Research Interest

The HK group focuses on developing organic functional materials from small molecules, polymers, and biopolymers. Our strategies for molecular design, synthesis, surface functionalization of biopolymers, coupled with techniques to control macromolecular assembly across length scales and nanofabrication, will address challenges in the development of organic materials. 

A. Chemical modification of biopolymers and their self-assemblies. 

Cellulose is an abundant biopolymer derived from polysaccharides and produced over 100 billion tons annually on the earth. Cellulose can be isolated from trees, cotton, bacteria and other bioresources. The processing difficulties associated with cellulose occur at the nanometre scale due to their inherent tendency to spontaneously aggregate and stickiness. In this context, we will synthesize functionalized cellulose nanocrystal (from naturally occurring one) and will investigate their self-assembly across length scales. We aim to bridge the gap between sources and resultant properties (such as photonics, viscoelastic).

 The uniqueness of CNCs lies in retaining chiral nematic structure on solid films upon evaporation induced self-assembly. CNCs form nematic films which are iridescent and selectively reflect circularly polarized light. The formation of chiral nematic phase largely depends on the CNC aspect ratio, surface negative charges, and ionic strength of the suspension. But how the anisotropic phase and helicoidal assembly forms through spontaneous self-assembly is yet to be explored. We aim to investigate the equilibrium and non-equilibrium kinetics of helicoidal assembly formation after modifying surfaces with directing polymers (Janus type system). Success will open the door to the development of photonics materials.

 B. Responsive macromolecular systems

Stimulus-responsive supramolecular polymers have received much attention in the recent past owing to their exciting properties for applications in fields ranging from biomedical engineering to miniaturized electronic devices. In this context, our goal is to develop electrochromic materials that can undergo formation and dissociation through oxidation and reduction processes. Most of the electrochromic materials are based on inorganic oxide such as tungsten trioxide (WO3). Problematically, they suffer from some limitations, such as high cost, difficult processing, and poor color tunability. Several approaches have been implemented for the development of all-organic electrochromic materials. For example, the synthesis of electro-active polymers which can undergo successive redox processes, with each redox state are characterized by a distinct color. Controlling redox states and the ability to switch between charge states are essential for having a range of optical color states and device applications.