Polymers are present in everything, from plastics to clothing to DNA. Long chains of the repeating units known as monomers are used to create polymers, which are extremely versatile materials. Polymers with metal complexes on their side chains offer a wide range of applications as hybrid materials.
With the addition of numerous metal species to the polymers, this potential will only grow. However, because it is difficult to control the composition of metal species in the final polymer, current methods of manufacturing polymers with metal complexes are not suitable for the fabrication of multimetallic polymers.
A new polymerization technique that can get around this restriction has just been proposed by a research team from Tokyo University of Science, lead by Assistant Professor Shigehito Osawa and Professor Hidenori Otsuka.
Dr. Osawa explains, “The usual method of preparing such complexes is to design a polymer with ligands (molecular ‘backbones’ that join together other chemical species) and then add the metal species to form complexes on it. But each metal has a different binding affinity to the ligand, which makes it complicated to control the resulting structure. By considering polymerizable monomers with complexes of different metal species, we can effectively control the composition of the resulting copolymer.”
The work was made available online on April 1, 2022, and on April 30, 2022, it was published in Chemical Communications, Volume 58, Issue 34.
A polymer is referred to as a copolymer when the monomers that build it up are also polymers. The researchers created the dipicolylamine acrylate (DPAAc) monomer for their research.
The usual method of preparing such complexes is to design a polymer with ligands (molecular ‘backbones’ that join together other chemical species) and then add the metal species to form complexes on it. But each metal has a different binding affinity to the ligand, which makes it complicated to control the resulting structure. By considering polymerizable monomers with complexes of different metal species, we can effectively control the composition of the resulting copolymer.
Assistant Professor Shigehito Osawa
DPA was selected because it is a superior metal ligand and has been applied in a number of biological processes. Then, they used zinc (Zn) and platinum (Pt) to polymerize DPAAc, resulting in the formation of two polymer chains containing the metal complexes DPAZn(II)Ac and DPAPt(II)Ac.
The two monomers were then copolymerized. They discovered that by adjusting the feeding content of the monomers, they could not only successfully produce a copolymer but also regulate its metal composition.
They then used plasmid deoxyribonucleic acid (DNA) as a template to create nanoparticles using this copolymer as a building block. The two monomers that make up the system are known to attach to plasmid DNA, therefore that is why it was chosen as the template.
High-resolution scanning tunneling electron microscopy and energy-dispersive X-ray spectroscopy were used to demonstrate the formation of the resultant nanoparticle polymer complexes with DNA (polyplexes).
This process, which is now patent-pending, can be expanded to create a brand-new way to create intermetallic nanostructures.
“Intermetallic catalytic nanomaterials are known to have significant advantages over nanomaterials containing only a single metallic species,” says Dr. Osawa.
Because the polyplexes created in the study are DNA-binding molecules, it is possible that they will be employed to create gene carriers and anti-cancer medications. The suggested fabrication technique will also result in improvements in catalysis that shift away from platinum-based precious metals.
“These multimetallic copolymers can serve as building blocks for future macromolecular metal complexes of many varieties,” concludes Dr. Osawa.
The results of this work will undoubtedly have a significant impact on polymer chemistry.
