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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. Graphical abstract

Nanoconfinement offers opportunities to tune physical properties of molecular entities by altering their assembled structures. This also applies to acene-based molecules with potentially rich π–π interactions. Unlike most of the previous cases with acene-based guests directly incorporated into hosts, we take a further step by oligomerizing a fluorescent anthryl monomer, 9-vinylanthracene, inside nanochannels of a metal–organic framework, which is a pillared three-dimensional kagome net of [Zn2(bdc)2(dabco)] (bdc2– = 1,4-benzenedicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane). The fluorescence emission of the guest can be significantly enhanced after oligomerization, which is likely due to the suppressed nonemissive interaction between the oligomerized molecules in the nanospace and the MOF wall. The case we have demonstrated for fluorescence enhancement via confined oligomerization provides inspiration for the design of luminescent composites and is encouraging for further exploration of molecules in a nanoconfined space.

An ultra-thin, graphene oxide (GO) based, anticancer drug carrier was developed using Reversible Addition Fragmentation chain Transfer (RAFT) mediated emulsion polymerisation. Short chain macro-RAFT copolymer, BuPATTC-(BA4-stat-AA9-stat-StS5), was used to disperse the GO in water. Subsequent free radical emulsion polymerisation produced an aqueous suspension of partially polymer-coated GO (PPC-GO). The polymer coating was unevenly distributed, forming a patchy and extremely rough surface on the GO substrate. The use of macro-RAFT copolymers greatly improved the overall colloidal stability of the GO. Furthermore, particle morphologies were found to be controllable by adjusting the amount of monomer starve fed into the polymerisation. PPC-GO was demonstrated to be an effective carrier for the anti-cancer drug doxorubicin (Dox), storing equivalent to its own original weight in Dox. A releasing mechanism using L-ascorbic acid (L-AA) as an agent was reported. Dox release can be triggered by chemical reduction using L-AA, which weakens the hydrogen bonds between Dox and GO. After release of the Dox, the remaining PPC- reduced GO (PPC-rGO) was found to be stable in aqueous suspension.

We demonstrate a scalable continuous feed method for the synthesis of polymer Janus nanoparticles with different composition and with different aspect ratios between lobes, including with one hard cross-linked polystyrene lobe and one soft film-forming poly(methyl methacrylate-co-butyl acrylate) (P(MMA-co-BA)) lobe, through reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization. Snowman shaped particles of size around 40 nm are synthesized through a continuous monomer feeding method, which enables kilogram-scale synthesis of diverse polymer Janus nanoparticles, with a solids content greater than 30%. The Janus nanoparticles with the soft P(MMA-co-BA) lobes spontaneously self-assemble around solid particles in an aqueous phase, forming a thin (5 -100 nm) polymer film that completely encapsulates the solid particles. The process is achieved at room temperature and under mild conditions. The film-forming Janus nanoparticles show excellent encapsulation ability for a variety of solid particles, such as organic and inorganic pigments, carbon nanotubes and calcite, without requiring polymerization to be conducted in the presence of the solid particles. When the Janus nanoparticles were used to encapsulate calcite particles in low sheen paints, the encapsulation provided superior stain resistance to the formed paint film.

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.

Background The skin is both a target and a potential conduit for the delivery of drugs, but its cornified cell layer resists penetration by most molecules. This study investigated the potential of superparamagnetic iron oxide nanoparticles to facilitate the transdermal delivery of anticancer agents. Results Chemotherapeutic cancer drugs were applied with or without nanoparticles to the skin of hairless mice, and their ability to penetrate the skin was assessed using fluorescence microscopy and tumor growth. Nanoparticles enhanced the penetration of the skin by doxorubicin and 5-fluorouracil as determined by fluorescence microscopy and growth retardation of experimental melanoma in immunocompetent, syngeneic mice. This drug enhancement did not require conjugation or encapsulation of the drugs by the nanoparticles—simple co-administration sufficed. Nanoparticles applied topically to melanomas increased the cytotoxicity and immune cell infiltration induced by co-administered 5-fluorouracil, and also reduced vascularization of the tumors independently of 5-fluorouracil. Conclusion Correctly formulated superparamagnetic iron oxide nanoparticles can facilitate the chemotherapeutic effectiveness of cytotoxic drugs on skin tumors by both increasing their transdermal penetration and ameliorating host–tumor interactions. This enhancement of skin penetration occurs without the need for conjugation or encapsulation of the co-administered drugs, and so will likely be applicable to other drugs, also.

