Efficient RAFT polymerization of N-(3-aminopropyl)methacrylamide hydrochloride using unprotected “clickable” chain transfer agents (original) (raw)
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Macromolecules, 2011
RAFT polymerization of a "more activated monomer" (MAM) -N,N-dimethylacrylamide (DMAm)has been successfully achieved in aqueous solution using an acid/base switchable pyridyl-substituted dithiocarbamate RAFT agent. The effect of strength (pK a ) and stoichiometry of the acid used to switch the RAFT agent on the molecular weight and dispersity of PDMAm were examined, making use of high-throughput protocol. Best control was achieved with a stoichiometric amount of the strongest acid investigated, p-toluenesulfonic acid monohydrate. Use of weaker acids (higher pKa) or less than stoichiometric amounts of acid with respect to RAFT agent resulted in broader molecular weight distributions. These results can be rationalized in terms of the extent of protonation of the pyridine nitrogen of the RAFT agent (pK a ~3.13). The preparation of unimodal low dispersity block copolymers 2 of PDMAm with the "less-activated" monomers (LAMs) N-vinylcarbazole (NVC), vinyl acetate (VAc) and N-vinylpyrrolidone (NVP) demonstrated the fidelity of the RAFT end group in these experiments and provides a further example of the utility of switchable RAFT polymerization.
Journal of Polymer Science Part A: Polymer Chemistry, 2005
2-cyanoprop-2-yl dithiobenzoate (CPDB) mediated RAFT polymerization of dimethylaminoethyl methacrylate (DMAEMA) was carried out in dioxane at 90 8C. The influence of several parameters, such as the monomer to CPDB molar ratio (100 to 500), the monomer concentration (2 mol Á L À1 to 5.9 mol Á L À1 ), and CPDB to initiator molar ratio (1 to 10), was evaluated with regards to conversion and polymerization duration, as well as control of molar mass and molar mass distributions. Number average molar masses from 10,000 to 70,000 g Á mol À1 can be targeted. The determination of the molar masses has been carried out by size exclusion chromatography (SEC) with a refractometer detector with poly(methyl methacrylate) (PMMA) standards. The experimental values were lower than the expected ones. Then, SEC in aqueous medium with an online laser light scattering detector was used both to get absolute molar masses and to recalibrate the SEC column in THF. Characterization of well-controlled PDMAEMA samples has been performed by proton NMR spectroscopy and matrix assisted laser desorption ionization time of flight mass spectrometry. Finally, a chain extension experiment was evaluated with regard to living features. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3551-3565, 2005
Advanced Drug Delivery Reviews, 2015
RAFT-mediated polymerization, providing control over polymer length and architecture as well as facilitating post polymerization modification of end groups, has been applied to virtually every facet of biomedical materials research. RAFT polymers have seen particularly extensive use in drug delivery research. Facile generation of functional and telechelic polymers permits straightforward conjugation to many therapeutic compounds while synthesis of amphiphilic block copolymers via RAFT allows for the generation of selfassembled structures capable of carrying therapeutic payloads. With the large and growing body of literature employing RAFT polymers as drug delivery aids and vehicles, concern over the potential toxicity of RAFT derived polymers has been raised. While literature exploring this complication is relatively limited, the emerging consensus may be summed up in three parts: toxicity of polymers generated with dithiobenzoate RAFT agents is observed at high concentrations but not with polymers generated with trithiocarbonate RAFT agents; even for polymers generated with dithiobenzoate RAFT agents, most reported applications call for concentrations well below the toxicity threshold; and RAFT end-groups may be easily removed via any of a variety of techniques that leave the polymer with no intrinsic toxicity attributable to the mechanism of polymerization. The low toxicity of RAFT-derived polymers and the ability to remove end groups via straightforward and scalable processes make RAFT technology a valuable tool for practically any application in which a polymer of defined molecular weight and architecture is desired.
