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Richard C Larock - One of the best experts on this subject based on the ideXlab platform.
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new hybrid latexes from a soybean oil based waterborne polyurethane and acrylics via Emulsion Polymerization
Biomacromolecules, 2007Co-Authors: Richard C LarockAbstract:A series of new waterborne polyurethane (PU)/acrylic hybrid latexes have been successfully synthesized by the Emulsion Polymerization of acrylic monomers (butyl acrylate and methyl methacrylate) in the presence of a soybean oil-based waterborne PU dispersion using potassium persulfate as an initiator. The waterborne PU dispersion has been synthesized by a polyaddition reaction of toluene 2,4-diisocyanate and a soybean oil-based polyol (SOL). The resulting hybrid latexes, containing 15−60 wt % SOL as a renewable resource, are very stable and exhibit uniform particle sizes of 125 ± 20 nm as determined by transmittance electronic microscopy. The structure, thermal, and mechanical properties of the resulting hybrid latex films have been investigated by Fourier transform infrared spectroscopy, solid state 13C NMR spectroscopy, dynamic mechanical analysis, extraction, and mechanical testing. Grafting coPolymerization of the acrylic monomers onto the PU network occurs during the Emulsion Polymerization, leading ...
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new hybrid latexes from a soybean oil based waterborne polyurethane and acrylics via Emulsion Polymerization
Biomacromolecules, 2007Co-Authors: Richard C LarockAbstract:A series of new waterborne polyurethane (PU)/acrylic hybrid latexes have been successfully synthesized by the Emulsion Polymerization of acrylic monomers (butyl acrylate and methyl methacrylate) in the presence of a soybean oil-based waterborne PU dispersion using potassium persulfate as an initiator. The waterborne PU dispersion has been synthesized by a polyaddition reaction of toluene 2,4-diisocyanate and a soybean oil-based polyol (SOL). The resulting hybrid latexes, containing 15-60 wt % SOL as a renewable resource, are very stable and exhibit uniform particle sizes of 125 +/- 20 nm as determined by transmittance electronic microscopy. The structure, thermal, and mechanical properties of the resulting hybrid latex films have been investigated by Fourier transform infrared spectroscopy, solid state 13C NMR spectroscopy, dynamic mechanical analysis, extraction, and mechanical testing. Grafting coPolymerization of the acrylic monomers onto the PU network occurs during the Emulsion Polymerization, leading to a significant increase in the thermal and mechanical properties of the resulting hybrid latexes. This work provides a new way of utilizing renewable resources to prepare environmentally friendly hybrid latexes with high performance for coating applications.
Steven P Armes - One of the best experts on this subject based on the ideXlab platform.
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in situ small angle x ray scattering studies during reversible addition fragmentation chain transfer aqueous Emulsion Polymerization
Journal of the American Chemical Society, 2019Co-Authors: Emma E Brotherton, Fiona L Hatton, Amy A Cockram, Matthew J Derry, Adam Czajka, Erik J Cornel, Paul D Topham, Oleksandr O Mykhaylyk, Steven P ArmesAbstract:Polymerization-induced self-assembly (PISA) is a powerful platform technology for the rational and efficient synthesis of a wide range of block copolymer nano-objects (e.g., spheres, worms or vesicles) in various media. In situ small-angle X-ray scattering (SAXS) studies of reversible addition-fragmentation chain transfer (RAFT) dispersion Polymerization have previously provided detailed structural information during self-assembly (see M. J. Derry et al., Chem. Sci. 2016 , 7 , 5078 - 5090 ). However, conducting the analogous in situ SAXS studies during RAFT aqueous Emulsion Polymerizations poses a formidable technical challenge because the inherently heterogeneous nature of such PISA formulations requires efficient stirring to generate sufficiently small monomer droplets. In the present study, the RAFT aqueous Emulsion Polymerization of 2-methoxyethyl methacrylate (MOEMA) has been explored for the first time. Chain extension of a relatively short non-ionic poly(glycerol monomethacrylate) (PGMA) precursor block leads to the formation of sterically-stabilized PGMA-PMOEMA spheres, worms or vesicles, depending on the precise reaction conditions. Construction of a suitable phase diagram enables each of these three morphologies to be reproducibly targeted at copolymer concentrations ranging from 10 to 30% w/w solids. High MOEMA conversions are achieved within 2 h at 70 °C, which makes this new PISA formulation well-suited for in situ SAXS studies using a new reaction cell. This bespoke cell enables efficient stirring and hence allows in situ monitoring during RAFT Emulsion Polymerization for the first time. For example, the onset of micellization and subsequent evolution in particle size can be studied when preparing PGMA29-PMOEMA30 spheres at 10% w/w solids. When targeting PGMA29-PMOEMA70 vesicles under the same conditions, both the micellar nucleation event and the subsequent evolution in the diblock copolymer morphology from spheres to worms to vesicles are observed. These new insights significantly enhance our understanding of the PISA mechanism during RAFT aqueous Emulsion Polymerization.