The typical magnetized ferrofluid tip radius is ~0.1 mm, where capillary stress balances magnetostatic stress. Here we confirm experimentally the controlling role of magnetic saturation in more general conditions, even for ferrofluid menisci in highly nonuniform magnetic fields created by supporting them at a ferrous needle tip facing a strong magnet. We use a wide range of ferrofluid tensions and solvent polarities. Substantial changes in saturation magnetization are achieved with solvent evaporation, and record tip radii to 9.5 mm demonstrated at high volume fractions of magnetic particles.

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.

Hydrophobic ionic liquid ferrofluids (ILFFs) are studied for use in electrospray thrusters for microsatellite propulsion under nonatmospheric and in high-temperature environments. We synthesized a hydrophobic ILFF by dispersing sterically stabilized γ-Fe2O3 nanoparticles (NPs) in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A diblock copolymer, C4-RAFT-AA10-DEAm60, was synthesized to facilitate multipoint bidentate anchoring to the NP through the acrylic acid block. The DEAm60 layer was incorporated to generate steric repulsion between particles to protect against the aggregation of magnetized particles arising from dipole–dipole attraction. The effect of shearing and variation in the magnetic field strength on the steric repulsion was examined using the DLVO theory. The effect of varying the magnetic field strength and particle concentration on the viscoelastic properties of the ferrofluid was evaluated using rheometry. The viscosity of the ferrofluid increased with the...

The mechanism of the decomposition of ammonium nitrate fuel oil (ANFO) and of ammonium nitrate (AN) emulsions has been investigated. The formation of NO gas bubbles at the end of an induction period was observed, which led to the evolution of brown NO2 gas on contact with air. Inhibition of the decomposition reaction could be achieved by reducing the NO concentration in the gas phase, with inhibitors not in physical contact with the reaction mixture. NO adsorbing clay minerals (hydrotalcite) were effective inhibitors, indicating multiple mechanisms of inhibition. A central role is assigned to nitrous acid (HNO2): sequestering NO prevents its formation, base inhibitors keep it in the non-reactive form of the nitrite ion (pKa of HNO2 ∼ 3), and urea in acidic conditions decomposes it to harmless N2. Our results have implications in industries where NOx emissions can cause significant environmental problems for both aquatic and marine life as well as for human health.

We explore the effect of an applied homogeneous magnetic field on the electrospraying characteristics of a ferrofluid in the cone-jet mode. A sulfolane-based ferrofluid mixed with the ionic liquid ethyl ammonium nitrate has been synthesized. These mixtures have negligible volatility under ambient conditions and remain stable under a very wide range of electrical conductivities $K$. Magnetized Taylor cones spray with the same current emission characteristics as their non-magnetized counterparts in the shared voltage and flow rate parameter space. However, the magnetized Taylor cones studied remained stable at voltages 23 % lower than the non-magnetized spray; they also access flow rates 30 % and 40 % lower in ferrofluids with $K=0.3$ and $0.01~\text{S}~\text{m}^{-1}$. In the lower voltage ranges available only to magnetized tips, unusually long stable cones are observed. The magnetic stabilization mechanism responsible for these two effects remains unclear. It is noteworthy that these strong effects arise even when the tip curvature of the strictly magnetized liquid is orders of magnitude smaller than that for the strictly electrified liquid.

We report the use of the ‘grafting from’ approach to produce inherently rod-shaped polymer nanoparticles with triggered drug release. Cylindrical polymer brushes (CPBs) can be directly used to yield functional polymer nanorods for pH-sensitive drug release of doxorubicin (DOX). Water-soluble CPBs have been produced via a straightforward one-step grafting of vinyl benzaldehyde (VBA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) comonomers, in which the VBA distributed throughout the CPBs provides a cost-effective and simple functionality for the subsequent conjugation of DOX using imine chemistry. Atomic force microscopy (AFM) underlined the rod-like conformation of the CPBs prior and after drug conjugation. Fluorescence spectroscopy studies revealed faster drug release in acidic environments (pH 5.0) compared to physiological pH conditions (pH 7.4). Fluorescence lifetime imaging microscopy (FLIM) and in vitro cell studies further highlighted the intracellular DOX release from the CPB drug carriers within MCF-7 breast cancer cells.

