Shelf stable polymer chains with side structures
Novel PDTL monomer allows amine compounds to stably bind to poly(disulfide)s and impart various functionalities.
Image Credit: Osaka Metropolitan University
Scientific Frontline: "At a Glance" Summary: Versatile Degradable Polymers via Novel Domino Polymerization
- Main Discovery: Researchers developed N-(2-oxotetrahydrothiophen-3-yl)-3-(pyridin-2-yldisulfanyl) propanamide, abbreviated as PDTL, a novel monomer that enables the synthesis of reductively degradable poly(disulfide)s with customizable side-chain structures.
- Methodology: The synthesis utilizes domino polymerization, combining amine compounds with PDTL to extend polymer chains via amine-mediated thiolactone ring-opening polymerization and a subsequent disulfide formation reaction, which was validated through nuclear magnetic resonance spectroscopy, gel permeation chromatography, and mass spectrometry.
- Key Data: The versatile polymerization system successfully accommodates primary amines, secondary amines, and ammonia compounds to form stable copolymers, while laboratory testing confirmed that the resulting polymers systematically degrade upon exposure to specific reducing agents like zinc, phosphine-based agents, and dithiothreitol.
- Significance: The process eliminates the costly requirement of designing individual monomers from scratch for specific uses, allowing scientists to rapidly control polymer properties and functionality simply by swapping out inexpensive and readily available amine additives.
- Future Application: The resulting poly(disulfide)s hold significant potential for targeted medical drug delivery systems operating inside cellular reducing environments, as well as serving as eco-friendly plastic alternatives capable of safely breaking down on the seafloor.
- Branch of Science: Polymer Chemistry, Materials Science, and Environmental Science.
- Additional Detail: Pending research will focus on optimizing the polymers' mechanical and thermal physical properties, including tensile strength and heat resistance, alongside rigorous biological and ecological safety profiling of the resulting degraded byproducts.
Plastic, once ingenious for its durability and versatility, has become a global environmental issue that is affecting every aspect of life. This, in turn, fuels the development of degradable polymers as alternative solutions. Among contending the possibilities are poly(disulfide)s, which have garnered attention as redox-degradable polymers with various polymerization techniques that can break down in reductive environments, such as the seafloor. However, according to the specific objective, it is necessary to design and synthesize each monomer to control polymer properties and impart functionality.
Fortunately, a research group led by Associate Professor Yukiya Kitayama at Osaka Metropolitan University’s Graduate School of Engineering has developed a possible solution in the form of N-(2-oxotetrahydrothiophen-3-yl)-3-(pyridin-2-yldisulfanyl) propanamide (PDTL), a novel monomer for domino polymerization which enables the synthesis of poly(disulfide)s with arbitrary side-chain structures by combining amine compounds with PDTL. This method extends polymer chains through the sequential progression of amine-mediated thiolactone ring-opening polymerization followed by the subsequent disulfide formation reaction. With amine compounds being readily available at a low cost, simply changing the one used results in a structure that is easily introduced into the side chains of poly(disulfide)s, enabling main-chain degradability with amine-derived functionality.
Under testing, the formation of the target poly(disulfide)s was confirmed through analysis using nuclear magnetic resonance spectroscopy, gel permeation chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The researchers further demonstrated that all polymers obtained can be degraded with reducing agents, such as phosphine-based agents, zinc, and dithiothreitol.
Furthermore, primary amines, secondary amines, and ammonia compounds are usable in this polymerization system. Flexible molecular design was also enabled by mixing two or more types of amine compounds, which demonstrated the synthesis of copolymers featuring side chains derived from the structures and functional groups of each amine.
“Poly(disulfide) is a polymer that degrades not only in reducing environments such as the seafloor but also within cellular reducing environments. Therefore, it shows promise as a carrier in drug delivery systems for medical applications,” said Professor Kitayama. “Moving forward, we plan to conduct a more detailed evaluation of the mechanical and thermal properties of the synthesized poly(disulfide), such as its tensile strength, flexibility, and heat resistance. We will then attempt to optimize the molecular design to enhance its physical properties to a practical level suitable for specific applications. Furthermore, it is necessary to thoroughly demonstrate the rate at which polymers degrade under complex conditions, such as ocean environments and biological systems, as well as determine the environmental and biological safety of the degraded products.”
Funding: This study was supported by JSPS KAKENHI (grant numbers 21H02004, 23K21137, and 24K01559 for YK) and JST PRESTO Grant Number JPMJPR24M3, Japan (for YK). This study was partially supported by the Leading Initiative for Excellent Young Researchers (MEXT, Japan) and the 2025 Osaka Metropolitan University (OMU) Strategic Research Promotion Project (Young Researcher) (for YK).
Published in journal: Angewandte Chemie International Edition
Authors: Yukiya Kitayama, Ryodai Sakamoto, and Atsushi Harada
Source/Credit: Osaka Metropolitan University
Reference Number: chm040326_01
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