Daniel Crespy

Patchy Nanocapsules of Poly(vinylferrocene)-Based Block Copolymers for Redox-Responsive Release

Nanocapsules composed of a poly(vinylferrocene)-block-poly(methyl methacrylate) shell and a hydrophobic liquid core are prepared in water. The nanocapsule shells display a patchy structure with poly(vinylferrocene) patches with sizes of 25 ± 3 nm surrounded by poly(methyl methacrylate). The functional nanopatches can be selectively oxidized, thereby influencing the colloidal morphology and introducing polar domains in the nanocapsule shell. The hydrophobic to hydrophilic transition in the redox-responsive nanopatches can be advantageously used to release a hydrophobic payload encapsulated in the core by an oxidation reaction.

Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers

Summary The miniemulsion technique is a particular case in the family of heterophase polymerizations, which allows the formation of functionalized polymers by polymerization or modification of polymers in stable nanodroplets. We present here an overview of the different polymer syntheses within the miniemulsion droplets as reported in the literature, and of the current trends in the field.

Redox Responsive Release of Hydrophobic Self-Healing Agents from Polyaniline Capsules

Redox-responsive nanocapsules consisting of conductive polyaniline and polypyrrole shells were successfully synthesized by using the interface of miniemulsion droplets as a template for oxidative polymerizations. The redox properties of the capsules were investigated by optical spectroscopies, electron microscopy, and cyclic voltammetry. Self-healing (SH) chemicals such as diglycidyl ether or dicarboxylic acid terminated polydimethylsiloxane (PDMS-DE or PDMS-DC) were encapsulated into the nanocapsules during the miniemulsion process and their redox-responsive release was monitored by (1)H NMR spectroscopy. The polyaniline capsules exhibited delayed release under oxidation and rapid release under reduction, which make them promising candidates for anticorrosion applications.

Redox‐Responsive Self‐Healing for Corrosion Protection

Raspberry-shaped redox-responsive capsules for storing corrosion inhibitors are introduced, targeted to solve the drawbacks of conducting-polymer-based coating systems for corrosion protection. These capsules synthesized via the miniemulsion technique have a remarkable release property upon reduction (onset of corrosion) and cease release upon reoxidation (passivation of the defect). The self-healing capability is demonstrated by application of these capsules as part of a composite coating on zinc.

Colloid-Electrospinning: Fabrication of Multicompartment Nanofibers by the Electrospinning of Organic or/and Inorganic Dispersions and Emulsions

Solution-, melt-, and co-axial electrospinning are well-known methods for producing nano- and microfibers. The electrospinning of colloids (or colloid-electrospinning) is a new field that offers the possibility to elaborate multicompartment nanomaterials. However, the presence of colloids in the electrospinning feed further complicates theoretical predictions in a system that is dependent on chemical, physical, and process parameters. Herein, we give a summary of recent important results and discuss the perspectives of electrospinning of colloids for the synthesis and characterization of multicompartment fibers.

Encapsulation of Self-Healing Agents in Polymer Nanocapsules

Considerable attention has been devoted to self-healing (SH) materials in recent years. [ 1 ] Among them, extrinsic SH materials play an important role, for which the healing process is achieved by embedding containers fi lled with a healant in a matrix. When damage occurs, the healant is released from the containers into the cracks and heals the materials by polymerization, [ 1a , 2 ] or solventor plasticizer-assisted welding. [ 3 ] Compared with monolithic particles, polymer capsules can encapsulate a larger quantity of guest substances within their cores and release the substances on demand at a later stage. [ 4 ] This characteristic allows polymer capsules to fi nd application as containers for healants, examples including capsules with poly(urea-formaldehyde) (PUF), [ 5 ]

Preparation of Microporous Melamine-based Polymer Networks in an Anhydrous High-Temperature Miniemulsion

We report the first example of a successful preparation of a microporous organic polymer within the droplet phase of an inverse non-aqueous miniemulsion. Stable nanoparticles with enhanced specific surface area could be obtained despite the harsh conditions regarding reaction temperature (180 °C) and time (72 h) needed for building melamine-based Schiff base networks. Our new flexible method can in principle be applied to other water-sensitive protocols suitable for the bulk synthesis of MOPs that are based on Friedel-Crafts, Sonogashira-Hagihara or Yamamoto chemistry.

Design and characterization of functionalized silica nanocontainers for self-healing materials

Silica nanocapsules functionalized with thiol or amine groups with sizes between 100 and 400 nm could be successfully synthesized using the interface of direct miniemulsion droplets for the hydrolysis and condensation of silicon alkoxides. We show that healing agents such as monomers and catalysts can be successfully encapsulated in the silica shell. The catalyst was encapsulated as a solution to allow a better mobility when released for a self-healing reaction. The functional groups were quantified by 29Si MAS-NMR, XPS, and chemical titration. Therefore a precise picture for the gradient of concentration of functional groups inside the shell could be given. The encapsulated reagents were found to be still active and the self-healing reaction could be successfully monitored by solid-state NMR spectroscopy and thermogravimetry.

Characterization via two-color STED microscopy of nanostructured materials synthesized by colloid electrospinning.

A model system for multicompartment nanofibers was fabricated by colloid electrospinning. The obtained nanostructured material consisted of fluorescent polymer nanoparticles that were synthesized in a miniemulsion and then embedded in fluorescently labeled polymer nanofibers. Because of the absence of contrast between both polymers, the immobilized nanoparticles cannot be reliably identified in the nanofibers via electron microscopy or other techniques. Here, we describe investigations on the hybrid material with two-color STED microscopy to localize the nanoparticles and to quantify their distribution along nanofibers with particle and fiber radii down to 50 nm.

Phase behavior of binary mixtures of block copolymers and a non-solvent in miniemulsion droplets as single and double nanoconfinement

Nanoparticles consisting of different molecular weight poly(styrene-block-methyl methacrylate) (P(S-b-MMA)) copolymers and nanocapsules consisting of the same copolymers, but additionally with hexadecane as liquid core material were prepared by the miniemulsion process. The dependence of the morphology of block copolymer assemblies on the nanoconfinement was investigated. We introduced two nanoconfinement parameters, that are the nanoparticle diameter D and the shell thickness d; D was controlled by varying the concentration of surfactant in the miniemulsion, while d was controlled by the ratio hexadecane/copolymer. As the diameter D of the high molecular weight (Mw ∼ 203,700 g mol−1) P(S-b-MMA) nanoparticles increased, first Janus-particles (at D 1800 nm) were obtained. Nanocapsules with 0 < d < D also showed an onion-like structure. In both cases the outmost layer was PMMA as identified by XPS and the lamellar thickness was in agreement with theoretical considerations. Nanoparticles and nanocapsules prepared with a low-molecular weight (Mw ∼ 19,500 g mol−1) P(S-b-MMA) displayed patchy structures. This is the first time that the morphology of block copolymers was studied under double nanoconfinement in colloids.