- Controlled free radical polymerization in water-borne dispersion using reversible addition-fragmentation chain transfer
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A novel approach to conducting controlled free radical polymerization in water-borne organic dispersions using reversible addition-fragmentation chain transfer (RAFT) has been studied. The novel approach in this study focused on eliminating monomer and oligomer transport and comprised two fundamental steps: the synthesis of dithiobenzoate-end-capped styrene oligomers in bulk followed by emulsification of these oligomers to yield a polymerizable water-borne dispersion. Dithioesters that act as chain transfer agents in the RAFT process were synthesized in situ. The free radical polymerization of the dithiobenzoate-end-capped styrene oligomers in the water-borne organic dispersion proceeded in a controlled manner: molar mass increased in a linear fashion with increasing conversion, while polydispersities remained low. The familiar red layer formation associated with RAFT polymerization in conventional emulsions was not observed under these conditions. The effects of changing the costabilizer (hydrophobe) and the degree of polymerization of the emulsified oligomers were investigated. Better control was achieved with a less hydrophilic costabilizer and for the shorter of the oligomers tested.
- Vosloo,De Wet-Roos,Tonge,Sanderson
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Read Online
- Intramolecular folding of triblock copolymers via quadrupole interactions between poly(styrene) and poly(pentafluorostyrene) blocks
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β-Hairpin formation is one of the fundamental folding actions in biomacromolecules. We present a linear triblock copolymer synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, that is able to mimic on a very basic level hairpin formation by using π-π stacking interactions between phenyl and 2,3,4,5,6-pentafluorophenyl residues. This journal is the Partner Organisations 2014.
- Lu, Jie,Ten Brummelhuis, Niels,Weck, Marcus
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Read Online
- Ubiquitous Nature of Rate Retardation in Reversible Addition-Fragmentation Chain Transfer Polymerization
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Reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the most powerful reversible deactivation radical polymerization (RDRP) processes. Rate retardation is prevalent in RAFT and occurs when polymerization rates deviate from ideal conventional radical polymerization kinetics. Herein, we explore beyond what was initially thought to be the culprit of rate retardation: dithiobenzoate chain transfer agents (CTA) with more active monomers (MAMs). Remarkably, polymerizations showed that rate retardation occurs in systems encompassing the use of trithiocarbonates and xanthates CTAs with varying monomeric activities. Both the simple slow fragmentation and intermediate radical termination models show that retardation of all these systems can be described by using a single relationship for a variety of monomer reactivity and CTAs, suggesting rate retardation is a universal phenomenon of varying severity, independent of CTA composition and monomeric activity level.
- Bradford, Kate G. E.,Petit, Leilah M.,Whitfield, Richard,Anastasaki, Athina,Barner-Kowollik, Christopher,Konkolewicz, Dominik
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p. 17769 - 17777
(2021/11/10)
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- Design, synthesis, and phase behaviors of a novel triphenylene-based side chain liquid crystalline diblock copolymer
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A novel double Tp-based liquid crystalline (LC) diblock copolymer (PMTS-b-PMT6S) composed of poly[3,6,7,10,11-pentakis (hexyloxy)-2-oxytriphenylene] (PMTS) and poly{6-[3,6,7,10,11-pentakis(hexyloxy)-2-oxytriphenylene]} (PMT6S) was designed and successfully synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. While PMTS is a rigid columnar-shaped (ΦN) polymer, PMT6S is a stable hexagonal columnar phase (ΦH) polymer. The phase behaviors of diblock copolymers were studied by DSC, POM and 1D WAXD. The results showed that the weight fraction of PMT6S (fPMT6S) has a significant effect on the LC phase behaviors and phase structures of diblock copolymers. Both glass transition temperature and phase transition temperature of the diblock copolymers from LC phase to isotropic phase reduced with the weight fraction of PMT6S in the feed. When the fPMT6S ≤ 58.1%, PMTS-b-PMT6S-1 to PMTS-b-PMT6S-3 show similar properties to PMTS, which formed a stable columnar nematic phase (ΦN), while when the fPMT6S ≥ 64.2%, PMTS-b-PMT6S-4 and PMTS-b-PMT6S-5 show similar properties to PMT6S, which presented a hexagonal symmetry columnar phase (ΦH). Comparison between the diblock copolymer and homopolymer (PMTS and PMT6S) indicates that the content of the spacer was crucial to determine the LC structures. Through the study one can better understand the interrelation of microstructures and Tp DLC orders, which constitutes the key basis for various applications.
