en] Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical polymerization (CRP) in scCO2 has started to gain attention. Among all the controlled processes, Atom Transfer Radical Polymerization has emerged as a robust tool for the preparation of polymers with well-defined molecular weight, architecture and chain-end functionality. In a very recent paper, we reported the first efficient dispersion ATRP of methyl methacrylate (MMA) in scCO2 using a fluorinated polymeric ligand that had a dual role, i.e., the complexation of the copper salt and the stabilization of PMMA growing particles. In this contribution, we extended this new system to the dispersion ATRP of styrene2, to the synthesis of diblock copolymers beads2 or to the preparation of PMMA particles by AGET ATRP. Because both ATRP and alkyne-azide Huisgens 1,3-dipolar cycloaddition relies on the use of a ...
ENGLISH ABSTRACT: The effect of various organic reducing agents, in the. form of monosaccharide reducing sugars, on the rate of atom transfer radical polymerization (ATRP) of n-butyl methacrylate and methyl methacrylate is reported in this study. The addition of the reducing sugars has a positive effect on the rate of ATRP. Up to 100% increase in the rate of polymerization was recorded, in some cases. These organic reducing agents have little effect on the molecular weight and molecular weight distribution of the polyin-butyl methacrylate) and polydispersity indexes remain well below 1.2. The molecular weight of the poly(methyl methacrylate), when glucose and galactose are added to the reaction mixture, compares well with the theoretical expected values. An explanation for these observations is the ability of the reducing sugars to reduce part of the Cu(II) species, that serves to deactivate the growing radicals, to Cu(I), thereby ensuring a shift in the equilibrium between active and dormant ...
Highly branched polystyrene was prepared by atom transfer radical polymerization of styrene with p-styrenesulfonyl chloride as an initiator. The molecular weights and molecular weight distributions of the polymers obtained at different ratios of the initiator to the monomer and different monomer conversions were determined by gel permeation chromatography. It was found that the molecular weights were higher than the calculated ones by assuming that one polymer chain was generated per p -styrenesulfonyl chloride molecule, and that the molecular weight distributions were broad with multi-peaks.
Reversible addition-fragmentation chain transfer or RAFT polymerization is one of several kinds of reversible-deactivation radical polymerization. It makes use of a chain transfer agent in the form of a thiocarbonylthio compound (or similar, from here on referred to as a RAFT agent, see Figure 1) to afford control over the generated molecular weight and polydispersity during a free-radical polymerization. Discovered at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) of Australia in 1998, RAFT polymerization is one of several living or controlled radical polymerization techniques, others being atom transfer radical polymerization (ATRP) and nitroxide-mediated polymerization (NMP), etc. RAFT polymerization uses thiocarbonylthio compounds, such as dithioesters, thiocarbamates, and xanthates, to mediate the polymerization via a reversible chain-transfer process. As with other controlled radical polymerization techniques, RAFT polymerizations can be performed with conditions ...
TABLE-US-00003 TABLE 2 Toner particles External additive (zeolite) Addition amount Addition amount of negative with respect to charge control External Aluminum 100 parts of Toner Toner resin D50t Average additive ratio toner particles No. particle No. Production method (part(s)) (μm) circularity No. (%) (part(s)) Example 1 (1) (1) Suspension polymerization method 0.3 6.3 0.985 (1) 1.8 0.3 Example 2 (2) (2) Suspension polymerization method 0.7 6.5 0.980 (2) 11.3 0.1 Example 3 (3) (2) Suspension polymerization method 0.7 6.5 0.980 (3) 7.0 0.1 Example 4 (4) (1) Suspension polymerization method 0.3 6.3 0.990 (4) 0.3 0.3 Example 5 (5) (2) Suspension polymerization method 0.7 6.5 0.980 (5) 22.5 0.1 Example 6 (6) (3) Suspension polymerization method -- 7.2 0.975 (1) 1.8 0.1 Example 7 (7) (4) Pulverization method 0.3 8.1 0.970 (1) 1.8 0.3 Example 8 (8) (5) Pulverization method 10.0 8.7 0.965 (1) 1.8 1.0 Comparative (9) (1) Suspension polymerization method 0.3 6.3 0.990 -- -- -- Example 1 Comparative ...
