Download or read book Synthesis of Hyperbranched Polyacrylates Using Self condensing Vinyl Polymerization SCVP Atom Transfer Radical Polymerization ATRP by Diverse Initiation Techniques in Aqueous Dispersed Systems written by Guillermina C. Garcia and published by . This book was released on 2013 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: A major thrust of polymer research in both industry and academia is being driven by the push for sustainable raw materials, environmentally friendly production processes and products that are biodegradable. Hyperbranched polyacrylates were synthesized by atom transfer radical polymerization by self-condensing vinyl polymerization (ATRP-SCVP) using a new class of inimers based on a naturally occurring amino acid, L-serine. The structure of these hyperbranched polyacrylates (HP) includes an ester group at the branch points and in the polymer backbone of many of the repeat units, which provide sites for biodegradation via hydrolysis. In contrast to previous studies, which were performed in bulk or solution and took long periods of time to reach high molecular weight (Mn), we synthesized our hyperbranched polyacrylate using emulsions and mainly miniemulsions polymerization techniques. This provides an environmentally friendly system, high number average molecular weight in the range of 105 to 106 Da, particle size distribution in the range of 50 to 500 nm, high functionality and high reactivity rate. The emulsion and/or miniemulsion conditions that were performed include normal ATRP, reverse ATRP, simultaneous reverse normal initiation SRNI-ATRP, and activator generated by electron transfer AGET-ATRP. The physical and chemical properties of the hyperbranched polyacrylates were studied in detail by 11H, and 13C 1D nuclear magnetic resonance (NMR) spectroscopies. The molecular weights were determined by gel permeation chromatography using light scattering (GPCLS) and reflactive index (GPCPSt) detectors. Thermal properties, such as glass transitions and melting temperatures were determined by differential scanning calorimetry, and the morphology by scanning electron microscopy (SEM). Emulsions and miniemulsions that were sonicated in OMNOVA were analyzed by traditional test methods, including particle size average distribution (number and volume) by DLS (nanotrac), surface tension energy, pH, thermal transition, number average molecular weight Mn, weight average molecular weight Mw and molecular weight distribution (PDI). The rheological properties of these latexes were evaluated using a Brookfield viscometer. The presence of branching in the hyperbranched polyacrylates was analyzed using 2D NMR spectroscopy based on heterogeneous and homogenous techniques such as 1H-1H COSY, 1H-1H TCOSY, 1H-13C HMBC and 1H-13C HSQC NMR. Finally biodegradation studies from these samples were followed by degradation procedures previously reported in our group. This dissertation's results provided us with a better option to produce hyperbranched polyacrylates with a high degree of functionality, in a single-pot, in aqueous conditions controlling molecular weight, and particle size distribution maintained colloidal stable miniemulsions.

Download or read book Synthesis and Characterization of Gradient Hyperbranched Copolymers by Atom Transfer Radical Polymerization written by and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The synthesis of linear and (hyper)branched polymers possessing varying compositions using atom transfer radical polymerization (ATRP) was conducted. The synthesis of linear random and gradient copolymers from styrene/n-butyl acrylate and methyl methacrylate/n-butyl acrylate systems were evaluated by studying the copolymerization kinetics of the respective monomers pairs in ATRP. Development in the preparation of materials with advanced architectures was achieved by the synthesis of novel hyperbranched polymers using the self-condensing vinyl polymerization (SCVP) by ATRP. Subsequent end-group transformation reactions of these hyperbranched polymers yielded low viscosity materials with reactive functionalities. Additionally, novel highly branched nanocomposites were also prepared by the use of a functional colloid (diameter = 15 nm) as a macroinitiator for the synthesis of homo- and block copolymers tethered to a particle surface.

