Polymerization mechanisms of the polydiacetylene DCHD

What is it about?

In this work, we studied the role of bonding and nonbonding atomic interactions in the topochemically controlled solid-state polymerization and assembly of the polymer DCHD (1,6-di(N-carbazolyl)-2,4- hexadiyne). For this we carried out a high brilliance SPring-8 (Hyogo, Japan) synchrotron X-ray study of DCHD monomer and polymer crystals in the temperature range from 20 to 420 K. Since topochemical polymerization is interplay of the monomer and polymer lattices, a comparative analysis of the both monoclinic structures allows us to uncover important insights into the structural machinery controlling formation and stability of polymer DCHD.

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Why is it important?

For advance details, we examined the structures on a charge density level using Maximum Entropy Method (MEM) upgraded to determine the electrostatic potential, electric field and atomic polarization in structure [1], [2]. The MEM maps based on highly reliable polyDCHD x-ray data viewed the hydrogen bond as electron density path bridging acceptor-donor atoms, linkage of electrostatic potential contour and flux of electric field vector from donor to acceptor sites. They allow us to reveal that polyDCHD assembled by networks of unconventional Η−bonds, C−H∙∙∙π(C≡C) between sidechain C−H and π-electron clouds of the triple bond segment of nearby backbone in layer and C−H∙∙∙π amongst the interlayer carbazolyl rings packed in a herringbone motif.

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