Exploring polymer solubility with thermally-responsive Diels-Alder monomers: Revisiting the monkey's fist

Thermo-responsive monomers were designed to contain a Diels-Alder (DA) adduct such that cyclo-reversion would yield either the maleimide or the furan unit attached to the polymer chain. These thermally responsive monomers were then copolymerized with N-isopropylacrylamide (NIPAM) via reversible addition-fragmentation chain-transfer (RAFT) polymerization to yield linear gradient-copolymer structures as a comparison to existing nanogel/starlike systems to understand how polymer topology and composition influence solution-state properties. Using UV–Vis spectroscopy, it was determined that solution-state properties were thermally dependent and influenced by a number of variables such as comonomer feed ratio, polymer chain end functionality, and polymer backbone length and composition. Manipulation of the feed ratio allowed for control over the cloud point, including the breadth and location of phase separation. Thermal treatment of these copolymers revealed tunable and predictable variations in previously observed transitions, directly correlated to cleavage of the DA adducts and change in polymer backbone composition. Finally, on cooling cycles, a double sigmoid was sometimes observed, indicating a complex globule to random coil transition correlated to polymer chain end composition. These studies help understand how to untie the “monkey's fist.”     

Optical properties and dynamic process in metal ions doped on CdSe quantum dots sensitized solar cells

In recent years, the nanostructure for solar cells have attracted considerable attention from scientists as a result of a promising candidate for low cost devices. In this work, quantum dots sensitized solar cells with effective performance based on a co-sensitized Cd S∕Cd Se:Mn~(2+)(or Cu~(2+)) nanocrystal, which was made by successive ionic layer absorption and reaction, are discussed. The optical, physical, chemical, and photovoltaic properties of quantum dots sensitized solar cells were sensitized to Mn~(2+)and Cu~(2+)dopants. Therefore, the short current(JSC)of the quantum dot sensitized solar cells is boosted dramatically from 12.351 mA∕cm~2 for pure Cd Se nanoparticles to 18.990 mA∕cm~2 for Mn~(2+)ions and 19.915 mA∕cm~2 for Cu~(2+)ions. Actually, metal dopant extended the band gap of pure Cd Se nanoparticles, reduced recombination, enhanced the efficiency of devices, and improved the charge transfer and collection. In addition, Mn~(2+)and Cu~(2+)dopants rose to the level of the conduction band of pure Cd Se nanoparticles, which leads to the reduction of the charge recombination, enhances the lightharvesting efficiency, and improves the charge diffusion and collection. The results also were confirmed by the obtained experimental data of photoluminescence decay and electrochemical impedance spectroscopy.     

A sulfonated calix[4]resorcinarene with l-pipecolinic acid groups as a water-soluble chiral NMR solvating agent

A water-soluble calix[4]resorcinarene containing l-pipecolinic acid groups is investigated as a chiral NMR solvating agent for aromatic-containing substrates. The substrates form complexes by insertion of the aromatic ring into the cavity of calix[4]resorcinarene. Compounds with phenyl, naphthyl, indole, indoline and pyridyl rings were investigated. The substrates also have ammonium or carboxylate functional groups. The effectiveness of the calix[4]resorcinarene with l-pipecolinic acid groups is compared to similar reagents with proline, hydroxyproline, and α-methylproline moieties that have previously been reported. The derivative with l-pipecolinic acid usually produces better enantiomeric discrimination compared to previous calix[4]resorcinarene reagents.     

Continuous Selections,Collectively Fixed Points and Weak Knaster–Kuratowski–Mazurkiewicz Mappings in Optimization

We prove theorems on continuous selections, collectively fixed points, collectively coincidence points, weak Knaster–Kuratowski–Mazurkiewicz mappings and provide their applications in various optimization-related problems. Each of our theorems is demonstrated by using its preceding assertions. The results contain and improve a number of existing ones in the recent literature. They are shown to be also more advantageous in applications in optimization.     

Well-posedness of a parametric traffic network problem

We define kinds of approximate solutions of a traffic network problem and obtain relations to approximate solutions of the corresponding quasivariational inequality. Using these results we establish sufficient conditions for the Tikhonov well-posedness in the sense of Levitin–Polyak of our traffic network problem.