TH Nguyen Pham,1 Nigel A Lengkeek,2 Ivan Greguric,2 Byung J Kim,1 Paul A Pellegrini,2 Stephanie A Bickley,3 Marcel R Tanudji,3 Stephen K Jones,3 Brian S Hawkett,1 Binh TT Pham1 1Key Centre for Polymers and Colloids, School of Chemistry, University of Sydney, 2Radioisotopes and Radiotracers, NSTLI, Australian Nuclear Science and Technology Organisation, Sydney, 3Sirtex Medical Limited, North Sydney, NSW, Australia Abstract: Physiologically stable multimodality imaging probes for positron emission tomography/single-photon emission computed tomography (PET/SPECT)-magnetic resonance imaging (MRI) were synthesized using the superparamagnetic maghemite iron oxide (γ-Fe2O3) nanoparticles (SPIONs). The SPIONs were sterically stabilized with a finely tuned mixture of diblock copolymers with either methoxypolyethylene glycol (MPEG) or primary amine NH2 end groups. The radioisotope for PET or SPECT imaging was incorporated with the SPIONs at high temperature. 57Co2+ ions with a long half-life of 270.9days were used as a model for the radiotracer to study the kinetics of radiolabeling, characterization, and the stability of the radiolabeled SPIONs. Radioactive 67Ga3+ and Cu2+-labeled SPIONs were also produced successfully using the optimized conditions from the 57Co2+-labeling process. No free radioisotopes were detected in the aqueous phase for the radiolabeled SPIONs 1week after dispersion in phosphate-buffered saline (PBS). All labeled SPIONs were not only well dispersed and stable under physiological conditions but also noncytotoxic in vitro. The ability to design and produce physiologically stable radiolabeled magnetic nanoparticles with a finely controlled number of functionalizable end groups on the SPIONs enables the generation of a desirable and biologically compatible multimodality PET/SPECT-MRI agent on a single T2 contrast MRI probe. Keywords: magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, SPIONs, radiolabeling

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.

This paper presents a novel fabrication technique for hydrogen gas sensor based on polymer nanofiber and pure palladium metal. The polymer nanofiber was produced from 7 wt% poly vinyl alcohol (PVA) solution through electrospinning system. The multilayer PVA nanofibers was utilized as a substrate to create a networks of palladium nanofibers hydrogen sensor. The palladium nanofiber with a thickness of 30 nm was deposited on the surface of the multilayer PVA nanofibers by using E-beam evaporation system and shadow mask. During the hydrogen detection test, the novel hydrogen sensor was presented as a set of hydrogen-actuated switches with high sensitivity. The fabrication process was simple and inexpensive, and the sensor can be mass-produced.

Ammonium nitrate (NH4NO3, AN) is a major commodity chemical. Its principal uses are as a fertilizer and an explosive. Ammonium nitrate is inherently unstable and has been the cause of numerous accidental explosions, sometimes with hundreds of deaths. We have investigated the thermal decomposition and methods of inhibiting the critical reactions of ammonium nitrate. NOx gas was shown to accumulate during an induction period and lead to the generation of nitrous acid (HNO2). Removal of NOx by adsorption or reduction provides alternative approaches to inhibition. In this work we reveal alternative methods to inhibit accidental ammonium nitrate explosions. Layered double hydroxides, such as hydrotalcite, were found to be very effective at inhibiting and delaying detonation by adsorbing NOx. Urea, traditionally used to inhibit explosions, was found to be very ineffective at higher temperatures (above ∼ 80 °C). However, the addition of MnO2 catalysts to urea increased its efficiency at temperatures up to ∼ 130 °C. The urea/MnO2 catalyst system was a highly effective inhibitor for preventing thermal decomposition of ammonium nitrate over a wide temperature range.

Hydroxyapatite nanoparticles (HAP NPs) are important for medicine, bioengineering, catalysis, and water treatment. However, current understanding of the nanoscale phenomena that confer HAP NPs their many useful properties is limited by a lack of information about the distribution of the atoms within the particles. Atom probe tomography (APT) has the spatial resolution and chemical sensitivity for HAP NP characterization, but difficulties in preparing the required needle-shaped samples make the design of these experiments challenging. Herein, two techniques are developed to encapsulate HAP NPs and prepare them into APT tips. By sputter-coating gold or the atomic layer deposition of alumina for encapsulation, partially fluoridated HAP NPs are successfully characterized by voltage- or laser-pulsing APT, respectively. Analyses reveal that significant tradeoffs exist between encapsulant methods/materials for HAP characterization and that selection of a more robust approach will require additional technique development. This work serves as an essential starting point for advancing knowledge about the nanoscale spatiochemistry of HAP NPs.