Download or read book Synthesis and Functionalization of Hyperbranched Poly methyl Methacrylate written by Chenying Zhao and published by . This book was released on 2019 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hyperbranched polymers have unique physical and chemical properties that make them interesting to people in both academia and industry. One way to make hyperbranched polymers is to use self-condensing vinyl polymerization (SCVP). Hyperbranched polymethacrylates can be prepared from methacrylate inimers (inimers are monomers that contain both initiation and polymerizable groups) by atom transfer radical polymerization (ATRP) and self-condensing vinyl polymerization (SCVP). The methyl methacrylate inimer was synthesized by reacting the carboxylic acid group of 2-bromo-3-hydroxy-2- methylpropionic acid with methacrylic acid and esterifying the alcohol group with methanol.4 This methyl methacrylate inimer was then polymerized under atom transfer radical polymerization conditions. Post-polymerization functionalization is often used to change and/or improve the properties of polymers. For hyperbranched polymers made by atom transfer radical polymerization, the halogen atoms (chlorine or bromine) remaining in the polymer backbone provide sites for post-polymerization functionalization. The halogen atoms in polymethacrylates are bonded to tertiary carbons, which are more hindered and less electrophilic than the halogen sites in hyperbranched polyacrylates, but are presumably more susceptible to cationic rearrangement. The hyperbranched poly(methyl methacrylate) is rearrangeable with heating and to give a primary bromine.

Download or read book Synthesis of Hyperbranched Polymethacrylates by a Bromoinimer Approach written by Chenwei Liu and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of new methacrylate inimers (a molecule having both an initiating site and a polymerizable group) was designed based on 2-bromo-3-hydroxy-2-methylpropionic acid. These inimers can be homopolymerized using self-condensing vinyl polymerization (SCVP) and atom transfer radical polymerization (ATRP), to produce hyperbranched polymethacrylates that are true architectural analogues of linear polymethacrylates. The polymers contain an ester group attached to every other carbon along the polymer backbone and each repeat unit contains a free ester pendant group. The synthetic pathway is suitable for different alkyl ester functional groups such as methyl, butyl, and dodecyl. The hyperbranched polymethacrylates were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC).

Download or read book Functionalization of Hyperbranched Polyacrylates by Radical Quenching written by Zewei Wang and published by . This book was released on 2014 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hyperbranched polyesters have drawn great attention in many applications, including lubricants, paints, catalyst supports, and drug delivery. Similar to dendrimers, hyperbranched polymers have high branching densities which contribute to higher solubilities and lower viscosities as compared to linear polymers. Furthermore, they have a considerable amount of terminal functional groups throughout their structures, which contribute to their excellent ability to encapsulate molecules and act as a catalyst support. There are many publications on further grafting on hyperbranched polymers, but few reports on the modification of their end groups. This project concentrates on the synthesis of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) derivatives which will be coupled to the bromine end groups of hyperbranched poly(n-butyl acrylate) by nitroxide radical coupling (NRC). The substituted functional groups include hydroxy, alkene, azido, cyano and nitro groups. TEMPO derivatives are being synthesized from 4-hydroxy TEMPO to form ester or ether by multiple coupling methods such as DCC coupling, mesylation, and alkoxidation. Further nitroxide mediated radical polymerizations may be carried out to modify the behavior of the polymers, mostly by addition of styrenes. The hyperbranched polymers are being synthesized by self-condensing vinyl polymerization (SCVP) of a bromo acrylate inimer.

