Preparation and size control of monodispersed surface charged polystyrene nanoparticles by reversible addition fragmentation transfer reaction

Highly monodispersed polystyrene (PS) nanoparticles were prepared via reversible addition fragmentation transfer (RAFT) living radical emulsion polymerization technique. Two types of novel sur-iniferters with different hydrophilic lipophilic balance (HLB) values, 4-diethythiocarbonylsulfanylmethyl-benzoic acid and 4-(2-hydroxyethyl)piperazine-1-carbodithioicacid benylether, were synthesized for the PS RAFT reaction and their chemical synthesis was identified using nuclear magnetic resonance spectroscopy. Scanning electron microscope and dynamic light scattering experiments showed that the size distribution of the particles prepared was highly monodispersed. The average particle size was affected by the type and concentration of sur-iniferters. It increased with decreasing sur-iniferter concentrations, and the use of sur-iniferters with higher HLB values led to increases of particle sizes, as the particles were growing from, initially, much larger monomer droplets. The surfaces of the nano particles prepared were ionically charged. The surface charge measured was −50 mV, which enabled particles to be stably dispersed in aqueous medium.     

Noncovalent attachment of pyro-pheophorbide a to a carbon nanotube

Pyrene mediated noncovalent attachment of a chlorophyll derivative, pyro-pheophorbide a, to a soluble single wall carbon nanotube is reported and the resultant CD, UV-Vis absorbance, fluorescence and 1H NMR spectra are discussed.     

Castor oil-based biopolyurethane reinforced with wood microfibers derived from mechanical pulp

Wood fibers with high lignin content show promise to function in numerous applications with advantageous properties if the fiber features are appropriately exploited. The present study introduces a new approach to disintegrate and disperse wood fibers from groundwood pulp (GWP) directly to polyol without additional solvent exchanges or chemical modifications. In comparison bleached chemical pulp with low lignin content was ground in the polyol, but only low consistency (1 wt%) operation was possible, whereas up to 5 wt% consistency with GWP was carried out with ease. The micron sized fibers in polyol were reacted with polymeric diphenylmethane diisocyanate to produce fiber reinforced biopolyurethane (bioPU) composites. The mechanical properties of the composites improved compared to reference bioPU showing 14.6% increase in Young’s modulus, 54.5% in tensile strength and 26.1% in strain at break. The tan δ peaks shifted to higher temperature from 5.5 to 10.4 °C when fibers up to 5.1 wt% were incorporated to bioPU. Overall, the bulk microfibers from GWP with low degree of processing were cost-effective reinforcements for bioPUs, which improved the qualities of the fabricated composites and showed good compatibility with polyurethane.     

Synthesis,Aromaticity and Photophysical Behaviour of Ferrocene‐ and Ruthenocene‐Appended Semisynthetic Chlorin Derivatives

Two novel synthetic strategies to covalently link a metallocene electron‐donor unit to a chlorin ring are presented. In one approach, pyropheophorbide a is readily converted into its 13¹‐ferrocenyl dehydro derivative by nucleophilic addition of the ferrocenyl anion to the 13¹‐carbonyl group. In another approach, the corresponding 13¹‐pentamethylruthenocenyl derivative is synthesised from 13¹‐fulvenylchlorin by a facile ligand exchange/deprotonation reaction with the [RuCp*(cod)Cl] (Cp*=pentamethylcyclopentadienyl; cod=1,5‐cyclooctadiene) complex. The resulting metallocene–chlorins exhibit reduced aromaticity, which was unequivocally supported by ring‐current calculations based on the gauge‐including magnetically induced current (GIMIC) method and by calculated nucleus‐independent chemical shift (NICS) values. The negative ring current in the isocyclic E ring suggests the antiaromatic character of this moiety and also clarifies the spontaneous reactivity of the complexes with oxygen. The oxidation products were isolated and their electrochemical and photophysical properties were studied. The ruthenocene derivatives turned out to be stable under light irradiation and showed photoinduced charge transfer with charge‐separation lifetimes of 152–1029 ps.     

Muckenhoupt Ap-properties of Distance Functions and Applications to Hardy–Sobolev -type Inequalities

Potential Analysis - Let X be a metric space equipped with a doubling measure. We consider weights w(x) = dist(x,E)?α, where E is a closed set in X and $\alpha \in \mathbb {R}$ . We...     

Block copolymers as nanoscopic templates

Block copolymers self‐assemble into well‐ordered, microphase separated morphologies having dimensions on the molecular scale. The key to the use of these nanoscopic structures lies in controlling the spatial orientation of the morphology, particularly in thin films. The preferential interactions of the segments of the blocks with interfaces forces an alignment of the morphology parallel to the interface. Here we describe the use of controlled interfacial interactions and electric fields to manipulate the orientation of the morphology and subsequent steps towards the generation of nanoporous templates as scaffolds for nanoscopic structures.