The development of processing methods to precisely control the solution state properties of semiconducting polymers in situ have remained elusive. Herein, a facile solution seed nucleation processing method is presented in which nucleated poly(3-hexylthiophene) (P3HT) solutions are blended with well-solvated, non-nucleated counterparts as a means to promote the formation of interconnected polymer networks. Nucleation and growth of these networks was induced by preprocessing the solution with UV irradiation and subsequent solution aging prior to deposition via blade-coating. This process was adopted for both batch and continuous flow processing. Superior charge carrier (hole) mobilities were observed in samples with nucleated seeds compared to controls with 0% nucleated P3HT and 100% nucleated P3HT. UV–vis spectral analysis identified that an intermediate degree of solution aggregation (15–20%) is most conducive to enhanced charge transport. The role of intrachain and interchain ordering and alignment on the mesoscale and macroscale is characterized via X-ray scattering, atomic force microscopy, and optical microscopy techniques. The results presented here provide a framework to enable in situ control of the nucleation and growth process to achieve targeted solution state properties resulting in reliable and reproducible performance when the solutions are used for device fabrication.
The rheology of emulsions dictates their performance in many scientific and industrial applications. Here, we demonstrate that high-molecular-weight telechelic triblock copolymers composed of polystyrene end blocks with a poly(ethylene oxide) midblock effectively modify the rheology of a suspension of cyclohexane nanodroplets. Because of their telechelic structure, these polymers bridge between droplets to generate elastic networks with shear moduli on the order of 1000 Pa. The network elasticity increases with polymer concentration and molecular weight as the polymers more effectively form bridges. Furthermore, we tune the nanoscale interactions that control the polymer partitioning by decreasing the temperature below the cloud point of the system. At low temperatures, the polystyrene end blocks no longer preferentially partition into the cyclohexane droplets, and the emulsions begin to exhibit terminal viscous relaxations. These results identify key properties of telechelic block copolymers that can be exploited to significantly enhance nanoemulsion elasticity to improve the processability and transport of complex fluids in applications ranging from 3D printing to functional hydrogels.
Atomically thin MoS 2 nanosheets are of interest due to unique electronic, optical, and catalytic properties that are absent in the bulk material. Methods to prepare nanosheets from bulk material that facilitate studies of 2D-MoS 2 and the fabrication of useful devices have consequently assumed considerable importance. Here, we report the simultaneous exfoliation and stable dispersion of MoS 2 nanosheets in a liquid crystal. Exfoliation of bulk MoS 2 in mesogen-containing solutions produced stable dispersions of 2D-MoS 2 that retained suspension stability for several weeks. Solvent removal in cast films yielded nanocomposites of 2D-MoS 2 . Preservation of single-and few-sheet MoS 2 was confirmed utilizing UV−vis and Raman spectroscopy in the nematic and isotropic fluid states of the system and, remarkably, in the solid crystal as well. Importantly, the MoS 2 nanosheets remained welldispersed upon polymerization of the reactive mesogen to form a liquid crystal polymer. The ability to stably disperse 2D-MoS 2 in a structured fluid opens up new possibilities for studying anisotropic properties of MoS 2 and for exploiting such properties in responsive materials.
Soft materials possessing tunable rheological properties are desirable in applications ranging from 3D printing to biological scaffolds. Here, we use a telechelic, triblock copolymer polystyrene-b-poly(ethylene oxide)-b-polystyrene (SEOS) to form elastic networks of polymer-linked droplets in cyclohexane-in-water emulsions. The SEOS endblocks partition into the dispersed cyclohexane droplets while the midblocks remain in the aqueous continuous phase, resulting in each chain taking on either a looping or bridging conformation. By controlling the fraction of chains that form bridges, we tune the linear elasticity of the emulsions and generate a finite yield stress. Polymers with higher molecular weight (M w) endblocks form stronger interdroplet connections and display a higher bridging density. Beyond modifying the linear rheology, the telechelic, triblock copolymers also alter the yielding behavior and processability of the linked emulsions. We examine the yield transition of these polymer-linked emulsions through large amplitude oscillatory shear (LAOS) and probe the emulsion structure through confocal microscopy, concluding that polymers that more readily form bridges generate a strongly percolated network, whereas those that are less prone to form bridges tend to produce networks composed of weakly linked clusters of droplets. When yielded, the emulsions consisting of linked clusters break apart into individual clusters that can rearrange upon the application of further shear. By contrast, when the systems containing a more homogeneous bridging density are yielded, the system remains percolated but with reduced elasticity and bridging density. The demonstrated ability of telechelic triblock copolymers to tune not only the linear viscoelasticity of complex fluids but also their nonlinear yield transition enables the use of these polymers as versatile and robust rheological modifiers. We expect our findings to therefore aid the design of the next generation of complex fluids and soft materials.
Many have extolled the virtues of the data age and encouraged the proliferation of data; from social media on mobile phones to direct sensor integration into distributed BLOB databases. Despite this ubiquity, ecologists typically collect data manually, with a note pad and pen, and this can lead to an array of practical complications; note pads get wet, lost, or damaged, writing is illegible, or spelling is incorrect. Should the notepad survive, the manual data must be transcribed, and is often then isolated in a project-specific dataset. Thanks to the open science movement, there is growing proliferation of environmental data, however project-level regional and sub-regional data remains fragmented, and is frequently un-verified, and asynchronous. Modern digital collection techniques such as UAV, IoT sensors, remote cameras, eDNA, and acoustic sensors, are assisting in mitigating the real-time issue and limited spatial scope of ecological and environmental data collection deployment at scale. These digital techniques can record huge volumes of data in a distributed way and allow the collection of nearreal time data across an entire region using various competitive agents. Despite these capacities however, this form of data is typically unstructured (collected by multiple parties, in multiple ways), isolated, and remains at the project level. For ecological and environmental data to be relevant and used to inform management decisions, it needs to have the following properties: validity, volume, velocity, variety, veracity, value, distribution, and be in near real-time. Blockchain represents a valuable opportunity in this space. With collaborators, we are developing a consolidated, tamper proof, generator-owned, data repository, which uses micropayments as an incentive-based system for collection, verification, indexing, and dissemination. This system provides micropayment access to volumes (or snippets) of high-quality data, which is verified, indexed and instantly auditable. It is proposed that this self-serve model of a data service will allow local, regional, and continental based environmental and ecological modelling and monitoring to proliferate beyond previous limitations and effectively address pressing global issues such as language, cultural, and biodiversity loss.Biography. Daniel Keane is a tropical ecologist, born and raised in the Wet Tropics region of Queensland, Australia. He is the co-founder and managing director of Predict Ecology, an environmental and ecological consulting firm with a focus on rigorous science, real-world data, and predictive modelling. During his career, Daniel has been involved with a variety of projects ranging from environmental surveys, mine closure and rehabilitation, tropical ecosystem restoration and conservation, and environmental modelling. Working in the resources, mining, and infrastructure sectors, he has unique insights into multi-discipline environmental management and sustainable development planning. Living in the Wet Tropics Area, Daniel developed appreciation ...
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