We present a superhydrophobic coating made from waterborne, all-polymeric ‘raspberry’ particles, composed of a micrometric spherical core decorated with a corona of nanometric spherical particles. As-cast particles produced hydrophobic coatings that were highly adhesive to almost-spherical droplets of water, resembling the properties of some types of rose petals. The coatings could be made slippery to spherical water droplets, like the lotus leaf, by surface activation with air plasma followed by reaction with an alkyl-trichlorosilane. The silanisation of films of latex particles was investigated on two model surfaces (a flat polystyrene film and a monolayer of polystyrene waterborne microparticles) by X-ray photoelectron spectroscopy and water contact angle measurements, and applied to our recently-developed ‘raspberry’ particles to produce a superhydrophobic coating.

We present the preparation of 11 nm polyacrylamide-stabilized polystyrene latex particles for conjugation to a microRNA model by surfactant-free RAFT emulsion polymerization. Our synthetic strategy involved the preparation of amphiphilic polyacrylamide-block-polystyrene copolymers, which were able to self-assemble into polymeric micelles and "grow" into polystyrene latex particles. The surface of these sterically stabilized particles was postmodified with a disulfide-bearing linker for the attachment of the microRNA model, which can be released from the latex particles under reducing conditions. These nanoparticles offer the advantage of ease of preparation via a scaleable process, and the versatility of their synthesis makes them adaptable to a range of applications.

Nanomedicine is an emerging field with great potential in disease theranostics. We generated sterically stabilized superparamagnetic iron oxide nanoparticles (s-SPIONs) with average core diameters of 10 and 25 nm and determined the in vivo biodistribution and clearance profiles. Healthy nude mice underwent an intraperitoneal injection of these s-SPIONs at a dose of 90 mg Fe/kg body weight. Tissue iron biodistribution was monitored by atomic absorption spectroscopy and Prussian blue staining. Histopathological examination was performed to assess tissue toxicity. The 10 nm s-SPIONs resulted in higher tissue-iron levels, whereas the 25 nm s-SPIONs peaked earlier and cleared faster. Increased iron levels were detected in all organs and body fluids tested except for the brain, with notable increases in the liver, spleen, and the omentum. The tissue-iron returned to control or near control levels within 7 days post-injection, except in the omentum, which had the largest and most variable accumulation of s-SPIONs. No obvious tissue changes were noted although an influx of macrophages was observed in several tissues suggesting their involvement in s-SPION sequestration and clearance. These results demonstrate that the s-SPIONs do not degrade or aggregate in vivo and intraperitoneal administration is well tolerated, with a broad and transient biodistribution. In an ovarian tumor model, s-SPIONs were shown to accumulate in the tumors, highlighting their potential use as a chemotherapy delivery agent.

Mossbauer spectroscopy was used for direct experimental measurement of the Neel barrier height for magnetization reversal in ensembles of interacting γ-Fe2O3 nanoparticles. As the barrier height is proportional to the size of the magnetic cluster, these measurements enable an evaluation of the relative sizes of the magnetically coupled clusters that are formed during the manufacture of the magnetic hyperthermia beads. For the hyperthermia beads, which were synthesized and studied in the work, an increase in the size of the magnetically coupled cluster corresponds to a reduction of the specific loss power.

This work describes a versatile method to encapsulate graphene oxide (GO) with polymers using reversible addition-fragmentation chain transfer (RAFT) mediated emulsion polymerization. A living low molecular weight anionic macro-RAFT statistical copolymer of sodium styrene sulfonate, acrylic acid, and butyl acrylate (BA) was synthesized using 2-{[(butylsulfanyl)carbonothioyl] sulfanyl} propanoic acid as the chain transfer agent. GO was dispersed in water by pretreating the surface with poly(allylamine hydrochloride) (PAH), before being stabilized by the addition of the anionic macro-RAFT copolymer. PAH was used to facilitate the adsorption of the macro-RAFT copolymer to the GO surface via electrostatic attraction between opposite charges. The dispersed GO sheets were encapsulated with polymer by the free radical emulsion polymerization of methyl methacrylate and BA under starved fed conditions. The polymer shells encapsulating the GO sheets were formed by the chain extension of the adsorbed living macro-RAFT copolymer. TEM, SEM, FTIR, and AFM were used to confirm the presence of the polymer layer on the surface of the GO. The thickness of the polymer coating can be adjusted by controlling the amount of monomer fed into the system. Partial polymer coatings of the GO could be achieved by varying the amount of PAH. The encapsulated GO was found to be easily dispersed in both aqueous and organic solvents over a range of polarities. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1413–1421

