New Insights into the Formulation and Polymerization of Pickering Emulsions Stabilized by Natural Organic Particles

Pickering emulsions are known to be an efficient and greener alternative to surfactant-stabilized emulsions. Particles, as key component of these systems, are responsible for their higher kinetic stability, and in recent years, the use of natural organic stabilizers has emerged as a solution to promote sustainability. By conferring them stimuli-responsiveness and/or by polymerizing the Pickering emulsion itself, the design of smart and advanced systems can be achieved. Radical polymerization has been by far the most studied polymerization route, and a wide range of materials were successfully synthesized: foams, composites, capsules, or imprinted microspheres. Not only the sustainability of these materials is improved, but also their performances and features are also generally enhanced thanks to the presence of the natural organic stabilizers. This Perspective is putting into light groundbreaking efforts in the field of the polymerization of Pickering emulsions, suggesting the range of accessible material that can be obtained through this powerful pathway

Latex particles by miniemulsion ring-opening metathesis polymerization

Polynorbornene latexes were prepared by ring-opening metathesis polymerization of norbornene (NB) in water carried out in miniemulsion. The ability of both lipophilic or hydrophilic initiators to polymerize NB under miniemulsion conditions has been investigated. With an oil-soluble initiator ((Cy3P)(2)Cl2Ru=CHPh) the miniemulsion polymerization of NB resulted in the formation of large and poorly stabilized particles that eventually coagulated. On the contrary, with a water-soluble initiator based on RuCl3 and an alcohol stable particles could be obtained as a result of the miniemulsion polymerization of NB. For each miniemulsion polymerization the role played by ionic and steric stabilizers such as sodium dodecyl sulfate and poly(styrene-b-ethylene oxide), respectively, on both the course of polymerization in miniemulsion and the particle stabilization has been investigated in detail

Organic-inorganic hybrid materials designed by controlled radical polymerization and mediated using commercial dual functional organophosphorous coupling agents

Hybrid materials that are composed of a polymeric material interfaced with an inorganic, metal oxide material have been a rapidly expanding research area in the last few decades. However, interfacial regions remain an important area of focus, and as such hybrid materials do not always possess a very robust or stable interface. Tailor-made interfacial molecules have been successfully reported but material scientists wishing to develop composite interfacial materials would favorably use commercial solutions. Our study shows how we can leverage a commercially available organophosphonic acid group that is coupled with a 2-bromo isobutyrate initiator for surface initiated atom transfer radical polymerization (SI-ATRP) for use as a strong interfacial molecule. We illustrate this mechanism with both nanoparticles of titania and flat titania substrates used as the grafting support and polymerization anchoring points. We demonstrate that the size of the organophosphonic acid initiator, specifically the carbon spacer between the reactive groups, controls the stability of the molecule. The actual covalent linkage between the phosphonic acid group and the titania surface while also leaving the ATRP initiating group able to start the polymerization, is confirmed via P-31 solid state NMR spectroscopy, liquid H-1 NMR spectroscopy XPS, DLS and SEM

Separation study of organic bases on new polymeric stationary phases under basic conditions

Crosslinked monodisperse polymer microparticles have been synthesized and evaluated as stationary phases for the separation of basic drug molecules in reversed-phase high performance liquid chromatography. The polymer beads were prepared by free-radical copolymerization of divinylbenzene and styrene or vinylbenzyl chloride in acetonitrile with toluene as porogen agent using the precipitation method. Their efficiency as stationary phase was investigated at both acid (5.6) and basic (12) pH, and the results compared with those of a commercial polymeric reversed-phase column. Separation of the organic bases was achieved with the chlorobenzyl particles at pH 12. (C) 2011 Elsevier Ltd. All rights reserved

Elaboration of capsules from Pickering double emulsion polymerization stabilized solely by cellulose nanocrystals

International audiencePickering double oil-in-water-in-oil emulsions O/W/O were stabilized using solely cellulose nanocrystals (CNCs), which were modified by introducing surface brominated functions. The emulsions were formulated using only bio-friendly components, among which isopropyl myristate as oil phase, hydroxyl oligoethylene glycol methacrylate (OEGMA) as macromonomer, tetraethylene glycol diacrylate (TEGDA) as cross-linker, and CNCs as stabilizing particles. Formulation parameters could be tuned easily to modulate the fraction of inner emulsion droplets within the double emulsion drops or change the monomer(s) composition within the aqueous phase. The latter was further polymerized to synthesize matrix capsules. The obtained objects showed good resistance to the vacuum and were efficiently used as promising encapsulation vessels. Both hydrophobic and hydrophilic model dyes were encapsulated, with an encapsulation efficiency of about 90%

