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Yuman Li


Postgraduate Research Student

Academic and research departments

Department of Chemistry.

My publications

Publications

Noy Janina-Miriam, Li Yuman, Smolan Willi, Roth Peter J. (2019) The Azide?para-Fluoro Substitution on Polymers: Multi-purpose Precursors for Efficient Sequential Postpolymerization Modification,Macromolecules 52 (8) pp. 3083-3091 American Chemical Society
The 2,3,4,5,6-pentafluorobenzyl group has become a popular reactive functionality in polymer chemistry because of its high susceptibility to para-fluoro substitution with thiols. Herein, it is demonstrated postpolymerization that the para-fluoride can be substituted using sodium azide and that the resulting 4-azido-2,3,5,6-tetrafluorobenzyl-functional polymers are versatile precursors for a multitude of onward modifications with click-like efficiencies. Quantitative azide?para-fluoro substitution was found for poly(2,3,4,5,6-pentafluorobenzyl methacrylate) and the related Passerini ester?amide (meth)acrylic (co)polymers when heated in DMF with sodium azide to 80 °C for 60?90 min. Conversely, the azidation of poly(2,3,4,5,6-pentafluorostyrene) under similar conditions resulted in ~90% substitution efficiency. Azide-functional (co-)polymers were thermally stable below 100 °C and were subsequently modified with (i) four different alkynes (CuBr, triethylamine, DMF, 55 °C, overnight) to give 1,4-substituted 1,2,3-triazoles in >95% conversions; (ii) potassium thioacetate (DMF, RT, 15 min) with quantitative amidation to the acetanilide derivative; and (iii) DL-dithiothreitol (methanol/DMF, RT, 90 min) resulting in complete reduction of the azides to primary amines, which were subsequently acylated with two different acyl chlorides. Products were characterized by 1H NMR, 19F NMR, and FT-IR spectroscopies, and size exclusion chromatography. Given their adaptability, perfluorophenylazides have large potential as multi-purpose intermediates in polymer and materials chemistry.
Spick Matt, Bingham Nathaniel, Li Yuman, De Jesus Janella, Costa Catia, Bailey Melanie, Roth Peter (2020) Fully Degradable Thioester-functional Homo- and Alternating Copolymers Prepared through Thiocarbonyl Addition?Ring-opening RAFT Radical Polymerization,Macromolecules American Chemical Society
The radical ring-opening polymerization (RROP) of thionolactones provides access to thioester backbone-functional copolymers but has, to date, only been demonstrated on acrylic copolymers. Herein, the thionolactone dibenzo[c,e]oxepane-5-thione (DOT) was subjected to azobisisobutyronitrile (AIBN)-initiated free-radical homopolymerization, which produced a thioester-functional homopolymer with a glass-transition temperature of 95 °C and the ability to degrade exclusively into predetermined small molecules. However, the homopolymerization was impractically slow and precluded the introduction of functionality. Conversely, the reversible addition?fragmentation chain-transfer (RAFT)-mediated copolymerization of DOT with N-methylmaleimide (MeMI), N-phenylmaleimide (PhMI), and N-2,3,4,5,6-pentafluorophenylmaleimide (PFPMI) rapidly produced well-defined copolymers with the tendency to form alternating sequences increasing in the order MeMI j PhMI