Preparation And Study Of Functional Modified Materials Of Polydicyclopentadiene

In the field of synthesis of macromolecular materials,ring-opening metathesis polymerization(ROMP)has been the most successful and widely demonstrated.ROMP is a chain growth polymerization process in which cycloolefin is converted to unsaturated polymer materials by Chauvin mechanism,which can improve the ease and accuracy of related commercial materials,has high practicality,and can be massproduced.Ideal ROMP candidates are usually cycloalkenes with large ring strains that are already widely used.Currently,commercially available catalysts are used to produce polymers through the ROMP process under mild conditions.The most widely commercialized ROMP polymer is polydicyclopentadiene(PDCPD).PDCPD is a thermosetting resin with excellent rigidity and toughness,chemical corrosion resistance,light density and low temperature resistance.However,there are also problems of insufficient mechanical properties and thermal stability in some fields.At the same time,as a thermosetting resin,it cannot be dissolved or melted after being discarded,which is not in line with green environmental protection and sustainable development.Therefore,in order to expand its application field,copolymerization modification is a very effective technical means.The monomers involved in copolymerization modification should first meet the polymerization mechanism of ROMP.Therefore,we screened and designed a variety of modified monomers,and played a role in toughening,strengthening and degradation modification of PDCPD.This paper mainly focuses on the functional modification of PDCPD.Through molecular design,different types of modified monomers are introduced.ROMP is used to connect the modified monomers to the network structure of PDCPD to obtain highperformance modified PDCPD thermosetting materials.The specific contents are as follows:(1)In the bio-based source of terpene compounds,caryophyllene(Car)monomer containing a force-responsive group was selected as the monomer.The caryophyllene structure contains a cyclobutane ring structure.When subjected to external force,the force-responsive group preferentially breaks,which can play a toughening effect.PDCPD/PCar cross-linked materials with adjustable thermomechanical properties were rapidly prepared by FROMP.Compared with other copolymerization systems,the toughening effect of the force-responsive group is obvious,and the elongation at break can reach 1160 %.At the same time,caryophyllene can act as an inhibitor,broaden the processing window,and liquid resin can be formed by 3D printing.(2)Polyimide is a special engineering plastic with outstanding thermal stability and mechanical properties.By referring to the molecular structure of polyimide and designing it,it can be used as a modification of PDCPD to improve the thermal properties of materials.Four kinds of bisnorbornene imide monomers were synthesized respectively,and high-performance thermosetting materials for in-situ reinforced modified PDCPD were prepared by ROMP with dicyclopentadiene.The introduction of four monomers can improve the thermal mechanical properties and volume resistivity of PDCPD to varying degrees,and the density and water absorption of the material after copolymerization are still low.At the same time,the dielectric properties of PDCPD can be regulated by introducing the impassable group into the molecular structure of the monomer.(3)Compared with thermoplastic polymers,PDCPD,as a thermosetting polymer,is difficult to reprocess or recycle after waste,because they cannot be molded again and will not degrade under mild conditions.With the improvement of environmental awareness and the rise of dual-carbon strategy,the degradation of thermosetting polymers is imperative.PDCPD can be degraded by introducing degradable groups,but the introduction of degradable modified monomers often reduces its mechanical properties and thermal stability.Based on the above considerations,we synthesized an embedded cross-linking agent containing degradable bonds for PDCPD to prepare high-performance degradable thermosetting materials.Three phosphate ester monomers with different functionalities were synthesized,and the effects of functionalities and positions of degradable bonds on degradation properties,thermal stability and mechanical properties were analyzed by comparison.