Yuehan Qian,Fuhao Dong,Lizhen Guo,Shanling Lu,Xu Xu,He Liu
Polyurethane materials will come into contact with different solvents in daily life, and at the same time, they will be subject to different degrees of collision, wear and tear. Failure to take corresponding preventative or reparative measures will result in a waste of resources and an increase in costs. To this end, we prepared a novel polysiloxane with isobornyl acrylate and thiol groups as side groups, which was further used in the preparation of poly(thiourethane-urethane) materials. Thiourethane bonds generated by the click reaction of thiol groups with isocyanates endow poly(thiourethane-urethane) materials with the ability to heal and reprocess. Isobornyl acrylate with a large sterically hindered rigid ring promotes segment migration, accelerating the exchange of thiourethane bonds, which is beneficial to the recycling of materials. These results not only promote the development of terpene derivative-based polysiloxanes but also show the great potential of thiourethane as a dynamic covalent bond in the field of polymer reprocessing and healing.
It is of great significance to disclose the diverse aging pathways for polymers under multiple factors, so as to predict and control the potential aging evolution. However, the current methods fail to distinguish multiple pathways (multi-paths) of polymer aging due to the lack of spatiotemporal resolution. In this work, using polyimide as a model polymer, the hydroxyl, carboxyl, and amino groups from the polyimide aging process were labeled using specific fluorescent probes through boron-oxygen, imine, and thiourea linkages, respectively. When the excitation and emission wavelengths of each fluorescent probe were controlled, the multi-paths in polyimide aging can be visualized individually and simultaneously in three-dimensional fluorescent images. The overall aging process under hydrothermal treatment was destructured into the pyrolysis and hydrolysis pathways. Three-dimensional dynamic studies discovered that the increased humidity, along with the decreased oxygen content, could hamper the pyrolysis reaction and accelerate the hydrolysis reaction, leading to severe degradation of the overall polyimide aging. More importantly, the oxygen showed a higher regulation coefficient in accelerating the pyrolysis reaction, than the water vapor in motivating the hydrolysis reactions. Such a multidimensional identification methodology is able to guide the long-term use of polymers and control their aging process to a harmless direction in advance by tuning the contents of oxygen and water vapor.
危险品化学品经营许可证（带存储）