Living anionic polymerization using a microfluidic reactor.

Living anionic polymerizations were conducted within aluminum-polyimide microfluidic devices. Polymerizations of styrene in cyclohexane were carried out at various conditions, including elevated temperature (60 degrees C) and high monomer concentration (42%, by volume). The reactions were safely maintained at a controlled temperature at all points in the reactor. Conducting these reactions in a batch reactor results in uncontrolled heat generation with potentially dangerous rises in pressure. Moreover, the microfluidic nature of these devices allows for flexible 2D designing of the flow channel. Four flow designs were examined (straight, periodically pinched, obtuse zigzag, and acute zigzag channels). The ability to use the channel pattern to increase the level of mixing throughout the reactor was evaluated. When moderately high molecular mass polymers with increased viscosity were made, the patterned channels produced polymers with narrower PDI, indicating that passive mixing arising from the channel design is improving the reaction conditions.

A microfluidic platform for integrated synthesis and dynamic light scattering measurement of block copolymer micelles.

Microfluidic devices were developed that integrate the synthesis of well defined block copolymers and dynamic light scattering (DLS) measurement of their micelle formation. These metal devices were designed to operate in contact with organic solvents and elevated temperatures for long periods, and thus were capable of continuous in-channel atom transfer radical polymerization (ATRP) of styrene and (meth)acrylate homopolymers and block copolymers. These devices were equipped with a miniaturized fiber optic DLS probe that included several technology improvements, including a measurement volume of only 4 microlitres, simple alignment, and reduced multiple scattering. To demonstrate the integrated measurement, poly(methyl methacrylate-b-lauryl methacrylate) and poly(methyl methacrylate-b-octadecyl methacrylate) block copolymers were processed on the device with a selective solvent, dodecane, to induce micelle formation. The in situ DLS measurements yielded the size and aggregation behavior of the micelles. For example, the block copolymer solutions formed discrete micelles (D(H) approximately = 25 nm) when the corona block was sufficiently long (f(MMA) < 0.51), but the micelles aggregated when this block was short. This study demonstrates the utility of these new devices for screening the solution behavior of custom synthesized polymeric surfactants and additives.

Hybrid System of an Optical Nanofibre and a Single Quantum Dot Operated at Cryogenic Temperatures.

Recent progress in quantum nanophotonics brings novel ways for manipulating single photons in various nano-waveguides. Among them, one promising approach is to use optical nanofibres (ONFs), tapered optical fibres with sub-wavelength diameter waists. Here, we develop a hybrid system of an ONF and a single quantum dot (QD) operated at cryogenic temperatures. We deposit a single colloidal CdSe QD on an ONF waist and observe emitted photons through the fibre guided modes. We systematically investigate emission characteristics for both the neutral exciton and charged exciton (trion) for one specific QD. We quantitatively show that the trion at cryogenic temperatures acts as an excellent quantum emitter for the ONF and QD hybrid system. The present ONF/QD hybrid system at cryogenic temperatures paves the way for quantum information technologies for manipulating single photons in fibre networks.

Tailored synthesis of structurally defined polymers by organotellurium-mediated living radical polymerization (TERP): synthesis of poly(meth)acrylate derivatives and their di- and triblock copolymers.

The organotellurium-mediated living radical polymerization (TERP) method allows the synthesis of various polyacrylate and polymethacrylate derivatives with precise control of molecular weight and with defined end groups. The method can be applied to the synthesis of AB-diblock and ABA- and ABC-triblock copolymers composed of different families of monomers.

Organotellurium compounds as novel initiators for controlled/living radical polymerizations. Synthesis of functionalized polystyrenes and end-group modifications.

Polymer-end mimetic organotellurium compounds initiate controlled/living radical polymerization of styrene derivatives that allows accurate molecular weight control with defined end-groups. Transformations of the end-groups via radical and ionic reactions provide a variety of end-group modified polystyrenes.

Mechanism-based invention of high-speed living radical polymerization using organotellurium compounds and azo-initiators.

Kinetic analysis reveals the existence of two competing pathways in the organotellurium-mediated living radical polymerization (TERP) at elevated temperature. The rate-determining step, namely, the thermal dissociation process, could be bypassed by the addition of conventional radical initiators, and the polymerization proceeded at low temperature by the degenerative transfer-mediated polymerization. The polymerization conditions are applicable to a variety of vinyl monomers, and the desired polymers form in a highly controlled manner.

Highly versatile organostibine mediators for living radical polymerization.

A new versatile method for conducting living radical polymerization has been developed in which organostibines induce consecutive group-transfer radical reactions with alkenes. The method has been successfully applied, for the first time, to the controlled polymerization of both conjugated and unconjugated vinyl monomers, and the desired polymers with predetermined molecular weight and low polydispersity index were obtained in excellent yields. This characteristic feature of this method is exemplified in the first synthesis of block copolymers composed of conjugated and unconjugated monomers, which would be of great importance as functional smart organic nanomaterials.