transition is observed at higher temperatures and pH-responsivity is observed at pH 7.0–10.0. Finally, morphology of the neat and polymer-grafted NCCs was studied by scanning and transmission electron microscopies.