BIT’s progress in the purification of triisocyanate adhesive assisted by flexible porous high polymers

News Resource: School of Materials Science and Engineering

Editor: News Agency of BIT

Translator: Guo Yating, News Agency of BIT


Recently, Professor Huang Muhua’s research group of Beijing Institute of Technology (BIT) has used ring-opening ectopic polymerization reaction process of tension cyclic alkene to achieve the "rigid-flexible transformation" porous material functionalization strategy, and applied the flexible porous high polymer (such as BIT-POP-10) to the efficient purification and decolorization of highly reactive polyisocyanate (such as Desmodur®RE or JQ-1). This work was published in Chem. Mater. (2022, 34, 5184-5193. DOI: 10.1021/acs.chemmater.2c00780) under the title Flexible porous organic polymers with alkene linkage for decolorizing the highly reactive triisocyanate in ethyl acetate. Peng Shanqing, a doctoral student at the School of Materials Science and Engineering of BIT, is the first author of the paper. Professor Huang Muhua and Associate Professor Li Xiaodong are the corresponding authors.


Figure 1 Designing flexible porous norbornene for purification of highly reactive triisocyanate adhesives

Porous high polymers (POPs) materials, entirely formed by C, H, O, N and other light elements connected through covalent bonds, with the characteristics of low skeleton density, good chemical stability and easy functional modification, have developed into an important new member of the porous material family. However, most of the porous high polymers reported have cross-linked rigid skeleton structures. How to design porous high polymers with flexible skeleton and expand their application with "flexible" as functionality has become a frontier research topic in this field.

Professor Huang Muhua's research group from the School of Materials Science and Engineering of BIT, has always been concerned about the practical preparation and application technology of functional porous high polymer materials (Figure 2).


Figure 2 Porous high polymers materials reported by Professor Huang Muhua's research group

This research group uses the NaBH4-mediated reduction coupling reaction to rapidly prepare the porous high polymers linked by azo bond Azo-POP-1-3 (J. Mater. Chem. A, 2018, 6, 5608). Based on the azo coupling polymerization of 1,3,5-triaminobenzene and double nitrogen salt, the porous high polymer with aminoazobenzene structure Azo-POP-4~6 is synthesized (Chem. Mater. 2019, 31, 5421). The first soluble azobenzene porous high polymer Azo-POP-7 is synthesized using a conformation twisted monomer and successfully used for organic / water two-phase catalytic reactions (J. Mater. Chem. A, 2019, 7, 15048). Based on the reductive coupling polymerization reaction of dinitrodiphenylamine, a class of main chain azobenzene high polymer materials MCPABs can be quickly constructed, and it is found that the azo bonds in the polymer main chain can be rapidly protonated and discolored in acidic gas (J. Phys. Chem. Lett. 2021, 12, 3655). The ketone-hydrazone porous high polymer materials TKH-POP-1~4 is rapidly prepared, using the irreversible isomerization of tris (β-hydroxy-azo) benzene to the structure of tris (β-keto-hydrazone) cyclohexane which is discovered by accident (ChemComm. 2020, 56, 2103). And the correctness of the above structure is confirmed for the first time by the combination of solid-state nuclear magnetic and isotopic labeling techniques (J. Phys. Chem. Lett. 2021,12, 6767).

Based on ring-opening metathesis polymerization (ROMP) of diimide, the porous high polymer BIT-POP-1~BIT-POP-8 is rapidly prepared (Polym. Chem. 2021, 12, 6745). Azo-POP-13~14 is rapidly prepared by combining ROMP with reductive coupling polymerization coupling (Polym. Chem. 2020, 11, 6429). Interestingly, in the course of carrying out the above work, they find that the porous polynorbornenes skeleton structure linked by isolated double bonds is somewhat flexible. To further improve the specific surface area, they design the trifunctional and tetrafunctional imides for ROMP polymerization to quickly obtain the porous high polymer material BIT-POP-9~ BIT-POP-12. The chemical structure of these porous high polymers is confirmed by infrared spectroscopy, solid nuclear magnetic and elemental analysis, the porosity is confirmed by the nitrogen isothermal (77 K) adsorption-desorption test (BET method), and the unique helical and loose network skeleton of the porous polymer is characterized by SEM and TEM.


