chemical and physical properties, including high mechanical strength, flexi bility, and unique optical and electrical properties. [1,2] The flexibility and stretch ability of carbon nanotubes, combined with their potential for comparable elec trical performance to traditional rigid materials (such as polysilicon and metal oxides) makes them particularly attractive for applications in wearable electronics, prosthetics, and flexible and printed elec tronics. [3] Their capacity for high charge carrier mobilities, [4] combined with solu tion processability, has resulted in the incorporation of SWNTs into photovol taics, [5] field effect transistors, [6] chem ical and biological sensors, [7][8][9] logic circuits, [10,11] and infrared photodetectors for telecommunications. [12] The structural polydispersity of as synthesized SWNTs, both in atomic struc ture and length, remains a major issue hindering widespread applications of these materials into electronics devices. [13] While some synthetic control over the diameter distribution can be achieved, all common techniques produce a dis tribution of chiralities and a mixture of both metallic and semiconducting nano tubes. [14] These mixtures are normally comprised of a ratio of ≈2:1 semiconducting SWNTs (scSWNTs) to metallic SWNTs (mSWNTs), in addition to the retention of impurities such as catalyst particles and amorphous carbon. This disparity in terms of electrical properties is not suitable for organic elec tronic devices, as mSWNTs can act as percolating or directly bridging paths that electrically short SWNT transistors, making the isolation of pure scSWNTs from a raw mixture of the utmost importance. [15] Additionally, SWNTs have poor solu bility and require the introduction of ancillary dispersants to properly exfoliate tube bundles to allow for the fabrication of uniform networks.Significant progress in the dispersion and separation of SWNTs according to electronic character, [16] chirality, [17] diameter, [18] or length [19] has been made over the past two decades. Density gradient ultracentrifugation, [20] gel chromatography, [21] DNA wrapping combined with ion The realization of organic thin film transistors (OTFTs) with performances that support low-cost and large-area fabrication remains an important and challenging topic of investigation. The unique electrical properties of singlewalled carbon nanotubes (SWNTs) make them promising building blocks for next generation electronic devices. Significant advances in the enrichment of semiconducting SWNTs, particularly via π-conjugated polymers for purification and dispersal, have allowed the preparation of high-performance OTFTs on a small scale. The intimate interaction of the conjugated polymer with both SWNTs and the dielectric necessitates the investigation of a variety of conjugated polymer derivatives for device optimization. Here, the preparation of polymer-SWNT composites containing carbazole moieties, a monomer unit that has remained relatively overlooked for the dispersal of large-diameter semiconducting...

What is the most significant result of this study? Post-polymerization methylation of pyridine units within ac onju-gated polymer enabled aswitch in polymer electronics from an initial electron-rich structure to af inal electron-deficient one, without changing polymer length or appreciably affecting polymer confor-mation. The interactions of the nonmethylated (electron-rich) and methylated (electron-deficient) polymers with single-walled carbon nanotubes (SWNTs) were found to be significantly different,t hat is, the electron-rich polymer exclusively dispersed semiconducting SWNTs, while the electron-deficient counterpart exhibited am uch greater tendency to disperse metallic SWNTs. We have, therefore, uncovered ar ational approach for the design of conjugated polymers that enables selective dispersion of carbon nanotubes of aspecific electronic nature. What aspects of this project do you find most exciting? For me, the exciting part of this project is that it uncovers new design principles for imparting selectivity to the polymer-nano-tube interaction. This indicates that certain types of polymers are preferentially attracted to specific carbon nanotubes, based on electron rich/poor characteristics. This allows us to investigate al arge variety of other polymer types, with increasing differences in their electron-rich or-poor character,t oc ontinually improve the degree of selectivity that we have observed in this work. This involves challenges in polymer design, synthesis, characterization, and application. The project also represents as tarting point along ap ath that will ultimately lead to ab etter understanding of the supramolecular polymer-nanotube interaction. What other topics are you working on at the moment? Apart from our work on selective interactions between conjugated polymers and carbon nanotubes, we are investigating an umber of topics involving controlled polymer architectures. We are interested in ways to generate libraries of different conjugated polymers, without changing their average length, through efficient post-poly-merization chemistry.T his not only allows systematic investigation of polymer-nanotube interactions, but also enables the development of new,f unctional polymer structures for applications in ther-apeutics and biosensing. We are also interested in new dendrimer structures for diagnostic imaging, and easily crosslinkable polymers for hydrogel synthesis. Invited for the cover of this issue is the group of Alex Adronov at McMaster University.T he image depicts as tylized view of am etallicc arbon nanotube that is being pulled intos olution, and is related to the findingst hat the electronic nature of ac onjugated polymer has an impact on its selectivity for metallicv ersuss emiconducting single-walled carbon nanotubes, allowingtheir selectivedissolution. Read the full text of the article at