- Ban, Jianfeng,Pan, Lulu,Shi, Bo,Zhang, Hailiang
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p. 13581 - 13588
(2018/08/21)
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- Tert-amyl methyl ether preparation method and light gasoline modification method
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The invention discloses a tert-amyl methyl ether preparation method and a light gasoline modification method. The tert-amyl methyl ether preparation method comprises that methanol and isopentene contact an etherification catalyst under an etherification reaction condition to obtain the reaction product containing tert-amyl methyl ether, wherein the etherification catalyst is a polymer supported ionic liquid catalyst, and has a structure represented by a formula (I) or a formula (II). With the method of the present inventin, the tert-amyl methyl ether preparation reaction can maintain the highreactivity.
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Paragraph 0088
(2018/06/14)
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- Synthesis, characterization, and biological interaction of glyconanoparticles with controlled branching
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Branched amphiphilic copolymers were synthesized through the reversible addition - fragmentation chain transfer (RAFT) chain extension of a poly(methyl acrylate) macro-chain transfer agent using a protected galactose monomer and a polymerizable chain transfer agent branching unit. After galactose deprotection, the copolymers were self-assembled via nanoprecipitation. The resultant nanoparticles were analyzed for their size, shape, and biological interaction with a galactose binding lectin. Using light scattering, the nanoparticles were determined to be solid spheres. Nanoparticles containing branched glycoblocks bound significantly more lectin than those containing comparable linear blocks. By adjusting the molecular weight and branching of the copolymer, the size of the self-assembled nanoparticle and the saccharide density on its surface can be varied. (Figure Presented).
- Liau, Walter T.,Bonduelle, Colin,Brochet, Marion,Lecommandoux, Sbastien,Kasko, Andrea M.
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p. 284 - 294
(2015/01/30)
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- Intracellular nitric oxide delivery from stable NO-polymeric nanoparticle carriers
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The encapsulation of S-nitrosoglutathione into polymeric nanoparticles substantially improves NO stability in aqueous media without affecting the efficacy of intracellular delivery. The combination of nano-NO delivery and chemotherapy has been found to enhance antitumour activity of chemotherapeutics, as demonstrated using preliminary in vitro experiments with neuroblastoma cells.
- Duong, Hien T. T.,Kamarudin, Zulkamal M.,Erlich, Rafael B.,Li, Yang,Jones, Mathew W.,Kavallaris, Maria,Boyer, Cyrille,Davis, Thomas P.
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p. 4190 - 4192
(2013/05/23)
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- Visible-light degradable polymer coated hollow mesoporous silica nanoparticles for controlled drug release and cell imaging
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A core-shell nanocomposite based on photo-degradable polymer coated hollow mesoporous silica nanoparticles (HMS) was successfully prepared for targeted drug delivery and visible-light triggered release, as well as fluorescence cell imaging. The HMS nanoparticles were first modified by the long-chain hydrocarbon octadecyltrimethoxysilane (C18) and fluorescent agent Rhodamine B isothiocyanate (RITC), and then encapsulated by a photodegradable amphiphilic copolymer via a self-assembly process. The obtained nanocarrier showed a high drug loading content due to the hollow core and mesopores of the HMS and could target folic acid receptor over-expressed tumor cells efficiently for conjugating folic acid (FA) in the amphiphilic polymer. The drug release could be triggered by the irradiation of green light (500-540 nm) due to the photodegradation of amphiphilic copolymer coated on the HMS. Furthermore, the targeted drug delivery and controlled release processes could be tracked by fluorescence imaging for the doping of RITC on the HMS. The In vitro results suggested that a smart visible light responsive drug delivery system was successfully prepared for the potential applications of cancer diagnosis and therapy.