Figure 3 Synthesis and characterization of porous polynorbornenes BIT-POPs

Using the 1H relaxation decay spectrum of low-field nuclear magnetic, they study the flexibility of the porous norbornenes BIT-POP-10 (SBET ="""1138""" m2.g-1) and BIT-POP-12 (SBET = 1202 m2.g-1) in dry powder state. For example, the rigid part of BIT-POP-10 is approximately 80.5% and the flexibility ratio is about 19.5%, while the rigid part of BIT-POP-12 is approximately 95.2% and the flexibility ratio is only about 4.8%. They investigate the kinetic behavior of BIT-POP-10 and BIT-POP-12 and the effect of the solvents on the material pore, using methanol, dimethyl sulfoxide, chloroform, ethyl acetate and water as solvents. Based on this analysis method, the movement rate order of the test solvents in BIT-POP-10 and BIT-POP-12 is: chloroform> methanol> ethyl acetate> dimethyl sulfoxide> water.


Figure 4 Using low-field NMR to interpret flexible features of porous skeleton

At the same time, Huang Muhua’s research group, during carrying out the resource utilization engineering practice of the decommissioned energy-containing materials, finds that triisocyanate (such as Desmodur®RE or JQ-1) has a very high using value, but its high reactivity and high boiling point lead to its difficulties of purification, so these tapes have a deep color. Given that JQ-1 (or Desmodur®RE) is usually dissolved in ethyl acetate for sale and use, they use their own prepared BIT-POP-10 to selectively adsorb dark color impurities in the JQ-1. After the enrichment of impurities by porous polynorbornenes and the systematic analysis and detection, the dark color impurities are finally confirmed as the hydrochloric alkaline red 9.


Figure 5 Flexible porous norbornene for purification of JQ-1

After the purification of the porous polynorbornenes BIT-POP-10, the directly commercialized purchased Desmodur®RE color was changed from purple to colorless, and the light transmittance of the glass sheet made by Desmodur®RE after decolorization does not decrease with the increase of the added quality.This indicates that the colorless Desmodur®RE is expected to be used in the high-end adhesive field with high transparency requirements.

All in all, this work skillfully uses the process of tension cyclic alkene (rigid monomer), which is prone to ring-opening metathesis polymerization (ROMP) generating isolated alkene connected to norbornene (flexible skeleton), and realizes the "rigid-flexible transformation" strategy to build flexible porous materials. This work uses the flexible porous skeleton to promote organic solvents into the pore, and then expands the efficient purification of porous materials in highly reactive triisocyanates (such as Desmodur®RE or JQ-1), which will provide a good reference for the rational design of porous materials.

This research was strongly supported by the Beijing Municipal Natural Science Foundation (No.2202049) and the National Natural Science Foundation of China (No.21772013).

Shan-Qing Peng, Tianyu Yang, Wenhao Fan, Shumeng Chi, Boya Kuang, Fan Lei, Xiaodong Li* and Mu-Hua Huang*

Experimental Center for Advanced Materials, School of Materials Science and Engineering, Beijing Institute of Technology, No. 5, Zhongguancun South Street, Beijing 100081, China

Chem. Mater. 2022, 34, 5184-5193.

Paper link:

About the corresponding author:  

Huang Muhua is the long-term professor and doctoral supervisor of BIT. His main research interest is to carry out the structure and function innovation of porous high polymer oriented by the resource utilization of decommissioned energy-containing materials by means of synthetic chemistry, so as to realize the multi-disciplinary interdisciplinary fusion research from basic research to engineering application. As the project leader, he has undertaken more than 10 projects including the National Natural Science Foundation of China and Beijing Municipal Natural Science Foundation. He has published more than 40 research papers in Nature Chemistry, Journal of Materials Chemistry A, Chemistry of Materials and other magazines, and applied for 25 Chinese invention patents (17 authorized) and 4 PCT international patents as the first inventor. In recent years, 4 graduate students he has guided have been awarded national scholarships.