Self-assembly of amphiphilic block copolymers in solution yields nanoscale aggregates which are the primary focus of research in our group. In early studies with polystyrene-b-poly(acrylic acid) in aqueous media, we document spheres, rods, lamellae, vesicles and higher-order morphologies. Our present research can be divided into six main areas:
1. Novel morphologies: By modifying the medium, the polymer, and the colloid forming conditions, we see new and interesting morphologies such as tubules, compartmented spheres, "pin cushions" etc.
2. Aggregation mechanisms and thermodynamics: Scattering techniques (static light, dynamic light, small angle neutron and x-ray scattering) as well as the more common spectroscopic methods, along with electron microscopy, have allowed us to create a phase diagram for the self-assembled aggregates. Careful interpretation provides an avenue for the elucidation of the order and reversibility of the self-assembly. Characterization also allows determination of thermodynamic parameters.
3. Kinetics of morphological change: Time dependent turbidity studies coupled with electron microscopy have allowed us to determine the detailed kinetics and mechanisms of some morphological transitions, e.g. from rods to vesicles or from spheres to rods. A range of techniques is now being applied to this problem.
4. Bio-pharmaceutical applications: Polymer systems are actively being developed for systemic and asystemic biomedical applications. Our asystemic approach is to sequester toxins before they are absorbed from the intestinal tract into the bloodstream. In addition, we are also developing drug delivery vehicles which will allow the site-specific delivery of lipophilic drugs.
5. Organometallic/inorganic and catalysis applications: Given that the nano-scale assemblies provide microphase-separated domains of controlled size by using them as nano-reactors, it is possible to synthesize semi-conducting quantum dots as well as catalytically active sites within the assembly architecture.
6. Surface studies: The surface properties of block-copolymers, especially as two dimensional micelles, are being investigated by Langmuir trough studies in conjunction with electron microscopy, atomic force microscopy and neutron reflectivity techniques.