- Yang, Shun,Li, Najun,Chen, Dongyun,Qi, Xiuxiu,Xu, Yujie,Xu, Ying,Xu, Qingfeng,Li, Hua,Lu, Jianmei
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p. 4628 - 4636
(2013/09/12)
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- A new selenium-based RAFT agent for surface-initiated RAFT polymerization of 4-vinylpyridine
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A new selenium-based reversible addition-fragmentation chain transfer (RAFT) agent, 4-cyanopentanoic acid diselenobenzoate (RAFT-Se), was synthesized and utilized in the surface-initiated RAFT polymerization of 4-vinylpyridine (4VP) on silicon substrate. The results indicate that the RAFT-Se can control the surface-initiated RAFT polymerization, as evidenced by the number-average molecular weight that increase linearly with monomer conversion, molecular weights that agreed well with the predicted values, and the relatively low polydispersity indexes. The surface-initiated RAFT polymerization with the RAFT-Se was the same polymerization mechanism as its analog, 4-cyanopentanoic acid dithiobenzoate (RAFT-S). The grafting density of the poly(4-vinylpyridine) brushes prepared in the presence of RAFT-Se (σRAFT-Se) and RAFT-S (σRAFT-S) was estimated to be about 0.51 and 0.66 chains/nm2, respectively. In addition, the end of polymer chains on silicon substrate contains selenium element which may be useful in biosensor applications.
- Demirci, Serkan,Kinali-Demirci, Selin,Caykara, Tuncer
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p. 5345 - 5350
(2013/09/23)
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- Coumarin-containing photo-responsive nanocomposites for NIR light-triggered controlled drug release via a two-photon process
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A new multifunctional nanovehicle for tumor therapy and cell imaging was fabricated by coating NIR light-responsive polymers (HAMAFA-b-DDACMM) onto the surface of octadecyltrimethoxysilane (C18)-modified hollow mesoporous silica nanoparticles (HMS@C18) via self-assembly. First, the targeting NIR light-responsive block copolymer was synthesized by the RAFT living polymerization of [7-(didodecylamino) coumarin-4-yl] methyl methacrylate with hydroxyethylacrylate and N-(3-aminopropyl) methacrylamide hydrochloride and then grafted with folic acid (FA). The copolymers could be disrupted by excitation by a femtosecond NIR light laser (800 nm) via a two-photon absorption process due to the high two-photon absorption cross-section of the coumarin moiety. In order to enhance the drug loading capacity and biological stability of the nanovehicle, HMS nanoparticles modified by hydrophobic octadecyl chains were selected as the "core", which had a considerable drug loading efficiency of more than 70%. Then the core-shell nanocomposites (HMS@C18@HAMAFA-b-DDACMM) were obtained by coating the amphiphilic copolymers onto the core via self-assembly. Under excitation by NIR light at 800 nm, the pre-loaded drugs could be released from the nanocomposites due to the degradation of the light-responsive copolymers and the release efficiency was correlated with the irradiation time and light power. The in vitro experiments indicated that the nanocomposites were easily targeted into the tumor cells that over-expressed folic acid receptor (FR(+)) such as KB cells by endocytosis. Furthermore, the copolymer itself had strong fluorescence, which could be used to track the process of drug delivery.
