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The critical chain length (jcrit) in dispersion polymerization is systematically investigated utilizing low molecular weight poly(methyl methacrylate) oligomers synthesized by catalytic chain transfer polymerization. The solubility of these oligomers in methanol/water media of different compositions and at different temperatures has been visually determined. The results show that the solubility of the oligomers increases with increasing methanol fraction and increasing temperature. The constructed solubility map allows for an estimate of jcrit as a function of these important polymerization parameters. Furthermore, it is found that the value of jcrit changes with the concentration of the oligomers in the methanol/water medium, an important consideration for understanding the nucleation stage of a dispersion polymerization. The obtained results have been successfully correlated to earlier data reported on the dispersion polymerization of methyl methacrylate.

Starch nanoparticles (SNP) were modified with synthetic polymers using the “grafting to” approach and nitroxide-mediated polymerization. SG1-capped poly(methyl methacrylate-co-styrene) (P(MMA-co-S)...

Modification of starch nanoparticles (SNP) was conducted with styrene oxide (STO) to change their hydrophilic/hydrophobic character. Unmodified SNP and modified SNP-STO were investigated as Pickering stabilizers in miniemulsion polymerization and emulsion polymerization. The influence of varying the degree of substitution (DS) was explored in terms of interfacial activity with saturated analogues of the monomers used to prepare the miniemulsions. Pickering miniemulsion stability tests conducted with styrene, methyl methacrylate and butyl acrylate showed no apparent coalescence when using SNP-STO (DS 0.10). Pickering miniemulsion polymerization results (using the oil-soluble Vazo-52 initiator) suggest a synergistic stabilization effect between styrene and SNP-STO due to interactions between the aromatic rings present on both styrene and modified SNP-STO. Pickering emulsion polymerizations prepared using persulfate initiator and SNP-STO exhibited additional colloidal stability compared to the miniemulsions, likely provided by the persulfate anions.

Cold water-soluble starch (CWS) is a polysaccharide that is industrially important for several applications including paper coatings, but the high viscosity of starch solutions limits the amount of starch that can be incorporated in many applications. Due to the poor mechanical properties of starch and poor dispersibility of starch in hydrophobic matrices, it is often chemically modified to make it more useful. Herein, we report the first grafting from (co)polymerisation of CWS via nitroxide-mediated polymerisation (NMP) of methyl methacrylate-co-styrene, methyl acrylate, and acrylic acid. Our three step approach consists of: (1) modification of CWS with 4-vinylbenzyl chloride; (2) functionalisation with 2-methyl-2-[N-tertbutyl-N-(diethoxy-phosphoryl-2,2-dimethylpropyl)-aminoxy] propionic acid initiator; and (3) grafting from (co)polymerisation via NMP. The (co)polymerisations were well controlled showing linear reaction kinetics for all monomers and relatively low dispersities (

Starch nanoparticles (SNPs) were used to partially replace petroleum-based polymers in a biobased latex adhesive application. Modification of SNPs (i.e., increasing cross-link density, functionalizing using a sugar-based monomer, and tuning SNP hydrophobicity) was performed prior to their incorporation in a semibatch emulsion polymerization to produce stable SNP-based latexes. SNP loadings and latex solids content were varied to study their effect on latex stability and properties (e.g., viscosity, particle size, adhesive properties, particle morphology). Stable and low viscosity latexes with up to 45 wt % SNP loadings and 55 wt % latex solids were achieved. STEM images confirmed the presence of the core–shell morphology, where SNPs were located in the particle cores and provided biocontent, while the acrylic polymers were present as the shell and governed the application properties. Pushing the limits of SNP loading and latex solids was shown to come at a cost to adhesive and other properties.

