Hoyong Chung, Ph.D.
California Institute of Technology
Chemistry and Applications of Biologically-Inspired and Bio-Derived Polymers
Polymer science and biomedical science are inseparable fields. It is amazing to look at the recent advances in polymer science being used for various biomedical applications, however, there are still many remaining aspects to be learned from nature. Among many recent bio-inspired materials, bio-adhesives are gaining extensive interest in the bio-polymer community. One example is the polymers used by marine organisms such as mussels. The key feature of mussels-inspired adhesives is strong adhesion in water. The wet adhesion properties are derived from a special amino acid, 3,4-dihydroxylphenylalanine (DOPA). This DOPA moiety was thus integrated into various artificial polymers as a way to overcome the limitations of current artificial adhesives, namely their poor wet adhesion properties. The strong wet adhesion can be applied to biomedical adhesives because the human body is composed of 60% water. A new pressure sensitive adhesive was also developed from DOPA containing polymers that was combined with microfibrillar structures inspired from Gecko’s feet. The new pressure sensitive adhesive showed excellent repeatable dry/wet adhesion. The DOPA containing adhesive’s chemical structure-property relation, viscoelasticity, coating technique and aging have been extensively studied to enhance the material’s adhesion properties.
Lignin is the second most abundant biopolymer derived from plants, and it is a major byproduct from pulp and paper production. However, lignin’s utility is limited because of its complex chemical structure, low reactivity, poor processability and variability depending on source and extraction method. Therefore, new methods of lignin modification are required to use lignin productively for commodity materials. A Lewis-acid-catalyzed modification was developed to copolymerize the lignin with petroleum-derived polymers. Many state of the art methods, such as controlled radical polymerization and click chemistry, were successfully performed to integrate lignin and the synthetic polymers. The prepared lignin-based polymers showed enhanced mechanical properties in many aspects and can be a promising renewable and sustainable biomaterials.
Hoyong Chung has been a postdoctoral scholar in Prof. Robert H. Grubbs’ group at the California Institute of Technology since 2011. Before arriving at Caltech, Hoyong completed his Ph.D. in Chemistry at Carnegie Mellon University. His research experience includes the synthesis and appropriate characterization of bio-inspired medical adhesives, medically applied temperature sensitive polymers to remove ophthalmological impurities, targeted microbubbles for kidney stone fragmentation, Ru-based olefin metathesis polymerization catalysts and chemical modification to lignin-based biopolymers. His combined research experience is highly interdisciplinary including aspects of mechanical engineering, clinical medical practice, material science and bio-medical engineering. Although his initial background is in polymer synthesis, he proactively developed various practical engineering skills to optimize the performance of new polymeric materials. His capability as a practical interdisciplinary polymer chemist was proved by 5 patents and 13 peer-reviewed journal publications. He has also mentored four undergraduate students while at Caltech and Carnegie Mellon University. He wishes to continue his research to develop new biomedical polymers relevant to human health.