When NH4NO3 emulsions are used in blast holes containing pyrite, they can exothermally react with pyrite, causing the emulsion to intensively heat and detonate prematurely. Such premature detonations can inflict fatal and very costly damages. The mechanism of heating of the emulsions is not well understood though such an understanding is essential for designing safe blasting. In this study the heating of an emulsion in model blast holes was simulated by solving the heat equation. The physical factors contributing to the heating phenomenon were studied using microscopic and calorimetric methods. Microscopic studies revealed the continuous formation of a large number of gas bubbles as the reaction progressed at the emulsion-pyrite interface, which made the reacting emulsion porous. Calculations show that the increase in porosity causes the thermal conductivity of a reacting region of an emulsion column in a blast hole to decrease exponentially. This large reduction in the thermal conductivity retards heat dissipation from the reacting region causing its temperature to rise. The rise in temperature accelerates the exothermic reaction producing more heat. Simulations predict a migration of the hottest spot of the emulsion column, which could dangerously heat the primers and boosters located in the blast hole. © 2014 Elsevier B.V. All rights reserved.

The elastic properties and strength upon compression of commercial Ropaque polystyrene hollow particles were investigated by atomic force microscopy (AFM). These particles are commonly used in paints as opacifying agents, as their internal air void effectively scatters light. A sharp AFM tip was used to apply a point load to the particle surface, and increased to probe both the elastic and plastic deformation of the shell, and then further until the shell broke. For small deformations, the deformation increased linearly with applied force. The Young’s modulus was calculated by accounting for the effect of the rigid substrate, and compare the modulus obtained from the Reissner and Hertz models. The minimum stress needed to destroy the integrity of the shell was extracted and found to be smaller than or close to that of silica hollow particles with different shell thickness tested in the literature. Australian Research Council and DuluxGroup Australia through Linkage grant

Clot retraction refers to the process whereby activated platelets transduce contractile forces onto the fibrin network of a thrombus, which over time increases clot density and decreases clot size. This process is considered important for promoting clot stability and maintaining blood vessel patency. Insights into the mechanisms regulating clot retraction at sites of vascular injury have been hampered by a paucity of in vivo experimental models. By pairing localized vascular injury with thrombin microinjection in the mesenteric circulation of mice, we have demonstrated that the fibrin network of thrombi progressively compacts over a 2-hour period. This was a genuine retraction process, as treating thrombi with blebbistatin to inhibit myosin IIa-mediated platelet contractility prevented shrinkage of the fibrin network. Real-time confocal analysis of fibrinolysis after recombinant tissue-type plasminogen activator (tPA) administration revealed that incomplete proteolysis of fibrin polymers markedly facilitated clot retraction. Similarly, inhibiting endogenous fibrinolysis with tranexamic acid reduced retraction of fibrin polymers in vivo. In vitro clot retraction experiments indicated that subthreshold doses of tPA facilitated clot retraction through a plasmin-dependent mechanism. These effects correlated with changes in the elastic modulus of fibrin clots. These findings define the endogenous fibrinolytic system as an important regulator of clot retraction, and show that promoting clot retraction is a novel and complementary means by which fibrinolytic enzymes can reduce thrombus size.

Electrical impedance spectroscopy (EIS) was conducted to investigate the micelle formation process for ionic emulsifiers, sodium dodecyl sulfate (SDS) and Aerosol MA80. Electrical impedance values were measured with variable emulsifier concentrations at frequencies ranging from 1 Hz to 100 kHz. The data were analyzed with the help of equivalent circuits to resolve the conductance, capacitance and phase angle parameters as a function of frequency and sample concentration. The EIS parameters were found to exhibit sharp changes due to structured transformations in emulsion and established that critical micelle concentration (CMC) could be determined accurately at specific frequency ranges. We compared the capability and accuracy of measuring the CMC using the EIS impedimetry approach with that of DC conductivity measured using a conductometer for the ionic emulsifiers. We found that conductometry is not able to identify the CMC of Aerosol MA80, while the EIS is able to determine the CMC accurately for both types of emulsifiers.

