Yinhui Li

Amylose-directed synthesis of CuS composite nanowires and microspheres

Reported are the synthesis and characterization of CuS composite nanowires and microspheres in the presence of amylose. The preparation involved first the complexation of amylose with Cu(2+) of CuCl(2) at 70°C. Cu(2+) complexation was confirmed by a conductivity reduction of CuCl(2) after amylose addition. Also, the aggregation state of the amylose changed after Cu(2+) as revealed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). At the Cu(2+) to α-D-glucopyranosyl unit molar ratio r of 0.70 and 1.41, the amylose aggregated into microspheres that were approximately 150 and 250 nm in diameter. Adding sodium thiosulfate resulted in the production of an amorphous precipitate consisting presumably of CuS(2)O(3). At r=0.70 and 1.41, CuS(2)O(3) precipitated inside the template of Cu(2+)/amylose microspheres as nanoparticles, while a twisted nanowire-like structure was produced at r=0.92. CuS(2)O(3) decomposed under heating at 100 °C to yield crystalline CuS nanoparticles.

Superhydrophobic Hierarchically Assembled Films of Diblock Copolymer Hollow Nanospheres and Nanotubes

Reported are the formation of rough particulate films from cross-linked diblock copolymer vesicles and nanotubes and the wetting properties of the resultant films. The diblock copolymers used were F66M200 and F95A135, where the subscripts denote the repeat unit numbers, whereas M, A, and F denote poly(2-cinnamoyloxyethyl methacrylate), poly(2-cinnamoyloxyethyl acrylate), and poly(2,2,2-trifluoroethyl methacrylate), respectively. The precursory polymers to F66M200 and F95A135 were prepared by atom transfer radical polymerization. In 2,2,2-trifluoroethyl methacrylate (FEMA), a selective solvent for F, vesicles and tubular micelles were prepared from F66M200 and F95A135, respectively. Photo-cross-linking the M and A blocks of these aggregates yielded hollow nanospheres and nanotubes bearing F coronal chains. These particles were dispersed into CH2Cl2/methanol, where CH2Cl2 was a good solvent for both blocks and methanol was a poor solvent for F. Casting CH2Cl2/methanol dispersions of these particles yielded films consisting of hierarchically assembled diblock copolymer nanoparticles. For example, the hollow nanospheres fused into microspheres bearing nanobumps after being cast from CH2Cl2/methanol at methanol volume fractions of 30 and 50%. The roughness of these films increased as the methanol volume fraction increased. The films that were cast at high methanol contents were superhydrophobic, possessing water contact angles of ∼160° and water sliding angles of ∼3°.

Metal ion induced-assembly of amylose in aqueous solution

Cu(2+)/amylose assemblies of various sizes were prepared through the Cu(2+) ion induced-assembly of amylose. These assembly structures were characterized via transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), dynamic light scattering (DLS), (1)H NMR analysis, fluorescence spectroscopy (FL) and UV-vis absorption spectroscopy (UV-vis). The results from these characterizations revealed the existence of a complexation effect and/or a bridging effect between the hydroxyl groups of amylose and Cu(2+) ions, and that the formation of the hydrophobic domains promoted the formation of Cu(2+)/amylose assemblies. The use of other metal ions to induce the formation of spherical, flower- and wire-like amylose assemblies was investigated as well. A preliminary investigation on the ability of amylose to capture various metal ions was also performed, and the results of this work demonstrated that amylose could bind quantitatively metal ions that were at low concentrations. This work provided an alternative strategy for the recovery of precious metals from metal ion-containing aqueous solutions and the reduction of water pollution.

Enhanced copper-catalyzed “click” reaction between homopolymers with terminal azide and alkyne groups in the presence of water

Abstract We report here that the efficiency of the click chemistry between the terminal azide and alkyne groups of different polymer chains could be drastically increased with the addition of an optimum amount of water into a reaction system. That is, the efficiency was only slightly promoted by the addition of a small amount of water into the reaction mixture. However, the reaction efficiency was increased dramatically near the water volume fraction to lead the reaction mixture into nanosized phase separation. Further increasing in water content caused the polymer(s) to undergo macroscopic phase separation and the click reaction efficiency was decreased once again. The enhanced efficiency of click coupling reaction including conversion and rate was also demonstrated via in-situ 1H-NMR. The reaction kinetics as well as reaction rate constant for these reaction system with typical water content were also evaluated. This finding on enhanced click reaction is of practical value, because click reactions in polymer synthesis are generally more difficult to be carried out and proceed relative slowly at low yield in most case because of the strong steric hindrance effect from “large and long” polymer chains, as compared to “click” reactions which are employed for preparation of the low molecular weight organic compounds.

SYNTHESIS AND SELF-ASSEMBLY BEHAVIORS OF BLOCK COPOLYMER A- b -(B- r -C) BEARING RANDOM COMPONENTS: SYNTHESIS AND SELF-ASSEMBLY BEHAVIORS OF BLOCK COPOLYMER A- b -(B- r -C) BEARING RANDOM COMPONENTS

通过原子转移自由基（ATRP）方法合成了其中一个嵌段是由2种单体无规共聚的两嵌段聚合物——聚丙烯酸肉桂酸乙酯-b-（聚苯乙烯-r-聚丙烯酸叔丁酯）,（记为PCEA-b-（PtBA-r-PS））.讨论了聚合过程中影响分子量分布以及分子量控制的各种因素.通过氢核磁（1H-NMR）确定各嵌段的重复单元数分别为50,111,138.通过透射电镜（TEM）观察,研究了该嵌段聚合物在选择性溶剂1-氯癸烷以及环戊烷中的自组装行为,发现该嵌段聚合物在环己烷中直接分散可以形成有聚集倾向的短棒状或球形胶束,而在1-氯癸烷中直接分散得到的胶束,在膜表面随着1-氯癸烷溶剂的缓慢挥发可以组装得到具有规则微纳结构的相互连接的柱状胶束.