presenter
Associate Professor Yukiya Kitayama, Graduate School of Engineering, Osaka Public University
overview
The development of degradable plastics is an important issue for reducing waste and recycling resources. Plastics have a long chain-like structure made up of small molecules (monomers) linked together, so by inserting easy-to-break joints in the middle, plastics can be decomposed in nature. However, many monomers are difficult to cause chemical reactions, and the number of monomers that can form joints is limited.
This research group is investigating the Laplace pressure generated within minute droplets.*1We have developed a method that uses internal pressure, known as pyrolysis, as the driving force for reactions that connect large numbers of monomers. As a result, we succeeded in synthesizing a degradable plastic using monomers that were previously thought to be unusable.
The results of this research were published online in the international academic journal "Macromolecules" on June 23, 2026.
Figure 1 Image of polymerization reaction using Laplace pressure
point
- The Laplace pressure generated due to curvature within a minute droplet isCreate large molecules (polymers) by combining many monomersDeveloped a method to use it as a driving force for polymerization reactions.
- By applying pressure to react with monomers that had previously been thought to be unusable, they succeeded in synthesizing a degradable plastic with breakable bonds within the molecule.
- When the developed plastic was treated with a chemical called amine, it was confirmed that it was decomposed.
Rather than changing the shape of molecules, we discovered that we can use the physical force of pressure to cause monomers that were previously unusable to react. Since it is a simple method, we hope that it will lead to practical application. In the future, I would like to expand this pressure effect to other reactions and different monomers.
Associate Professor Yukiya Kitayama
Research background
Plastic is extremely useful and is used in many products such as plastic bottles, plastic bags, and toys, but it has the problem of being difficult to decompose in nature. Discarded plastics are broken into small pieces and become microplastics, which accumulate in the ocean and are eaten by fish and other animals, raising concerns about their impact on living creatures. To solve this problem, there is a need to develop plastics that decompose after use. Plastics have a long chain-like structure made up of many small molecules (monomers) linked together, and by inserting breakable joints in the middle of these chains, they can be decomposed in nature. However, many monomers were considered unusable because they were difficult to cause chemical reactions, and special types of monomers were required to create the joints.
Research content
This research group conducted radical ring-opening polymerization of 3-phenylthionophthalide (PTP), a monomer that was previously thought to be unusable.*2Miniemulsion polymerization using nano-sized droplets as a reaction field for application to*3We focused on this method.Inside a tiny droplet, an internal pressure called Laplace pressure is naturally generated due to its curvature. This pressure, which reaches tens of kilopascals (kPa) for droplets of about 100 nanometers (nm), was used as the driving force necessary for the reaction. As a result, PTP, which did not react at all during solution polymerization at normal pressure, efficiently copolymerized with n-butyl acrylate (nBA) during miniemulsion polymerization, resulting in a ring-opened degradable thioester bond.*4was introduced into the main chain. When the resulting copolymer was treated with an amine, the thioester bonds were cleaved and the molecular weight decreased, confirming that the main chain was degradable.
Figure 2 Synthesis of polymers with thioester bonds in the main chain structure by pressure-assisted radical ring-opening polymerization
Second, multiple independent experiments confirmed that pressure was the essential factor. In experiments, we conducted suspension polymerization with large droplets and low pressure (droplet size approximately 5 micrometers).μm) and Laplace pressure of approximately 7.3 kPa), the PTP reaction rate was low and copolymerization was poor. Compared to miniemulsion polymerization, where the droplet size is approximately 100 nm, the particle size is several tens of times larger in suspension polymerization, resulting in a smaller Laplace pressure and lower PTP reactivity. This suggests that pressure is important for PTP reactivity. Furthermore, in order to directly confirm the pressure effect, we performed homogeneous solution polymerization using a high-pressure reaction vessel, and found that the conversion rate of PTP increased as the external pressure was increased. This makes it clear that pressure itself controls the reaction.
Furthermore, it was revealed that in mini-emulsion polymerization, the termination reaction is suppressed by compartmentalization, in which radicals within the droplets are isolated from each other, and in combination with the pressure effect, the reaction efficiency is further increased.
Expected effects and future developments
This research has demonstrated that it is possible to use materials that were previously thought to be unusable simply by applying pressure, without having to make any complicated changes to the molecular structure of the monomer. This greatly expands the material options for making degradable plastics. Additionally, this method does not require any special and difficult mechanisms, so it is considered easy to use in actual factories.
In the future, it is hoped that this technology will lead to the creation of environmentally friendly plastics that are reliably decomposed and will help solve the problem of plastic waste in the ocean. Additionally, the new idea of using pressure as a reaction tool has the potential to be used in a variety of chemical situations in the future.
Funding information
This research was supported by the Japan Science and Technology Agency (JST) PRESTO (JPMJPR24M3), JSPS KAKENHI (JP21H02004, JP23K21137, JP24K01559), and the Ministry of Education, Culture, Sports, Science and Technology's "Outstanding Researcher Project."
Glossary
*1 Laplace pressure: The pressure applied to the inside of a round liquid, such as a water droplet or a soap bubble. The smaller the particle, the stronger it becomes, reaching several tens of kPa for nano-sized droplets. In this study, this Laplace pressure was used as a force to advance the reaction. In this study, it is calculated to be approximately 77 kPa.
*2 Radical ring-opening polymerization: Radicals (free radicals) are atoms or molecules with unpaired electrons, and are generally highly reactive chemical species. Radical polymerization is a method of polymerizing monomers using radicals as active species. Radical ring-opening polymerization is a polymerization method that uses radicals as active species and connects ring-shaped monomers into chains while opening the ring. When the ring opens, it creates a degradable joint, making it useful for synthesizing degradable plastics.
*3 Miniemulsion polymerization: A method of making plastic by reducing monomer droplets dispersed in water to nanometer size and using each droplet as a reaction site.
*4 Thioester bond: A bond that has a structure in which a thiol group and a carboxyl group are condensed, and can be broken down by hydrolysis. In this research, we synthesize degradable polymers by introducing this bond into the main chain structure.
Magazine information
[Publication magazine] Macromolecules
[Paper title] Laplace Pressure-Enabled Radical Ring-Opening Polymerization of a Thionolactone
【author】 Kaito Fuji, Yukiya Kitayama, Atsushi Harada
[Publication URL] https://doi.org/10.1021/acs.macromol.6c01012
Contact information regarding research detailsOsaka Public University Graduate School of Engineering
Associate Professor Yukiya Kitayama
TEL: 072-254-9330
E-mail: kitayama[at]omu.ac.jp
*Please change [at] to @.
Osaka Public University Public Relations Division
Person in charge: Tani
TEL: 06-6967-1834
E-mail: koho-list[at]ml.omu.ac.jp
*Please change [at] to @.
Source: https://www.omu.ac.jp/info/research_news/entry-25464.html