Superparamagnetic Iron Oxide Nanoparticles (SPIONs) has been the focus in medical imaging as MRI contrast agents. SPIONs demonstrate intriguing properties that not only advantageous in diagnostic imaging but also for therapeutic application. In this study, the radiosensitization characteristic of SPIONs in electron beam radiotherapy and brachytherapy were investigated. This study was conducted in-vitro using HeLa cells with SPIONs (15 nm) concentration of 1, 2 and 3 mMol/L. Irradiations were done at doses ranging from 0 to 10 Gy using electron beams of energy 6 and 12 MeV as well as 0.38 MeV 192Ir brachytherapy source. Cell survivals were determined from clonogenic assay. Radiosensitization characterization was performed by analyzing the sensitization enhancement ratio (SER) expolated from the survival curves. The results show SPIONs induce radiosensitization effects in electron beams especially at lower energy with SER value obtained up to 1.5. The radiosensitization is more prominent for brachytherapy with SER value around 2. Concentrations of SPIONs also play important roles in which higher SPIONs concentration are more likely to increase radiosensitization effects. In conclusion, radiosensitization are dependent on radiation energy and concentration of the SPIONs. Further characterization of the radiosensitization induced by SPIONs may enable clinical translation of SPIONs as radiosensitizer in radiotherapy.

Radiosensitization effects caused by high atomic number (Z) metallic nanoparticles have been extensively explored with a wide range of X-ray based radiotherapy beams that seem to provide intriguing results for potential clinical applications. In this study, the radiobiological consequences of gold nanoparticles (AuNPs), superparamagnetic iron oxide nanoparticles (SPIONs), Platinum Nanodendrites (PtNDs) and Bismuth Oxide Nanorods (BiNRs) on Human Colon Carcinoma cells (HCT 116) irradiated with 150 MeV proton beams were investigated. Cell survival and reactive oxygen species (ROS) generation were measured. BiNRs demonstrates the highest sensitization enhancement ratio (SER) of 4.93 followed by PtNDs with SER value of 3.08. Meanwhile, AuNPs and SPIONs depict SER values around 2.64 and 1.95 respectively. The ROS generation corresponded to the level of radiosensitization with the highest ROS obtained for BiNRs and followed by PtNDs, AuNPs and SPIONs. In conclusion, high Z nanoparticles possess the potential to be clinically applied in proton beam therapy. Keywords: Gold nanoparticles, Superparamagnetic iron oxide nanoparticles, Platinum nanoparticles, Bismuth nanoparticles, Radiosensitization, Proton beam

The optical magnetic chaining technique (MCT) developed by Leal-Calderon, Stora, Mondain-Monval, Poulin & Bibette [Phys. Rev. Lett.(1994),72, 2959–2962] allows precise measurements of force profiles between droplets in monodisperse ferrofluid emulsions. However, the method lacks anin situdetermination of droplet size and, therefore, requires a combination of separately acquired measurements of droplet chain periodicityversusan applied magnetic field from optical Bragg scattering and droplet diameter inferred from dynamic light scattering (DLS) to recover surface force–distance profiles between the colloidal particles. Compound refractive lens (CRL) focused small-angle neutron scattering (SANS) MCT should result in more consistent measurements of droplet size (form factor measurements in the absence of field) and droplet chaining period (from structure factor peaks when the magnetic field is applied), and, with access to shorter length scales, extend force measurements to closer approaches than possible by optical measurements. This article reports on CRL-SANS measurements of monodisperse ferrofluid emulsion droplets aligned in straight chains by an applied field perpendicular to the incident beam direction. Analysis of the scattering from the closely spaced droplets required algorithms that carefully treated resolution and its effect on mean scattering vector magnitudes in order to determine droplet size and chain periods to sufficient accuracy. At lower applied fields, scattering patterns indicate structural correlations transverse to the magnetic field direction owing to the formation of intermediate structures in early chain growth.