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In situ small-angle x-ray scattering studies during reversible addition–fragmentation chain transfer aqueous Emulsion Polymerization
2019Co-Authors: Emma E Brotherton, Amy A Cockram, Matthew J Derry, Adam Czajka, Erik J Cornel, Paul D Topham, Oleksandr O Mykhaylyk, Fiona Hatton, Steven P ArmesAbstract:Polymerization-induced self-assembly (PISA) is a powerful platform technology for the rational and efficient synthesis of a wide range of block copolymer nano-objects (e.g., spheres, worms or vesicles) in various media. In situ small-angle X-ray scattering (SAXS) studies of reversible addition-fragmentation chain transfer (RAFT) dispersion Polymerization have previously provided detailed structural information during self-assembly (see M. J. Derry et al., Chem. Sci. 2016 , 7 , 5078 - 5090 ). However, conducting the analogous in situ SAXS studies during RAFT aqueous Emulsion Polymerizations poses a formidable technical challenge because the inherently heterogeneous nature of such PISA formulations requires efficient stirring to generate sufficiently small monomer droplets. In the present study, the RAFT aqueous Emulsion Polymerization of 2-methoxyethyl methacrylate (MOEMA) has been explored for the first time. Chain extension of a relatively short non-ionic poly(glycerol monomethacrylate) (PGMA) precursor block leads to the formation of sterically-stabilized PGMA-PMOEMA spheres, worms or vesicles, depending on the precise reaction conditions. Construction of a suitable phase diagram enables each of these three morphologies to be reproducibly targeted at copolymer concentrations ranging from 10 to 30% w/w solids. High MOEMA conversions are achieved within 2 h at 70 °C, which makes this new PISA formulation well-suited for in situ SAXS studies using a new reaction cell. This bespoke cell enables efficient stirring and hence allows in situ monitoring during RAFT Emulsion Polymerization for the first time. For example, the onset of micellization and subsequent evolution in particle size can be studied when preparing PGMA29-PMOEMA30 spheres at 10% w/w solids. When targeting PGMA29-PMOEMA70 vesicles under the same conditions, both the micellar nucleation event and the subsequent evolution in the diblock copolymer morphology from spheres to worms to vesicles are observed. These new insights significantly enhance our understanding of the PISA mechanism during RAFT aqueous Emulsion Polymerization
Robert G. Gilbert - One of the best experts on this subject based on the ideXlab platform.
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Emulsion Polymerization state of the art in kinetics and mechanisms
Polymer, 2007Co-Authors: Stuart C Thickett, Robert G. GilbertAbstract:Over decades of carefully designed kinetic experiments and the development of complementary theory, a more or less complete picture of the mechanisms that govern Emulsion Polymerization systems has been established. This required means of determining the rate coefficients for the individual processes as functions of controllable variables such as initiator concentration and particle size, means of interpreting the data with a minimum of model-based assumptions, and the need to perform experiments that had the potential to actually refute a given mechanistic hypothesis. Significant advances have been made within the area of understanding interfacial processes such as radical entry and exit into and out of an Emulsion Polymerization particle, for electrostatic, steric and electrosteric stabilizers (the latter two being poorly understood until recently). The mechanism for radical exit is chain transfer to monomer within the particle interior to form a monomeric radical which can either diffuse into the water phase or propagate to form a more hydrophobic species which cannot exit. Entry is through aqueous-phase propagation of a radical derived directly from initiator, until a critical degree of Polymerization z is reached; the value of z is such that the z-meric species is sufficiently surface active so that its only fate is to enter, whereas smaller aqueous-phase radical species can either be terminated in the aqueous phase or undergo further propagation. For both entry and exit, in the presence of (electro)steric stabilizers, two additional events are significant: transfer involving a labile hydrogen atom within the stabilizing layer to form a mid-chain radical which is slow to propagate and quick to terminate, and which may also undergo β-scission to form a water-soluble species. Proper consideration of the fates of the various aqueous-phase radicals is essential for understanding the overall kinetic behaviour. Intra-particle termination is explained in terms of diffusion-controlled chain-length-dependent events. A knowledge of the events controlling entry and exit, including the recent discoveries of the additional mechanisms operating with (electro)steric stabilizers, provides an extension to the micellar and homogeneous nucleation models which enables particle number to be predicted with acceptable reliability, and also quantifies the amount of secondary nucleation occurring during seeded growth. This knowledge provides tools to understand the kinetics of Emulsion Polymerization, in both conventional and controlled/living Polymerization systems, and to optimize reaction conditions to synthesize better polymer products.