Existing oral or injectable antipsychotic drug delivery strategies typically demonstrate low bioavailability to targeted brain regions, incentivizing the development of alternative delivery strategies. Delivery via the nasal cavity circumvents multiple barriers for reaching the brain but requires drug delivery vehicles with very specific properties to be effective. Herein, we report in situ-gelling and degradable bulk nanoparticle network hydrogels consisting of oxidized starch nanoparticles (SNPs) and carboxymethyl chitosan (CMCh) that enable intranasal delivery via spray, high nasal mucosal retention, and functional controlled release of the peptide drug PAOPA, a positive allosteric modulator of dopamine D2 receptor. PAOPA-loaded SNP-CMCh hydrogels can alleviate negative symptoms like behavioural abnormalities associated with schizophrenia (i.e. decreased social interaction time) for up to 72 h in an MK-801-induced pre-clinical rat model of schizophrenia at a low drug dosage (0.5 mg/kg); in comparison, conventional PAOPA administration via the intraperitoneal route requires twice the PAOPA dose to achieve a therapeutic effect that persists for only a few hours. This strategy offers potential for substantially decreasing re-administration frequencies and overall drug doses (and thus side-effects) of a range of potential antipsychotic drugs via a minimally-invasive administration route.

Starch nanoparticles (SNPs) are chosen as renewable alternatives to partially replace petroleum-based monomers and produce bio-based latexes for adhesive applications. To maintain adhesive performance, SNPs are modified (i.e., via increasing cross-link density, vinyl functionalization, and adjusting hydrophilic/hydrophobic balance) to facilitate their incorporation into the latex particles. The modified SNPs are then polymerized in a semi-batch emulsion polymerization at 60 °C, and yield low viscosity latexes with up to 17 wt% SNP loading and 42 wt% solids. TEM/STEM imaging is performed and reveals the presence of a core-shell particle morphology. This is supported by comparing the adhesive properties of SNP-containing latex films from an in situ preparation vs. a blend of acrylic latex with SNPs. The results suggest that the modified SNPs were largely encapsulated into the latex particles rather than in the aqueous phase or at the latex particle/water interface.

In this review we highlight the progress in the synthesis of carbohydrate functionalized hybrid latex particles, focusing on different synthetic approaches which use carbohydrates as a surfactant/stabilizer, initiator, grafting site and/or as a macromonomer. These nanocomposites are receiving increasing attention in academia as well as in industry, due to increasingly stringent societal demands for biobased, biodegradable, and biocompatible materials. Furthermore, we will report on the use of nanostructured carbohydrate materials, such as cellulose nanocrystals, starch nanocrystals, and starch nanoparticles. These novel materials represent an interesting emerging field, and examples of latex nanocomposites have only recently been reported. It is the authors' opinion that using carbohydrate materials for the synthesis and production of latex polymers will become of increasing importance as we move towards a more sustainable future.

The incorporation of charge within in situ covalently gelling poly(oligo ethylene glycol methacrylate) (POEGMA) precursor polymers enables the fabrication of hydrogels that exhibit both pH-responsive swelling and tunable network structures due to multimechanism cross-linking interactions. The gelation times, swelling responses, degradation kinetics, and mechanics of the resulting gels were strongly influenced by both the type of charge(s) incorporated and pH, with both amphoteric gels and anionic gels showing clear evidence of dual network formation. While the amphoteric dual network was anticipated due to charge interactions, the mechanism of the 5-fold enhancement in mechanical properties observed with the anionic gel relative to the neutral gel was revealed by isothermal titration calorimetry and small-angle neutron scattering to relate to the formation of a zippered chain structure based on dipole–dipole interactions. Consequently, rational design of the chemistry and the microscopic network structure...

Starch is an attractive biomaterial given its low cost and high protein repellency, but its use in forming functional hydrogels is limited by its high viscosity and crystallinity. Herein, we demonstrate the use of fully amorphous starch nanoparticles (SNPs) as functional hydrogel building blocks that overcome these challenges. Methacrylation of SNPs enables hydrogel formation via photopolymerization, with the low viscosity of SNPs enabling facile preparation of pre-gel suspensions of up to 35 wt% SNPs relative to10 wt% with linear starch. Small angle neutron scattering indicates a significantly different microstructure in SNP-based hydrogels compared to linear starch-based hydrogels due to the balance between inter- and intra-particle crosslinks, consistent with SNPs forming denser and stiffer hydrogels. Functionalized SNPs are highly cytocompatible at degree of substitution values0.25 and, once gelled, can effectively repel cell adhesion. The physicochemical versatility and biological functionality of SNP-based hydrogels offer potential in various applications.

