This work is mainly focused on the investigation of the influence of the amount of a few CeO2 on the physicochemical and catalytic properties of CeO2-doped TiO2 catalysts for NO reduction by a CO model reaction. The obtained samples were characterized by means of XRD, N2-physisorption (BET), LRS, UV-vis DRS, XPS, (O2, CO, and NO)-TPD, H2-TPR, in situ FT-IR, and a NO + CO model reaction. These results indicate that a small quantity of CeO2 doping into the TiO2 support will cause an obvious change in the properties of the catalyst and the TC-60 : 1 (the TiO2/CeO2 molar ratio is 60 : 1) support exhibits the most extent of lattice expansion, which indicates that the band lengths of Ce-O-Ti are longer than other TC (the solid solution of TiO2 and CeO2) samples, probably contributing to larger structural distortion and disorder, more defects and oxygen vacancies. Copper oxide species supported on TC supports are much easier to be reduced than those supported on the pure TiO2 and CeO2 surface-modified TiO2 supports. Furthermore, the Cu/TC-60 : 1 catalyst shows the highest activity and selectivity due to more oxygen vacancies, higher mobility of surface and lattice oxygen at lower temperature (which contributes to the regeneration of oxygen vacancies, and the best reducing ability), the most content of Cu(+), and the strongest synergistic effect between Ti(3+), Ce(3+) and Cu(+). On the other hand, the CeO2 doping into TiO2 promotes the formation of a Cu(+)/Cu(0) redox cycle at high temperatures, which has a crucial effect on N2O reduction. Finally, in order to further understand the nature of the catalytic performances of these samples, taking the Cu/TC-60 : 1 catalyst as an example, a possible reaction mechanism is tentatively proposed.

Enzyme-mediated injectable hydrogels based on a poly(l-glutamic acid) graft copolymer with tunable physicochemical properties, biodegradability and good biocompatibility were developed.

The confined crystallization behavior, melting behavior, and nonisothermal crystallization kinetics of the poly(ethylene glycol) block (PEG) in poly(L-lactide)poly(ethylene glycol) (PLLA-PEG) diblock copolymers were investigated with wideangle X-ray diffraction and differential scanning calorimetry. The analysis showed that the nonisothermal crystallization behavior changed from fitting the Ozawa equation and the Avrami equation modified by Jeziorny to deviating from them with the molecular weight of the poly(L-lactide) (PLLA) block increasing. This resulted from the gradual strengthening of the confined effect, which was imposed by the crystallization of the PLLA block. The nucleation mechanism of the PEG block of PLLA15000-PEG5000 at a larger degree of supercooling was different from that of PLLA2500-PEG5000, PLLA5000-PEG5000, and PEG5000 (the numbers after PEG and PLLA denote the molecular weights of the PEG and PLLA blocks, respectively). They were homogeneous nucleation and heterogeneous nucleation, respectively. The PLLA block bonded chemically with the PEG block and increased the crystallization activation energy, but it provided nucleating sites for the crystallization of the PEG block, and the crystallization rate rose when it was heterogeneous nucleation. The number of melting peaks was three and one for the PEG homopolymer and the PEG block of the diblock copolymers, respectively. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: [3215][3216][3217][3218][3219][3220][3221][3222][3223][3224][3225][3226] 2006

Poly­(l-lactide)/poly­(butylene succinate) (PLLA/PBS) blends were prepared by melt mixing with a PLLA-based compatibilizer (PBS-PLLA) and a chain extender triarm block copolymer (PLLA-block-poly­(glycidyl methacrylates))3 (PLLA-b-PGMA)3. The tensile testing showed significant improvement in mechanical properties and remarkably maintained high strength. Rheological investigation of PLLA/PBS/PBS-PLLA/(PLLA-b-PGMA)3 indicated that the viscosity and storage modulus was improved greatly compared with neat PLLA. Elongational viscosity measurements exhibited strong strain-hardening behavior. The increase of the torque indicated the occurrence of chain branching and chain extension reaction. The imperfect crystallization of PLLA/PBS/PBS-PLLA/(PLLA-b-PGMA)3 blends was demonstrated by the lowered melt point of PLLA. SEM showed that the PBS-PLLA and (PLLA-b-PGMA)3 significantly improved the compatibility of the PLLA/PBS blends. It was indicated that the synergistic effects of PBS-PLLA and (PLLA-b-PGMA)3 in PLLA/PBS blends played a key role in properties enhancement. With copolymerization and in situ reactive compatibilization, PLLA/PBS/PBS-PLLA/(PLLA-b-PGMA)3 blends not only improved the toughness but also improved the melt strength.

