Mechanistic insights into the formation of polyion complex aggregates from cationic thermoresponsive diblock copolymers.

HYPOTHESIS: The formation of polyion complexes (PICs) comprising thermoresponsive polymers is intended to result in the formation of aggregates that undergo significant structural changes with temperature. Moreover the observed modifications might be critically affected by polymer structure and PICs composition. EXPERIMENTS: Different block copolymers based on cationic poly(3-acrylamidopropyltrimethylammonium chloride) and thermoresponsive poly(N-isopropylacrylamide) were synthesized by aqueous RAFT/MADIX polymerization at room temperature. Addition of poly(acrylic acid) in a controlled fashion led to the formation of PICs aggregates. The structural changes induced by temperature were characterized by differential scanning calorimetry, Nuclear Magnetic Resonance spectroscopy and scattering methods. FINDINGS: Thermoresponsive PICs undergo significant structural changes when increasing temperature above the cloud point of the thermoresponsive block. The reversibility of these phenomena depends strongly on the structural parameters of the block copolymers and on PICs composition.

Ionic Flash NanoPrecipitation (iFNP) for the facile, one-step synthesis of inorganic-organic hybrid nanoparticles in water.

Ionic Flash NanoPrecipitation (iFNP) was evaluated as a novel method for the synthesis of inorganic-organic hybrid nanomaterials and proved to be remarkably effective, fast and practical. To prove the potential of iFNP, various nanostructured GdPO4-based materials of biomedical imaging relevance were easily prepared in a one-step, tunable and highly controlled manner using only water as solvent.

Doubly thermo-responsive copolymers in ionic liquid.

We report the behaviour of thermoresponsive block copolymers of n-butyl acrylate and N-alkyl acrylamides in [C2mim][NTf2]. Poly(N-isopropylacrylamide) exhibits an upper critical solution temperature in [C2mim][NTf2] whereas poly(n-butyl acrylate) has a lower critical solution temperature. Consequently, these polymers exhibit double thermo-responsiveness correlated with the macromolecular structure. Moreover, a switching from micellar to reverse micellar structures was induced by a change in temperature. This property enables the development of reversible shuttles between ionic liquids and water.

Comparison of methods for the fabrication and the characterization of polymer self-assemblies: what are the important parameters?

The ability to self-assemble was evaluated for a large variety of amphiphilic block copolymers, including poly(ethyleneoxide-b-ε-caprolactone), poly(ethyleneoxide-b-d,l-lactide), poly(ethyleneoxide-b-styrene), poly(ethyleneoxide-b-butadiene) and poly(ethyleneoxide-b-methylmethacrylate). Different methods of formation are discussed, such as cosolvent addition, film hydration or electroformation. The influence of experimental parameters and macromolecular structures on the size and morphology of the final self-assembled structures is investigated and critically compared with the literature. The same process is carried out regarding the characterization of these structures. This analysis demonstrates the great care that should be taken when dealing with such polymeric assemblies. If the morphology of such assemblies can be predicted to some extent by macromolecular parameters like the hydrophilic/hydrophobic balance, those parameters cannot be considered as universal. In addition, external experimental parameters (methods of preparation, use of co-solvent, …) appeared as critical key parameters to obtain a good control over the final structure of such objects, which are very often not at thermodynamic equilibrium but kinetically frozen. A principal component analysis is also proposed, in order to examine the important parameters for forming the self-assemblies. Here again, the hydrophilic/hydrophobic fraction is identified as an important parameter.

Biocompatible, hyperbranched nanocarriers for the transport and release of copper ions.

Core-shell and core-multishell nanocarriers were designed to transport copper ions into cells. Herein, we present their synthesis and physicochemical characterization and demonstrate the high influence of their architectures on the loading and release of copper. Their low toxicity may open a new way to balance the Cu-homeostasis in neurodegenerative diseases.

Sorption properties of functionalized liquid crystalline networks.

Functionalized polydomain chiral elastomers were obtained by cross-linking side-chain liquid crystalline polysiloxanes bearing acid functions. Sorption experiments were performed by the use of an electronic microbalance, in the presence of one enantiomer of a chiral amine molecule, able to interact with the acid groups. The results showed that Fick's diffusion law is not valid anymore as soon as an interaction between the material and the molecule is present. Moreover, it was demonstrated that the grafting of interacting groups on a chiral elastomer enhanced both the capacity and selectivity toward one enantiomer.

Enantioselective absorption of chirally doped liquid crystalline networks studied by the use of an electronic microbalance.

A polydomain cholesteric elastomer was obtained by cross-linking a nematic side-chain polysiloxane in the presence of a chiral dopant. After extraction of the chiral dopant, sorption experiments were performed, by the use of an electronic microbalance, in the presence of each enantiomer of a chiral amine molecule. The sorption kinetics corresponds to a Fickian diffusion behavior. They allowed us to determine the diffusion coefficients and to show that the doped polymer has a more pronounced affinity toward one of the enantiomers.

Chiral molecular imprinting in liquid-crystalline network.

A cholesteric imprinted elastomer was obtained by cross-linking a nematic side-chain polysiloxane around a chiral template. The template was first linked to some functionalised groups of the polymer via hydrogen-bound interactions, then was removed by washing. The sample was macroscopically oriented during the synthesis; so, both a molecular chirality and a supramolecular phase chirality were topologically imprinted inside the network. Batch rebinding experiments, performed in the presence of the template or of the other enantiomer, showed that the imprinted polymer has a pronounced stereo-selectivity towards the template enantiomer. The rebinding capacity appeared to be greater than an unimprinted mesogenic network as well as than an imprinted non mesogenic one.