Download or read book Utilization of Atom Transfer Radical Polymerization for Synthesis of Graft Copolymer of Natural Rubber and Poly methylmethacrylate written by Lapporn Vayachuta and published by . This book was released on 2009 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atom Transfer Radical Polymerization (ATRP) technique was applied for synthesis of natural rubber-grafted-poly(methyl methacrylate) (NR-g-PMMA). Active sites on macromolecular chains of NR were created by fixation of bromoalkyl groups via a two-step chemical modification: partial epoxidation on unsaturated carbon-carbon bonds, followed by nucleophilic addition of a bromoalkyl-functionalized carboxylic acid on the oxirane rings of the epoxidized natural rubber (ENR) obtained. The resulting bromoalkyl-functionalized rubber was then used as macroinitiator to initiate the ATRP of methyl methacrylate (MMA) from NR chains by varying reaction conditions. The study was successively envisaged with 4-methyloct-4-ene (a model molecule of NR repeating unit), a synthetic cis-1,4-polyisoprene, and natural rubber. In the first part, the feasibility of the grafting reaction is verified by studying the ATRP of MMA from model molecules of bromoalkyl-functionalized 1,4-polyisoprene units. The model of the 1,4-polysisoprene unit, 4-methyloct-4-ene, is transformed in various models of bromoalkyl-functionalized 1,4-polyisoprene units via a chemical modification procedure carried out in two-steps: epoxidation performed with m-chloroperbenzoic acid (CPBA) followed by the addition of the bromoalkyl-functionalized carboxylic acid (2-bromopropionic acid, A1, or 2-bromo-2-methylpropionic acid, A2) on the oxirane ring formed. The addition of the acid occurs according to an SN2 mechanism with fixation of the acid group on the less substituted carbon of the oxirane ring and is competed with a secondary reaction of rearrangement of oxirane ring, leading to the formation of two allyl alcohols. The yield of the addition depends on the acidity of the carboxylic acid used. Afterwards, resulting O-(2-hydroxy-2-methyl-1-(n-propyl)pentyl)-2-bromopropionate and O-(2-hydroxy-2-methyl-1-(n-propyl)pentyl)-2-bromoisobutyrate, were used to initiate the ATRP of MMA at 90°C in toluene using Cu(I)Br complexed with a polyamine ligand. Several ligands were tested: N-(n-octyl)-2-pyridylmethanimine (NOPMI), N-(n-octadecyl)-2-pyridylmethanimine (NODPMI), and 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA). A good control of molecular weights (SECn,M) and polydispersity indexes (PDI) were obtained with O-(2-hydroxy-2-methyl-1-(n-propyl)pentyl)-2-bromoisobutyrate as the initiator in presence of CuBr/NOPMI as catalytic system. In the second part, the synthetic cis-1,4-polyisoprene (PI) is transformed into a bromoalkyl-functionalized polyisoprene (PI-Br) macroinitiator using a two-step chemical modification procedure similar to that used for synthesis of the model. PI was partially epoxidized using CPBA in dichloromethane, and then the epoxidized PI (EPI) obtained was reacted with A2. The addition of the acid occurs according to an SN2 mechanism with fixation of the acid group on the less substituted carbon of the oxirane ring ([beta]-addition) and is competed with rearrangement reactions of oxirane rings, leading to external allyl alcohol. SECn,M and PDI of PMMA grafts were determined by Size Exclusion Chromatography after separation from the PI backbone by hydrolysis of the ester bond using trifluoroacetic acid. An internal first order kinetic plot with respect to monomer and an increase of SECn,M with MMA conversion were observed using Cu(I)Br complexed with bidentate (NOPMI and NODPMI) and tridentate (PMDETA) ligands, as catalytic systems. With bidentate ligands, the PDI of grafts is better controlled. Moreover, the control of SECn,M and PDI of PMMA grafts was affected by increasing the degree of initiating units in PI-Br. In the last part, NR is used as a starting material. It was partially epoxidized in ENR in latex medium by reaction with performic acid generated in-situ from formic acid and hydrogen peroxide, and then ENR was transformed in bromoalkyl-functionalized NR (NR-Br) by nucleophilic addition of A2 on the oxirane rings. The addition of the acid is similar to that observed during the studies performed with 4-methyloct-4-ene and PI. Resulting NR-Br was then used to initiate the graft polymerization of MMA from NR chains using normal ATRP in toluene solution and in aqueous dispersed medium, respectively. AGET-ATRP was also considered in aqueous dispersed medium to study the effect of water for further ATRP graft copolymerization studies with NR latices. By normal ATRP in toluene solution, the termination reactions by recombination decreased as MMA concentration deceased, from 30 wt% to 10 wt%. PDIs of PMMA grafts vary in range from 1.7 (at 8.1 % MMA conversion) to 2.0 (at 52.0 % MMA conversion). A better control of the SECn,M and PDI of PMMA grafts was obtained by using normal ATRP in aqueous dispersed medium, more especially when CuBr was complexed with NODPMI. In these conditions, PDIs of PMMA grafts were low (closed to 1.5 at low MMA conversion). In AGET-ATRP performed in aqueous dispersed medium, it was shown that the efficiency of graft copolymerization is affected by the concentration in ascorbic acid used as reducing agent. The chemical structures obtained were characterized by FT-IR, and by 1H and 13C NMR. The thermal properties of the graft copolymers synthesized were studied by Differential Scanning Calorimetry (DSC). The presence of two Tgs, at about -14°C and 99°C respectively, on the DSC curves when the amounts of PMMA in NR-g-PMMAs are higher than 65 wt%, shows that these materials adopt a biphasic morphology.

