The 1,5-Cyclooctadiene (COD) and dicyclopentadiene (DCPD) copolymers prepared by step-wise polymerization (CD-SP) can simultaneously enhance the tensile strength and breaking elongation of polymers, compared with those prepared by frontal polymerization (CD-FP). For example, the stress and strain of the 30%CD-SP are 2.7 times and 1.8 times that of 30%CD-FP, respectively. This step-wise polymerization (SP) is determined by the curing kinetic parameters and the conversion difference of COD and DCPD by non-isothermal DSC and non-model kinetics (MFK method), that is, SP: 35 degrees C, 4 h; 60 degrees C, 30 h. In addition, energetic composite materials consisting of 85% solid fillers and COD-DCPD copolymers are prepared by SP, and its mechanical properties are far better than those of traditional energetic composite materials. Specifically, the breaking elongation increases from less than 100% to more than 500%, and the tensile strength is higher than 1 MPa. It is expected to be used as a new binder in energetic composite materials and other composite materials.

In general, ultrahigh loading fillers can increase the hardness and hinder the interfacial healing progress in polymer composites. Therefore, the healing ability and mechanical strength of polymer composites with ultrahigh filler loading are contradictory properties and are difficult to optimize simultaneously. Herein, self-healing hard polymer composites consisting of 72.4 vol% fillers and self-healing thermoplastic elastomers based on surface energy and disulfide bonds were fabricated. The results showed that in the case that of ultrahigh filler loading, polymer composites not only obtained a high mechanical strength of -3.21 MPa and a high self-healing efficiency of -92.8%, but also possessed the strong reshape ability. Besides, a physical model was used to describe the self-healing mechanism. The adhesion effectively closed cracks and the surface energy driven the movement of polymer chains as well as disulfide bonds reconstructed new polymer chains at the interfaces, resulting in recovering heal mechanical property.