Browsing by Author "Liu, Yu"
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Item Reversible Electronic Patterning of a Dynamically Responsive Hydrogel Medium(Wiley, 2023-05-14) Yang, Chen; Liu, Yu; Wang, Manya; Hu, Hui; Zhao, Zhongtao; Deng, Hongbing; Payne, Gregory F.; Shi, XiaowenA dynamically responsive hydrogel medium is prepared from two self-assembling components, a polysaccharide (chitosan) and a surfactant (sodium dodecyl sulfate; SDS). It is shown that this medium can be patterned using an electrode “pen” to reconfigure supramolecular structure: cathodic writing induces neutral chitosan chains to form a crystalline network, while anodic writing generates cationic chitosan chains that electrostatically crosslink with anionic SDS micelles. Both supramolecular structures are re-configurable and each is stabilized by structure-induced shifts in chitosan's pKa, thus electronically written patterns can be erased, new patterns can be written, and patterns can be written in three dimensions. Further, it is shown that NaCl-induced morphological transitions of the SDS micelles allow patterns to be reversibly concealed or revealed. To demonstrate the versatility of this medium for information storage, a quick response (QR) code is electronically written and it is shown that this code can be recognized by a standard cellphone app. This QR code can be concealed by making the medium opaque (i.e., by obscuring the pattern) or by making the pattern evanescent (i.e., by making pattern invisible). Overall, this work demonstrates that a dynamically responsive medium composed of simple, safe and sustainable components can be reversibly patterned with spatial and quantitative control using top-down electronic inputs.Item Synthesis of Functionalized Diazoacetoacetates via Mukaiyama-type Condensations(2011) Liu, Yu; Doyle, Michael P; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Mukaiyama-type condensation reactions of 3-tert-butyldimethylsiloxy-2-diazo-3-butenoate and different electrophiles are effective methods for the synthesis of highly substituted diazoacetoacetates. With 0.5-3 mol% of Zn(OTf)2 as Lewis acid catalyst, Mukaiyama-Michael reactions of vinyldiazoacetates and &alpha,&beta-unsaturated ketones proceed at ambient temperature to afford functionalized diazoacetoacetates in good yields. By carefully choosing the reaction conditions, both Mukaiyama-Michael adducts in either silyl enol ether form or in ketone form can be synthesized. Addition products obtained from these Mukaiyama-Michael reactions are investigated in dirhodium(II) catalyst induced dinitrogen extrusion reactions. Enedione-diazoester derived from Mukaiyama-Michael reaction of 3-tert-butyldimethylsiloxy-2-diazo-3-butenoate and 4-methoxy-3-bute-2-one can be converted to resorcinol derivatives under base catalysis. This novel transformation was investigated and developed into a synthetic methodology for the preparation of poly-substituted resorcinol compounds. Orthoesters also react with 3-tert-butyldimethylsiloxy-2-diazo-3-butenoate in the presence of Lewis acid catalysts. Diazoacetoacetates that contain acetal functionality can be assembled by these reactions. Rhodium(II) acetate promoted dinitrogen extrusion reactions of these adducts can give &beta-alkoxycyclbutanone products, which are useful synthons in organic synthesis.