Figure 3: Mass spectra of early stages of polymerization.

Mass spectrum for the samples from early period of polymerization of HB polyBDA, showing the chemical composition within the polymerization system. (a) Mass spectrum of 0.5 h sample in Fig. 2a; (b) mass spectrum of 1 h sample in Fig. 2a. The number gap between each major peak is exactly the molecular weight of BDA, which indicates that the molecular weight increases by 1 monomer unit and the vinyl groups of the divinyl monomer are mainly consumed on one side instead of on both sides at the beginning period.