Direct characterization of a polymer network through its retainable units
Direct and quantitative characterization of polymer networks without theoretical assumptions remains a big challenge in polymer and materials science due to their insolubility. Here we propose a partially decrosslinkable network (PDN) as a platform for the direct characterization of the entire network through analyzing its retainable units after decrosslinking. A PDN is synthesized by the polymerization of monomers having at least two uncleavable and several cleavable functional groups. It contains cleavable chains and loops formed by cleavable and uncleavable groups, respectively. After decrosslinking, the PDN transforms into soluble oligomers including unaltered network chains, dangling chains and various loops that can be directly qualified and quantified by normal techniques. Besides linear oligomers, various loops with up to eight units have been directly observed and the primary, secondary and tertiary loops have been quantitatively probed. The PDN provides a powerful protocol for direct and quantitative characterization of linear and cyclic units of polymer networks. The direct measurement of retainable loops provides comprehensive information of high-order topologies within the network, which leads to a profound understanding of the polymerization–structure–performance relationship.