A novel cationic nanodiamond-polymer brush was synthesized by 2-bromoisobutyrate-modified nanodiamond (ND) surface-initiated atomic transfer radical polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA). Elemental analysis, FTIR, HRTEM, TGA and zeta potential analysis were used to confirm the successful synthesis of ND-polymer brushes. It was shown that the ND-brushes were capable of condensing plasmid DNA into stable nanoparticles, protecting DNA from enzyme degradation. Transfection studies demonstrated that the ND-brushes could not only efficiently deliver plasmids into COS-7 cells, but also mediate higher expression than PEI25k with lower cytotoxicity. The green fluorescence of ND-brushes could also be detected by laser scanning confocal microscopy, making the nanodiamond-polymer brushes an excellent multifunctional gene vector with not only high transfection efficiency but allowing for bioimaging.. ...
X- RAY INTEN S TY June 4, 1974 w E 3,814,607 CRYSTALLINE PHOTOPOLYMERIZABLE COMPOSITIONS WITH IMPROVED STORAGE LIFE Filed Aug. 7, 1972 DIFFRACTION ANGLE 29 United States Patent 3,814,607 CRYSTALLINE PHOTOPOLYMERIZABLE COM- POSITIONS WITH IMPROVED STORAGE LIFE William John Nebe, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. Filed Aug. 7, 1972, Ser. No. 278,459 Int. Cl. G03c 1/70 U.S. Cl. 96-115 P 11 Claims ABSTRACT OF THE DISCLOSURE Predominantly crystalline photopolymerizable compositions containing a reducing agent such as 4-dimethylamino-3-propionyloxybenzophenone have excellent storage life without significant loss of photographic speed. BACKGROUND OF THE INVENTION Field of the invention This invention relates to photopolymerization, especially to predominantly crystalline compositions characterized in having high photographic speed. The invention is specifically concerned with improving the storage life of the photopolymerizable compositions. ...
In Nature, the polypeptide chains required for the preparation of a target protein are of the same length and composition, having a polydispersity index (PDI) of exactly 1. As protein function arises due to precise chain folding of these monodisperse polypeptides, an important target for polymer chemists is the preparation of monodisperse macromolecules that will minimize structural defects during self-assembly. A range of covalent polymerization methods that approximate to living processes54 have been developed for the preparation of block copolymers, including anionic,55 cationic,56 atom transfer radical polymerization (ATRP),57 reversible addition-fragmentation transfer (RAFT) polymerization,58 nitroxide-mediated radical polymerization59 and ring-opening metathesis polymerization (ROMP).60 The solution self-assembly of such amphiphilic block copolymers is arguably one of the most important methods for the preparation of well-defined and functional nanostructures.61,62 Above the critical ...
The authors report a photochemically controlled ATRP polymerization of MMA. The polymerization is copper catalyzed, uses visible light wavelengths, and results in living polymerizations with low (~1.1) PDI ...
a) a method in which a monomer mixture is allowed to undergone polymerization reaction with a suspension polymerization method, an emulsification polymerization method, a seed polymerization method or a dispersion polymerization method, to thereby produce a dispersion liquid of resin particles; (b) a method in which a monomer mixture is allowed to undergone polymerization, and the obtained resin is then pulverized using a fine pulverizer of, for example, mechanically rotating type or jetting type, followed by classifying, to thereby produce resin particles; (c) a method in which a monomer mixture is allowed to undergone polymerization, and the obtained resin is then dissolved in a solvent, followed by spraying of the resultant resin solution, to thereby produce resin particles; (d) a method in which a monomer mixture is allowed to undergone polymerization, the obtained resin is dissolved in a solvent, another solvent is added to the resultant resin solution to precipitate resin particles, and ...
As part of the design of the modification of nanoporous platforms with polymer brushes, PMAA brushes were grafted from flat silicon surfaces using surface-initiated atom transfer radical polymerization (SI-ATRP).. Chapter 4 describes growth kinetics of the pH-responsive polymer layers were investigated in mixtures of water and methanol with different ratios. The pH-induced swelling and collapse of the brush were characterized by in situ ellipsometry, and showed a fast and reversible switching of the PMAA layers with swelling factors that increased by decreasing the methanol content of the atom transfer radical polymerization mixture. Fourier transform infrared (FTIR) spectra recorded in titration experiments indicated that the effective pKa of the PMAA films were shifted to the value of 6.5 ± 0.2 from the bulk pKa value of PMAA. The shift is due to ion confinement effects in the dense brush, and brings the conformational switching of PMAA brushes closer to physiological conditions. This is ...
