Copolymerization of Polythiophene and Sulfur To Improve the Electrochemical Performance in Lithium–Sulfur Batteries

We first report on the copolymerization of sulfur and allyl-terminated poly­(3-hexylthiophene-2,5-diyl) (P3HT) derived by Grignard metathesis polymerization. This copolymerization is enabled by the conversion of sulfur radicals formed by thermolytic cleavage of S₈ rings with allyl end-group. The formation of a C–S bond in the copolymer is characterized by a variety of methods, including NMR spectroscopy, size exclusion chromatography, and near-edge X-ray absorption fine spectroscopy. The <b>S-P3HT</b> copolymer is applied as an additive to sulfur as cathode material in lithium–sulfur batteries and compared to the use of a simple mixture of sulfur and P3HT, in which sulfur and P3HT were not covalently linked. While P3HT is incompatible with elementary sulfur, the new <b>S-P3HT</b> copolymer can be well dispersed in sulfur, at least on the sub-micrometer level. Sulfur batteries containing the <b>S-P3HT</b> copolymer exhibit an enhanced battery performance with respect to the cycling performance at 0.5C (799 mAh g^–1 after 100 cycles for <b>S-P3HT</b> copolymer versus only 544 mAh g^–1 for the simple mixture) and the C-rate performance. This is attributed to the attractive interaction between polysulfides and P3HT hindering the dissolution of polysulfides and the charge transfer (proven by electrochemical impedance spectroscopy) due to the homogeneous incorporation of P3HT into sulfur by covalently linking sulfur and P3HT

Functionalization of P3HT with Various Mono- and Multidentate Anchor Groups

<div><p>Due to its favorable optoelectronic properties and the accessibility via Grignard metathesis (GRIM) polymerization, poly(3-hexylthiophene) (P3HT) is one of the most applied conjugated polymers. The ‘living' nature of GRIM polymerization enables the modification of the polymer and the installation of desired properties. In the present study, two versatile approaches for the synthesis of anchor group-modified P3HT have been developed, which enable the functionalization of various inorganic nanoparticles. Depending on the polymerization conditions, mono- and bifunctional ethynyl-terminated P3HT or solely monofunctionalized aldehyde-terminated P3HT was synthesized. Afterwards, the quantitative introduction of amine, mono- and multidentate disulfide and catechol anchor groups was performed by copper-catalyzed 1,3-dipolar cycloaddition or via imine formation reactions. The influence of the polymeric ligand structure on the functionalization of nanoparticles was then investigated for CdSe@ZnS quantum dots and TiO2 nanorods by transmission electron microscopy (TEM) and infrared (IR) spectroscopy.</p></div

Light-Mediated Atom Transfer Radical Polymerization of Semi-Fluorinated (Meth)acrylates: Facile Access to Functional Materials

A highly efficient photomediated atom transfer radical polymerization protocol is reported for semi-fluorinated acrylates and methacrylates. Use of the commercially available solvent, 2-trifluoromethyl-2-propanol, optimally balances monomer, polymer, and catalyst solubility while eliminating transesterification as a detrimental side reaction. In the presence of UV irradiation and ppm concentrations of copper­(II) bromide and Me₆-TREN (TREN = tris­(2-aminoethyl amine)), semi-fluorinated monomers with side chains containing between three and 21 fluorine atoms readily polymerize under controlled conditions. The resulting polymers exhibit narrow molar mass distributions (<i><i>Đ</i></i> ≈ 1.1) and high end group fidelity, even at conversions greater than 95%. This level of control permits the <i>in situ</i> generation of chain-end functional homopolymers and diblock copolymers, providing facile access to semi-fluorinated macromolecules using a single methodology with unprecedented monomer scope. The results disclosed herein should create opportunities across a variety of fields that exploit fluorine-containing polymers for tailored bulk, interfacial, and solution properties

Controlled Formation and Binding Selectivity of Discrete Oligo(methyl methacrylate) Stereocomplexes

The triple-helix stereocomplex of poly­(methyl methacrylate) (PMMA) is a unique example of a multistranded synthetic helix that has significant utility and promise in materials science and nanotechnology. To gain a fundamental understanding of the underlying assembly process, discrete stereoregular oligomer libraries were prepared by combining stereospecific polymerization techniques with automated flash chromatography purification. Stereocomplex assembly of these discrete building blocks enabled the identification of (1) the minimum degree of polymerization required for the stereocomplex formation and (2) the dependence of the helix crystallization mode on the length of assembling precursors. More significantly, our experiments resolved binding selectivity between helical strands with similar molecular weights. This presents new opportunities for the development of next-generation polymeric materials based on a triple-helix motif