Starch nanoparticles (SNP) are attracting increased attention as a renewable bio-based alternative to petroleum-based polymers in the materials community. In this work, we describe the grafting from of SNP with synthetic polymers via nitroxide-mediated polymerization (NMP). Varying amounts of poly(methyl methacrylate-co-styrene) (P(MMA-co-S)), poly(methyl acrylate) (PMA) and poly(acrylic acid) (PAA) were grafted from the surface of SNP in a three-step process. The grafting of synthetic polymers from the surface of SNP was confirmed by FTIR, 1H NMR, elemental analysis and thermogravimetric analysis. These new tailor-made starch-based hybrid materials could find use in paper coatings, adhesives, paints, as well as in polymer latex applications.

Injectable, dual-responsive, and degradable poly(oligo ethylene glycol methacrylate) (POEGMA) hydrogels are demonstrated to offer potential for cell delivery. Charged groups were incorporated into hydrazide and aldehyde-functionalized thermoresponsive POEGMA gel precursor polymers via the copolymerization of N,N'-dimethylaminoethyl methacrylate (DMAEMA) or acrylic acid (AA) to create dual-temperature/pH-responsive in situ gelling hydrogels that can be injected via narrow gauge needles. The incorporation of charge significantly broadens the swelling, degradation, and rheological profiles achievable with injectable POEGMA hydrogels without significantly increasing nonspecific protein adsorption or chronic inflammatory responses following in vivo subcutaneous injection. However, significantly different cell responses are observed upon charge incorporation, with charged gels significantly improving 3T3 mouse fibroblast cell adhesion in 2D and successfully delivering viable and proliferating ARPE-19 human retinal epithelial cells via an "all-synthetic" matrix that does not require the incorporation of cell-adhesive peptides.

The enhanced mechanics, unique chemistries, and potential for domain formation in interpenetrating network (IPN) hydrogels have attracted significant interest in the context of biomedical applications. However, conventional IPNs are not directly injectable in a biological context, limiting their potential utility in such applications. Herein, we report a fully injectable and thermoresponsive interpenetrating polymer network formed by simultaneous reactive mixing of hydrazone cross-linked poly(N-isopropylacrylamide) (PNIPAM), and thiosuccinimide cross-linked poly(N-vinylpyrrolidone) (PVP). The resulting IPN gels rapidly (

“Off the shelf design” principles are applied to fabricate injectable poly(oligoethylene glycol methacrylate) (POEGMA) hydrogels with well-defined thermal phase transitions by mixing two sets of aldehyde and hydrazide-functionalized hydrogel precursors, one set with a low lower critical solution temperature (LCST) and one set with a high LCST, at different ratios. Macroscopically, gelation rates, swelling kinetics, degradation kinetics, and mechanical properties of hydrogels produced by mixing different precursor polymers can be predicted and designed based on the simple rule of mixtures. Microscopically, phase separated domains result in localized phase transitions within the hydrogels, inducing significant changes in protein affinity, drug release kinetics, transparency, and cell adhesion compared to hydrogels with only single-LCST precursors that may be leveraged in biomedical applications. Such an “off the shelf” design approach involving the simple mixing of a limited number (four) of precursor polymers with different LCSTs can thus achieve a full range of hydrogel properties while avoiding laborious polymerization steps each time a gel with different properties is required.

