We describe a simplified method to synthesize film forming polymer Janus particles by phase separation during RAFT-based free radical emulsion polymerization. Fully crosslinked snowman- or football-shaped polystyrene Janus particles (PSJPs) were first produced in a one-step batch process using amphiphilic triblock macro-RAFT copolymers as stabilizers. Such particles were in turn employed as seeds in a continuous emulsion polymerization in which a monomer mixture of methyl methacrylate (MMA) and butyl acrylate (BA) (1/1 by weight) was constantly injected into the reaction in the presence of a water soluble initiator. The added monomers wetted seed particle surface and their polymerization led to formations of 93-nm film forming single- or two-headed Janus particles. The resulted latex was successfully used to disperse and encapsulate solid calcite extender.

A novel method is demonstrated to encapsulate titanium dioxide pigment using directed polymerization-induced self-assembly (PISA) with reversible addition-fragmentation chain-transfer (RAFT) controlled emulsion polymerization. The polymerization is carried out in a batch process in which both styrene (Sty) and the pigment are emulsified using triblock amphiphilic macro-RAFT copolymers as stabilizers. RAFT-controlled chain growth leads to directed lamellar self-assembly, forming polystyrene (PS) shells' encapsulating pigment particles with 100% efficiency. The pigment resides either at centers of single-void vesicles or within the interior of multivoid vesiculated particles. The presence of complex morphologies such as spherical particles, nanofibers, nanoplatelets, and polymer vesicles confirms the PISA pathway. The process is optimized to preferably produce polymer-vesiculated pigment for use as an enhanced opacifier in water-based paint.

Janus nanoparticles with soft lobes can self-assemble on the surface of solid substrates in aqueous phase and coalesce to form a complete polymer shell encapsulating the entire solid substrate.

A robust polymerization technique that enables the surfactant-free aqueous synthesis of a high solid content latex containing polymeric hollow particles is presented. Uniquely designed amphiphilic macro-reversible addition fragmentation chain transfer (RAFT) copolymers were used as sole stabilizers for monomer emulsification as well as for free-radical emulsion polymerization. The polymerization was found to be under RAFT control, generating various morphologies from spherical particles, wormlike structures to polymer vesicles. The final particles were dominantly polymeric vesicles which had a substantially uniform and continuous polymer layer around a single aqueous filled void. They produced hollow particles once dried and were successfully used as opacifiers to impart opacity into polymer paint films. This method is simple, can be performed in a controllable and reproducible manner, and may be performed using diverse procedures.

RAFT-mediated free-radical emulsion polymerization is successfully used to synthesize polystyrene nanofibers using triblock amphiphilic macro-RAFT copolymers as stabilizers. The polymerization is under RAFT control, producing various morphologies from spherical particles, nanofibers, nanoplatelets, and polymer vesicles. Optimum conditions are established for the synthesis of predominantly negatively charged polymer nanofibers. Superparamagnetic iron oxide nanoparticles (SPION)-decorated nanofibers are formed by simple mixing of the SPIONs with the fibers at an appropriate pH. The composite material has been found to be superparamagnetic and could be aligned under a magnetic field.

Polymer encapsulation of raw ferrofluids was carried out by free radical emulsion polymerization using macro-RAFT copolymers as stabilizers. The iron oxide cores with positively charged surface at the pH of encapsulation were dispersed in a solution of negatively charged random macro-RAFT copolymer by ultrasonication. Uniform polymer encapsulated super paramagnetic iron oxide nanoparticles (SPIONs) were produced by feeding the mixture of methyl methacrylate (MMA) and n-butyl acrylate (BA) monomers into the dispersion containing water soluble initiator 4,4’-azobis (4-cyanopentanoic acid) (V501). Shell thickness could be controlled by adjusting the amount of coating monomer added. Polymer encapsulation of SPIONs aligned in a magnetic field produced polymer encapsulated SPION rods. Monodispersed sterically stabilized crosslinked polymer encapsulated SPIONs were synthesized using diblock and random macro-RAFT copolymers as stabilizers. Rhodamine labeled SPIONs were found to be non-cytotoxic and suitable for cell labeling.

