Pepa Cotanda

Aldol reactions catalyzed by L-proline functionalized polymeric nanoreactors in water

The use of functional core-shell micelles as asymmetric catalytic nanoreactors for organic reactions in water is presented. An unprecedented increase in rate of reaction was achieved, which is proposed to be associated with the ability of the nanostructures to effectively concentrate the reagents in the catalytically active micelle core.

Hollow block copolymer nanoparticles through a spontaneous one-step structural reorganization.

The spontaneous one-step synthesis of hollow nanocages and nanotubes from spherical and cylindrical micelles based on poly(acrylic acid)-b-polylactide (P(AA)-b-P(LA)) block copolymers (BCPs) has been achieved. This structural reorganization, which occurs simply upon drying of the samples, was elucidated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). We show that it was necessary to use stain-free imaging to examine these nanoscale assemblies, as the hollow nature of the particles was obscured by application of a heavy metal stain. Additionally, the internal topology of the P(AA)-b-P(LA) particles could be tuned by manipulating the drying conditions to give solid or compartmentalized structures. Upon resuspension, these reorganized nanoparticles retain their hollow structure and display significantly enhanced loading of a hydrophobic dye compared to the original solid cylinders.

The evolution of cyclopropenium ions into functional polyelectrolytes

Versatile polyelectrolytes with tunable physical properties have the potential to be transformative in applications such as energy storage, fuel cells and various electronic devices. Among the types of materials available for these applications, nanostructured cationic block copolyelectrolytes offer mechanical integrity and well-defined conducting paths for ionic transport. To date, most cationic polyelectrolytes bear charge formally localized on heteroatoms and lack broad modularity to tune their physical properties. To overcome these challenges, we describe herein the development of a new class of functional polyelectrolytes based on the aromatic cyclopropenium ion. We demonstrate the facile synthesis of a series of polymers and nanoparticles based on monomeric cyclopropenium building blocks incorporating various functional groups that affect physical properties. The materials exhibit high ionic conductivity and thermal stability due to the nature of the cationic moieties, thus rendering this class of new materials as an attractive alternative to develop ion-conducting membranes.

Molecular recognition driven catalysis using polymeric nanoreactors

The concept of using polymeric micelles to catalyze organic reactions in water is presented and compared to surfactant based micelles in the context of molecular recognition. We report for the first time enzyme-like specific catalysis by tethering the catalyst in the well-defined hydrophobic core of a polymeric micelle.

Tuning the aggregation behavior of pH-responsive micelles by copolymerization

Amphiphilic diblock copolymers, poly(2-(diethylamino)ethyl methacrylate-co-2-(dimethylamino)ethyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate), P(DEAEMA-co-DMAEMA)-b-PDMAEMA with various amounts of DEAEMA have been synthesized by RAFT polymerization. Their micellization in water has been investigated by scattering measurements over a wide pH range. It appeared that the polymers self-assembled into pH sensitive star like micelles. For a given composition, when the pH is varied the extent of aggregation can be tuned reversibly by orders of magnitude. By varying the copolymer composition in the hydrophobic block, the onset and extent of aggregation were shifted with respect to pH. This class of diblock copolymer offers the possibility to select the range of stimuli-responsiveness that is useful for a given application, which can rarely be achieved with conventional diblock copolymers consisting of homopolymeric blocks.

Catalytic Y-tailed amphiphilic homopolymers – aqueous nanoreactors for high activity, low loading SCS pincer catalysts

A new amphiphilic homopolymer bearing an SCS pincer palladium complex has been synthesized by reversible addition fragmentation chain transfer polymerization. The amphiphile has been shown to form spherical and worm-like micelles in water by cryogenic transmission electron microscopy and small angle neutron scattering. Segregation of reactive components within the palladium containing core results in increased catalytic activity of the pincer compound compared to small molecule analogues. This allows carbon-carbon bond forming reactions to be performed in water with reduced catalyst loadings and enhanced activity.