Conducting polymer networks synthesized by photopolymerization-induced phase separation

Abstract

Polymer mixtures composed of double networks of a polystyrene derivative (PSAF) and poly(methyl methacrylate) (PMMA) were alternatively synthesized by using ultraviolet (UV) and visible (Vis) light. The PSAF networks were generated by UV irradiation to photodimerize the anthracene (A) moieties labeled on the PSAF chains, whereas PMMA networks were produced by photopolymerization of methyl methacrylate (MMA) monomer and the cross-link reaction using ethylene glycol dimethacrylate (EGDMA) under Vis light irradiation. It was found that phase separation process of these networks can be independently induced and promptly controlled by using UV and Vis light. The characteristic length scale distribution of the resulting co-continuous morphology can be well regulated by the UV and Vis light intensity. In order to confirm and utilize the connectivity of the bicontinuous morphology observed by confocal microscopy, a very small amount, 0.1 wt%, of multi-walled carbon nanotubes (MWCNTs) was introduced into the mixture and the current–voltage (I–V) relationship was subsequently examined. Preliminary data show that MWCNTs are preferentially dispersed in the PSAF-rich continuous domains and the whole mixture became electrically conducting, confirming the connectivity of the observed bi-continuous morphology. The experimental data obtained in this study reveal a promising method to design various scaffolds for conducting soft matter taking advantages of photopolymerization-induced phase separation.

From Unregulated Networks to Designed Microstructures: Introducing Heterogeneity at Different Length Scales in Photopolymers for Additive Manufacturing

“…Apart from the significant effect of improved toughening on usability in different industries (aerospace, automotive, medicine, etc. ), heterogenization enables tailoring specific photopolymer characteristics, including optical 251 and electrical properties, 309 data storage, 310 electromagnetic absorption, 311 and shape memory. 115,312 This further emphasizes the importance of heterogenization in jewelry and decoration, dentistry, electronics, and robotics applications.…”

Increasing Ductility and Toughness of Photocurable Thermosets with Microstructures Controlled by Phase Separation

“…Various techniques have been developed to create heterogeneous polymeric materials including polymer blends, − block copolymer self-assembly, − the addition of elastomeric particles and of nanoparticles, − and polymerization-induced phase separation (PIPS). ,,− All of these methods have their own advantages and disadvantages, such as the cost and strict processing conditions. However, among them, PIPS offers unique opportunities such as the development of various microstructures, including droplet-like or interpenetrating subdomains, obtained by a simple variation of the chemical composition and/or light intensity used for photopolymerization.…”

“…PIPS begins with an initially homogeneous liquid photocurable mixture consisting of monomers, which polymerize into a thermosetting network, and a phase-separating agent, which phase-separates upon polymerization. ,,,− This process can be initiated through several reactive pathways such as anionic, cationic, thermal, or radical-light-initiated polymerization (photo-PIPS). Among these polymerization processes, photo-PIPS was selected for this work due to the ease of controlling the polymerization kinetics.…”