Scientists have synthesized unique polymers with an unprecedented structure

20.01.2025/01/30 XNUMX:XNUMX    676


Development of polymer synthesis methods using diazocarbonyl compounds as monomers. For over 20 years, the Ihara research group at Ehime University has specialized in developing innovative polymer synthesis methods using diazocarbonyl compounds as monomers.

They found that diazoacetate can be polymerized using a palladium (Pd)-based initiator to produce carbon–carbon (C–C) backbone polymers, where each carbon atom in the backbone is linked to an alkoxycarbonyl (ester) group. Unlike traditional vinyl polymerization, where the polymer chain is built from two-carbon units of vinyl monomers such as ethylene and styrene, diazoacetate polymerization creates a C–C backbone from one-carbon units. This unique process, known as C1 polymerization, is a distinctive and important feature of this synthesis method.

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While the vinyl polymerization product of an alkyl acrylate has a substituent on every other carbon atom of the backbone, the C1 polymerization product has the same substituent on every carbon atom of the backbone. The structural difference is expected to result in unique physical properties and functions for the latter products. Author: Eiji Ihara The C1 polymerization products are expected to have improved physical properties and functionality. Since the first publication of this C1 polymerization project (E. Ihara, et al., Macromolecules, 36, 36 (2003)), many groups around the world have made intensive efforts on this C1 polymerization.

Improved properties of C1 polymers

The structure of Pd-based initiators has been developed, which has allowed for success in improving their activity for C1 polymerization. For example, it is now possible to obtain polymers with high molecular weight (molecular weight > 50000), control the stereostructure (tacticity) of the CC backbone, and quantitatively incorporate a functional group at one end of the polymer chain.

Examples of bisdiazocarbonyl compounds used for polycondensation
By exploiting the unique reactivity of the diazocarbonyl groups in these compounds, a variety of new polymers with unprecedented chemical structures have been obtained. Credit: Eiji Ihara

Furthermore, by exploiting the unique structures of C1 polymers, it was possible to obtain C1 polymers with increased acidity and much higher melting points, up to 130 °C, compared to their vinyl polymers with the same substituents. Furthermore, it was found that C1 polymers can be efficiently degraded into low molecular weight compounds under mild alkaline conditions, which is very important considering their potential as environmentally friendly polymer materials.




Meanwhile, it was demonstrated that bis(diazocarbonyl) compounds containing two diazocarbonyl groups in a molecule can be used as monomers for polycondensation, forming a variety of new polymers with unprecedented chemical structures. The unique reactive properties of diazocarbonyl groups, such as the introduction of OH and NH and the formation of a C=C bond, were utilized for the polycondensation. Based on this new polycondensation, polymers with easy degradability under mildly acidic conditions and electrochromic properties (reversible color change upon application of voltage in the film state) could be obtained. These results stimulated research worldwide in a similar project after the first publication of this polycondensation project (E. Ihara, et al., Macromolecules, 43, 4589 (2010)).

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