Effects of dual-crosslinking networks on shape memory performance of polynorbornene

In this article, Polynorbornene (PNB)/Zinc dimethacrylate (ZDMA)/Dicumyl peroxide (DCP) composites can form dual-crosslinking networks, which contain an ionic crosslinking network, and a part of the C─C covalent crosslinking network. DCP was used to initiate the polymerization of ZDMA to form ionic crosslinking bonds. With the increase of ZDMA, the total crosslink density (V_r) and ionic crosslink density (V_r2) increased. DCP was consumed in ZDMA polymerization, which made the PNB reduce the covalent crosslinking networks. Leading to the covalent crosslink density (V_r1) decreased. Compared with covalent crosslinking network, the dual-crosslinking networks stored more energy when deformed, provided better restoring force and a higher shape recovery ratio for materials. When ZDMA exceeded 3.9 wt%, the ZDMA aggregates hindered the movement of molecular chains leading to the shape recovery ratio slightly decreased. When ZDMA was 2.4 wt%, the composite had an optimum shape fixing and shape recovery ratio. This article provided the experimental basis for the research of PNB dual-crosslinking networks, also widened the research of PNB shape memory materials. © 2020 Wiley Periodicals Inc. J. Appl. Polym. Sci. 2020 , 137, 48955.