- Ji, Weidong,Li, Najun,Chen, Dongyun,Qi, Xiuxiu,Sha, Wenwei,Jiao, Yang,Xu, Qingfeng,Lu, Jianmei
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p. 5942 - 5949
(2013/11/19)
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- Photo-induced electron transfer in a pyrenylcarbazole containing polymer-multiwalled carbon nanotube composite
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A polymer incorporated with a pyrenylcarbazole pendant poly(12-(3-(pyren-1- yl)-carbazol-9-yl)dodecyl methacrylate, denoted as PCP) was synthesized and applied in the functionalization of multi-walled carbon nanotubes (MWCNTs) by noncovalent π-π interaction. The PCP-MWCNT hybrids were isolated and characterized by SEM, TEM, and UV-visible absorption and emission spectroscopies. The strong interaction between PCP and the MWCNT in a 1,1,2,2-tetrachloroethane (TCE) solution was studied. It demonstrated an effective quenching effect on emission from PCP by the MWCNTs. DFT calculations showed electron delocalization between the pyrene and carbazole moieties. The LUMO of PCP is mainly located on the pyrene moiety while the LUMO + 1 is predominantly positioned on the carbazole moiety. Femtosecond transient absorption (TA) experiments determined the characteristic TA peaks of the excited states, which have contributions from both the pyrene and carbazole moieties. The excited state lifetime of the polymer PCP was measured to be 659 ps and the photo-excited electrons were injected into the MWCNTs very effectively on a time scale of 420 fs.
- Yu, Lihong,Lo, Kin Cheung,Xi, Jingyu,Phillips, David Lee,Chan, Wai Kin
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p. 1833 - 1842
(2013/06/27)
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- First RAFT polymerization of captodative 2-acetamidoacrylic acid (AAA) monomer: An experimental and theoretical study
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A capto-dative monomer, 2-acetamidoacrylic acid (AAA), was homopolymerized through RAFT polymerization method using 2-(2-cyanopropanyl dithiobenzoate) (CPDB) as a chain transfer agent and AIBN free radical initiator in DMF at 70 C. DFT calculations were performed in the selection of the CTA for this unique monomer as well as to elucidate the influence of cd-stabilized growing radical on the kinetic parameters in comparison to methacrylic acid (MAA) and N-(prop-1-en-2-yl)acetamide (NPAA), which represent the captive and dative groups of AAA, respectively. Keq for these three monomers is in the order of AAA β > k-add for NPAA and MAA, for AAA k-add is about four orders of magnitude larger than kβ. This is the major disadvantage in the RAFT process of AAA using CPDB. Yet, poly(AAA) could be achieved with PDI as low as 1.49. Molecular weight of the polymer can be tuned by the monomer/AIBN ratio. First block copolymers of AAA with MAA and MMA using poly(AAA) as a macro-CTA were also synthesized, indicating the presence of active chain ends.
- Dedeo?lu, Burcu,U?ur, Ilke,De?irmenci, Isa,Aviyente, Viktorya,Bar?in, Bilin?,?ayli, G?khan,Acar, Havva Yagci
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p. 5122 - 5132
(2013/09/02)
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- Thermally controlled wettability of a nanoporous membrane grafted with catechol-tethered poly(N-isopropylacrylamide)
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A nanoporous membrane is coated with catechol-tethered poly(N- isopropylacrylamide). The thermosensitive variation of surface wettability determines the hindered diffusivity of dextran (40 kDa) through the nanopores.
- Kim, Jee Seon,Kim, Taek Gyung,Kong, Won Ho,Park, Tae Gwan,Nam, Yoon Sung
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supporting information; experimental part
p. 9227 - 9229
(2012/09/08)
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- PH-responsive polymeric carrier encapsulated magnetic nanoparticles for cancer targeted imaging and delivery
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Multifunctional drug delivery systems with favorable compatibility, high selectivity and efficiency are appropriate candidates for future medical applications. For this purpose, a multifunctional nanocomposite that enables selective magnetic resonance imaging and anticancer therapy by encapsulating hydrophobic superparamagnetic nanoparticles and chemotherapeutic agent doxorubicin with a novel biodegradable pH-activated polymeric carrier was synthesized. The as-synthesized amphiphilic polymer has excellent biocompatibility and pH-responsivity. The obtained nanocomposites selectively release the encapsulated drug and magnetic nanoparticles in mildly acidic endosomal/lysosomal compartments due to the degradation of the pH-responsive bonds, resulting in a change of imaging signal and cancer therapy. Furthermore, when compared with the nanocomposites without a targeting moiety, as studied from over-expression of the folic acid receptor tumor cell culturing, the conjugates with folic acid showed a significantly more potent targeting capability.
