Synthesis of Star Polymers using RAFT Polymerization: What is Possible?

2006 ◽  
Vol 59 (10) ◽  
pp. 719 ◽  
Author(s):  
Christopher Barner-Kowollik ◽  
Thomas P. Davis ◽  
Martina H. Stenzel
Keyword(s):  
Raft Polymerization ◽  
Star Polymers ◽  
Vinyl Pyrrolidone ◽  
Side Reactions ◽  
Radical Concentration ◽  
Reversible Addition ◽  
Polymer Architectures ◽  
Raft Agent ◽  
Poly Vinyl Pyrrolidone ◽  
Careful Design

Various pathways to generate star polymers using reversible addition–fragmentation transfer (RAFT) are discussed. Similar to other polymerization techniques, star polymers can be generated using arm-first and core-first approaches. Unique to the RAFT process is the subdivision of the core-first approach into the R-group and Z-group approaches, depending on the attachment of the RAFT agent to the multifunctional core. The mechanism of the R- and Z-group approaches are discussed in detail and it is shown that both techniques have to overcome difficulties arising from termination reactions. Termination reactions were found to broaden the molecular weight. However, these side reactions can be limited by careful design of the synthesis. Considerations include RAFT and radical concentration, number of arms, type of RAFT agent and monomer. Despite obvious challenges, the RAFT process is highly versatile, allowing the synthesis of novel polymer architectures such as poly(vinyl acetate) and poly(vinyl pyrrolidone) star polymers.

Synthesis and characterization of a naphthalimide–dye end-labeled copolymer by reversible addition–fragmentation chain transfer (RAFT) polymerization

2011 ◽  
Vol 89 (3) ◽  
pp. 317-325 ◽  
Author(s):  
Binxin Li ◽  
Daniel Majonis ◽  
Peng Liu ◽  
Mitchell A. Winnik
Keyword(s):  
Chain Transfer ◽  
Raft Polymerization ◽  
Polymer Composition ◽  
Cooh Group ◽  
Agent Based ◽  
Molecular Weights ◽  
Reversible Addition ◽  
Raft Agent ◽  
End Use ◽  
Naphthalimide Dye

We describe the synthesis of an end-functionalized copolymer of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-hydroxysuccinimide methacrylate (NMS) by reversible addition–fragmentation chain transfer (RAFT) polymerization. To control the polymer composition, the faster reacting monomer (NMS) was added slowly to the reaction mixture beginning 30 min after initating the polymerization (ca. 16% HPMA conversion). One RAFT agent, based on azocyanopentanoic acid, introduced a –COOH group to the chain at one end. Use of a different RAFT agent containing a 4-amino-1,8-naphthalimide dye introduced a UV–vis absorbing and fluorescent group at this chain end. The polymers obtained had molecular weights of 30 000 and 20 000, respectively, and contained about 30 mol% NMS active ester groups.

scholarly journals Photo-Responsive Polymersomes as Drug Delivery System for Potential Medical Applications

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5147
Author(s):  
Wanting Hou ◽  
Ruiqi Liu ◽  
Siwei Bi ◽  
Qian He ◽  
Haibo Wang ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Block Copolymers ◽  
Drug Delivery System ◽  
Delivery System ◽  
Raft Polymerization ◽  
Amphiphilic Block Copolymers ◽  
Medical Applications ◽  
Drug Molecules ◽  
Reversible Addition ◽  
Raft Agent

Due to a strong retardation effect of o-nitrobenzyl ester on polymerization, it is still a great challenge to prepare amphiphilic block copolymers for polymersomes with a o-nitrobenzyl ester-based hydrophobic block. Herein, we present one such solution to prepare amphiphilic block copolymers with pure poly (o-nitrobenzyl acrylate) (PNBA) as the hydrophobic block and poly (N,N’-dimethylacrylamide) (PDMA) as the hydrophilic block using bulk reversible addition-fragmentation chain transfer (RAFT) polymerization of o-nitrobenzyl acrylate using a PDMA macro-RAFT agent. The developed amphiphilic block copolymers have a suitable hydrophobic/hydrophilic ratio and can self-assemble into photoresponsive polymersomes for co-loading hydrophobic and hydrophilic cargos into hydrophobic membranes and aqueous compartments of the polymersomes. The polymersomes demonstrate a clear photo-responsive characteristic. Exposure to light irradiation at 365 nm can trigger a photocleavage reaction of o-nitrobenzyl groups, which results in dissociation of the polymersomes with simultaneous co-release of hydrophilic and hydrophobic cargoes on demand. Therefore, these polymersomes have great potential as a smart drug delivery nanocarrier for controllable loading and releasing of hydrophilic and hydrophobic drug molecules. Moreover, taking advantage of the conditional releasing of hydrophilic and hydrophobic drugs, the drug delivery system has potential use in medical applications such as cancer therapy.