Ultrapure semiconducting single-walled carbon nanotube (sc-SWNT) dispersions produced through conjugated polymer sorting are ideal candidates for the fabrication of solution-processed organic electronic devices on a commercial scale. Protocols for sorting and dispersing ultrapure sc-SWNTs with conjugated polymers for thin-film transistor (TFT) applications have been well refined. Conventional wisdom dictates that removal of excess unbound polymer through filtration or centrifugation is necessary to produce high-performance TFTs. However, this is time-consuming, wasteful, and resource-intensive. In this report, we challenge this paradigm and demonstrate that excess unbound polymer during semiconductor film fabrication is not necessarily detrimental to device performance. Over 1200 TFT devices were fabricated from 30 unique polymer-sorted SWNT dispersions, prepared using two different alternating copolymers. Detailed Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) studies of the random-network semiconductor films demonstrated that a simple solvent rinse during TFT fabrication was sufficient to remove unbound polymer from the sc-SWNT films, thus eliminating laborious polymer removal before TFT fabrication. Furthermore, below a threshold polymer concentration, the presence of excess polymer during fabrication did not significantly impede TFT performance. Preeminent performance was achieved for devices prepared from native polymer-sorted SWNT dispersions containing the “original” amount of excess unbound polymer (immediately following enrichment). Lastly, we developed an open-source Machine Learning algorithm to quantitatively analyze AFM images of SWNT films for surface coverage, number of tubes, and tube alignment.

The emergence of 3D bioprinting has allowed a variety of hydrogel-based “bioinks” to be printed in the presence of cells to create precisely defined cell-loaded 3D scaffolds in a single step for advancing tissue engineering and/or regenerative medicine. While existing bioinks based primarily on ionic cross-linking, photo-cross-linking, or thermogelation have significantly advanced the field, they offer technical limitations in terms of the mechanics, degradation rates, and the cell viabilities achievable with the printed scaffolds, particularly in terms of aiming to match the wide range of mechanics and cellular microenvironments. Click chemistry offers an appealing solution to this challenge given that proper selection of the chemistry can enable precise tuning of both the gelation rate and the degradation rate, both key to successful tissue regeneration; simultaneously, the often bio-orthogonal nature of click chemistry is beneficial to maintain high cell viabilities within the scaffolds. However, to date, relatively few examples of 3D-printed click chemistry hydrogels have been reported, mostly due to the technical challenges of controlling mixing during the printing process to generate high-fidelity prints without clogging the printer. This review aims to showcase existing cross-linking modalities, characterize the advantages and disadvantages of different click chemistries reported, highlight current examples of click chemistry hydrogel bioinks, and discuss the design of mixing strategies to enable effective 3D extrusion bioprinting of click hydrogels.