In this work, we present a novel platform to synthesize polymeric “raspberry” particles and explore their use to fabricate surfaces with low wettability and high water adhesion, resembling the properties of naturally occurring surfaces such as the rose petal. The raspberry particles were obtained by layer-by-layer self-assembly of 850 nm core polystyrene particles bearing surface carboxylate groups and corona nanoparticles of different sizes and polymers (polystyrene, poly(para-fluorostyrene) or poly(2,3,4,5,6- penta-fluorostyrene), also bearing surface carboxylates), interleaved with positively charged poly(ally amine) hydrochloride.The raspberry particles were then bound together by covalent coupling of the carboxylate groups with the amine groups of the polymeric interlayer. The films produced by drop-casting the raspberry particles exhibited static water contact angles between ∼135° and ∼146°, depending on the nature of the corona, hysteresis of ∼135° and high adhesion of water droplets. Since all particles were synthesized from scratch by surfactant free emulsion polymerization in air and every step of the protocol was performed in water, this platform is up-scalable and environmentally friendly.

Diffusion of active cytotoxic agents throughout an entire solid tumour is a particular challenge to successful drug delivery. Here we show the simple and robust generation of non-toxic, 10-15 nm superparamagnetic iron oxide nanoparticles (SPIONs) that have been sterically stabilized by either 100% anionic or 100% cationic or 100% neutral end-functionalized steric stabilizers or by novel combinations of cationic and neutral end-functionalized polymer. When these nanoparticles were co-administered with various anti-cancer drugs, a significant increase in the diffusion and effectiveness of the cytotoxin in a 3-dimensional model of a solid tumour was shown for specific combinations of surface functionality and cytotoxin. The critical determinant of enhanced cytotoxin diffusion and effectiveness was the end functionality of the steric stabilizers and not the core composition (either iron oxide, silica or gold). We provide evidence that SPIONs stabilized with heterogeneous steric stabilizers enhance nuclear uptake of doxorubicin across multiple cell layers.

In this study, we propose an alternative method to produce high solids, micrometer-sized polystyrene (PS) latexes with narrow size distribution, based on the use of large amounts of polymerization initiator and allowing the presence of oxygen in the reaction vessel. We have demonstrated that the deoxygenation of the reaction mixture in surfactant-free emulsion polymerization becomes redundant if enough radical initiator is employed, and that particles with narrow size distribution can be obtained in the presence or absence of oxygen. The significance of this method lies in its simplicity and robustness: the method requires only a single-neck flask sealed with a rubber septum, a magnetic stirrer, and an oil bath. We also show that the use of large amounts of radical initiator allows the preparation of latexes with particularly high solid contents (up to 20 wt %), which is uncommon in systems with no added stabilizing agent.

We report the fabrication of both single-scale and hierarchical superhydrophobic surfaces, created by exploiting the spontaneous wrinkling of a rigid Teflon AF film on two types of shrinkable plastic substrates. Sub-100 nm to micrometric wrinkles were reproducibly generated by this simple process, with remarkable control over the size and hierarchy. Hierarchical Teflon AF wrinkled surfaces showed extremely high water repellence (contact angle 172°) and very low contact angle hysteresis (2°), resulting in droplets rolling off the surface at tilt angles lower than 5°. The wrinkling process intimately binds the Teflon AF layer with its substrate, making these surfaces mechanically robust, as revealed by macroscale and nanoscale wear tests: hardness values were close to that of commercial optical lenses and aluminum films, resistance to scratch was comparable to commercial hydrophobic coatings, and damage by extensive sonication did not significantly affect water repellence. By this fabrication method the size of the wrinkles can be reproducibly tuned from the nanoscale to the microscale, across the whole surface in one step; the fabrication procedure is extremely rapid, requiring only 2 min of thermal annealing to produce the desired topography, and uses inexpensive materials. The very low roll-off angles achieved in the hierarchical surfaces offer a potentially up-scalable alternative as self-cleaning and drag-reducing coatings.