Hydrogels based on poly(ethylene glycol) (PEG) and derivatives have attracted significant interest in recent years given their capacity to be well-tolerated in vivo in the context of drug delivery and tissue engineering applications. Injectable, in situ-gelling analogues of such hydrogels offer the additional advantages of being easy and non-invasive to administer via the injection of low-viscosity precursor polymer solutions, expanding their scope of potential applications. In this highlight, we first review the design criteria associated with the rational design of in situ-gelling hydrogels for in vivo applications. We then discuss recent progress in the design of injectable PEG hydrogels, specifically highlighting our ongoing work on PEG-analogue hydrogels based on poly(oligoethylene glycol methacrylate) for targeted biomedical applications.

Injectable, in situ-gelling nanostructured hydrogels have been prepared from hydrazide and aldehyde-functionalized polymer precursors based on a copolymer of oligo(ethylene glycol) methacrylate (OEGMA) and an oligo(lactic acid) macromonomer (OLA) with varying lactic acid chain lengths. The resulting hydrogels contain a mix of chemical (hydrazone bond formation between hydrazide and aldehyde groups) and physical (hydrophobic interactions between OLA chains) cross-links which form competitively as a function of the OLA chain length and density. An increase in the OLA chain length and density results in the formation of more physical cross-links and fewer chemical cross-links. Tuning the relative prevalence of physical and chemical cross-link formation facilitated largely independent tuning of gel mechanics relative to gel swelling and degradation. Small-angle neutron scattering of these OLA-containing hydrogels reveals a microstructure consisting of associative hydrophobic domains, based on an increased scattering intensity and decreased blob size relative to that observed for POEGMA hydrogels prepared without the OLA co-monomer. The presence of hydrophobic OLA domains increases the uptake and slows the release of bovine serum albumin, a protein well-known to associate with hydrophobic domains. Coupled with the observed cytocompatibility of the reactive precursor polymers used to prepare the hydrogels, we anticipate significant potential applications of these hydrogels for the prolonged release of hydrophobic cargoes.

While injectable, in situ gelling hydrogels have attracted increasing attention in the biomedical literature due to their minimally invasive administration potential, little is known about the internal morphology of these hydrogels and thus how to engineer precursor polymer compositions to achieve desired hydrogel properties. In this paper, the internal morphology of injectable in situ gelling hydrogels based on hydrazide and aldehyde-functionalized poly(oligoethylene glycol methacrylate) precursors with varying lower critical solution temperatures (LCSTs) is investigated using a combination of spectrophotometry, small-angle neutron scattering, and light scattering. If two precursor polymers with similar LCSTs are used to prepare the hydrogel, relatively homogeneous hydrogels are produced (analogous to conventional step-growth polymerized hydrogels); this result is observed provided that gelation is sufficiently slow for diffusional mixing to compensate for any incomplete mechanical mixing in the double-b...

The substitution of petroleum-based synthetic polymers in latex formulations with sustainable and/or bio-based sources has increasingly been a focus of both academic and industrial research. Emulsion polymerization already provides a more sustainable way to produce polymers for coatings and adhesives, because it is a water-based process. It can be made even more attractive as a green alternative with the addition of starch, a renewable material that has proven to be extremely useful as a filler, stabilizer, property modifier and macromer. This work provides a critical review of attempts to modify and incorporate various types of starch in emulsion polymerizations. This review focusses on the method of initiation, grafting mechanisms, starch feeding strategies and the characterization methods. It provides a needed guide for those looking to modify starch in an emulsion polymerization to achieve a target grafting performance or to incorporate starch in latex formulations for the replacement of synthetic polymers.

Nitroxide-mediated polymerization (NMP) is employed to graft synthetic polymers from polysaccharides. This work demonstrates the first successful polymer grafting from starch nanoparticles (SNPs) via NMP. To graft synthetic polymers from the SNPs' surface, the SNPs are first functionalized with 4-vinylbenzyl chloride prior to reaction with BlocBuilder MA yielding a macroinitiator. Methyl methacrylate with styrene, acrylic acid, or methyl acrylate are then grafted from the SNPs. The polymerizations exhibited linear reaction kinetics, indicating that they are well controlled. Thermal gravimetric analysis and spectroscopic techniques confirmed the synthesis of the precursors materials and the success of the grafting from polymerizations. The incorporation of hydrophobic synthetic polymers on hydrophilic SNPs yields new hybrid materials that could find use in several industrial applications including paper coatings, adhesives, and paints.

