Hydrogel networks based on ABA triblock copolymers.

BACKGROUND: Triblock copolymers from hydrophilic oligo(ethylene glycol) segment A and oligo(propylene glycol) segment B, providing an ABA structure (OEG-OPG-OEG triblock), are known to be biocompatible and are used as self-solidifying gels in drug depots. A complete removal of these depots would be helpful in cases of undesired side effects of a drug, but this remains a challenge as they liquefy below their transition temperature. Therefore we describe the synthesis of covalently cross-linked hydrogel networks. METHOD: Triblock copolymer-based hydrogels were created by irradiating aqueous solutions of the corresponding macro-dimethacrylates with UV light. The degree of swelling, swelling kinetics, mechanical properties and morphology of the networks were investigated. RESULTS: Depending on precursor concentration, equilibrium degree of swelling of the films ranged between 500% and 880% and was reached in 1 hour. In addition, values for storage and loss moduli of the hydrogel networks were in the 100 Pa to 10 kPa range. CONCLUSION: Although OEG-OPG-OEG triblocks are known for their micellization, which could hamper polymer network formation, reactive OEG-OPG-OEG triblock oligomers could be successfully polymerized into hydrogel networks. The degree of swelling of these hydrogels depends on their molecular weight and on the oligomer concentration used for hydrogel preparation. In combination with the temperature sensitivity of the ABA triblock copolymers, it is assumed that such hydrogels might be beneficial for future medical applications - e.g., removable drug release systems.

A versatile approach for the processing of polymer nanocomposites with self-assembled nanofibre templates.

The incorporation of nanoparticles into polymers is a design approach that is used in many areas of materials science. The concept is attractive because it enables the creation of materials with new or improved properties by mixing multiple constituents and exploiting synergistic effects. One important technological thrust is the development of structural materials with improved mechanical and thermal characteristics. Equally intriguing is the possibility to design functional materials with unique optical or electronic properties, catalytic activity or selective permeation. The broad technological exploitation of polymer nanocomposites is, however, stifled by the lack of effective methods to control nanoparticle dispersion. We report a simple and versatile process for the formation of homogeneous polymer/nanofibre composites. The approach is based on the formation of a three-dimensional template of well-individualized nanofibres, which is filled with any polymer of choice. We demonstrate that this template approach is broadly applicable and allows for the fabrication of otherwise inaccessible nanocomposites of immiscible components.