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average termination rate coefficients in Emulsion Polymerization effect of compartmentalization on free radical lifetimes
Journal of Polymer Science Part A, 2005Co-Authors: Stuart W. Prescott, Mathew John Ballard, Robert G. GilbertAbstract:A method is presented by which the time-dependent average termination rate coefficient in an Emulsion Polymerization may be calculated as an appropriate average of the chain-length-dependent termination rate coefficients. The method takes advantage of the fact that the overall termination rate is dominated by terminations between rapidly moving short radicals and much slower long ones. This termination rate coefficient is suitable for use in the Smith-Ewart equations describing the compartmentalization of radicals in an Emulsion Polymerization. Rate data in Emulsion Polymerizations can be quantitatively interpreted if the kinetics fall into one of two categories: zero-one (showing compartmentalization; intraparticle termination is not rate-determining) or pseudo-bulk (no compartmentalization; intraparticle termination is rate-determining). The new method can be used to interpret rate data for systems falling between these categories and also can be used to find termination rate coefficients from Monte Carlo simulations of termination kinetics. The latter is especially useful for predicting and understanding kinetics in controlled radical Polymerizations in disperse media. (C) 2005 Wiley Periodicals, Inc.
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raft in Emulsion Polymerization what makes it different
ChemInform, 2003Co-Authors: Stuart W. Prescott, Mathew J Ballard, Ezio Rizzardo, Robert G. GilbertAbstract:Reversible addition-fragmentation chain transfer (RAFT) Polymerization techniques have been the focus of a great deal of recent work, particularly in their application to Emulsion Polymerization, which is the method of choice for implementing most free-radical Polymerizations on an industrial scale. RAFT/Emulsion Polymerizations have considerable technical potential: to 'tailor-make' material properties, to eliminate added surfactant from surface coatings, and so on. However, considerable difficulties have been experienced in using RAFT in Emulsion Polymerization systems. Here, progress in the application of RAFT techniques to Emulsion Polymerization is reviewed, summarizing the difficulties that have been experienced and mechanisms that have been postulated to explain the observed behaviour. Possible origins of the difficulties in implementing RAFT in Emulsion Polymerizations include Polymerization in droplets, water sensitivity of some RAFT agents, slow transport of highly hydrophobic RAFT agents across the water phase, and surface activity of some RAFT agents.
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effective ab initio Emulsion Polymerization under raft control
Macromolecules, 2002Co-Authors: Christopher J Ferguson, Robert G. Gilbert, Robert J Hughes, Binh T T Pham, Brian S Hawkett, And Algirdas K Serelis, Christopher Henry SuchAbstract:Emulsion Polymerization offers consider-able advantages for such industrial synthesis. Hitherto,attempts to implement RAFT in ab initio (unseeded)Emulsion have met with problems such as loss ofmolecular weight control, loss of colloidal stability, and/or formation of an intractable oily layer (e.g., ref 2).Various reasons for these problems have been suggested(e.g., refs 2 and 3), including hydrolysis of the RAFTagent, poor transport of RAFT agent through the waterphase, and formation of oligomers in droplets (i.e.,droplet Polymerization) arising from the presence ofRAFT agent therein. On the other hand, it has provedpossible to eliminate all these problems by performingRAFT in a seeded Emulsion Polymerization using a (78nm diameter) seed and a highly hydrophobic RAFTagent which was transported to the seed particles usingacetone, the acetone being subsequently removed byrotary evaporation prior to Polymerization.
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Emulsion Polymerization a mechanistic approach
1995Co-Authors: Robert G. GilbertAbstract:Kinetic and thermodynamic processes: free-radical Polymerization reactions initiation propagation bimolecular termination chain transfer rates in coPolymerizations cross-linking reactions the locus of Polymerization in Emulsion systems the rate of an Emulsion Polymerization the three intervals of Emulsion Polymerization ab initio and seeded systems for mechanistic studies monomer concentration in latex particles phase-transfer events in Emulsion Polymerizations inhomogeneities in latex particles scope and methods for mechanistic investigation. Theory of the kinetics of particle growth: overview the simple zero-one system general description of zero-one systems the Smith-Ewart equation chain-length-dependent kinetics - the pseudo-Bulk equation chain-length-dependent compartmentalized systems summary and roadmap for modelling particle growth conclusions. Rate kinetics of particle growth - applications and mechanistic conclusions: rate coefficients and mechanism for entry rate coefficients and mechanisms for exit termination conclusions. Particle size distributions: introduction measurement of PSDs the evolution equations for the PSD solutions of the PSD evolution equations obtaining kinetic data from the PSD conclusions. Molecular weight distributions: the importance of molecular weight in polymer systems definitions of molecular weight distributions and averages rate parameters determining MWD modelling the MWD sample calculation of MWDs experimental measurement of MWDs some experimental results conclusions. Particle formation: introduction particle formation below the CMC particle formation above the CMC some important influences on nucleation conclusions.
