Magnetic Field Directed Self-assembly: a facile route to enable Nanotechnology with Soft Matter

The realization of nano-structured soft materials by self-assembly is complicated by the persistence of structural defects which render the system properties isotropic on macroscopic length scales. The ability to control the structure of materials that displays novel functional properties has been well advanced in hard materials, while for soft materials it still remains shockingly challenging. Development of facile scalable approaches to precisely control the self-assembly and orientation of soft materials including block copolymers, polymer-nanocomposites, surfactant systems over relevant length scales in the bulk as well as in thin films is critical for the utilization of these materials for many desired applications ranging from separation membranes, photovoltaics, optical materials, organic field effect transistors and lithography where long range order and global orientation maximize the performance of the devices. The use of external magnetic field is discussed in this context which offers a scalable, high throughput route to directing the self-assembly and alignment of diamagnetic soft matter systems over large areas within reasonable time scales. Near-single crystal quality alignment obtained in Li+-conducting block copolymer membranes by external magnetic field shows an order of magnitude enhancement in anisotropic conductivity of the system. Potential applications of aligned block copolymers as templates for the synthesis of nanomaterials, filtration applications and the use of supramolecular route to engineer novel organic semiconducting nanostructures will be discussed. The need for engineering interfacial interactions of LC block copolymers for device fabrication will be addressed. Our recent efforts on understanding the phase behavior and alignment dynamics of liquid crystalline block copolymers in high magnetic fields using in-situ X-ray scattering will be discussed. Future directions on understanding and predicting structure-property relationships of soft materials using X-ray scattering studies will be highlighted.