Download or read book Living controlled Polymerization Conducted in Aqueous Based Systems written by Ryan W. Simms and published by . This book was released on 2007 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last decade processes known as living/controlled radical polymerizations (L/CRP) have been developed which permit the synthesis of high-value specialty polymers. Currently, the three processes that have demonstrated the most potential are: reverse addition fragmentation chain transfer polymerization (RAFT), atom transfer radical polymerization (ATRP) and stable free radical polymerization (SFRP). While each process has their strengths and weaknesses with regard to specific polymers and architecture, the viability of these systems to industrial scale production all lie in the ability to perform the polymerization in a water based system because of process, environmental and economic advantages. The most effective method of controlling the polymerization of vinyl acetate in bulk has been RAFT. We have developed a miniemulsion RAFT polymerization using the xanthate methyl (ethoxycarbonothioyl)sulfanyl acetate. The miniemulsion is stabilized with 3 wt% sodium lauryl sulfate, initiated with the azo-based water-soluble VA-060. The main focus of this research was adapting ATRP to a miniemulsion system. It was determined that ionic surfactants can be successfully employed in emulsion-based ATRP. The cationic surfactant cetyltrimethylammonium bromide provides excellent stability of the latex over a range of surfactant loadings (allowing the particle size to be easily manipulated), at temperatures up to 90 C, for a wide variety of ATRP formulations. A new method of initiation was developed for reverse ATRP, using the redox pair hydrogen peroxide/ascorbic acid. This nearly eliminated the induction period at the start of the polymerization, increased the polymerization rate 5 fold and, surprisingly, enabled the formation of well-controlled polymers with a number-average molecular (Mn) weight approaching 1 million (typically ATRP is limited to ~200 000). The ability to control the particle size and the number of polymer chains (through the target Mn) over a wide range of values allowed us to determine that ATRP is influenced by compartmentalization effects. The knowledge gained from our work in L/CRP was used to develop the surfactant-free SFRP of styrene. A multi-stage approach was adopted starting from dilute styrene/water solutions to favor the formation of the alkoxyamine and short chain SG1-oligomers (stage one) before the addition of the majority of the styrene (stage two).

Download or read book Living Radical Polymerization in Aqueous Dispersed Systems with Water Soluble Catalysts written by and published by . This book was released on 2015 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: Living radical polymerization is an important technique for synthesizing advanced macromolecules including block copolymers. Since its discovery in the early 1990s the capability of the field has expanded with new types of chemistry and techniques. One of the most widely used chemistries is atom transfer radical polymerization (ATRP) also known as "metal mediated living radical polymerization" (Mt-LRP). Mt-LRP has also expanded its use to aqueous dispersed systems including emulsion, miniemulsion and microemulsion, with the biggest advancements seen in miniemulsion where the droplets act as nanosized reactors. Extremely hydrophobic catalyst complexes are typically used in miniemulsion. While effective in controlling the polymerization, these hydrophobic catalyst complexes also get trapped in the final polymer particles and are difficult to remove. Herein I report the progress made using thermoresponsive polymer bound catalysts for Mt-LRP reactions in miniemulsion, which allow the successful LRP in miniemulsion with facile catalyst removal. Polymers could be prepared with less than 10 ppm of ruthenium in the final polymer compared to >500 ppm in the reaction mixture. The polymerizations were improved by the addition of ferrocene (FeCp2) in miniemulsion, to give almost complete conversion in significantly shorter times. The addition of ferrocene adds a second catalytic cycle that is ionic in nature and requires excess halogens present for a successful polymerization to occur. The ionic species in this catalytic cycle meant that the use of cationic surfactants with halogen counter-ions could directly affect the polymerization chemistry, which was shown by increasing rates with the addition of a bromine counter-ion versus a chlorine counter ion in the cationic surfactant used. Water-soluble FeCp2 derivative cocatalysts were also used to improve the rates and conversions of Mt-LRP of ruthenium catalyzed polymerizations while also allowing colourless polymers to be synthesized. Finally, the ligand EHA6TREN, was found to be active in bulk or solution (anisole) when complexed to iron (III) bromide with reverse ATRP, or to iron (II) bromide with AGET ATRP, yielding an iron-mediated living radical polymerization.