Reversible addition fragmentation chain transfer polymerization - RAFT
Hemijska industrija, 2004
Well-defined homopolymers of pentafluorophenyl acrylate (PFPA) and AB diblock copolymers of N,N-dimethylacrylamide (DMA) and poly(ethylene glycol) methyl ether acrylate (PEGA) with PFPA were prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization. Three PFPA homopolymers of different molecular weights were reacted with the commercially available amidine and guanidine species histamine (HIS) dihydrochloride and L-arginine methyl ester (ARG) dihydrochloride in the presence of S-methyl methanethiosulfonate to yield, quantitatively, the corresponding amidine and guanidinebased acrylamido homopolymers. Both the HIS and ARG homopolymers are known to reversibly bind CO 2 with, in the case of the former, CO 2 fixation being accompanied with a switch from a hydrophobic to hydrophilic state. The RAFT synthesis of PFPA-DMA and PEGA-PFPA diblock copolymers yielded well-defined materials with a range of molar compositions. These precursor materials were converted to the corresponding HIS and ARG block copolymers whose structure was confirmed using 1 H NMR spectroscopy. Employing a combination of dynamic light scattering and transmission electron microscopy, we demonstrate that the DMA-HIS and PEGA-HIS diblock copolymers are able to undergo reversible and cyclable self-directed assembly in aqueous media using CO 2 and N 2 as the triggers between fully hydrophilic and amphiphilic (assembled) states. For example, in the case of the 54:46 DMA-HIS diblock, aggregates with hydrodynamic diameters of about 40.0 nm are readily formed from the molecularly dissolved state.
Materials Research, 2014
Poly(2-(dimethylamino)ethylmethacrylate-b-methymethacrylate) (PDMAEMA-b-PMMA) poly(2-(dimethylamino)ethylmethacrylate-b-vinylcaprolactam-b-(2-(dimethylamino)ethyl methacrylate) (PDMAEMA-b-PVCL-b-PDMAEMA) and poly(vinylcaprolactam-b-(2-(dimethylamino) ethylmethacrylate-b-vinylcaprolactam) (PVCL-b-PDMAEMA-b-PVCL) block copolymers were obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization, and the effect of the solution pH on the particle size was investigated. In the case of PDMAEMA-b-PMMA, PDMAEMA was first synthesized using 2-cyanoprop-2-yl dithiobenzoate (CPDB) as a chain transfer agent (CTA), which was subsequently used for the RAFT polymerization of MMA. The triblock copolymers were obtained using PDMAEMA or PVCL as macro-CTAs prepared using dibenzyl trithiocarbonate (DBTTC) as a bifunctional RAFT agent. The structure and formation of the copolymers was confirmed through 1 H NMR and SEC analysis. The particle size varied considerably depending on the pH of the aqueous solutions of copolymers indicating that these materials could be potential candidates for biomedical applications.
Polymer, 2004
New chain transfer agents for free radical polymerisation via reversible addition-fragmentation chain transfer (RAFT) were synthesised that are particularly suited for aqueous solution polymerisation. The new compounds bear dithioester and trithiocarbonate moieties as well as permanently ionic groups to confer solubility in water. Their stability against hydrolysis was studied, and compared with the one of a frequently employed water-soluble RAFT agent, using UV -Vis-spectroscopy and 1 H-NMR measurements. An improved resistance to hydrolysis was found for the new RAFT agents compared to the reference one, providing good stabilities in the pH range between 1 and 8, and up to temperatures of 70 8C. q
A facile route to ureidopyrimidinone-functionalized polymers via RAFT
Journal of Polymer Science Part A: Polymer Chemistry, 2010
Three new ureidopyrimidinone(UPy)-functionalized chain-transfer agents (CTAs) have been synthesized for use in reversible addition-fragmentation chain transfer (RAFT) polymerization. These UPy-CTAs are able to polymerize a wide variety of vinyl monomers to yield UPy-functionalized polymers, including homopolymers, block copolymers, and amphiphilic block copolymers. These polymers have been characterized via 1 H and 13 C NMR spectroscopy, gel permeation chromatogra-phy (GPC), UV/visible spectroscopy and differential scanning calorimetry (DSC) to demonstrate end-group fidelity. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5833-5841, 2010
Polymer, 2005
This paper provides an overview and discusses some recent developments in radical polymerization with reversible additionfragmentation chain transfer (RAFT polymerization). Guidelines for the selection of RAFT agents are presented. The utility of the RAFT process is then illustrated with several examples of the synthesis of polymers with reactive end-groups. Thus, RAFT polymerization with appropriately designed trithiocarbonate RAFT agents is successfully applied to the synthesis of narrow polydispersity carboxy-functional poly(methyl methacrylate) and primary amino-functional polystyrene. Methods for removing the thiocarbonylthio end-group by aminolysis, reduction and thermal elimination are discussed. It is shown that the thiocarbonylthio end-group can be cleanly cleaved by radical induced reduction with tri-n-butylstannane, to leave a saturated chain end, or by thermolysis, to leave an unsaturated chain end. q