A world-leader in the development, manufacturing and commercialization of polymers via atom transfer radical polymerization (ATRP), a revolutionary process for designing and building highly-engineered intelligent ingredients that improve products used in the oilfield chemicals and cosmetic markets. ...
Increasing evidence shows that sex hormones exert a protective effect on the vasculature, especially in the regulation of the active vasomotor responses. However, whether sex hormones affect vascular remodelling is currently unclear. In the present study, we tested the hypothesis that testosterone in males and β-oestradiol in females prevent inward remodelling, possibly through inhibition of cross-linking activity induced by enzymes of the TG (transglutaminase) family. Small mesenteric arteries were isolated from male and female Wistar rats. Dose-dependent relaxation to testosterone and β-oestradiol was inhibited by the NO synthase inhibitor L-NAME (NG-nitro-L-arginine methyl ester), confirming that these hormones induce NO release. When arteries were cannulated, pressurized and kept in organ culture with ET-1 (endothelin-1) for 3 days we observed strong vasoconstriction and inward remodelling. Remodelling was significantly inhibited by testosterone in males, and by β-oestradiol in females. ...
Novel photopolymerizable recording materials suitable in particular for producing photoresist layers and lithographic printing plates are composed of one or more photopolymerizable, olefinically unsaturated organic compounds, optionally a polymeric binder, a photopolymerization initiator, a color-forming system composed of a color former and a photooxidant, a certain benzotriazole compound as a sensitizer and optionally further additive and/or auxiliary substances.
The importance of finding new applications for cellulose‐based products has increased, especially to meet the demand for new environmentally friendly materials, but also since the digitalization of our society will eventually decrease the need for paper. To expand the application area of cellulose, modification to improve and/or introduce new properties can be a requisite. Thus, the focus of this study has been to achieve fundamental knowledge about polymer grafting of cellulose via well‐controlled radical polymerization.. Cellulose, in the form of filter paper, has successfully been grafted via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) of the monomers: methyl methacrylate, styrene, and glycidyl methacrylate. The advantages of ARGET ATRP are that only a small amount of a copper catalyst is required and the reaction can be performed in limited amount of air; yet, providing for relatively well‐controlled reactions. These benefits can render ...
In this work, an investigation concerning differences between covalent and physical attachment of poly(ε-caprolactone) (PCL) to a nanocellulose modell surface was conducted. For the covalent attachment, ring-opening polymerization (ROP) was performed using the "grafting-from" approach, building the polymer from the surface. For the physical attachment, a block copolymer consisting of PCL and poly(di(methylamino)ethyl methacrylate) (PDMAEMA) was made combining ROP and atom transfer radical polymerization (ATRP). The PDMAEMA-part was then quaternized, which resulted in a charged chain - a polyelectrolyte. The charges allow for the PDMAEMA-PCL copolymer to be adsorbed onto the nanocellulose modell surface. The length of the PDMAEMA-part was kept constant (DP=20), and the length of PCL was varied (DP=150, 300, 600) for both the covalently attached polymer and for the copolymer. Finally, differences between the two approaches were evaluated regarding for example surface coverage and ...
This book is the first volume in a two-volume compilation on controlled/living radical polymerization. It combines all important aspects of controlled radical polymerization: from synthetic procedures, to rational selection of reaction components, to understanding of the reaction mechanisms, to materials and applications.This book is focused on recent progress in the rapidly developing field of controlled/living radical polymerization.
Polymerization rates were proportional to initial Sn(Oct)(2) concentration at low [Sn(Oct)(2)](0)/[PrOH](0) values, but began to level off at higher values. When [Sn(Oct)(2)](0)/[PrOH](0) was significantly greater than unity, the opposite behavior occurred. Tin(H) alkoxide concentration became limited by the initial PrOH concentration and independent of initial Sn(Oct)(2) concentration. Addition of 2-ethylhexanoic acid caused polymerization rate retardation, without affecting molecular weight. A control polymerization was conducted in the absence of PrOH. The molecular weight of the resulting polymer was consistent with the measured water content (3.7 wt % by Karl Fisher titration) of the as-received Sn(Oct)(2). The polymerization rate in the absence of PrOH was slow, and this suggested that water is less efficient than an alcohol in creating polymerization-active stannyl ether bonds. (C) 2004 Wiley Periodicals, Inc.
