A triphenylene-based small molecule compatibiliser using incompatible pendent chains

Abstract

To demonstrate that incompatible pendent chains can be used as a strategy to control the morphology of blends of immiscible materials, we have developed a novel triphenylene-based amphiphile-like mesogen with hydrophobic (alkyl) chains and hydrophilic (2-(2-methoxyethoxy)ethoxy) pendent chains, named TP6Gall hereafter. TP6Gall is a room-temperature liquid crystal presenting a cubic phase with a clearing point of 30 °C. Blends of TP6Gall in various amounts with an equimolar mixture of the hydrophobic 2,3,6,7,10,11-hexahexyloxytriphenylene (TP6) and hydrophilic 2,3,6,7,10,11-hexa(2-(2-methoxyethoxy)ethoxy)triphenylene (TP6EO2M) have been studied by polarised optical microscopy (POM), differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). Without TP6Gall, the TP6 : TP6EO2M mixture exhibits large incompatible domains of pure TP6 and pure TP6EO2M. As the quantity of TP6Gall increases in the blend, the size of the domains decreases significantly. Ultimately, when the proportion of TP6Gall reaches 50 mol% of the blend, μm-featured interpenetrated networks of crystalline TP6EO2M and of TP6 mixed with TP6Gall are obtained. Interestingly, a single liquid phase is obtained above the clearing point of the blend. Furthermore, no macrophase separation is observed upon multiple temperature cycles between room-temperature and the temperature above the clearing point of the blend and the interpenetrated network is reliably reformed upon cooling.