Athel Beckwith chose to embark on a career in free radical chemistry at a time when it was largely ignored by all but a small coterie within the broader Organic Chemistry community. Of his many contributions in this area, the mechanistic clarification and exploitation of the cyclization of hex-5-enyl radical-containing systems is undoubtedly the most significant, leading to what is now, in a multitude of variants, a universally-used, powerful, sophisticated, selective, general synthetic methodology. This account revisits and highlights the early studies carried out by the Beckwith group at The University of Adelaide from the late-1960s to 1980, a period when the main breakthroughs in kinetic and mechanistic understanding were made, and the implications for wider synthetic utility in more complex hex-5enyl systems became apparent.

Kinetics of copolymerization reactions of 2-(dimethylamino)ethyl acrylate (DMAEA) and styrene by reversible addition fragmentation transfer (RAFT) in N,N-dimethylformamide (DMF) are reported. Novel approaches in the online monitoring of the synthesis of the amphiphilic copolymers by Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP) are presented. Automatic withdrawal of separate reactor streams and their subsequent dilution throughout the reaction with organic and aqueous solvents, respectively, allowed different features to be captured. Thus, light scattering data combined with spectroscopic and viscometric measurements in DMF, together with conductivity measurements in aqueous medium provided in real time comonomer conversion, copolymer mass, reduced viscosity, and composition. Continuous data gathered allowed observing and quantifying the DMAEA-linked macroRAFT control agent decomposition, with significant effects on the reaction.kinetics. Deviations from controlled behavior were investigated during (co)polymerization reactions under different conditions.Multi-detector Size Exclusion Chromatography (SEC) and NMR were used to bring additional information on the system investigated. Published by Elsevier Ltd.

Introduction Reversible addition fragmentation transfer (RAFT) belongs to the group of the controlled radical polymerization (CPR) methods, intensively employed in the synthesis of polymers with complex architectures and structures. 1,2 pH-responsive amphiphilic copolymers synthesized by RAFT, lead to materials with versatile properties. Optimization of the reaction kinetics during RAFT polymerization of 2-(dimethylamino)ethyl acrylate (DMAEA) in N,N-dimethylformamide (DMF) was investigated in this study, followed by the synthesis of DMAEA/styrene amphiphilic diblock copolymers, using Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP). Poly(DMAEA) is a pH sensitive polymer with wide applications in pharmaceutical and water treatment industries yet challenging due to possible interaction of its amino group with catalysts. 3,4 Experimental Materials. DMAEA, DMF, butyl acrylate (BA), styrene (Sty) and 2,2”azoisobutironitrile (AIBN) were used as received from Aldrich. The RAFT agent, a thrithiocarbonate (TTC), 2-{[(dodecylsulfanyl) carbonothioyl] sulfanyl} propanoic acid (DoPAT) was provided by Dulux, Australia. The polymerization reactions were carried out with a total of ~30% by mass of monomer in DMF at 80oC in a 150ml three-neck round bottom reactor equipped with a condenser, under magnetic stirring and nitrogen flow. Instrumentation. ACOMP,5 based on a simultaneous and automatic dilution of the reactor solution on which measurements can be made, was used to monitor the RAFT (co)polymerization reactions studied. Dilution with DMF of the 30% reactor solution occurred in two stages with a total dilution of 142x, and the diluted reactor solution was passed at 2ml/min through detectors comprising a Brookhaven (BI-MwA) multi-angle light scattering detector, a Shimadzu differential refractometer (RID-10A), a single capillary viscometer, and a Shimadzu photodiode array (SPM-20A, 200-800nm). Simultaneous dilution with water of a second stream from reactor allowed conductivity measurements to be made. Multi-detector Size Exclusion Chromatography (SEC) was carried out offline in DMF using the ACOMP detector train, to which a0.1ml loop injector and two PLgel individual size 500 μm and 50μm chromatographic columns connected in series were added. Automatic continuous mixing (ACM) was used to characterize reaction end-products through light scattering and combined spectroscopic detectors. Dynamic light scattering (DLS) measurements were made on a Brookhaven Instruments Corp. 90 Plus particle size detector on polymer solutions at different pH values. The structures of the DoPAT and DMAEA are shown in Scheme 1.

