The Synthesis Of Polyolefin Materials Via ROMP And The Crosslinking Research

After years of development,olefin metathesis polymerization has become one of the most effective synthetic methods of polymer materials.The ring-opening metathesis polymerization(ROMP)based on Grubbs ruthenium catalyst system has attracted extensive attention of many researchers because of its unique reaction mechanism,mild reaction conditions and strong functional group tolerance.Since the discovery of Grubbs catalyst,the design of catalyst in olefin metathesis polymerization has made a major breakthrough,but the research of catalyst is still the fresh source in this field.The ruthenium catalyst can catalyze different monomers to polymerize in different polymerization forms and finally prepare various types of polymer materials.Among them,ring-opening metathesis polymerization,represented by cyclooctene,has shown great application value in preparing polyolefin materials.However,this polymerization catalyst system still faces many scientific problems,such as the residue of catalyst in polymer and how to prepare polyolefin materials with higher added value based on efficient post-functionalization route.Therefore,the research contents of this paper include the application of ruthenium catalyst supported on SiO2 in ring-opening metathesis polymerization and the group transformation on the basis of existing telechelic polymers,which further enriches the types of polyolefin materials and improves the properties of materials through crosslinking.The specific innovations are as follows.1.Firstly,a series of functionalized telechelic polyolefin materials were prepared by using ruthenium metal catalyst supported on SiO2 to catalyze the polymerization of cyclooctane and various polar internal olefin monomers.Heterogeneous ruthenium metal catalyst can be used to continuously catalyze ring-opening metathesis polymerization,and realize the recycling of catalytic system.Not only the utilization rate of the catalyst is improved,but also the hydrogenation reaction of the obtained polymer can be further catalyzed to prepare saturated telechelic polyolefin,thus simplifying the technological process.2.Secondly,the telechelic unsaturated polyolefin with reactive groups prepared by ring-opening metathesis polymerization was crosslinked to obtain crosslinked polyolefin material with good material properties.Specifically,in the presence of chain transfer agent,ruthenium metal catalyst catalyzed ring-opening metathesis polymerization of cyclooctene to synthesize telechelic polyolefin terminated with acetoacetic acid group.Under mild conditions,a variety of covalent crosslinkingetworks were constructed by introducing di/trtri-functionalliphatic acrylate as cross-linking agent by using the reaction type of Michael addition of acetoacetic acid end groups,and the mechanical properties of polyolefin materials were enhanced.3.Compared with the permanent cross-linked network mentioned above,the construction of dynamic cross-linked network is of great value for the repeated processing of polymer materials.Therefore,based on the rich reactivity of acetoacetic acid groups and the dynamic covalent exchange characteristics of disulfide bonds,boric acid bonds and bond-checking,we carried out Michael addition and Stork enamine alkylation crosslinking reactions on the above-mentioned telechelic polymers,thus preparing a variety of polyolefin materials with dynamic cross-linked network also known as Vitrimers.The obtained polyolefin material shows good mechanical properties,self-healing properties,reprocessing properties and biodegradability.