Microgels based on thermally responsive polymers have been widely investigated in the context of controlled release applications, with increasing recent interest on developing a clearer understanding of what physical, chemical, and biological parameters must be considered to rationally design a microgel to deliver a specific drug at a specific rate in a specific physiological context. In this contribution, we outline these key design parameters associated with engineering responsive microgels for drug delivery and discuss several recent examples of how these principles have been applied to the synthesis of microgels or microgel-based composites. Overall, we suggest that in vivo assessment of these materials is essential to bridge the existing gap between the fascinating properties observed in the lab and the practical use of microgels in the clinic. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3027–3043

A high-sensitivity flow-based immunoassay is reported based on a gold-coated quartz crystal microbalance (QCM) chip functionalized directly in the QCM without requiring covalent conjugation steps. Specifically, the irreversible adsorption of a biotinylated graphene oxide-avidin complex followed by loading of a biotinylated capture antibody is applied to avoid more complex conventional surface modification chemistries and enable chip functionalization and sensing all within the QCM instrument. The resulting immunosensors exhibit significantly lower nonspecific protein adsorption and stronger signal for antigen sensing relative to simple avidin-coated sensors. Reproducible quantification of rabbit IgG concentrations ranging from 0.1 ng/mL to 10 μg/mL (6 orders of magnitude) can be achieved depending on the approach used to quantify the binding with simple mass changes used to detect higher concentrations and a horseradish peroxidase-linked detection antibody that converts its substrate to a measurable precipitate used to detect very low analyte concentrations. Sensor fabrication and assay performance take ∼5 h in total, which is on par with or faster than other techniques. Quantitative sensing is possible in the presence of complex protein mixtures, such as human plasma. Given the broad availability of biotinylated capture antibodies, this method offers both an easy and flexible platform for the quantitative sensing of a variety of biomolecule targets.

Hyperbranched polymers are synthesized via a cobalt(II) mediated emulsion copolymerization of methyl methacrylate and diethylene glycol dimethacrylate. The concentration of divinyl monomer and chain transfer activity have to be balanced in order to prevent gelation of the polymer particles. The physiochemical properties of the cobalt(II) complex, specifically the intrinsic chain transfer activity and the partitioning behavior, play a crucial role in governing the polymer architecture (i.e., branched versus cross-linked). Furthermore, an empirical correlation, based on the chain transfer frequency and the divinyl monomer mol fraction, is presented and validated with the results obtained in emulsion polymerization as well as with available literature data.

A simple one-step procedure, based on the sonochemical degradation of water-soluble polymers in aqueous solution in the presence of a hydrophobic monomer leads to functional hairy polymer particles in a residual-free serum. The versatility of this procedure is illustrated with a range of hydrophobic monomers and water-soluble polymers.

We present the first population balance calculations which encompass the complete molecular weight distribution (MWD) to discuss the implications of both radical and catalytic chain transfer agent (CCTA) compartmentalization in a catalytic chain transfer (CCT) mediated emulsion polymerization system. Compartmentalization effects are attributed to reduced frequencies of entry and exit of the CCTA (bis[(difluoroboryl)dimethylglyoximato]cobalt(II) or COBF). Two limiting scenarios were identified. In instances of fast CCTA entry and exit, monomodal MWDs are obtained governed by a global CCTA concentration. In instances of slow entry and exit, bimodal MWDs are obtained; one peak can be attributed to the generation of a bimolecular termination product produced in polymer particles devoid of CCTA, while a transfer-derived peak can be attributed to polymer particles containing one or more CCTA molecules. We present theoretical evidence that experimentally observed multimodal MWDs ( Macromolecules 2009, 42, 7332-7341) originate from a reduced mobility of the CCTA and that when viscosity is high in the polymer particles, compartmentalization of the CCTA becomes important.