Automatic continuous online monitoring of polymerization reactions (ACOMP) was used to follow kinetic trends in the reversible addition-fragmentation chain transfer (RAFT) polymerization of butyl acrylate (BA) in butyl acetate, using 2-{[(dodecylsulfanyl)carbonothioyl]sulfanyl} propanoic acid (DoPAT) as the RAFT agent and 2,2-azobis(isobutyronitrile) as the initiator (AIBN). The goals were to demonstrate the use of ACOMP for RAFT studies and to examine the trend in conversion and evolution of weight-average molar mass M-w and weight-average intrinsic viscosity [eta](w) for a series of experiments in which the RAFT agent concentration was decreased over a wide range while all the other reaction conditions were held constant; [DOPAT]/[AIBN] ranged from 0 to 2.4. This allowed monitoring the transition from "living"-like behavior in the "controlled radical polymerization" (CRP) regime, where sufficient RAFT agent was used, to the noncontrolled radical polymerization regime as RAFT agent was progressively reduced to zero. The conversion kinetics were found to be essentially zeroeth order in DoPAT, and deviations from living behavior allowed estimates of radical efficiency. The evolution of M-w vs monomer conversion varied dramatically from near-ideal living behavior at high [DoPAT]/[AIBN] to classical radical polymerization behavior at [DoPAT] = 0. All but one experiment showed a nonzero M-w at f = 0, and the conversion behavior of M, points to transfer and branching side reactions, depending on [DoPAT]. ACOMP should prove to be a useful tool both for fundamental RAFT research and process development.

A new method is described, based on living amphipathic random macro-RAFT copolymers, which enables the efficient polymeric encapsulation of both inorganic and organic particulate materials via free-radical polymerization. The mechanism for this new approach is examined in the context of the polymer coating of zirconia- and alumina-coated titanium dioxide particles and its breadth of application demonstrated by the coating of organic phthalocyanine blue pigment particles. The particulate materials were first dispersed in water using a macro-RAFT copolymer as a stabilizer. Monomer and water-soluble initiator were then added to the system, and the monomer polymerized to form the coating. If nucleation of new polymer particles in the aqueous phase was to be avoided, it was found necessary to use a macro-RAFT copolymer that did not form micelles; within this constraint, a broad range of RAFT agents could be used. The macro-RAFT agents used in this work were found not to transfer competitively in the aqueous phase and therefore did not support growth of aqueous-phase polymer. Successful encapsulation of particles was demonstrated by TEM. The process described enables 100% of the particles to be encapsulated with greater than 95% of the polymer finishing up in the polymeric shells around the particles. Moreover, the coating reaction can be carried out at greater than 50% solids in many cases and avoids the agglomeration of particles during the coating step.

High conversion and selectivity can be obtained for the cross-metathesis of 2-butene with triglycerides and unsaturated fatty acid esters derived from natural oils. This can be achieved with remarkably high productive catalyst turnovers using second-generation ruthenium-based olefin metathesis catalysts.

Controlled radical polymerization using RAFT has the potential to make polymers with virtually any desired molecular architecture. For this to be implemented on an industrial scale, it must be performed by polymerization in disperse media. However, simply adding a RAFT agent to a conventional emulsion polymerization recipe leads to a loss of molecular weight control and formation of coagulum, probably because of nucleation in droplets, which is normally an unlikely phenomenon in emulsion polymerizations. Recently, a method has been devised for implementing RAFT in ab initio emulsion polymerization that avoids droplets in the particle formation stage. The molecular weight distribution of the polymer thus formed shows that molecular weight control is maintained throughout the polymerization. A model is developed to predict the particle size formed in this new type of emulsion polymerization. The new methodology enables synthesis of novel dispersions where molecular architecture can be precisely controlled, such as structured core-shell particles.