- Chen, Dongyun,Xia, Xuewei,Gu, Hongwei,Xu, Qingfeng,Ge, Jianfeng,Li, Yonggang,Li, Najun,Lu, Jianmei
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p. 12682 - 12690
(2012/01/05)
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- Synthesis and characterization of a naphthalimide-dye end-labeled copolymer by reversible addition-fragmentation chain transfer (RAFT) polymerization
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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 30000 and 20000, respectively, and contained about 30 mol% NMS active ester groups.
- Li, Binxin,Majonis, Daniel,Liu, Peng,Winnik, Mitchell A.
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experimental part
p. 317 - 325
(2011/06/22)
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- Versatile grafting approaches to star-shaped POSS-containing hybrid polymers using RAFT polymerization and click chemistry
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An alkyne-bearing polyhedral oligomeric silsesquioxane (POSS) core was used to prepare POSS-containing polymer hybrids using 'grafting to' or 'grafting from' strategies in combination with reversible chain transfer and click chemistry.
- Ye, Yun-Sheng,Shen, Wei-Chung,Tseng, Chi-Yung,Rick, John,Huang, Yao-Jheng,Chang, Feng-Chih,Hwang, Bing-Joe
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supporting information; experimental part
p. 10656 - 10658
(2011/11/29)
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- Synthesis of biodegradable hydrogel nanoparticles for bioapplications using inverse miniemulsion RAFT polymerization
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We report the synthesis of biodegradable hydrogel nanoparticles using a RAFT inverse miniemulsion cross-linking polymerization process with 2-(dimethylamino)ethyl methacrylate (DMAEMA) as monomer. The experimental conditions were optimized to yield a colloidally stable miniemulsion polymerization, which required protonation of DMAEMA using aqueous hydrogen chloride to ensure minimal partitioning to the continuous phase (cyclohexane). The nanoparticles were cross-linked using a disulfide cross-linker, thereby enabling subsequent degradation of the polymer network to its constituent primary chains by exposure to a reductive environment. The molecular weight distributions of the constituent primary chains were consistent with satisfactory control/livingness during the polymerization. These biodegradable hydrogel nanoparticles may have potential application as nanocarriers for encapsulation and controlled release of siRNA.
- Oliveira, Marco Antonio M.,Boyer, Cyrille,Nele, Marcio,Pinto, Jose Carlos,Zetterlund, Per B.,Davis, Thomas P.
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experimental part
p. 7167 - 7175
(2012/04/10)
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- Simplification of the synthesis of the reversible addition-fragmentation chain transfer agent 2-(2-cyanopropyl)-dithiobenzoate
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The general literature procedure for the preparation of the reversible addition-fragmentation chain transfer (RAFT) agent 2-(2-cyanopropyl)- dithiobenzoate (CPDB) was modified by omitting the recrystallisation of the intermediate di(thiobenzoyl)disulphide. The yield of the CPDB in the simplified synthesis was increased four times compared to the standard one. The behaviour of the CPDB obtained by the modified procedure and by the standard one in the polymerisation of methyl methacrylate was investigated. The CPDB synthesized by the simplified procedure showed itself to be a good RAFT agent, giving excellent control over the polymerisation of methyl methacrylate and it behaved in the same manner as the CPDB prepared by the literature method. The obtained poly(methyl methacrylate) had a narrow molecular weight distibution (PD = 1.1).
- Milovanovic, Milos B.,Avramovic, Milena,Katsikas, Lynne,Popovic, Ivanka G.
