Polydiacetylene photocomposite material obtained by orthogonal chemistry: a detailed study at the mesoscopic scale

Abstract

A recent paper reported the spatially controlled photopolymerization and subsequent 3D printing of polydiacetylene (PDA) by orthogonal chemistry using dual-wavelength polymerization. Diacetylene monomers were dispersed in an acrylate resin to form a photocomposite in a two-step process: a first irradiation photopolymerizes the acrylate freezing the diacetylene monomers which were polymerized in a second step at a different wavelength. In the present article, for a better understanding of the organization of the generated functional composites, this process is studied at the mesoscopic scale by performing optical and scanning electron microscopy combined with correlative Raman, AFM and cathodoluminescence measurements. We have diluted the PCDA/acrylate blend in dichloromethane (CH₂Cl₂) and performed drop casting deposition on graphite. We discovered that the acrylate-diacetylene mixture promotes dramatically the formation of large PDA crystals. The confinement of PDA crystals inside the polyacrylate hindered their thermochromic blue-to-red transition, as revealed by correlative Raman microscopy. Cathodoluminescence measurements on the photocomposite have also shown that the light emission properties of PDAs are strongly modified by the induced confinement.