Brian S Hawkett - One of the best experts on this subject based on the ideXlab platform.
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particle formation in ab initio raft mediated Emulsion Polymerization systems
Macromolecules, 2007Co-Authors: Desislava E Ganeva, Christopher Henry Such, Ewan Sprong, Hank De Bruyn, Gregory G Warr, Brian S HawkettAbstract:Amphiphilic, RAFT-capped, (acrylic acid)x(styrene)y diblock copolymers (x = 10, y ) 10, 5, 0) were synthesized and used as stabilizers in Emulsion Polymerization. Above the critical micelle concentration (cmc) of the diblocks and under appropriate reaction conditions micelles of the more hydrophobic diblocks were sufficiently nonlabile to be nucleated and act as seed particles for latex particle formation. The key parameters which allow control over the system are diblock hydrophobicity and initiator concentration. A homogeneous nucleation mechanism is most likely to operate below the cmc of the diblocks.
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effective ab initio Emulsion Polymerization under raft control
Macromolecules, 2002Co-Authors: Christopher J Ferguson, Robert G. Gilbert, Robert J Hughes, Binh T T Pham, Brian S Hawkett, And Algirdas K Serelis, Christopher Henry SuchAbstract:Emulsion Polymerization offers consider-able advantages for such industrial synthesis. Hitherto,attempts to implement RAFT in ab initio (unseeded)Emulsion have met with problems such as loss ofmolecular weight control, loss of colloidal stability, and/or formation of an intractable oily layer (e.g., ref 2).Various reasons for these problems have been suggested(e.g., refs 2 and 3), including hydrolysis of the RAFTagent, poor transport of RAFT agent through the waterphase, and formation of oligomers in droplets (i.e.,droplet Polymerization) arising from the presence ofRAFT agent therein. On the other hand, it has provedpossible to eliminate all these problems by performingRAFT in a seeded Emulsion Polymerization using a (78nm diameter) seed and a highly hydrophobic RAFTagent which was transported to the seed particles usingacetone, the acetone being subsequently removed byrotary evaporation prior to Polymerization.
Christopher Henry Such - One of the best experts on this subject based on the ideXlab platform.
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particle formation in ab initio raft mediated Emulsion Polymerization systems
Macromolecules, 2007Co-Authors: Desislava E Ganeva, Christopher Henry Such, Ewan Sprong, Hank De Bruyn, Gregory G Warr, Brian S HawkettAbstract:Amphiphilic, RAFT-capped, (acrylic acid)x(styrene)y diblock copolymers (x = 10, y ) 10, 5, 0) were synthesized and used as stabilizers in Emulsion Polymerization. Above the critical micelle concentration (cmc) of the diblocks and under appropriate reaction conditions micelles of the more hydrophobic diblocks were sufficiently nonlabile to be nucleated and act as seed particles for latex particle formation. The key parameters which allow control over the system are diblock hydrophobicity and initiator concentration. A homogeneous nucleation mechanism is most likely to operate below the cmc of the diblocks.
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effective ab initio Emulsion Polymerization under raft control
Macromolecules, 2002Co-Authors: Christopher J Ferguson, Robert G. Gilbert, Robert J Hughes, Binh T T Pham, Brian S Hawkett, And Algirdas K Serelis, Christopher Henry SuchAbstract:Emulsion Polymerization offers consider-able advantages for such industrial synthesis. Hitherto,attempts to implement RAFT in ab initio (unseeded)Emulsion have met with problems such as loss ofmolecular weight control, loss of colloidal stability, and/or formation of an intractable oily layer (e.g., ref 2).Various reasons for these problems have been suggested(e.g., refs 2 and 3), including hydrolysis of the RAFTagent, poor transport of RAFT agent through the waterphase, and formation of oligomers in droplets (i.e.,droplet Polymerization) arising from the presence ofRAFT agent therein. On the other hand, it has provedpossible to eliminate all these problems by performingRAFT in a seeded Emulsion Polymerization using a (78nm diameter) seed and a highly hydrophobic RAFTagent which was transported to the seed particles usingacetone, the acetone being subsequently removed byrotary evaporation prior to Polymerization.