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experimental part
p. 1711 - 1719
(2011/10/02)
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- RAFT polymer end-group modification and chain coupling/conjugation Via disulfide bonds
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End-group modification of polymers prepared by reversible additionfragmentation chain transfer (RAFT) polymerization was accomplished by the conversion of trithiocarbonate or dithioester end-groups into a pyridyl disulfide (PDS) functionality. Several different polymers, such as poly(methyl methacrylate), polystyrene, poly(oligoethylene glycol-acrylate), poly(hydroxypropylacrylamide), and poly(N-isopropylacrylamide) were prepared by RAFT polymerization, and subjected to aminolysis in the presence of 2,2′-dithiodipyridine to yield thiol-terminated polymers with yields in the range 6590% dependent on the polymer structure. Furthermore, this PDS end-group was utilized to generate higher-order architectures, such as diblock copolymers with high yields and selectively. In addition, the PDS end-groups were used for the bioconjugation of different biomolecules, such as oligonucleotides, carbohydrates, and peptides. The successful modification of well-defined polymers was confirmed by a combination of UV-vis, NMR spectroscopy, and gel permeation chromatography.
- Boyer, Cyrille,Liu, Jingquan,Bulmus, Volga,Davis, Thomas P.
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experimental part
p. 830 - 847
(2010/03/02)
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- Dispersion polymerisation in supercritical CO2 using macro-RAFT agents
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Fluorinated macro-RAFT agents can act as in situ stabilisers while exhibiting good control over block copolymers formed by dispersion polymerisation in supercritical CO2 to yield well-defined spherical particles with a fluorinated "halo". The Royal Society of Chemistry.
- Zong, Mengmeng,Thurecht, Kristofer J.,Howdle, Steven M.
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supporting information; experimental part
p. 5942 - 5944
(2009/05/06)
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- SYNTHESIS OF DITHIOESTER CHAIN TRANSFER AGENTS
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This invention relates to the synthesis of dithiocarboxylic acid esters by reaction of bis(thioacyl) disulphides, thioacetals or vinylidane bis(thioether) with free-radicals (optionally in the presence of monomers). The invention also relates to processes for the synthesis of polymers utilising these dithioesters as polymerisation regulators (chain transfer agents) or to the use of bis(thioacyl) disulphides to generate dithioester chain transfer agents in situ.
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Page/Page column 13-14
(2009/01/24)
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- Imparting nanoparticle function with size-controlled amphiphilic polymers
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Herein we report our method of water solubilization and subsequent functionalization of a variety of nanoparticle systems with amphiphilic polymers containing build-in "chemical handles". We have used these polymers, which have narrow polydispersity indices, to impart water solubility and chemical sensitivity toward targeted species (here: pH). These material systems have high chemical conjugation efficiencies in aqueous conditions which may be used to create a variety of chemical and biological multifunctional materials. Copyright
- Chen, Yingchuan,Thakar, Rahul,Snee, Preston T.
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p. 3744 - 3745
(2008/09/20)
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- Ultra-fast microwave enhanced reversible addition-fragmentation chain transfer (RAFT) polymerization: Monomers to polymers in minutes
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Microwave mediated RAFT polymerization leads to ultra-fast polymerizations, whilst keeping excellent control over molecular weights and molecular weight distributions; this is the first example of such a dramatic effect of microwaves on living radical polymerization kinetics, and it shows the potential for chemists to produce very well controlled polymers in a matter of minutes. The Royal Society of Chemistry.
- Brown, Steven L.,Rayner, Christopher M.,Graham, Susan,Cooper, Andrew,Rannard, Steven,Perrier, Sebastien
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p. 2145 - 2147
(2008/02/09)
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- Facile preparation of bis(thiocarbonyl)disulfides via elimination
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A robust facile synthetic preparation of bis(thiocarbonyl)disulfides is presented. The route follows an elimination mechanism rather than the more common oxidation. Addition of p-tosyl chloride to a thiocarbonyl thiolate results in the elimination of the chloride by the trithiocarbonate anion and subsequent elimination of the tosyl leaving group (by a second thiocarbonyl thiolate). The side products of the reaction are bis(4-methylphenyl)disulfone and tosylate salts/acids.
