Norbornadiene End-Capping of Cross-Coupling Polymerizations: A Facile Route to Triblock Polymers

The potential use of conjugated polymers in device applications is often limited by their less than optimal physicochemical properties. This work describes an efficient protocol to end-cap conjugated polymers synthesized via palladium-catalyzed cross-coupling polymerizations with norbornene groups. Specifically, the hydroarylation of norbornadiene is shown to be a high-yielding end-capping method. These strained bicyclic alkenyl end groups can be transformed into macroinitiators via ring-opening metathesis polymerization and can polymerize other strained monomers, such as norbornene, yielding elastomeric triblock copolymers

Determination of the Energy Band Gap Depending on the Oxidized Structures of Quantum Dots

Theoretical and experimental studies on the changes of the optical properties of CdSe/CdS/ZnS (core/double-shell) quantum dots (QDs) during the oxidation process were first performed. An effective medium approach using the modified Khon–Sham equation presents a new method to predict the effects of the oxidation and to determine the oxidized ratio of nanoscale materials by a quantitative comparison with the experimental photoluminescence (PL) changes. As the oxidation progressed from the CdSe/CdS/ZnS nanocrystal surface, the PL peak shifted to longer wavelength and the quantum efficiency (QE) continuously decreased. It was also found that such changes were accelerated when the thickness of the outermost ZnS shell became thinner than a monolayer. The radial wave functions showed that the electron carriers rapidly extended into the shell region while the hole carriers spread very little into the core region. This indicates that the electrons are the key carriers to induce the changes in the energy band gap and the QE