The effect the catalytic chain transfer agent, bis[(difluoroboryl) dimethylglyoximato] cobalt(II) (COBF), on the course of the ab initio emulsion polymerization of methyl methacrylate, and the product properties in terms of the molecular weight distribution were investigated. The emulsion polymerization kinetics have been studied with varying surfactant, initiator, and COBF concentrations. The experimentally determined average number of radicals per particle strongly depends on the concentration of COBF and proves to be in good agreement with the results of model calculations. The apparent chain transfer constant, determined up to high conversion, is in excellent agreement with the predicted value based on a mathematical model based on COBF partitioning and the Mayo equation. The results of this work enhance the fundamental understanding of the influence a catalytic chain transfer agent has on the course of the emulsion polymerization and the control of the molecular weight distribution.

The existence of mass transport limitations in catalytic chain transfer mediated emulsion polymerization of methyl methacrylate (MMA) using bis[(difluoroboryl)dimethylglyoximato]cobalt(II) (COBF) was investigated. The rate of mass transport of COBF from the aqueous phase toward the polymer particles proved to depend strongly on the viscosity of the polymer particles and consequently on the instantaneous conversion. At high instantaneous conversion the exchange of COBF between the particles and the aqueous phase is severely hindered. As a result, the control of the molecular weight distribution is hampered. At low instantaneous conversion COBF is readily transferred between the aqueous phase and polymer particles, resulting in immediate molecular weight control. The chain transfer activity of COBF inside the polymer particles during the polymerization was successfully quantified using the chain length distribution method. The results of this work show that the presence of a catalytic chain transfer agent can severely affect the course of the emulsion polymerization. Furthermore, it was demonstrated that molecular weight control during the final stages of an emulsion polymerization is affected by the increasing viscosity of the polymer particles. © 2009 American Chemical Society.

The effect of catalyst partitioning over the organic and water phases in the catalytic chain transfer mediated miniemulsion polymerization was investigated and a mathematical model developed to describe the instantaneous degree of polymerization of the formed polymer. Experimental and predicted instantaneous degrees of polymerization prove to be in excellent agreement. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5839–5849, 2008

The passivation of nonspecific protein adsorption to paper is a major barrier to the use of paper as a platform for microfluidic bioassays. Herein we describe a simple, scalable protocol based on adsorption and cross-linking of poly(oligoethylene glycol methacrylate) (POEGMA) derivatives that reduces nonspecific adsorption of a range of proteins to filter paper by at least 1 order of magnitude without significantly changing the fiber morphology or paper macroporosity. A lateral-flow test strip coated with POEGMA facilitates effective protein transport while also confining the colorimetric reporting signal for easier detection, giving improved performance relative to bovine serum albumin (BSA)-blocked paper. Enzyme-linked immunosorbent assays based on POEGMA-coated paper also achieve lower blank values, higher sensitivities, and lower detection limits relative to ones based on paper blocked with BSA or skim milk. We anticipate that POEGMA-coated paper can function as a platform for the design of portable, disposable, and low-cost paper-based biosensors.

The potential of poly(oligoethylene glycol methacrylate) (POEGMA) hydrogels with varying thermosensitivities as soft materials for biomedical applications is demonstrated. Hydrogels are prepared from hydrazide and aldehyde functionalized POEGMA precursors, yielding POEGMA hydrogels with a volume phase transition temperature (VPTT) below (PO0), close to (PO10) and well above (PO100) physiological temperature. Hydrogels with VPTTs close to and above physiological temperature exhibit biological properties similar to those typically observed for poly(ethylene glycol) hydrogels (i.e. low protein adsorption, low cell adhesion and minimal inflammatory responses in vivo) while hydrogels with VPTTs lower than physiological temperature exhibit biological properties more analogous to poly(N-isopropylacrylamide) above its phase transition temperature (temperature-switchable cell adhesion, higher protein adsorption and somewhat more acute inflammation in vivo). As such, the use of POEGMA precursors with varying chain lengths of ethylene oxide grafts offers a versatile platform for the design of hydrogels with tunable physiological properties via simple copolymerization.