Doubly-responsive hyperbranched polymers and core-crosslinked star polymers with tunable reversibility

2015 ◽  
Vol 6 (45) ◽  
pp. 7871-7880 ◽  
Author(s):  
Sunirmal Pal ◽  
Megan R. Hill ◽  
Brent S. Sumerlin
Keyword(s):  
Chain Transfer ◽  
Raft Polymerization ◽  
Star Polymers ◽  
Hyperbranched Polymers ◽  
Reversible Addition ◽  
Redox Responsive

Thermo- and redox-responsive hyperbranched copolymers were prepared by statistical copolymerization of N-isopropylacrylamide (NIPAM) and N,N′-bis(acryloyl)cystamine (BAC) by reversible addition–fragmentation chain transfer (RAFT) polymerization.

Facile Access to Chain Length Dependent Termination Rate Coefficients via Reversible Addition−Fragmentation Chain Transfer (RAFT) Polymerization:  Influence of the RAFT Agent Structure

2004 ◽  
Vol 37 (7) ◽  
pp. 2404-2410 ◽  
Author(s):  
Achim Feldermann ◽  
Martina H. Stenzel ◽  
Thomas P. Davis ◽  
Philipp Vana ◽  
Christopher Barner-Kowollik
Keyword(s):  
Chain Length ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Rate Coefficients ◽  
Termination Rate ◽  
Reversible Addition ◽  
Raft Agent ◽  
Agent Structure

EFFECT OF REVERSIBLE ADDITION-FRAGMENTATION CHAIN TRANSFER EMULSION STYRENE–BUTADIENE RUBBER ON THE PROPERTIES OF SILICA COMPOUNDS

2020 ◽  
pp. 000-000 ◽  
Author(s):  
Hyunsung Mun ◽  
Kiwon Hwang ◽  
Gwanghoon Kwag ◽  
JaeKon Suh ◽  
Duseong Ahn ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Raft Polymerization ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Narrow Molecular Weight Distribution ◽  
Reversible Addition ◽  
Raft Agent ◽  
Styrene Butadiene

ABSTRACT In recent years, solution styrene–butadiene rubber (SSBR), which has a narrow molecular weight distribution, controllable microstructure, and chain end functionality, is mainly used as base rubber for passenger car tire tread compounds. However, SSBR has a lower molecular weight than that of emulsion SBR (ESBR) because it is difficult to increase the molecular weight of SSBR. In contrast, ESBR can easily increase the molecular weight; however, it has a broad molecular weight distribution. The reversible addition-fragmentation chain transfer (RAFT) polymerization technique is applicable to the emulsion polymerization. Polymers with narrow molecular weight distributions can be obtained by the RAFT polymerization because the RAFT agent prevents the coupling reaction of the growing chain radicals. In this case, ESBR having a narrow molecular weight distribution, which is an advantage of SSBR, and a high molecular weight, which is an advantage of ESBR, can be synthesized. Therefore, we synthesized RAFT ESBR and fabricated its compounds with silica filler. We confirmed that the physical properties of the RAFT ESBR silica compound are different from those of the ESBR silica compound. In addition to the narrow molecular weight distribution of the RAFT ESBR, the trithiocarbonyl group of the RAFT agent in the RAFT ESBR chain molecules affects the physical properties.

scholarly journals Synthesis and characterization of triphenylamine and Bbis(indolyl)methane center-functionalized polymer via reversible addition-fragmentation chain transfer polymerization

