Research

Development of Polymer Recognition Systems

Molecular recognition technology, which identifies and separates small molecules, has made great progress in the framework of supramolecular chemistry and is now being applied to various molecular separation technologies. However, recognition of polymer structures is extremely difficult, and it has been considered impossible with conventional molecular recognition methods. Polymers are generally in the shape of long strings, and can take various conformations. As a result, traditional molecular recognition techniques have not been able to identify small differences hidden in their long, large structures. 

We are trying to realize polymer recognition by using a porous crystal called a metal-organic framework (MOF) as a recognition medium. If polymer recognition technology is developed, it will not only dramatically improve the purity of various polymeric materials that have been difficult to purify until now, but it will also be an innovative technology that enables us to obtain polymers with an unprecedented structure.

Furthermore, recognizing monomer sequences of polymers is reading the information recored on the polymer chain. As biological systems uses DNA as the storage of genetic information, we can utilize synthetic polymer chains as the information media. Therefore, polymer recognition technology will lead not only to polymer separation and analytical breakthroughs but also to innovation for polymer synthesis, and information technology.

MOF Column Chromatography for Ultimate Polymer Separation

While previous studies on MOF-based separation applications have predominantly focused on small molecules, we have recently made a significant discovery that expands their potential. We have found that MOFs are capable of adsorbing large polymeric compounds and demonstrating promising abilities in polymer recognition and separation. This breakthrough is attributed to the infiltration of polymer chains into the nanopores of MOFs. Specifically, long polymer chains are spontaneously inserted into the nanoporous pores of MOFs, allowing for precise recognition of structural differences among polymer chains. Consequently, this enables efficient separation of polymers. The MOF-based polymer separation technique we have developed is particularly remarkable as it facilitates the discrimination of minute differences in polymer structures. Traditional methods struggle to precisely differentiate aspects such as end groups, topology, and minute monomer alterations. However, our technique successfully achieves this level of discrimination.

Building upon the principle of polymer insertion-based recognition, we have designed a novel approach to separate polymers using a MOF column chromatography system. When employed as the stationary phase in liquid chromatography, MOFs packed into the column exhibit exceptional recognition and separation capabilities for polymers, operating on a unique separation mode based on polymer insertion into MOFs. It holds immense potential for enabling previously unattainable polymer separations based on factors such as monomer composition and sequences, stereoregularity, regioregularity, helicity, and block sequences. This breakthrough has strong prospects for realizing previously impossible polymer separations based on monomer composition and sequences, stereoregularity, regioregularity, helicity, and block sequences, not only in synthetic polymers but also in biomacromolecules. 

Material-Driven Polymer Sequencing: Reading Polymer Codes by Nanoporous Materials

The blueprint of living organisms is stored in a polymeric DNA string as a sequence of four base units. The genetic code is precisely read and used for biological protein synthesis. Use of such polymeric strings as a medium for data storage can be a golden method discovered during evolution. Synthetic copolymers also contain the information on monomer arrangement. However, accessing this molecular information is challenging because of the lack of a platform for reading and recognizing the microstructures of synthetic copolymers.

We explore new methods for recognizing monomer sequences of synthetic copolymers by introducing them into nano-sized pores of a metal-organic framework (MOF) crystals. This technology will lead to a new trend in the separation and characterization of synthetic copolymers. Importantly, in this paradigm, synthetic polymers are no longer raw materials in chemical industry, instead they are information media.

Hybridization of Polymer and Crystals: A New Style of Polymer Composite

The introduction of polymers into nanopores serves as a principle for investigating novel composite modes involving porous crystals and polymers. Traditional polymer and crystalline material composites are typically created by a simple mixture of the two components. However, our current focus is on developing innovative composite modes by effectively threading extremely long polymers into the entire porous crystals. Up to now, we have achieved successful synthesis of a polymer/MOF composite where the polymer penetrates the entire MOF crystals through their nanopores (namely "MOFaxane"). We anticipate the emergence of distinctive physical properties resulting from the necklace-like structure formed by the polymers penetrating the crystals.