Injectable PEG-analogue hydrogels based on poly(oligoethylene glycol methacrylate) have been developed based on complementary hydrazide and aldehyde reactive linear polymer precursors. These hydrogels display the desired biological properties of PEG, form covalent networks in situ following injection, and are easily modulated for improved control over their functionality and physiochemical properties.

Hydrogels that can form spontaneously via covalent bond formation upon injection in vivo have recently attracted significant attention for their potential to address a variety of biomedical challenges. This review discusses the design rules for the effective engineering of such materials, and the major chemistries used to form injectable, in situ gelling hydrogels in the context of these design guidelines are outlined (with examples). Directions for future research in the area are addressed, noting the outstanding challenges associated with the use of this class of hydrogels in vivo.

International audience; The potential of an extremely hydrophobic cobalt(II) catalyst for the synthesis of polymer nanolatexes in microemulsion polymerization is investigated. Colloidally stable nanolatexes have been successfully synthesized in microemulsion polymerization of styrene, butyl methacrylate, and 2-ethylhexyl methacrylate and in the presence of bis[(difluoronoryl)-diphenylglyoximato]cobalt(II). The average particle diameter can be reduced from 50nm to approximately 10nm in the presence of minor quantities of the cobalt(II) complex. The small particle size, combined with the relatively narrow particle size distribution, results in nanolatexes that are virtually transparent in appearance. Furthermore, the nucleation efficiency can be enhanced by up to two orders of magnitude, corresponding to approximately 1 particle nucleated for every 10(1) micelles. This represents a significant improvement as in microemulsion polymerization generally 1 particle is nucleated for every 10(3) micelles.

We present an alternative method for the preparation of high solids content, water-borne latex products from a combination of catastrophic phase inversion (CPI) and miniemulsification. Miniemulsions are commonly prepared by the direct emulsification of a monomer in water and subsequent miniemulsification using a high-shear technique. Herein high solid content dispersions of up to 80 w/w% solids content monomer-in-water emulsions are prepared by catastrophic phase inversion followed by miniemulsification with a rotor-stator mixer. The subsequent miniemulsification of these monomer-in-water emulsions proves to be almost four times more energy efficient than is possible with direct miniemulsification using the same mixers and recipes. The highly concentrated miniemulsions thus obtained can be successfully diluted to different solid contents for polymerisation, without compromising the droplet size distribution, and used to produce colloidally stable latexes.

Catalytic chain transfer using low-spin cobalt(II) complexes is applied in the microemulsion polymerization of methyl and n-butyl methacrylate. In the presence of a catalytic chain transfer agent the rate of polymerization decreases with an increasing cobalt(II) catalyst loading. The course of the polymerization can be captured by the Morgan-Kaler model extended with radical desorption and aqueous phase termination. Proper molecular weight control (i.e. a molecular weight distribution with a dispersity of ∼2) is achieved, however, proves to be strongly dependent on the balance of cobalt(II) molecules and propagating radicals. The presence of a cobalt(II) catalyst enhances the likelihood of homogeneous nucleation, which decreases the colloidal stability in the methyl methacrylate microemulsion polymerizations. The n-butyl methacrylate microemulsion polymerizations on the other hand, display good colloidal stability and a remarkable increase in the nucleation efficiency.

A novel approach is presented for the synthesis of block-copolymers that resemble the architecture of a core cross-linked micelle. The polymers are synthesized from a combination of catalytic chain transfer polymerization (CCTP), thiol-Michael addition chemistry and reductive amination. A hydrophobic hyperbranched core is synthesized via CCTP of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA), which affords control over the polymer architecture and the degree of chain end-functionality. The vinyl unsaturations of the hyperbranched polymers are converted in nucleophilic pendant amines by thiol-Michael addition using cysteamine hydrochloride. A polysaccharide shell is grafted onto the hyperbranched core via reductive amination with dextran (DEX). The synthesized poly(MMA-co-EGDMA)-b-DEX polymers possess an amphiphilic character, are colloidally stable and resemble the topology of a core cross-linked micelle. The presented methodology provides a robust, modular, and tuneable approach towards the synthesis of amphiphilic core cross-linked micelle analogues.