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Jie Xu ◽  
Wei Shang ◽  
Jian Zhu ◽  
Zhenping Cheng ◽  
Nianchen Zhou ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Chloroform Solution ◽  
Monomer Conversion ◽  
Benzyl Ester ◽  
Chain Extension ◽  
Reversible Addition ◽  
Raft Agent ◽  
Cyclic Voltammetry Method

AbstractA novel bis-functional reversible addition-fragmentation chain transfer (RAFT) agent bearing triphenylamine (TPA) and bis(indolyl)methane (BIM) groups, {4-[bis(1-carbodithioic acid benzyl ester-indol-3-yl)methyl]phenyl}diphenylamine (BCIMPDPA), was synthesized and successfully used as the RAFT agent to mediate the polymerization of styrene (St). The polymerization results showed that reversible addition-fragmentation chain transfer (RAFT) polymerization of St could be well controlled. The kinetic plot showed it was of first order and the numberaverage molecular weight (Mn(GPC)) of the polymer measured by GPC increased linearly with monomer conversion, simultaneously, the molecular weight distribution of the polymer was also relatively narrow. In addition, the existence of the TPA and BIM groups in the middle of polymer chain was confirmed by chain extension reaction and 1H NMR spectrum. The optical properties of the functionalized polystyrene (PS) in chloroform solution were also investigated. Furthermore, the redox process of the RAFT agent and the functionalized PS were studied by cyclic voltammetry method.

scholarly journals Synthesis of Poly(lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) Copolymers with Controllable Block Structures via Reversible Addition Fragmentation Polymerization from Aminolyzed Poly(lactic acid)

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Wenwen Yu ◽  
Lijing Zhu ◽  
Jiangao Shi ◽  
Cunting Zhao
Keyword(s):  
Lactic Acid ◽  
Block Copolymers ◽  
Raft Polymerization ◽  
Poly Lactic Acid ◽  
Pseudo First Order Reaction ◽  
Oh Groups ◽  
Dimethylaminoethyl Methacrylate ◽  
Reversible Addition ◽  
Raft Agent ◽  
Different Temperatures

Poly(lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) (PLA-PDMAEMA) copolymers were synthesized from aminolyzed PLA via reversible addition fragmentation (RAFT) polymerization. PLA undergoes aminolytic degradation with ethylenediamine (EDA). The kinetics of the aminolysis reaction of PLA at different temperatures and EDA concentrations was investigated in detail. The molar masses of products rapidly decreased in the initial stage at low aminolytic degree. Meanwhile, reactive –NH2 and –OH groups were introduced to the end of shorter PLA chains and used as sites to further immobilize the RAFT agent. PLA-PDMAEMA block copolymers were synthesized. A pseudo-first-order reaction kinetics was observed for the RAFT polymerization of PDMAEMA at a low conversion. By controlling the aminolysis reaction of PLA and RAFT polymerization degree of DMAEMA, the length distributions of the PLA and PDMAEMA blocks can be controlled. This method can be extended to more systems to obtain block copolymers with controllable block structure.

Investigation into the Initialization Behaviour of RAFT-Mediated Styrene–Maleic Anhydride Copolymerizations

2006 ◽  
Vol 59 (10) ◽  
pp. 742 ◽  
Author(s):  
Eric T. A. van den Dungen ◽  
Jacques Rinquest ◽  
Nadine O. Pretorius ◽  
Jean M. McKenzie ◽  
James B. McLeary ◽  
...  
Keyword(s):  
Maleic Anhydride ◽  
Raft Polymerization ◽  
Polymerization Process ◽  
Unit Model ◽  
Reversible Addition ◽  
Raft Agent ◽  
Addition Rate ◽  
Leaving Groups ◽  
Chain Lengths ◽  
Alternating Copolymerization

The living radical alternating copolymerization of styrene and maleic anhydride mediated by the reversible addition–fragmentation chain transfer (RAFT) polymerization process has been studied at short chain lengths using two different dithiobenzoate RAFT agents. The results indicate specificity of addition of the RAFT-agent leaving groups for either styrene or maleic anhydride. The addition rate of the monomers and the fact that monomers are added individually favour the penultimate unit model of polymer propagation.

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