A photopolymerizable composition, element and method of photopolymerizing the composition or element are disclosed wherein the composition comprises an addition polymerizable compound containing ethylenic unsaturation and a co-initiator including a photopolymerization activator and a photosensitizer. In one aspect of the invention, the photosensitizer is selected to be a coumarin having an absorption maximum between about 250 and about 550 nm, and a ##STR1## substituent in the 3-position wherein R1 is alkyl or alkenyl having 1-12 carbon atoms, or a carbocyclic or heterocyclic group having 5-20 nuclear carbon and hetero atoms, the coumarin and the activator being present in an amount sufficient to provide, when the composition is coated, dried and exposed to a medium-pressure mercury light source, a speed which is at least about one-fifth that of the same composition coated, dried and exposed identically except with a co-initiator consisting of Michlers ketone and benzophenone. In another aspect of the
A photopolymerizable composition, element and method of photopolymerizing the composition or element are disclosed wherein the composition comprises an addition polymerizable compound containing ethylenic unsaturation and a co-initiator including a photopolymerization activator and a photosensitizer. In one aspect of the invention, the photosensitizer is selected to be a coumarin having an absorption maximum between about 250 and about 550 nm, and a ##STR1## substituent in the 3-position wherein R1 is alkyl or alkenyl having 1-12 carbon atoms, or a carbocyclic or heterocyclic group having 5-20 nuclear carbon and hetero atoms, the coumarin and the activator being present in an amount sufficient to provide, when the composition is coated, dried and exposed to a medium-pressure mercury light source, a speed which is at least about one-fifth that of the same composition coated, dried and exposed identically except with a co-initiator consisting of Michlers ketone and benzophenone. In another aspect of the
AB amphiphilic comb-like block copolymers of poly(oligo[ethylene glycol] methyl ether methacrylate) and polydimethylsiloxane were synthesised with a methodology based on atom transfer radical polymerization (ATRP). The anionic ring opening polymerisation of hexamethylcyclotrisiloxane followed by reaction with 3-(chlorodimethylsilyl) propyl 2-bromo-2-methylpropanoate propyldimethylchlorosilane gave suitable macroinitiators for the ATRP of oligo[ethylene glycol] methyl ether methacrylate. The latter synthetic procedure was optimised by performing a number of syntheses varying the reaction solvent, catalytic complex and the temperature used. Copolymers with relatively high polydispersity indices (Mw/Mn,1.3) could be synthesised at room temperature by employing a Cu(I)Br:N,N,N′,N′,N″-pentamethyldiethylenetriamine complex in n-propanol with Cu(II)Br. The optimum reaction conditions employed a Cu(I)Cl:N-(n-propyl)-2-pyridyl(methanimine) complex with an n-propanol/water mixture or toluene as ...
Compositions are provided that include a photoinitiator system for free radical polymerization reactions. More specifically, the photoinitiator includes an arylsulfinate ion and a triarylsulfonium ion. Polymerization methods are also provided those include the photoinitiator in a photopolymerizable composition. Additionally, triarylsulfonium arylsulfinate salts are disclosed.
Poly(acrylic acid) (PAA) was attached on both termini of Pluronic P85 copolymer (EO27PO39EO27)) via atom transfer radical polymerization (ATRP) to produce a novel block copolymer, PAA-b-P85-b-PAA (P85PAA). The P85PAA-DOX complex formation and drug loading were strongly dependent on the PAA segment and pH, where the protonation of the carboxyl groups in the PAA segment at pH,7.2 reduced the binding sites of DOX onto P85PAA chains, resulting less DOX uptake at low pH. The composition of the copolymer-DOX complexes that at pH 7.2 was close to the stoichiometric (1:1 mol Dox:carboxyl ratio), indicating the dominance of the electrostatic interactions between cationic DOX molecules and carboxyl groups. DOX loading at pH 5.0 reduced to 0.6:1 molar ratio of DOX:carboxyl indicated that protonation of the carboxyl reduced the DOX binding to the P85PAA block copolymer. DOX release from the complex is highly pH-responsive process, where 57% of encapsulated DOX was released in 30h at pH7.2, and the ...