Download or read book Photoinduced Atom Transfer Radical Polymerization written by Wendong Ren and published by . This book was released on 2021 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atom transfer radical polymerization (ATRP) is the most utilized controlled free-radical polymerization technique. Synthetic polymers can be prepared with predefined molecular weight, low dispersity, precisely selected end groups, and even different shapes via ATRP. In conventional ATRP, thermal stimulation is used to activate the reaction. Light stimulation is more effective and convenient than thermally driven techniques. In addition, transition metal catalysts (most commonly Cu(I)) in the ATRP system limit the potential use in biological and microelectronic applications which are sensitive to metal ion contamination. As a result, the trend in future research and exploration is the metal-free photoinduced ATRP system, in which organic photocatalyst is used.The goal of my research is to find a new photocatalyst. Typically, the catalyst needs to meet the following requirements: strong visible light absorption, high rate of ISC/ high triplet quantum yield, and sufficiently long lifetime for electron transfer to occur. Following these rules, we chose Coumarin 343 and verified whether it can be used as a photocatalyst for photoinduced metal-free ATRP. The first step in this research was the polymerization of methyl methacrylate catalyzed by Coumarin 343. The second step is the chain extension experiment. We used PMMA, which was synthesized in the first step, as a macroinitiator to initiate different monomers. The structure of polymers was studied by 1H nuclear magnetic resonance (NMR) spectroscopy and the molecular weights of polymers were determined by gel permeation chromatography (GPC). The characterization results prove that we have successfully synthesized PMMA and extended the polymer chains. In addition, we found that coumarin 343 can be used not only as a photocatalyst, but also as a photoinitiator, and we hypothesized its mechanism.

Download or read book Supported Aqueous phase Catalysis for Atom Transfer Radical Polymerization written by Ravi Aggarwal and published by . This book was released on 2010 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atom transfer radical polymerization (ATRP) which utilizes transition metal based catalysts is a versatile methodology for the synthesis of a wide spectrum of polymers with controlled architectures. However, high concentrations of soluble catalyst required in an ATRP process makes the final polymer colored and toxic. Thus, the catalyst removal/reduction/recycling remains a challenge in the field of ATRP. Supported catalysts on insoluble solids such as silica gel, polystyrene beads, etc. have been used in ATRP to facilitate the catalyst recovery and recycling. However, the ability of the supported catalysts to mediate a polymerization is substantially reduced due to their reduced mobility and leaching problems. In this thesis, we report a series of novel and recyclable physisorbed CuBr2/N, N, N', N'' -pentamethyldiethylene-triamine supported catalytic systems operating in conjunction with hydration. Supported aqueous-phase catalysis (SAPC) for ATRP was evaluated for different inorganic (Na-clay, silica and zeolite) and organic (polysaccharides) supports. The hydrated physisorbed supported catalysts were used for the polymerization of benzyl methacrylate and methyl methacrylate using an activator generated electron transfer ATRP process. The catalyst was effectively retained on the surface of supports through hydration as was verified by UV-Vis measurements. The supported catalyst was easily removed from the polymerization by simple filtration process affording a colorless polymer solution. The polymerizations produced high conversion and colorless polymers with moderately narrow polydispersity indices (PDI). The catalyst maintained high activity during the recycling experiments. We also investigated the kinetic and mechanistic behavior of these solid supported polymerization systems. Based on split kinetics experiments and UV-Vis studies it was believed that the activation and deactivation processes took place at the diffused hydrated interface between the solid support and organic phase. The branched (stars and graft) polymers were also synthesized using Na-clay supported catalyst. The produced polymers had narrow PDI and good initiator efficiencies. The functionality of the star polymers was confirmed using 1H NMR and dilute solution properties. The synthesis of graft-copolymer was confirmed by 1H NMR and atomic force microscopy. This thesis demonstrates the successful use of SAPC for ATRP to produce contamination free linear and branched polymers with moderately narrow PDI and high recycling efficiency.

