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Chemistry Department

Grand Forks, ND

 

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Qianli 'Rick' Chu

 

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Chu Group Research - Organic Nanomaterials

The main focus of our research group is the development of novel synthetic methods and the construction of innovative organic nanomaterials, e.g., covalently bonded nanowires. These materials will provide a variety of applications in nanoscience and sustainable technology. The study also offers new opportunities for molecular level structure-property studies.
Organic Nanomaterials As shown in the figure on the left, construction and characterization of organic nanomaterials is the cutting edge of chemical science and interdisciplinary research that requires knowledge in not only nanoscience and nanotechnology but also polymer chemistry, supramolecular chemistry and organic synthesis etc. It is a crucible within which the traditional disciplines are combining to form a new branch of science, thus representing a challenge to researchers. The diverse backgrounds of our group members offer us opportunities to learn from each other about all of the scientific fields necessary for preparing their synthetic targets.

Project 1: Strong and Lightweight Materials (SLIM) for Fuel-Efficient Transportation

A twenty percent reduction in the weight of an automobile will reduce its fuel consumption by ten percent. Replacement of metal with plastic is a proven success. With climate change and energy shortages looming, lighter yet stronger new materials are required to replace the traditional plastic and metal for fuel-efficient transportation.

Our research team has recently achieved stereo-regular polymeric ladders and two-dimensional (2D) polymers from symmetric monomers via topochemical polymerization. Ladder and 2D polymers are theorized to be stronger than traditional polymers because each monomer is connected with its neighbors by multiple covalent bonds in an organized way. Moreover, solid-state polymerization offers a unique opportunity to synthesize macromolecules with regio- and stereo-specificity because topochemical reaction proceeds with minimum movement of atoms. Stereoregularity is an important property of polymers with chiral centers that directly determines the performance of the polymeric materials. Stereoregular polymers often have an array of mechanical properties that are superior to those of corresponding non-stereoregular polymers.
Polymeric Ladder

Project 2: Polymeric Conducting Materials for Electronics

Conductive polymers can offer tunable electrical conductivity but do not show similar mechanical properties of classic conductors such as metal or semiconductors such as silicon. Consequently, an advantage of conductive polymers is their processability, mainly by dispersion. Meanwhile, their electrical properties can be fine-tuned using organic synthesis.

Our research team is using organic synthesis to achieve conductive polymers, such as the following nanowire. The initial step is the supramolecular self-assembly of a reversible non-covalent complex by intermolecular interactions such as hydrogen bonds between amide groups. In the second step, 1,4 polymerization of diene moieties will covalently lock the complex into a robust nanowire.
Nanowire

Project 3: Self-Assembly and Application of Supramolecular Atropisomers

Chiral materials are valuable for their applications ranging from nonlinear optics to chiral separation and catalysis. The construction of chiral materials from achiral molecules is valuable but challenging. Our research group has been exploring one aspect of the challenge by using supramolecular atropisomers.

Supramolecular atropisomer is an achiral molecule with one or more stereogenic axis that shows chirality when it forms aggregates. N,N’,N’’-tris(n-octyl)benzene-1,3,5-tricarboxamide (BTA) with three stereogenic axes is an example. The six atoms within each amide are nearly planar, and each amide group is partially tilted with respect to the core aryl ring to fulfill requirements of the hydrogen bonds’ orientations and close packing of the molecules. Two of the three amides are pointing toward the same direction. The distances of three C−C single bonds connecting the amide groups and benzene ring are approximately 1.51 Å, which is close to the typical bond length of a C−C single bond. However, due to the hydrogen bonds, the amide groups are not free to rotate around the C−C single bond axes in this supramolecular atropisomer, resulting in a three-dimensional chiral conformation fixed in the hydrogen bonded network.
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