
Current Position: Self-Employed
Undergraduate Institution: University of Illinois at Urbana-Champaign
M.S.E. Thesis Research:
In polymer science, tie chain molecules are of major interest as these chain fragments explain how semi-crystalline polymers derive their mechanical properties. In its simplest definition, tie chains are molecules that connect two or more crystals, and different quantities have different effects. For instance, abundant tie molecules in linear polyethylene are ductile while those in chemically-analogous paraffin wax are brittle. Because of their significant importance in polymer characteristics, there have been many efforts to predict the concentrations of tie molecules in each polymer. The most well-known model comes from the studies done by Huang and Brown. Notably, they were the first to calculate the tie chain probabilities in semi-crystalline polymers and showed that there are two scaling factors that describe the tie molecule formations. Huang and Brown concluded that the probabilities of tie chains depended on two length scales of the random coil dimension in the molten state and the crystal thickness in the solid-state. However, the predictions made by Huang and Brown failed when a narrowly distributed polyethylene (PE) was crystallized via different thermal histories. This inconsistency was predicted to occur due to the change in the degree of crystallinity and crystal thickness. The silver lining to this failure, however, was that the LPE synthesized here had yield strengths and tensile modulus similar to that of an engineering plastic yet were brittle due to the loss of the tie molecules. Therefore, this project aims to obtain and explain the advantages of the given benefits while avoiding undesirable brittle traits. Specifically, this project will use norbornene as a model system along with the well-known synthetic route of ring-opening metathesis polymerization (ROMP). Particularly, there will be two aims: first to obtain a new quantitative relationship between their solid-state structures and ductility, then use the new relationship to synthesize block copolymers of semi-crystalline and glassy copolymers. As norbornene is a model system, the knowledge gained in these two sections can be applied to other semi-crystalline polymers to enhance their yield strengths to that of an engineering plastic while retaining their ductility. Currently, such a design framework in which ductility and toughness of semi-crystalline polymers do not exist even if solid-state structures under different thermal histories are known. Therefore, this inability hinders the process of synthesizing highly mechanical strength ductile materials, and this research aims to solve this issue.