The cross-metathesis of synthetic and natural triglycerides containing unsaturated fatty acids with 2-butene can be achieved with high conversion and excellent productive turnovers. These reactions are catalysed by second-generation ruthenium-based olefin metathesis catalysts and can be conducted at -5 degrees C in liquid 2-butene.

A method is developed to enable emulsion polymerization to be performed under RAFT control to give living character without the problems that often affect such systems: formation of an oily layer, loss of colloidal stability, or loss of molecular weight control. Trithiocarbonate RAFT agents are used to form short stabilizing blocks from a water-soluble monomer, from which diblocks can be created by the subsequent polymerization of a hydrophobic monomer. These diblocks are designed to self-assemble to form micelles. Polymerization is initially performed under conditions that avoid the presence of monomer droplets during the particle formation stage and until the hydrophobic ends of the diblocks have become sufficiently long to prevent them from desorbing from the newly formed particles. Polymerization is then continued at any desired feed rate and composition of monomer. The polymer forming in the reaction remains under RAFT control throughout the polymerization; molecular weight polydispersities are generally low. The number of RAFT-ended chains within a particle is much larger than the aggregation number at which the original micelles would have self-assembled, implying that in the early stages of the polymerization, there is aggregation of the micelles and/or migration of the diblocks. The latexes resulting from this approach are stabilized by anchored blocks of the hydrophilic monomer, e.g., acrylic acid, with no labile surfactant present. Sequential polymerization of two hydrophobic monomers gives completely novel core-shell particles where most chains extend from the core of the particles through the shell layer to the surface.

Dimeric poly(ethylene oxide) surfactants (or nonionic gemini surfactants) with the structure (Cn−2H2n−3CHCH2O(CH2CH2O)mH)2(CH2)6 (or GemnEm), where n is the alkyl length and m is the average number of ethylene oxides per head group, were synthesized. Surfactants were synthesized with alkyl chain lengths n=12, 14, and 20 and m=5, 10, 15, 20, and 30. Water solubilities and cloud temperatures at 1 wt% were determined by measuring turbidity as a function of temperature. Cloud temperatures increase with m and decrease with n, as observed for conventional surfactants. For large m the cloud temperatures were all above 100°C. Surfactants with small m (i.e., n=12, 14, m=5 and n=20, m=10) were insoluble at room temperature, forming two-phase mixtures. Critical micelle concentrations (CMCs) were measured using a pyrene fluorescence method and are all in the range of 10−7 to 10−6 M, with the lowest values from the surfactants with large n and small m. CMCs of mixtures with both anionic and nonionic conventional (monomeric) surfactants were well described by an ideal mixing model.

A ruthenium bis(pyrazolyl)borate benzylidene has been synthesised. A single crystal X-ray diffraction study showed that the complex contained an agostic Ru⋯H–C interaction. The complex displayed catalytic activity for the ring closing metathesis of diethyl diallylmalonate in the presence of CuCl as a co-catalyst in refluxing toluene.

ADVERTISEMENT RETURN TO ISSUECommunication to the...Communication to the EditorNEXTMiniemulsion Polymerization Stabilized by Amphipathic Macro RAFT AgentsBinh T. T. Pham, Duc Nguyen, Christopher J. Ferguson, Brian S. Hawkett, Algirdas K. Serelis, and Christopher H. SuchView Author Information Key Centre for Polymer Colloids, Chemistry School F11, University of Sydney, NSW 2006, Australia, and Dulux Australia, McNaughton Road, Clayton, VIC 3168, Australia Cite this: Macromolecules 2003, 36, 24, 8907–8909Publication Date (Web):October 30, 2003Publication History Received10 August 2003Revised9 October 2003Published online30 October 2003Published inissue 1 December 2003https://pubs.acs.org/doi/10.1021/ma035175ihttps://doi.org/10.1021/ma035175irapid-communicationACS PublicationsCopyright © 2003 American Chemical SocietyRequest reuse permissionsArticle Views1510Altmetric-Citations100LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Emulsions,Monomers,Polymer particles,Polymers,RAFT polymerization Get e-Alerts