Synthesis and solid-state polymerization of a methylene-chain-modified butadiyne derivative

5,7-Dodecadiyn-1,12-diyl bis[N-(butoxycarbonylmethyl)carbamate] abbreviated as 4BCMU is one of the typical monomers for solid-state polymerization to form polydiacetylene. In this study, we modified 4BCMU by substituting methylene groups to oxygen atoms. Namely, 3,10-dioxa-5,7-dodecadiyn-1,12-diyl bis[N-(butoxycarbonylmethyl)carbamate] (DO-4BCMU) was synthesized and the replacement effects on the monomer properties were investigated. In powder X-ray diffraction experiments, spacings for the layered structure in 4BCMU and DO-4BCMU crystals were found to be 2.74 nm and 3.56 nm, respectively, and large crystal structural difference was confirmed. The polymer absorption maxima of 4BCMU and DO-4BCMU were observed at 630 nm and 580 nm, respectively. Since conversions of these monomers were similar, butadiyne moieties are aligned in polymerizable stacks and the different spacings seemed to be caused by folding structure differences in substituents. We also prepared mixed crystals of 4BCMU and DO-4BCMU with mixing ratio of 3:7 by melt crystal growth. In this crystal, the layered-structure spacing was 2.31 nm, and their similar molecular structures may be responsive for mixed crystal formation with a new phase. However, it was strangely observed that absorption spectrum of the polymer from the mixed crystals corresponded to summation of the spectra of original polymers from 4BCMU and DO-4BCMU.