Download or read book Atom Transfer Radical Polymerization written by Tharanikkarasu Kannan and published by LAP Lambert Academic Publishing. This book was released on 2010-05 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional radical polymerization is widely used in industries due to its simple polymerization conditions. But, molecular weight of polymers are difficult to control in this method. To achieve control over molecular weight and molecular weight distribution, many controlled radical polymerization methods have been proposed such as INIFERTER, NMP, RAFT and ATRP. In the field of ATRP, due to its simplicity and versatility, more than 7000 research articles have been published in the reputed journals during the last 15 years. But polyurethane-based tri-block copolymers have not been reported so far through ATRP and hence this book concentrates on novel routes to synthesize these tri-block copolymers via ATRP. Four different types of polyurethane macroinitiators for ATRP have been synthesized and used for the polymerization of vinyl and acrylate monomers. Results show that the present macroinitiators polymerize monomers through ATRP mechanism. These macroinitiators are highly potential to polymerize wide variety of monomers and resulting block copolymers would be very useful for academic as well as industrial research.

Download or read book Design and Precise Synthesis of Thermoresponsive Polyacrylamides written by Keita Fuchise and published by Springer. This book was released on 2016-09-27 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the author describes versatile and easy-to-use methods to control the properties of thermoresponsive polyacrylamides by developing novel synthetic methods for end-functionalized poly(N-isopropylacrylamide) (PNIPAM) and block copolymers of poly(N,N-diethylacrylamide) (PDEAA). The synthesis of various urea end-functionalized PNIPAMs was achieved by the atom transfer radical polymerization (ATRP) and the click reaction. The phase transition temperature of PNIPAM in water was controlled depending on the strength of the hydrogen bonding of the urea groups introduced at the chain end of the polymer. Novel living polymerization methods for N,N-dimethylacrylamide and N,N-diethylacrylamide were developed by group transfer polymerization (GTP) using a strong Brønsted acid as a precatalyst and an amino silyl enolate as an initiator. This process enabled the precise synthesis of PDEAA and its block copolymers—namely, thermoresponsive amphiphilic block copolymers and double-hydrophilic block copolymers.

Download or read book Radical Polymerization Kinetics in Aqueos Solution and in Systems with Secondary and Tertiary Radicals Studied by Novel Pulsed laser Techniques written by Pascal Hesse and published by Cuvillier Verlag. This book was released on 2008 with total page 325 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atom Transfer Radical Polymerization in Aqueous Dispersed Media written by Jian Qiu and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Controlled Radical Polymerization in the Dispersed Phase written by Mary E. Thomson and published by . This book was released on 2010 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlled radical polymerization (CRP) has emerged as a powerful method of creating polymers with tailored molecular architectures under mild reaction conditions. However, production of these polymers efficiently at an industrial scale will likely require them to be synthesized in the dispersed phase. Three types of CRP are explored, Atom Transfer Radical Polymerization (ATRP), Nitroxide Mediated Polymerization (NMP) and Catalytic Chain Transfer (CCT) to elucidate the intricacies of creating these novel polymer colloids. Compartmentalization in an ATRP dispersed phase system is explored theoretically to understand the effects of particle size and catalyst concentration on the polymerization. The results suggest that there is an optimal range of particle sizes where the rate of polymerization is greater than that in an equivalent bulk system while maintaining both a lower PDI (polydispersity index) and higher livingness. All three factors are desirable in ATRP but generally cannot be achieved simultaneously in bulk. Compartmentalization manifests itself differently in CCT dispersed phase systems, where the segregation of the CCT agents into different polymer particles leads to multimodal molecular weight distributions. Control over the particle size is notoriously difficult for nitroxide mediated polymerization, as it is challenging to decouple an increase in the particle size with an increase in target molecular weight using a two stage emulsion polymerization approach. This often leads to colloidally unstable latexes for low molecular weight, high solids conditions which are the result of superswelling. We offer several strategies to minimize this problem and create colloidally stable, high solids, n-butyl acrylate latexes by NMP with moderate to high molecular weight targets (>70 kg/mol). Using this synergy between target molecular weight and particle size, high solids (>40 wt.%), high molecular weight (