What is the most significant result of this study?Post-polymerization methylation of pyridine units within ac onjugated polymer enabled aswitch in polymer electronics from an initial electron-rich structure to af inal electron-deficient one, without changing polymer length or appreciably affecting polymer conformation. The interactions of the nonmethylated (electron-rich) and methylated (electron-deficient) polymers with single-walled carbon nanotubes (SWNTs) were found to be significantly different,t hat is, the electron-rich polymer exclusively dispersed semiconducting SWNTs, while the electron-deficient counterpart exhibited am uch greater tendency to disperse metallic SWNTs. We have, therefore, uncovered ar ational approach for the design of conjugated polymers that enables selective dispersion of carbon nanotubes of aspecific electronic nature. What aspects of this project do you find most exciting?For me, the exciting part of this project is that it uncovers new design principles for imparting selectivity to the polymer-nanotube interaction. This indicates that certain types of polymers are preferentially attracted to specific carbon nanotubes, based on electron rich/poor characteristics. This allows us to investigate al arge variety of other polymer types, with increasing differences in their electron-rich or -poor character,t oc ontinually improve the degree of selectivity that we have observed in this work. This involves challenges in polymer design, synthesis, characterization, and application. The project also represents as tarting point along ap ath that will ultimately lead to ab etter understanding of the supramolecular polymer-nanotube interaction.What other topics are you working on at the moment?Apart from our work on selective interactions between conjugated polymers and carbon nanotubes, we are investigating an umber of topics involving controlled polymer architectures. We are interested in ways to generate libraries of different conjugated polymers, without changing their average length, through efficient post-polymerization chemistry.T his not only allows systematic investigation of polymer-nanotube interactions, but also enables the development of new,f unctional polymer structures for applications in therapeutics and biosensing. We are also interested in new dendrimer structures for diagnostic imaging, and easily crosslinkable polymers for hydrogel synthesis.Invited for the cover of this issue is the group of Alex Adronov at McMaster University.T he image depicts as tylized view of am etallicc arbon nanotube that is being pulled intos olution, and is related to the findingst hat the electronic nature of ac onjugated polymer has an impact on its selectivity for metallicv ersuss emiconducting single-walled carbon nanotubes, allowingtheir selectivedissolution. Read the full text of the article at

The large-scale enrichment of metallic carbon nanotubes is a challenging goal that has proven elusive. Selective dispersion of carbon nanotubes by specifically designed conjugated polymers is effective for isolating semiconducting species, but a comparable system does not exist for isolating metallic species. Here, we report a two-polymer system where semiconducting species are extracted from the raw HiPCO or plasma-torch nanotube starting material using an electron-rich poly(fluorene- co -carbazole) derivative, followed by isolation of the metallic species remaining in the residue using an electron-poor methylated poly(fluorene- co -pyridine) polymer. Characterization of the electronic nature of extracted samples was carried out via a combination of absorption, Raman, and fluorescence spectroscopy, as well as electrical conductivity measurements. Using this methodology, the metallic species in the sample were enriched 2-fold in comparison to the raw starting material. These results indicate that the use of electron-poor polymers is an effective strategy for the enrichment of metallic species.

In article number https://doi.org/10.1002/aelm.201800539, Nicole A. Rice, Alex Adronov, Benoît Lessard, and co‐workers report a novel poly(carbazole‐co‐fluorene) conjugated polymer capable of producing highly enriched semiconducting single‐walled carbon nanotube (SWNT) composites. Organic thin film transistors prepared from this composite demonstrate superior mobility and on/off ratios compared to devices prepared from a commercially available polymer–SWNT dispersion. Operational hysteresis is almost completely removed by simple surface treatment with octyltrichlorosilane before depositing polymer–SWNT material.

There is an increasing demand for low-cost and high-performance electronics which has stimulated a need for new high-performance dielectric materials. We have developed a facile synthesis of poly(2-(methacryloyloxy)ethyl trimethylammonium bis(trifluoromethylsulfonyl)azanide-ran-methyl methacrylate) (P(METATFSI-MMA)), a polymeric ionic liquid that can be used as a high-performance dielectric for semiconducting single walled carbon nanotube (SWCNTs) thin film transistors (TFTs). The P(METATFSI-MMA) polymer was synthesized at both 35 and 62 mol% of 2-(methacryloyloxy)ethyl trimethylammonium bis(trifluoromethylsulfonyl)azanide and produced p- and n-type devices that functioned under ambient conditions. These TFTs were then used to study the impact of electrochemical doping on the performance of SWCNT TFTs when switching from n-type, where an electrical double layer is formed, to p-type, where the TFSI- anions are free to interact with the SWCNTs. The TFTs operating in p-type had higher current on/off ratios and a larger transconductance than those operating in n-type, which is characteristic of electrochemically doped transistors. Furthermore, we tested the impact of operating frequency on device performance and discovered that decreasing the operating frequency of the TFTs resulted in a decreased hysteresis. The decrease in hysteresis was also observed to be more significant for the 35 mol% polymer.