A. Szabó, Wacha, A., Thomann, R., Szarka, G., Bóta, A., and Iván, B., "Synthesis of poly(methyl methacrylate)-poly(poly(ethylene glycol) methacrylate)-polyisobutylene ABCBA pentablock copolymers by combining quasiliving carbocationic and atom transfer radical polymerizations and characterization thereof", Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, vol. 52, no. 4, pp. 252 - 259, 2015. ...
A. Szabó, Wacha, A., Thomann, R., Szarka, G., Bóta, A., and Iván, B., "Synthesis of poly(methyl methacrylate)-poly(poly(ethylene glycol) methacrylate)-polyisobutylene ABCBA pentablock copolymers by combining quasiliving carbocationic and atom transfer radical polymerizations and characterization thereof", Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, vol. 52, no. 4, pp. 252 - 259, 2015. ...
A. Szabó, Wacha, A., Thomann, R., Szarka, G., Bóta, A., and Iván, B., "Synthesis of poly(methyl methacrylate)-poly(poly(ethylene glycol) methacrylate)-polyisobutylene ABCBA pentablock copolymers by combining quasiliving carbocationic and atom transfer radical polymerizations and characterization thereof", Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, vol. 52, no. 4, pp. 252 - 259, 2015. ...
A. Szabó, Wacha, A., Thomann, R., Szarka, G., Bóta, A., and Iván, B., "Synthesis of poly(methyl methacrylate)-poly(poly(ethylene glycol) methacrylate)-polyisobutylene ABCBA pentablock copolymers by combining quasiliving carbocationic and atom transfer radical polymerizations and characterization thereof", Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, vol. 52, no. 4, pp. 252 - 259, 2015. ...
Homogeneous polymerization catalysts require large amounts of solvent and cannot control the polymer morphology. In order to solve this issue, a narrow-shaped spherical ZSM-5 zeolite was used in ethylene polymerization as a support for zirconocene (Cp2ZrCl2). Several heterogeneous catalytic precursors were prepared and used in ethylene polymerization reactions, which showed yields (between 980-8019 kg PE mol-1 h-1) and were efficient at promoting morphological replication of the support. So, a well-established protocol for slurry polymerization reaction was found, yielding well-defined polymer particles in an advantageous polymerization process ...
External and reversible control of the size and surface energy of the pores in mesoporous architectures has been achieved. The method involves modification of mesoporous silica by atom transfer radical polymerization of N-isopropyl acrylamide (the precursor to a stimuli-responsive polymer). The resulting polymer-grafted particles allow the adsorption and transport of molecular species to be dynamically controlled as illustrated in the Figure for the release of rhodamine 6G from the particles at 50degreesC ...
Organic superbases reacted with alkyl iodides (R-I) to reversibly generate the corresponding alkyl radicals (R•). Via this reaction, organic superbases were utilized as new and highly efficient organic catalysts in living radical polymerization. The superbase catalysts included guanidines, aminophosphines and phosphazenes. Low-polydispersity polymers (Mw/Mn = 1.1-1.4) were obtained up to high conversions (e.g., 80%) in reasonably short times (3-12 h) at mild temperatures (60-80 °C) for methyl methacrylate, styrene and several functional methacrylates. The high polymerization rate and good monomer versatility are attractive features of these superbase catalysts.
In the present invention, the amount of the polyfunctional initiator added (or the total amount of the polyfunctional initiator and the monofunctional initiator in the case where the monofunctional initiator is also used) is from 0.001 to 5 parts by weight per 100 parts by weight of the vinyl monomers described above. If the amount thereof added is below 0.001 part by weight, a relatively large proportion of the monomer is apt to remain unpolymerized, so that the resulting product not only emits the odor of the monomer, but has a low cohesive force. On the other hand, if the amount of the photopolymerization initiator exceeds 5 parts by weight, the odor of the decomposed photopolymerization initiator becomes severe and the performance of the resulting products become poor, resulting in disadvantage in cost, although the polymerization reaction can be sufficiently completed. Therefore, the amount of the photopolymerization initiator added is fixed, depending upon the desired molecular weight of ...
Photopolymerizable compositions are described containing a polymerizable ethylenically unsaturated monomer, a photoinitiator or initiator system, and selected acidic polymeric binders. The organic binder mixture contains a compound chosen from each of two selected classes. These photopolymerizable compositions yield superior processability, i.e., on developing and stripping, in solely aqueous alkaline media devoid of organic solvents, decreased softness and/or tackiness, and improved adhesion when compared to the prior art. The compositions are particularly useful for preparing photoresists.