Download or read book Atom Transfer Radical Polymerization with Low Catalyst Concentration in Continuous Processes written by Nicky C. F. Chan and published by . This book was released on 2012 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atom transfer radical polymerization (ATRP) is a dynamic technique that possesses tremendous potential for the synthesis of novel polymeric materials not possible through conventional free radical polymerization. However, its use on an industrial scale has been limited by the high level of transition metal complex required. Significant advances have been made in the last 5 years towards lowering the level of copper complexes used in ATRP, resulting in novel variants called "activator regenerated by electron transfer" (ARGET) and "single electron transfer-living radical polymerization" (SET-LRP). To fully realize the potential of ATRP, its use in industrially relevant processes must be studied. Continuous processes such as tubular flow reactors and stirred tank reactors (CSTR) can reduce waste, improve productivity and facilitate process scale-up when compared to common batch reactors. The combination of low copper concentration ATRP techniques and continuous processes are especially attractive towards the design of a commercially viable process. This thesis presents a study into ARGET ATRP and SET-LRP as applied to continuous tubular and stirred tank reactors for the production of acrylic and methacrylic polymers. The equilibrium which governs polymerization rate and control over molecular architecture is studied through batch ARGET ATRP experiments. The improved understanding of ARGET ATRP enabled the reduction of ligand from a 3 to 10 fold excess used previously down to a stoichiometric ratio to copper salts. ARGET ATRP was then adapted to a continuous tubular reactor, as well as to a semi-automated CSTR. The design of the reactors and the effect of reaction conditions such as reducing agent concentration and residence time are discussed. The use of common elemental copper(0) such as copper wire and copper tubing is also investigated with SET-LRP for room temperature polymerization of methyl acrylate. SET-LRP is adapted to a CSTR to observe the effects of residence time on reaction rate, molecular weight control as well as copper consumption rate. The use of copper tubing as a catalyst source for SET-LRP is demonstrated and the design of a continuous tubular reactor using a combination of copper and stainless steel tubing is discussed.

Download or read book Living controlled Radical Polymerization written by Delphine Chan-Seng and published by . This book was released on 2007 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emulsion polymerization is an important process for the industrial production of polymers. However, initial attempts at performing "living"/controlled radical polymerization under emulsion conditions were not particularly successful primarily due to latex instability. To address this problem a unique nanoprecipitation process was developed in our laboratory for the stable free radical polymerization (SFRP) process. The first part of this thesis describes attempts to generalize this process and extend it to the copper based atom transfer radical polymerization, ATRP, process. Details describing initial problems we had with reproducing some initial successful results are provided. Once the process was under control it was used to synthesize block copolymers. The ability of these block copolymers to self-assemble in aqueous solutions and in bulk were subsequently investigated and the results of these studies are detailed at the end of the discussion on the emulsion process. The second part of the thesis deals with the SFRP process and more specifically with the difficulty of the process to moderate the polymerization of acrylates. Two reasons have been advanced to account for this difficulty; a high bond dissociation energy between the C-O bond linking the nitroxide moiety to the end of the polymer chain and an accumulation of excess nitroxide, caused by unavoidable chain termination, which causes inhibition of the polymerization. To address the high bond dissociation energy a nitroxide, specifically, 1,1'-diadamantyl nitroxide, containing very bulky substituents that might cause the bond to weaken, was synthesized and studied. To address the accumulation of excess free nitroxide, high temperature additives, that would slowly dissociate over time and consume the excess nitroxides, were studied. The results of both of these approaches are provided enabling some insight into what might be actually restricting the polymerization of acrylates.