A novel method for the preparation of concentrated, colloidally stable, translucent polymer nanolatexes is presented. Herein nanolatexes are obtained from emulsion polymerization, utilizing the potential of catalytic chain transfer to enhance the particle nucleation efficiency. Low amounts of emulsifier are required (

Control of the molecular weight distribution in continuous emulsion polymerization in a pulsed sieve plate column (PSPC) is experimentally studied. A global model, based on the Mayo equation, incoporating catalyst partitioning and deactivation was used to quantitatively illustrate the effect of the COBF addition on the instantaneous degree of polymerization in a batch reactor and the PSPC. Operating conditions have a strong influence on the cumulative molecular weight distribution of the latex product produced in the PSPC.

Evidence of compartmentalization of the catalytic chain transfer agent in seeded emulsion polymerization of methyl methacrylate (MMA) is shown experimentally. The addition of bis[(difluoroboryl)dimethylglyoximato]cobalt(II) (COBF) to seed particles swollen below their maximum saturation concentration exhibited multimodal molecular weight distributions (MWD) which are attributed to a statistical distribution of COBF molecules over the polymer particles. The experimental observations suggest that there are two limits for catalytic chain transfer in emulsion polymerization: (i) at the earlier stages of the polymerization where a global COBF concentration governs the MWD and (ii) at the latter stages of the polymerization where a statistical distribution of COBF molecules governs the MWD. To the best of our knowledge, these results are the first to suggest evidence of compartmentalization in catalytic chain transfer mediated emulsion polymerization.

Due to its relevance in the synthesis of well-defined oligopeptides, the l-leucine-N-carboxyanhydride (leucine-NCA) synthesis was selected for fine chemical scale-up with a scope on application on larger scales. The heterogeneous gas-solid-liquid nature of the leucine-NCA synthesis implied a mass transfer limited reaction rate towards phosgenation and was investigated on bench scale. Upon scale increase, the liquid-gas mass transport of HCl is drastically reduced, retarding the reaction and consequently rendering the process unsuitable for scale-up. Addition of an HCl scavenger such as (+)-limonene prevented side reactions thus allowing a cost reduction, a considerably faster reaction, and minimization of the amount of phosgene source used. The modified leucine-NCA synthesis has successfully been made scalable, maintaining high product purity on a 1.0 dm3 scale.

The hydroformylation of disubstituted alkenes and related macromonomers in supercritical CO2 is demonstrated. Higher turnover frequencies were observed for the 1,2-disubstituted alkenes than for the 1,1-disubstituted alkenes. The turnover frequency for poly(styrene) macromonomer hydroformylation compares well with that observed for cyclohexene. The turnover frequency observed for poly(methyl methacrylate) macromonomer hydroformylation is considerably lower than that observed for methyl methacrylate. Unprecedented turnover frequencies are observed in comparison with previous studies where CO2 has been applied as a solvent. This is achieved using rhodium modified with a readily available bulky phosphite ligand without the need of ligand modification to improve solubility in supercritical CO2.

An overview is given of cobalt-catalyzed chain transfer in free-radical polymerization and the chemistry and applications of its derived macromonomers. Catalytic chain transfer polymerization is a very efficient and versatile technique for the synthesis of functional macromonomers. Firstly the mechanism and kinetic aspects of the process are briefly discussed in solution/bulk and in emulsion polymerization, followed by a description of its application to produce functional macromonomers. The second part of this review briefly describes the behavior of the macromonomers as chain transfer agents and/or comonomers in second-stage radical polymerizations yielding polymers of more complex architectures. The review ends with a brief overview of post-polymerization modifications of the vinyl endfunctionality of the macromonomers yielding functional polymers with applications ranging from initiators in anionic polymerization to end-functional lectin-binding glycopolymers.