In this work, successful polymer coating of COOH-functionalized multiwalled carbon nanotubes (MWCNTs) via reversible addition fragmentation chain transfer (RAFT) mediated emulsion polymerization is reported. The method used amphiphilic macro-RAFT copolymers as stabilizers for MWCNT dispersions, followed by their subsequent coating with poly(methyl methacrylate-co-butyl acrylate). Poly(allylamine hydrochloride) was initially used to change the charge on the surface of the MWCNTs to facilitate adsorption of negatively charged macro-RAFT copolymer onto their surface via electrostatic interactions. After polymerization, the resultant latex was found to contain uniform polymer-coated MWCNTs where polymer layer thickness could be controlled by the amount of monomer fed into the reaction. The polymer-coated MWCNTs were demonstrated to be dispersible in both polar and nonpolar solvents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

We demonstrate the ability of the reversible addition-fragmentation chain transfer (RAFT) process to produce well-defined block co-oligomers for which each block has a narrow molecular weight distribution and degrees of polymerization ranging from 2 to 33. We exploit RAFT versatility to control the structure of the co-oligomers and produce amphiphilic block co-oligomers of styrene, acrylic acid and ethylene glycol. A detailed study shows that the amphiphilic diblock co-oligomers self-assemble in solution and form micelles or particles, depending on the hydrophobicity of the diblock. These oligomers present an excellent alternative to traditional amphiphilic molecules, by combining the properties of polymers with those of single molecule surfactants.

In this work, successful synthesis of polymer nanorattles containing titanium dioxide pigment particles in the centers of air voids is reported. The method used amphiphilic macro-RAFT copolymers as stabilizers for pigment dispersion and the subsequent encapsulation of the pigment with polymer. The particles were first encapsulated by a water swellable hydrophilic layer, followed by a hard hydrophobic layer. Nanorattles were formed by swelling of hydrophilic polymer layers on the surface of the encapsulated pigment particles in a basic solution at elevated temperature. After swelling, the outer hard polymer shell was crosslinked to improve its strength. Air void sizes of the nanorattles were found to be controlled by swelling time, temperature, and the hydrophilic polymer layer thickness. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Two model polystyrene seed-latexes were studied by γ-irradiation dilatometry, with one latex stabilized by short chain poly(acrylic acid) the other stabilized by short chain poly(methacrylic acid),...

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.

We describe a method and conditions for the preparation of monodisperse latex particle dispersions using low molecular-weight, amphiphilic styrene-b-acrylic acid macro-RAFT diblock copolymers as sole stabilizers. The macro-RAFT copolymers are soluble in styrene monomer droplets when the acrylic acid is in its neutral, protonated form, but adsorb irreversibly at the interface between the monomer droplets and the aqueous phase to form an insoluble monolayer when conditions favor deprotonation. Droplets thus stabilized exhibited no coarsening by Ostwald ripening over at least several days. Polymerization yielded a one-to-one correspondence between the size of the initial droplets and the resultant latex particles, consistent with ideal miniemulsion polymerization, when the least labile macro-RAFT stabilizer was used. GPC analysis of molecular weights showed that in all cases the polymerization remained under RAFT control. The approach described enables true miniemulsion polymerization to proceed in the absen...

Chain transfer to polymer (CTP) in conventional free-radical polymerizations (FRPs) and controlled radical polymerizations (ATRP, RAFT and NMP) of n-butyl acrylate (BA) has been investigated using 13C NMR measurements of branching in the poly(n-butyl acrylate) produced. The mol-% branches are reduced significantly in the controlled radical polymerizations as compared to conventional FRPs. Several possible explanations for this observation are discussed critically and all except one refuted. The observations are explained in terms of differences in the concentration of highly reactive short-chain radicals which can be expected to undergo both intra- and inter-molecular CTP at much higher rates than long-chain radicals. In conventional FRP, the distribution of radical concentrations is broad and there always is present a significant proportion of short-chain radicals, whereas in controlled radical polymerizations, the distribution is narrow with only a small proportion of short-chain radicals which diminishes as the living chains grow. Hence, irrespective of the type of control, controlled radical polymerizations give rise to lower levels of branching, when performed under otherwise similar conditions to conventional FRP. Similar observations are expected for other acrylates and monomers that undergo chain transfer to polymer during radical polymerization.

We propose a model for the kinetics of reversible addition−fragmentation chain transfer (RAFT) polymerization. The essence of this model is that the termination of the radical intermediate formed by the RAFT process occurs only with the shortest active radicals. This model accounts for the absence of 3-armed stars predicted by other cross-termination models since the short radical makes a negligible difference to the overall molecular weight. The model is tested against experiments on styrene at 60 °C with cyanoisopropyl dithiobezoate (CPDB) as the RAFT agent. The predicted rate coefficients are consistent with slow fragmentation of the RAFT intermediate, and the overall concentration of radicals is consistent with ESR experiments. Overall, it demonstrates that the two conflicting models that have been proposed so far can actually coexist.