Dynamic transmission electron microscopy of the [1,6-di(N-carbazolyl)-2,4-hexadiyue] diacetylene monomer-polymer phase transformation

The monomer-polymer transformation has been directly imaged in [1,6-di(N-carbazoly1-2-4-hexadiyne] diacetylene crystals by low-dose dynamic transmission electron microscopy. The crystallography of the phase transition has been studied by dynamic selected-area electron diffraction. The polymerizatibn was found to be quasihomogeneous, with the lattice parameters changing continuously through a series of crystalline intermediate states. The solid-state reaction was found to be analogous to a martensitic phase transition with three invariant planes: (001), (220), and (220). The transformation matrix Tmp relating the monomer and polymer crystal reciprocal lattices was determined. Diffraction streaks developed along directions normal to the (200) and (220) planes during the phase transformation. These streaks fade away at the end of the polymerization. The microstructural evolution during the polymerization reaction was also examined by dynamic dark-field and high-resolution electron microscopy.