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Linear and four-armed poly(L-lactide)-block-poly(D-lactide) (PLLA-b-PDLA) block copolymers are synthesized by ringopening polymerization of D-lactide on the end hydroxyl of linear and four-armed PLLA prepolymers. DSC results indicate that the melting temperature and melting enthalpies of poly (lactide) stereocomplex in the copolymers are obviously lower than corresponding linear and four-armed PLLA/PDLA blends. Compared with the four-armed PLLA-b-PDLA copolymer, the similar linear PLLA-b-PDLA shows higher melting temperature (212.3 C) and larger melting enthalpy (70.6 J g 21 ). After these copolymers blend with additional neat PLAs, DSC, and WAXD results show that the stereocomplex formation between free PLA molecular chain and enantiomeric PLA block is the major stereocomplex formation. In the linear copolymer/linear PLA blends, the stereocomplex crystallites (sc) as well as homochiral crystallites (hc) form in the copolymer/PLA cast films. How-ever, in the four-armed copolymer/linear PLA blends, both sc and hc develop in the four-armed PLLA-b-PDLA/PDLA specimen, which means that the stereocomplexation mainly forms between free PDLA molecule and the inside PLLA block, and the outside PDLA block could form some microcrystallites. Although the melting enthalpies of stereocomplexes in the blends are smaller than that of neat copolymers, only twothirds of the molecular chains participate in the stereocomplex formation, and the crystallization efficiency strengthens. V C 2014

A new self-microemulsifying drug delivery system (SMEDDS) has been developed to increase the solubility, dissolution rate and oral bioavailability of vinpocetine (VIP), a poor water-soluble drug. The formulations of VIP-SMEDDS were optimized by solubility assay, compatibility tests, and pseudo-ternary phase diagrams analysis. The optimal ratio in the formulation of SMEDDS was found to be Labrafac : oleic acid : Cremophor EL : Transcutol P‫04؍‬ : 10 : 40 : 10 (w/w). The average particle diameter of VIP was less than 50 nm. In vitro dissolution study indicated that the dialysis method in reverse was better than the ultrafiltration method and the dialysis method in simulating the drug in vivo environment.

In order to obtain the forming regulation and structural evolution of poly(L-lactide)/poly(D-lactide) (PLLA/ PDLA) stereocomplexes (sc-PLA), a commercial high molecular weight PLLA was blended with a series of PDLAs with different weight-average molecular weights (M w ) in the range of 7.5−290 kg• mol −1 by solution blending. The thermal properties, morphology, and thermal stability of the PLLA/PDLA blends were investigated by differential scanning calorimetry (DSC), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). The crystallization of sc-PLA and homochiral PLA (homo-PLA) was competitive and controlled by the M w of PDLA. The phase structure of the PLLA/PDLA blends depended on the melting temperature. By quenching sc-PLA from 280 to 290 °C, a bicontinuous phase structure was observed for PLLA and PDLA. When quenching sc-PLA from 230 to 270 °C, a stereoamorphous mesophase of PLA (sam-PLA) was obtained, which originated from the residual strong hydrogen bonding between PLLA and PDLA. sam-PLA was a new discovery different from sc-PLA and homo-PLA. The PLLA/PDLA blends are not fully compatible among sam-PLA, PLLA, and PDLA. During melting, sc-PLA changed into sam-PLA, and the hydrogen bonding in sam-PLA was destroyed and weakened with increasing temperature at <∼270 °C. At higher than ∼270 °C, the hydrogen bonding became extremely weak and even disappeared.