- Weber, Wolfgang G.,McLeary, James B.,Sanderson, Ron D.
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p. 4771 - 4774
(2007/10/03)
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- Searching for more effective agents and conditions for the RAFT polymerization of MMA: Influence of dithioester substituents, solvent, and temperature
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A series of tertiary ditbiobenzoates differently substituted on the pbenyl group (Z) were synthesized in order to investigate the RAFT-mediated polymerization of MMA. The chain-transfer agent 2-cyanoprop-2-yl dithiobenzoate, although an excellent RAFT agent for polymerization of MMA, does not yield a very narrow polydispened polymer at low conversion. The introduction of electron-withdrawing substituents on the dithiobenzoate aromatic ring improves the activity of the chain-transfer agent narrowing the molecular weight distribution, especially in the first 2 h of the process; conversely, electron-donating substituents deteriorate the performance of the process in the early stages. Substituents on the dithiobenzoate that, for reasons of steric hindrance reduce the conjugation of the phenyl with the C-S double bond of the dithiogroup, diminish the effectiveness of the chain-transfer agent. The nature of the leaving group (R) also has a strong influence on the process: the substitution of 2-cyanoprop-2-yl with the bulkier 2-cyano-4-methylpent-2-yl as leaving group improves remarkably the MMA polymerization, especially in the early stages. The solvent effect on MMA RAFT polymerization using benzene, acetonitrile, and DMF was also investigated. The lower propagation rate constant of MMA in benzene gives rise to reduced rates of polymerization but narrower polydispersities of the polymer, especially at low conversions. The RAFT polymerizations of MMA were carried out at 60 and 90°C to assess the temperature dependence of the process. The higher temperature increases both the rate of polymerization and the transfer constant of the RAFT agent, resulting in lower polydispersities at a given conversion. Ab initio calculations confirmed the observed experimental results.
- Benaglia, Massimo,Rizzardo, Ezio,Alberti, Angelo,Guerra, Maurizio
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p. 3129 - 3140
(2007/10/03)
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- Water-soluble dithioesters and method for polymerization thereof
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Disclosed are water soluble dithioesters capable of acting as chain transfer agents in preparing a vinyl-based polymer to control molecular weight and molecular weight distribution thereof as well as being capable of living polymerization even in an aqueous solution, and a method for polymerization thereof.
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- Well-defined glycopolymers from RAFT polymerization: Poly(methyl 6-O-methacryloyl-α-D-glucoside) and Its Block Copolymer with 2-Hydroxyethyl Methacrylate
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The glycomonomer methyl 6-O-methacryloyl-α-D-glucoside was prepared by lipase-catalyzed transesterification of vinyl methacrylate with methyl α-D-glucoside in dry acetonitrile. The desired 6-O regioisomer was obtained in good yield and its structure confirmed by 1H- 1H and 1H-13C correlation NMR spectroscopy. Reversible addition-fragmentation chain transfer (RAFT) polymerization of the unprotected monomer was performed directly in aqueous solution using (4-cyanopentanoic acid)-4-dithiobenzoate as the chain transfer agent to give poly(methyl 6-O-methacryloyl-α-D-glucoside) with Mn between 16 and 103 kDa (1H NMR) and polydispersities as low as 1.10. Chain extension of one of these polymers with 2-hydroxyethyl methacrylate afforded the novel hydrophilic-hydrophilic block copolymer poly [(methyl 6-O-methacryloyl-α-D-glucoside)-block-(2-hydroxyethyl methacrylate)].
- Albertin, Luca,Stenzel, Martina,Barner-Kowollik, Christopher,Foster, L. John R.,Davis, Thomas P.
