Posted by A collaboratorative work performed by Nara Laboratory, Kyoeisha Chemical Co. and various departments of Osaka University, Japan might make a step further in achieving a sustainable society with the development of advanced degradable plastics including movable cyclodextrin crosslinking units. In a study published recently in Chem [1], the researchers have revealed that developing polymers with movable crosslinks not only increases their strength but also promotes degradation by enzymes under mild conditions. Cyclodextrin-based supramolecular cross-linking structure based on polyrotaxane architecture has been first reported by Okumura and Ito in 2001 [2], while such a polymeric material with freely movable cross-links was theoretically proposed as a sliding gel by de Gennes in 1999 [3].
Plastics need to achieve both favorable performance in terms of durability and strength, as well as triggerable degradation capability to enable their breakdown into monomers or fragments for reuse. At present, there is a tradeoff between these factors; i.e., increased toughness makes the polymer more difficult to degrade. The researchers have used movable cyclodextrin crosslinks to resolve this problem.
The movable crosslinks are cyclodextrins, which are threaded on one polymer strand and attached to another, endowing the resulting plastics with increased toughness and durability. Cyclodextrins being nontoxic, biodegradable, and widely available, making them attractive as a polymer component.
The cyclodextrin crosslinks also enabled degradation of the polymers during subsequent enzymatic treatment because their bulky structure increased the free volume in the polymer network, which improved access of the enzyme to the target cleavage sites on the polymer chains.
These advanced biodegradable plastics can readily be broken down by enzymes into useful precursor molecules that could be reused in further materials, suppressing waste generation and contributing to the development of a sustainable industry.
source: https://www.eurekalert.org/news-releases/1062964
[1] Jiaxiong Liu et al. Exploring enzymatic degradation, reinforcement, recycling, and upcycling of poly(ester)s-poly(urethane) with movable crosslinks. Chem, 2024, https://doi.org/10.1016/j.chempr.2024.09.026.
[2] Okumura, Y. and Ito, K. (2001), The Polyrotaxane Gel: A Topological Gel by Figure-of-Eight Cross-links. Adv. Mater., 13: 485-487. https://doi.org/10.1002/1521-4095(200104)13:7<485::AID-ADMA485>3.0.CO;2-T
[3] Pierre-Gilles de Gennes (1999), Sliding gels. Physica A: Statistical Mechanics and its Applications,
271(3–4), 231-237. https://doi.org/10.1016/S0378-4371(99)00227-7