Harnessing the power of latex solutions based on titania particles - using si-ATRP towards larger surface modification for applications in gas separation membranes

Membranes are vital and touch every aspect of our daily lives. For instance, they ensure that clean or pure drinking water can be produced, or they can purify our air. However, there is no one-membrane material that can perform all these objectives, and they must be catered for each specific application. As more traditional membrane materials are either polymer based or inorganic/ceramic based, each application will require a different material that can use one or both of these components. Currently, much research is dedicated to combining both polymer and inorganic based materials to form hybrid membranes that could "have the best of both worlds". The most common form of hybrid membranes are mixed matrix membranes, or MMM. However, their synthesis normally involves the direct addition of inorganic particles into an existing polymeric solution, leading to composite materials without strong interaction between organic and inorganic moieties. In this work, we explore the reversal of this process; that is, the formation of the polymeric component directly from the surface of these particles using surface-initiated atom-transfer radical polymerization, or si-ATRP. Such a method intends to provide a high intimacy between polymers and ceramics, and strong interconnection via covalent bonds. Using a latex based solution of these functionalized titania particles, we present two pathways, known as "Coating Onto" and "Grafting From" pathways, in which these latexes can be applied to larger, tubular membrane coatings. These latexes were first analyzed by TGA to determine their functionalization densities and degree of polymerization. SEM was then employed to visually assess the membrane surfaces to determine the final optimal conditions used for preliminary gas separation tests. (C) 2016 Elsevier B.V. All rights reserved

The ROMP: A Powerful Approach to Synthesize Novel pH-Sensitive Nanoparticles for Tumor Therapy

Fast clearance, metabolism, and systemic toxicity are major limits for the clinical use of anti-cancer drugs. Histone deacetylase inhibitors (HDACi) present these defects, despite displaying promising anti-tumor properties on tumor cells in vitro and in in vivo models of cancer. The specific delivery of anti-cancer drugs into the tumor should improve their clinical benefit by limiting systemic toxicity and by increasing the anti-tumor effect. This paper deals with the synthesis of the polymeric nanoparticle platform, which was produced by Ring-Opening Metathesis Polymerization (ROMP), able to release anti-cancer drugs in dispersion, such as histone deacetylase inhibitors, into mesothelioma tumors. The core-shell nanoparticles (NPs) have stealth properties due to their poly(ethylene oxide) shell and can be viewed as universal nano-carriers on which any alkyne-modified anti-cancer molecule can be grafted by click chemistry. A cleavage reaction of the chemical bond between NPs and drugs through the contact of NPs with a medium presenting an acidic pH, which is typically a cancer tumor environment or an acidic intracellular compartment, induces a controlled release of the bioactive molecule in its native form. In our in vivo syngeneic model of mesothelioma, a highly selective accumulation of the particles in the tumor was obtained. The release of the drugs led to an 80% reduction of tumor weight for the best compound without toxicity. Our work demonstrates that the use of theranostic nanovectors leads to an optimized delivery of epigenetic inhibitors in tumors, which improves their anti-tumor properties in vivo. 1. Background Despite important progress being made to treat different types of cancers, acquired resistance and some forms of aggressive or less frequent cancers are still waiting for efficient strategies. The new solutions proposed to solve these problems take into account the recent advances of our knowledge in general biology, and the biology of cancer in particular, but also relative solutions for a better distribution of the compounds in the patient's body, according to the type of cancer that needs to be treated. In the field of biology, the last two decades have seen the dawn of the epigenetic strategy [1,2]. If genetics are currently well understood by the scientific community, a question that remains for understanding why a genome common to all our cells (genotype) is able to produce different types of cells (phenotype). This question was solved by the observation that, for the same genome, only

ROMP in Dispersed Media

In this chapter a complete review of ROMP in dispersed media has been conducted. ROMP-made polymer particles by emulsion, dispersion and suspension processes are first described. Particular attention has been also devoted to the synthesis of functional nanoparticles for advanced materials. The final part reviews access to nanoparticle synthesis via self assembly of ROMP-made block copolymers