(284h) Engineering Polymer-Nanoparticle Systems Towards Sustainable Devices and Sensors

The future of organic electronics relies not only on the synthesis of new, high-performing polymers but also on engineering systems where the polymer structure and interactions can be controlled. Furthermore, there has been a push to incorporate renewable materials into device architectures for improved sustainability and recyclability. Here, we discuss efforts to utilize rodlike, bio-derived particles called cellulose nanocrystals (CNCs) and their liquid crystal phases in the design of polymer systems for device and sensor applications.

First, CNCs were used to induce long-range order in a semiconducting polymer, poly[3-(potassium-4-butanoate) thiophene-2,5-diyl] (PPBT). When mixed with CNCs, PPBT was incorporated into the liquid crystal “template” to form ordered structures. The π−π interactions between polymer chains, which contribute considerably to the energetics of the semiconducting system, were directly influenced by the presence and packing of the liquid crystal phase. The results of this study led to exploring a temperature “switchable” liquid crystal system. The thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM) was grafted from the surface of CNCs via surface-initiated atom transfer radical polymerization (SI-ATRP). These PNIPAM-modified particles formed a liquid crystal phase at room temperature but when brought above the lower critical solution temperature of PNIPAM (~32°C), the sample became dark under crossed polarizers and the liquid crystal was switched “off”. This “switchable” liquid crystal system could provide a basis for a sustainable sensor in smart packaging or other applications that require a response to temperature.