RESUMO
Infinite layer (IL) nickelates provide a new route beyond copper oxides to address outstanding questions in the field of unconventional superconductivity. However, their synthesis poses considerable challenges, largely hindering experimental research on this new class of oxide superconductors. That synthesis is achieved in a two-step process that yields the most thermodynamically stable perovskite phase first, then the IL phase by topotactic reduction, the quality of the starting phase playing a crucial role. Here, a reliable synthesis of superconducting IL nickelate films is reported after successive topochemical reductions of a parent perovskite phase with nearly optimal stoichiometry. Careful analysis of the transport properties of the incompletely reduced films reveals an improvement in the strange metal behavior of their normal state resistivity over subsequent topochemical reductions, offering insight into the reduction process.
RESUMO
We propose a fast, reliable chromatographic method to determine the grafting yield of a Polybutadiene-graft-Polystyrene (PB-g-PS) copolymer synthesized in our laboratory for High Impact Polystyrene applications. We used Liquid Chromatography at Critical Conditions of PS to separate non-grafted PS from graft product and ungrafted PB. Separation between grafted copolymer and non-grafted PS was very efficient and thanks to linearity of UV-detector response, we could quantify the amount of grafted PS in the copolymer, as well as calculate the grafting yield. Results shown here are for DOW BR1202D high-cis PB and BASF CB529T low-cis PB, Luperox TBIC M75 initiator at 8 x 10(-4) mol L(-1) and 125 degrees C reaction temperature.