PURPOSE:To improve the sensitivity of the composition to a visible ray by incorporating a specified iron allene complex, 3-substd. cumarine compd. and/or a pyridine derivative or its salt in the titled composition. CONSTITUTION:The titled composition comprises the iron allene complex which is composed of at least one kind of a nongaseous ethylenic unsatd. compd. at a room temp. and is shown by formula I, the 3-subst. cumarine compd. shown by formula II and/or the pyridine derivative or its salt shown by formula III. In the formulas I and II, R is hydrogen atom or alkoxy group, etc., X is BF4 or PF6, etc., R1-R4 are each hydrogen atom or alkyl group, etc., X is aryl or a heterocyclic ring group, etc., R5 is alkyl group, etc. In formula III, R1 and R2 are each 1-6C alkyl group, A is aryl group condensed with a pyridine ring. Thus, as the titled composition has the high sensitivity against the visible ray, the exposure light source with the low energy can be used, and great numbers of master plates
Imperfections in the surface of information carrying discs, such as video discs, are avoided by an improved process of manufacture. A bead of photopolymerizable mass is moved between two surfaces, one of which is a patterned surface and the other is a surface to which the photopolymerizable mass will bond upon polymerizing. By moving the liquid mass across the patterned surface, air within the pattern is removed by the leading edge of the bead, reducing imperfections.
TY - JOUR. T1 - Conformal barrier by interfacial polymerization in contact with cells and tissue. AU - Sawhney, A. S.. AU - Pathak, C. P.. AU - Cox, P. R.. AU - Hubbell, J. A.. PY - 1993/12/1. Y1 - 1993/12/1. N2 - We have previously described the rapid photopolymerization of water soluble polyethylene glycol based macromers using visible lasers in contact with tissue and cells. These polymerizations proceed throughout the bulk of the macromer solution. Here we describe a technique whereby this polymerization can be directly initiated form the tissue or cell surface itself and be confined to the interface between the polymerizing from and the bulk macromer solution. The effect of various treatments on the viability of HFF cells are summarized. In evaluating the effect of photopolymerization on cell viability, the objective was to compare the interfacial scheme of photopolymerization to the scheme in which the dye was present in the bulk. The interfacial approach was seen to have some but not a ...
Gelled compositions that include acrylate or other polymerizable monomers for coatings and other applications are disclosed. The gellant, preferably a ...
Publikations-Datenbank der Fraunhofer Wissenschaftler und Institute: Aufsätze, Studien, Forschungsberichte, Konferenzbeiträge, Tagungsbände, Patente und Gebrauchsmuster
Publikations-Datenbank der Fraunhofer Wissenschaftler und Institute: Aufsätze, Studien, Forschungsberichte, Konferenzbeiträge, Tagungsbände, Patente und Gebrauchsmuster
Principal Investigator:YAMADA Bunichiro, Project Period (FY):1998 - 1999, Research Category:Grant-in-Aid for Scientific Research (C), Section:一般, Research Field:高分子合成
Method for producing methacrylic polymer composition, and molded article | High performance Ziegler-Natta catalyst systems, process for producing such MgCl.sub.2 based catalysts and use... | Photopolymerizable compositions featuring novel amine accelerator for improved color stability and reduced... | Hyaluronic acid derivative, method of preparation thereof, method of modification thereof and use thereof | Sequential hydrothermal liquifaction (SEQHTL) for extraction of superior bio-oil and other organic compounds... |
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The process of polymerization is accomplished in one of two ways. The first way is by adding small molecules onto the active site of a chain of similar molecules to form giant molecules. The second...
Three brønsted acidic ionic liquids, 1-methylimidazolium acetate ([Hmim][CH3COO]), 1-methylimidazolium propionate ([Hmim][CH3CH2COO]) and 1-methylimidazolium butyrate ([Hmim][CH3CH2CH2COO]) were used as reaction medium for atom transfer radical polymerization of methyl methacrylate with ethyl 2-bromoisobutyrate (EBiB)/CuBr as the initiating system. Kinetic studies, chain extension and block copolymerization confirmed the well-controlled manner of these polymerizations in three brønsted acidic ionic liquids. The reactions were fast and the polydispersities of the polymers were quite narrow (1.10,Mw/Mn,1.34). The rate of polymerization in [Hmim][RCOO] decreased with the increasing alkyl chain lengths (n from 1 to 3), indicating a strong dependence of reaction rate on the length of the substituted groups of the anions in ionic liquids. ...
