Lee Y. Wang

Synthesis of novel conducting elastomers as polyaniline-interpenetrated networks of fullerenol-polyurethanes

A processing technique for fabrication of conductive elastomers was demonstrated involving in situ polymerization of aniline at the near-surface region of the fullerenol crosslinked poly(urethane-ether) networks. The synthetic chemistry led to a thin layer (roughly 20 μm in thickness) of conductive polyanilines interpenetrated inside the elastomer matrix. This IPN network exhibited an appreciable conductivity along the doped polyaniline layer without deteriorating much the elasticity and tensile strength of the parent supporting elastomer. As a result, its r.t. conductivity was found to be 2.6 Scm−1 which increased to 5.4 Scm−1 at 430% elongation of the polymer film. The data represented the strain-dependent electronic properties of conducting elastomers, showing an increase of conductivity even after the elastomer being stretched above a length as much as 500% of its original size.

Synthesis and properties of monodisperse conductive core-shell latexes

Monodisperse polystyrene/polyaniline core-shell latexes have been synthesized using cationic spheres as polymer core. These conductive colloids were characterized by IR. SEM and TEM. The conductivity percolation threshold was found to be around 3 wt% of polyaniline.

Utilization of polyhydroxylated C60 as a molecular core for the synthesis of star-shaped polymers

Abstract Polyhydroxylated C 60 derivative (fullerenol) was used as a molecular core in the design and synthesis of poly(urethane-ether) analog star-shaped polymers. Structure of these star-polymers were characterized to consist of 6 poly(urethane-ether) arms per C 60 , on average, in a remarkably narrow distribution of the number of arms per polymer molecule, when the reaction was performed under the described conditions.

Critical size effects on the magnetic resonance in Fe3O4 nanoparticles

In this work, Fe3O4 nanoparticles with two distinct diameters of 10 and 2nm are synthesized with different chemical methods in order to investigate the critical size effects on the magnetic resonance of Fe3O4 nanoparticles. Our results clearly demonstrate a difference in the dynamic behaviors of resonance field (Hr) and resonance linewidth between these two nanoparticles. Furthermore, the nonlinear temperature dependency of Hr in 2-nm Fe3O4 suggests that the surface anisotropy becomes dominating on the magnetodynamics of nanoparticles when the diameter of the nanoparticle is smaller than the critical size.

Synthetic aspects and free-radical scavenging efficiency of polyhydroxylated C60

Abstract The substitution effect of functional groups, attached on the aromatic ring of benzoic acid, to the nucleophilic replacement of fullerenic nitronium intermediates by carboxylic acids was demonstrated. The chemistry was utilized for the synthesis of water-soluble polyhydroxylated fullerenes (fullerenols). High reaction product yields (88–90%) of fullerenols were obtained using functional benzoic acids containing one or two electron-withdrawing substituents as nucleophilic reagents. On the contrary, the use of electron-releasing group substituted benzoic acids resulted in a relatively low product yield (38–62%). A competitive superoxide-radical absorbing reaction between DMPO and fullerenol molecules was carried out in a phosphate buffer using an enzymatic system of xanthine/xanthine oxidase for the generation of superoxide radicals. The overall superoxide-radical scavenging efficiency of fullerenols was found to be higher than that of DMPO molecules. Evidence of preferential attack of superoxide r...

Fullerene-derived star-burst conjugated polymers

Abstract Efficient syntheses of star-burst Ceo-based hexanilino, hexa(dianilino), hexa(tetranilino), and hexa(hexadecaanilino) [60]fullerenes were demonstrated using monodisperse hexanitro[60]fullerene as a precursor molecule.

Synthesis of Octadecahydroxylated C70

Abstract Synthesis of novel hydrophilic [70]fullerenols was described. The reaction involved an oleum-induced oxidative sulfation of the C70 molecules with a product yield of 86%. The rate of fullerene sulfation was accelerated either moderately or greatly by the addition of P2O5 or SeO2, respectively. Hydrolysis of the resulting polycyclosulfated C70 in H2O at 80°C afforded [70]fullerenols in a yield of more than 72%. The negative ion MALDI-TOF mass spectrum of [70]fullerenols showed a well-defined pattern of ion fragmentations with a nearly constant, consecutive weight increase in 17 mass units from the mass of C70. Detection of a molecular ion at m/z 1146 was indicative for the composition of [70]fullerenols as octadecahydroxyfullerenes, containing 18 hydroxy addends per C70 cage. That correlates the structure of their polycyclosulfated precursors to nonacyclosulfated [70]fullerenes, C70(SO4)9.

Thermal stability of fullerene-linked oligoaniline star macromolecules

Abstract Higher thermal stability of hexa(hexadecaanilino)[60]fullerene 1 than that of the parent hexadecaaniline was observed. Capping of the terminal amino group of oligoanilines with a C60 cage significantly reduced the terminal group-initiated thermal cleavage of bondings,

Thermally stimulated depolarization and polarization current study of C60-PU based conducting interpenetrated polymer networks (IPNs)

Abstract Rubber-like conductive polyaniline-polyurethane interpenetration networks (IPNs) were synthesized by a sequence of poly condensation and doping reactions. The thermally stimulated depolarization and polarization current (TSDC/TSPC) and the differential scanning calorimetry (DSC) techniques were used for the characterization of fullerenol-derived urethane copolymer and polyaniline/fullerenol-PU IPNs. Dual glass transitions of fullerenol-derived polyurethane copolymers at −71 °C and 72 °C have been assigned as the motion of PTMO soft segment in the glassy state and the motion of network around fullerenol crosslinking sites respectively. A major crystal melting transition at −3 °C for all polyurethanes and an additional electric field induced crystal-crystal transformation at 17°C of the fullerenol derived polyurethane network are seen. Within polyaniline/fullerenol-PU IPN, the network of polyaniline phase hinders the relaxation of higher Tg and the electric field induced crystal-crystal transformation. Physical aging treatment provides an indirect method for the characterization of glass transitions of current network structure. TSDC technique provides a higher sensitivity in detecting structural relaxation and serves as a direct measurement of phase transitions.

Fullerenol derived urethane-connected polyether dendritic polymers

Urethane-connected polyether star polymers utilizing fullerenol as a molecular core are synthesized as a soluble material containing six chemically bonded polymer arms per C60 on average, with a narrow distribution of the number of arms per molecule and a polydispersity index of 1.45.