(6cx) Molecular Engineering Strategies for Tunable Assemblies and Hybrid Materials

The intelligent use of processes such as self-assembly, combined with the ability to manipulate the chemical structure of polymers, can lead to a wide array of new materials. Such functional materials can be the solution to many 21^st century challenges in fields such as chemistry or bioengineering. Examples of polymer-based materials that combine these two elements will be presented. In the first example, complex coacervation (i.e. a liquid-liquid phase separation phenomenon) is used as a platform for soft material design. To understand the different aspects of complex coacervation (e.g. thermodynamics, affecting parameters, rheological and interfacial properties) polypeptides are used as a model system. More complex molecular design can be utilized wherein polyelectrolyte domains are connected to neutral polymer blocks. Use of such co-polymers can result in the formation of a variety of self-assembly structures with coacervate core domains including nanometer-sized micelles or tunable hydrogels. The second example includes a technique for polymer functionalization of carbon nanotubes (CNTs) that helps circumvent their inherent insolubility, and considerably widens the scope of nanocomposite materials that can be produced. The strategy involves attachment of substituted polymerization initiators onto a CNT surface. With a judicious choice of substitution, initiators of most popular polymerization techniques can be attached. Complete control over grafting percentage of initiator and surface-initiated polymerizations allows synthesis of nanocomposite materials with desired compositions, which is essential for any application. The resulting nanocomposite materials exhibit improved mechanical and thermal properties, compared to pure polymers.