Heavy weight NAT. Chem.: preparation of environmentally friendly polymers with degradation capacity by biomass norbornene romp

Ring opening metathesis polymerization (ROMP) of norbornene and its derivatives was used to prepare polymer materials with special functions, which have important applications in resin synthesis, catalysis, biomedicine and sensor fields At the same time, the graft romp of norbornene monomers (MMS) can also be used to prepare advanced polymers for drug delivery, molecular imaging and self-assembly Although the polymers based on norbornene have many excellent properties and application prospects, the disadvantages of its difficult degradation are the biggest obstacle to its application Nowadays, environmental protection issues are increasingly prominent, people have more urgent demand for green chemistry, and traditional polyolefin materials can not meet the standards of green chemistry The stability and degradability of polymers are just like the two ends of the balance How to control them to make polymer materials meet the requirements of practical and environmental protection at the same time needs to be explored deeply by researchers (photo source: Nat Chem.) 1 Recently, Jeremiah A Johnson, a polymer synthesis expert at MIT, successfully prepared norbornene based polymer materials with biodegradability, and conducted in-depth research on their biodegradability and biological properties Relevant research results were published on nature Chemistry (DOI: 10.1038 / s41557-019-0352-4) 2、 The homopolymer of norbornene is a kind of polymer with C-C and C = C bond on the main chain Because of the excellent chemical stability of these two covalent bonds, the degradation ability of norbornene homopolymer is weak However, the author designed a kind of octameric cycloolefin monomer with silicon ether bond, and copolymerized it with norbornene The copolymers have the silicon ether bond with poor stability, so as to realize the degradability of the copolymers The results showed that the copolymers could be degraded into oligomers with 1-3 repeat units, which fully proved that the binary copolymers were a statistical polymer rather than a block polymer: norbornene monomer was randomly distributed on a polymer chain (photo source: Nat Chem.) the author has studied the degradation of polymers copolymerized with a variety of norbornene derivative monomers and silicone ether olefin monomers, and found that the structure of norbornene has an important influence on the degradation This is due to the different structure of norbornene, which leads to the different reaction activity Due to the high reactivity of NB1 and Nb2, the number of nb1-nb1 and nb2-nb2 units in the statistical polymer prepared by copolymerization of NB1 and Nb2 with silicone ether olefin is large, so the oligomer produced by degradation has large molecular weight Then, the influence of copolymers prepared with different silica ether structures and pH of degradation environment on the degradation of copolymers was studied It was concluded that the degradation was carried out from the polymer main chain, and the stronger the environmental acid, the faster the degradation (photo source: Nat Chem.), the author also prepared brush and brush arm star polymers with different topological structures for degradation study The degradation of the brush like polymer is only carried out in the copolymerization part of norbornene and silylene, while the degradation of the advanced shell part of the brush arm star like polymer can be carried out in the case of strong acidity, so as to realize the overall degradation of the polymer At last, the biological test of the copolymer was carried out to prove its excellent biocompatibility and low toxicity 3 Conclusion the polymers with different topologies and degradability were successfully prepared by the copolymerization of norbornene and silylene, and the microstructure and degradation behavior of the polymers were studied Biological tests show that this kind of polymer has low toxicity and excellent biocompatibility, which lays a foundation for the application of this kind of polymer in the field of medicine.