Atom transfer radical polymerization (ATRP) is an example of a reversible-deactivation radical polymerization. Like its counterpart, ATRA or atom transfer radical addition, it is a means of forming a carbon-carbon bond through a transition metal catalyst. The polymerization from this method is called Atom transfer radical addition polymerization (ATRAP). As the name implies, the atom transfer step is the key step in the reaction responsible for uniform polymer chain growth. ATRP (or transition metal-mediated living radical polymerization) was independently discovered by Mitsuo Sawamoto and by Jin-Shan Wang and Krzysztof Matyjaszewski in 1995. The following scheme presents a typical ATRP reaction: IUPAC definition for ATRP Controlled reversible-deactivation radical polymerization in which the deactivation of the radicals involves reversible atom transfer or reversible group transfer catalyzed usually, though not exclusively, by transition-metal complexes. ATRP usually employs a transition metal ...
The ethanolic reversible addition-fragmentation chain transfer dispersion polymerization (RAFTDP), at 21 wt-%, of 2-(naphthalen-2-yloxy)ethyl methacrylate (NOEMA) and 2-phenoxyethyl methacrylate (POEMA) with a poly[2- (dimethylamino)ethyl methacrylate] macro-chain transfer agent (CTA) with an average degree of polymerization of 20 (PDMAEMA20) is described. DMAEMA20-b-NOEMAy (y¼20-125) block copolymers were readily prepared under dispersion conditions in ethanol at 708C. However, the polymerization of NOEMA was not well controlled, with size exclusion chromatograms being distinctly bi or multimodal with measured dispersities (Ð M=Mw/Mn) ≤ 1.69. Though NOEMA copolymerization was not ideal, the resulting series of block copolymers did exhibit the anticipated full spectrum of nanoparticle morphologies (spheres, worms, and vesicles). Interestingly, these morphology transitions occurred over a relatively narrow range of block copolymer compositions. In the case of POEMA, copolymerization was also ...
Until the mid 90s, free radical polymerization (FRP) was characterized by producing polymers with high average molecular weig hts (1×10 5-1×106) since the beginning of polymerization, index of polidispersity (PDI) greater than 1.5 and wide molecular weight distribution (MWD). When necessary to produce polymers with more defined structure, it was usually used anionic polymerization, which is capable to produce polymers with narrow molecular weight distribution and PDI around 1.0 (1.1-1.2). The ionic polymerization, however, needs to be held in a high degree of purity and in the absence of inhibitors, what make the ionic polymerization expensive and not very practical from the industrial point of view. A promising alternative to ionic polymerization has been the living radical polymerization (LFRP), which is much more robust to the impurities and kind of solvent and it is able to produce polymers with polidispersity close to one. Nevertheless, the LFRP presents lower polymerization rates ...
Bovine Serum Albumin (BSA) and lysozyme have been chemically transformed into macroinitiators for the synthesis of fluorescent bioconjugates by living radical polymerization. A new fluorescent monomer based on rhodamine B has been synthesized and incorporated Bovine Serum Albumin (BSA) and lysozyme have been chemically transformed into macroinitiators for the synthesis of fluorescent bioconjugates by living radical polymerization. A new fluorescent monomer based on rhodamine B has been synthesized and incorporated into the polymer backbone of the bioconjugate by copolymerization. This provides a new strategy for the synthesis of fluorescent bioconjugates with improved traceability in biological environments, during biomedical assays. [+] [-] ...
Polymerization-induced self-assembly and re-organization (PISR) was used to prepare polymeric nanostructured materials with a variety of morphologies. Reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene in a selective solvent, methanol, was carried out using cyanoisopropyl dithi
This talk focuses on the use of RAFT chemistry (Reversible Addition-Fragmentation chain Transfer polymerization) under different conditions. In the first section of the talk I will present how RAFT chemistry was employed to modify cellulose and a novel route to improve and tune the physical properties of cellulose. In a second part, I will present the syntheses of a range of glycopolymeric architectures (linear, branched and hyper branched) by a combination of RAFT and click chemistry. Finally, I will show the synthesis and in situ self-assembly of diblock and triblock functional copolymers; as well as the preparation of core-shell organic/inorganic particles using these self-assembled structures.. ...