Multivalent interactions, which rely upon noncovalent bonds, are essential ingredients in the mediation of biological processes, as well as in the construction of complex (super)structures for materials applications. A fundamental understanding of multivalency in supramolecular chemistry is necessary not only to construct motors and devices on the nanoscale but also to synthesize model systems to provide insight into how biological processes work. This Account focuses on the application of multivalency to supramolecular chemistry in particular and the nanosciences in general.

Most mono-and co-culture bioprocess applications rely on large-scale suspension fermentation technologies that are not easily portable, reusable, or suitable for on-demand production. Here, we describe a hydrogel system for harnessing the bioactivity of embedded microbes for on-demand small molecule and peptide production in microbial mono-culture and consortia. This platform bypasses the challenges of engineering a multi-organism consortia by utilizing a temperature-responsive, shear-thinning hydrogel to compartmentalize organisms into polymeric hydrogels that control the final consortium composition and dynamics without the need for synthetic control of mutualism. We demonstrate that these hydrogels provide protection from preservation techniques (including lyophilization) and can sustain metabolic function for over 1 year of repeated use. This approach was utilized for the production of four chemical compounds, a peptide antibiotic, and carbohydrate catabolism by using either mono-cultures or co-cultures. The printed microbe-laden hydrogel constructs' efficiency in repeated production phases, both pre-and post-preservation, outperforms liquid culture.

An improved two-step synthetic route to functionalized cyclic carbonate monomers that features a novel cyclic carbonate intermediate with an active pentafluorophenyl ester group (MTC-OPhF(5)) has been developed. The versatile pentafluorophenyl ester intermediate can be synthesized on the gram to kilogram scale in one high-yielding step and is easy to store and handle on the benchtop. The active pentafluorophenyl ester of MTC-OPhF(5) is amenable to further substitution with suitable nucleophiles such as alcohols and amines to generate functionalized cyclic carbonates in high yields. The substitution reaction is tolerant of a wide variety of functionalities, including various hydrophobic and hydrophilic groups, reactive functionalities (via thiol-ene click chemistry or alkyl halides), and protected acids, alcohols, thiols, and amines. In view of the ever-increasing need for biodegradable and biocompatible polymers, this new methodology provides a simple and versatile platform for the synthesis of new and innovative materials.

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We have prepared a series of cross-linkable oligo-and poly(dialkylfluorene)s by nickel(0)mediated polymerization of 2,7-dibromo-9,9-dialkylfluorene (alkyl ) n-hexyl) and 4-bromostyrene. The resulting fully soluble and processable, styryl-functionalized oligomers and polymers can be cross-linked via the vinyl end-groups by curing at 175-200 °C, consistent with the autopolymerization mechanism of styrene. These relatively mild conditions render the materials insoluble and enable multilayering of polymers in organic light emitting devices. At the same time, the electrical and/or optical properties of the cross-linked polymers are preserved and no deleterious species or undesirable byproducts are produced. Furthermore, the cross-linking allows control of the supramolecular ordering of the planarized rigid rodtype fluorene segments in the polymer backbone that leads to suppression of troublesome excimer/aggregate in the photo-and electrolumenescence.

Direct-write 3D printing enables the fabrication of three-dimensional objects via the extrusion from a nozzle. Stimuli responsive materials that shear-thin are well-suited as inks for these 3D printing systems. Poly­(isopropyl glycidyl ether)-block-poly­(ethylene oxide)-block-poly­(isopropyl glycidyl ether) ABA triblock copolymers were synthesized using controlled ring-opening polymerization to afford dual stimuli-responsive polymers that respond to both shear forces and temperature. These polymers were demonstrated to form hydrogels in water. The gels were observed to be thermoreversibledriven by the lower critical solution temperature of the poly­(isopropyl glycidyl ether) block which helps facilitate loading of the ink into the printer syringe. Rheological studies demonstrated that the gels had a rapid and reversible modulus response to shear stress. Thus, these materials were suitable as inks for direct-write 3D printing, as they were easily extruded during printing and maintained sufficient mechanical integrity which was necessary to support the next printed layer. Printed structures of high aspect ratio pillars and stacked layers were successfully demonstrated. These types of 3D hydrogel structures may ultimately have an impact in the biomedical field for applications such as tissue engineering.

We report a facile synthesis of monodisperse ferrimagnetic Co(x)Fe(3-x)O4 nanocubes (NCs) through thermal decomposition of Fe(acac)3 and Co(acac)2 (acac = acetylacetonate) in the presence of oleic acid and sodium oleate. The sizes of the NCs are tuned from 10 to 60 nm, and their composition is optimized at x = 0.6 to show strong ferrimagnetism with the 20 nm Co0.6Fe2.4O4 NCs showing a room temperature Hc of 1930 Oe. The ferrimagnetic NCs are self-assembled at the water-air interface into a large-area (in square centimeter) monolayer array with a high packing density and (100) texture. The 20 nm NC array can be recorded at linear densities ranging from 254 to 31 kfci (thousand flux changes per inch). The work demonstrates the great potential of solution-phase synthesis and self-assembly of magnetic array for magnetic recording applications.