Biobased polymers outperform polyolefins in tensile strength

Tokyo, Japan – The research group of Professor Kotohiro Nomura, Tokyo Metropolitan University, in cooperation with the research groups of Senior Researcher Hiroshi Hirano and Director Seiji Higashi, Osaka Research Institute of Industrial Science and Technology, and Associate Professor Hiroki Takeshita, The University of Shiga Prefecture, has developed biobased poly(ester amide)s from inedible bio-renewables, which can be easily chemical recyclable and exhibit better mechanical (tensile) properties in film than commodity plastics.

The development of biobased polymers, readily chemical recyclable and derived from non-edible renewable resources, has been recognized as promising sustainable materials in circular economy.  However, there have been few examples of development of materials exhibiting mechanical properties (e.g. tensile strength and elongation at break) beyond conventional polymers such as polyethylene and polypropylene.

In the JST Strategic Creative Research Promotion Project (hereafter, CREST), the research group led by Professor Kotohiro Nomura has developed biobased poly(ester amide)s ‒ consisting of plant oils, amino acids and sugars ‒ chemically recyclable, exhibiting excellent mechanical properties (tensile strength and strain at break in films) compared to the conventional polymers (Figure 1).  The poly(ester amide) containing phenylalanine also display unique fast self-healing properties at ambient temperature.  These materials are derived from non-edible vegetable oils, amino acids, and sugars (Figure 2), and are prepared by a catalytic olefin metathesis polymerization method*, affording high molecular weight polymers.  Moreover, these polymers are converted to starting organic compounds (monomers) by catalytic reactions with alcohol called transesterification (depolymerization, quantitative bond formation and dissociation).  These efforts should play an essential role to accelerate development of sustainable polymers for circular economy.

* Olefin metathesis polymerization method: “olefin” is a general term for hydrocarbons with one carbon-carbon double bond. The word “metathesis” means “substitution”. Therefore, the recombination reaction of substituents on the double bond of an olefin is called the olefin metathesis reaction. The polymer synthesis method using such reaction in the presence of catalyst is called the olefin metathesis polymerization method. The present method is a polycondensation synthesizing polymer through producing ethylene as by-product (acyclic diene metathesis polymerization).

The research was conducted under the JST CREST program, Research Area “Precise Material Science for Degradation and Stability,” Research Theme “Development of Bio-Based Advanced Polymers and their Depolymerization, Chemical Recycle.”