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p. 7530 - 7537
(2007/10/03)
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- 1,3-DITHIOLANES IN THE REACTION OF GEMINAL DITHIOLS WITH ACTIVATED ACETYLENES
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The salts of 1,1-ethylenedithiols and 1,1,-cyclohexanedithiol react with acetylenedicarboxylic esters and dibenzoylacetylene in buffer solutions with the formation of the respective 1,3-dithiolanes.
- Drozd, V. N.,Vyazgin, A. S.,Komarova, E. N.
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p. 2194 - 2198
(2007/10/02)
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- ELEKTROCHEMISCHE OXIDATION VON DITHIOCARBONSAEUREESTERN ZU ISOTHIAZOLEN
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Electrolysis of alkyl arenedithioates 1 in acetonitrile with benzyl-triethyl-ammonium chloride as supporting electrolyte yields 5-aryl-4-cyano-3-methyl-isothiazoles 4.A reaction path is discussed according to which the dithioesters 1 are chlorinated at the anode and subsequently react with 3-iminobutyronitrile (6), generated at the cathode, to form the isothiazoles 4.
- Voss, Juergen,Mischke, Peter,Adiwidjaja, Gunadi
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p. 261 - 274
(2007/10/02)
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- Preparation and Some Reactions of Thioacyl Diphenylthiophosphinoyl and Thioacyl Diphenylphosphino Sulfides
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The reaction of sodium or caesium dithiocarboxylates with diphenylthiophosphinic and diphenylselenophosphinic chlorides gives purple thioacyl diphenylthiophosphinoyl 5 and dark green thioacyl diphenylselenophosphinoyl sulfides 6, which are useful thioacylating reagents under mild reaction conditions.Thioacyl diphenylphosphino sulfides 22, which can be obtained by the similar method using diphenylphosphinous chlorides, react with methanol to yield the corresponding methyl dithiocarboxylates 15, while the reactions of 22 with N-chlorosuccinimide lead to hitherto unknown N-(thioacetylthio)succinimides 28.
- Kato, Shinzi,Goto, Masahisa,Hattori, Rikizoh,Nishiwaki, Koh-ichi,Mizuta, Masateru,Ishida, Masaru
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p. 1668 - 1683
(2007/10/02)
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- Synthesis, Spectroscopy, and X-Ray Crystallographic Analysis of (η3-Dithiobenzoato-SCS')oxo(trithioperoxybenzoato-S,S',S'')molybdenum(IV) and μ-Oxo-bis
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The title oxomolybdenum complexes IVO(S2CPh)(S3CPh)> and V2O3(S2CPh)4> have been obtained by the reaction of Na2 with in an acidic aqueous medium, followed by chromatographic separation on a silica column using carbon disulphide as eluant.They have been characterized by elemental analysis, i.r. and electronic spectroscopy.A single-crystal X-ray structure analysis of reveals a structure in which two MoVO(S2CPh)2 moieties are oxo-bridged.The monoclinic crystal, space group C2/c, has cell dimensions a = 38.951(9), b = 10.678(4), c = 16.777(3) Angstroem, β =111.28(1) deg, and Z=8.Block-diagonal least-squares refinement, based on 2340 independent reflections with /F/>3?(F), yields an R factor of 0.070.An X-ray structure analysis of has shown the presence of η3-dithiobenzoato- and trithioperoxybenzoato-ligands co-ordinated to oxomolybdenum(IV).The crystals are monoclinic, space group P21/c, with cell dimensions a = 15.614(2), b = 8.441(1), c = 13.125(2) Angstroem, β = 104.46(1) deg, and Z = 4.Least-squares refinement, based on 3767 independent reflections with /F/>3?(F), yields an R factor of 0.035.
- Tatsumisago, Masahiro,Matsubayashi, Gen-etsu,Tanaka, Toshio,Nishigaki, Satoshi,Nakatsu, Kazumi
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p. 121 - 128
(2007/10/02)
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