A superhydrophobic coating was facilely fabricated in one step by casting bisphenol A polycarbonate (PC) solution under moisture. Vapor-induced phase separation occurred during the solidifying process and a rough surface with a micro-nano-binary structure (MNBS) similar to the microstructure shown on lotus leaf was formed.

This work describes a simple but novel analytical method for in situ monitoring of the diffusion process of drugs in hydrogels based on refractive index measurements. The diffusion process was monitored by recording the refraction of a laser beam passing through a triangular cell, which allows the determination of changes in the refractive index distribution from the deviated distance of the linear beam. Compared to conventional methods, this new method exhibits advantages such as more simplicity, lower cost, and speed. Further, the refractive index method permits the determination of the concentration distribution of solutes in the hydrogels at any time during the diffusion process under nondestructive circumstances. The precision was determined by successfully applying this new method to the diffusion of a typical antibiotic drug, cefazolin sodium, in agarose gels of various concentrations. By employing Fick's second law, the diffusion behavior was investigated and the diffusion coefficients of cefazolin sodium in agarose gels were therefore obtained. Amsden's physical model based on obstruction effect was applied to the simulation of the diffusion process of cefazolin sodium and turned out to fit the results quite well.

Polymethylsilsesquioxane (PMSQ)/montmorillonite (MMT) nanocomposites has been prepared by in situ intercalative polymerization. The dispersion of the MMT layers with the matrix was verified using X-ray diffraction, revealing an intercalated morphology with layer spacing (3.42) nm. The layer spacing was not increased after the annealing at 150 ℃ for 3 h and the reason was explained in the light of molecular structure of PMSQ synthesized in and out of the nano-confined environment. The coherent order of the silicate layer was decreased after the annealing and the reason was given in the light of the change of PMSQ molecule during the annealing process.

Utilizing a novel solvent of cellulose, 6 wt % NaOH/5 wt % thiourea aqueous solution, for the first time, we prepared the thermally induced cellulose gel. We investigated the thermal gelation of cellulose solutions with rheometry and the structure of the gel with C-13 NMR, wide-angle X-ray diffraction, environmental scanning electron microscopy, and atomic force microscopy. The cellulose solutions revealed an increase in both the storage modulus (G') and the loss modulus (G") with an increase in the temperature during gelation. The temperature at the turning point, where G' overrides G" because of the onset of gelation, decreased from 38.6 to 20.1 degreesC with an increase of cellulose concentration from 4 to 6 wt %. Given enough time, G' of all solutions can exceed G" at a certain temperature slightly lower than the gelation temperature, indicating that the occurrence of the gelation is also a function of time. Each of the assigned peaks of NMR of the cellulose gel is similar to that of the cellulose solution, suggesting that the gelation resulted from a physical cross-linking. The gels were composed of relatively stable network units with an average diameter of about 47 nm. At either a higher temperature (at 60 degreesC for 30 s) or a longer gelation time (at 30 degreesC for 157 s), the gel in the 5 wt % cellulose solution could form. A schematic gelation process was proposed to illustrate the sol-gel transition: the random self-association of the cellulose chains having the exposed hydroxyl in the aqueous solution promotes the physical cross-linking networks.

Polysilsesquioxane nanosheets with a thickness of four nanometers and lateral dimensions of several hundreds of nanometers were synthesized by polymerization of a trifunctional monomer in the layer space of montmorillonite as the confined environment.

X-ray photoelectron spectroscopy and Raman spectroscopy were' used to determine the chemical change of polyphenylsilsesquioxane (PPSQ) during pyrolysis in flowing nitrogen. Two temperature ranges were found for pyrolysed PPSQ below and above 600degreesC, respectively. The former is related to the rearrangement of PPSQ backbone and the latter reflects that most of backbone structure of PPSQ might be broken down and unorganized. Carbon formed in carbonization of PPSQ sample pyrolysed at 900degreesC should be sp(3) bonded carbon with crystallite size effects or defects.

Polymethylsilsesquioxane (PMSQ)-montmorillonite (MMT) nanocomposites were prepared by in situ intercalative polymerization. The dispersion of the MMT layers within the matrix was verified by X-ray diffraction and transmission electron microscopy, which revealed an intercalated morphology with layer spacing of 3.42 nm. The layer spacing was not increased after annealing at 150degreesC for 3 h. The reason for this result is explained in light of the molecular structure of PMSQ synthesized in and out of the nanoconfined environment. The coherent order of the silicate layer was decreased after the annealing, possibly because of the change in the PMSQ molecule during the annealing process. (C) 2002 Wiley Periodicals, Inc.

Changes of composition and structure of various samples of polymethylsilsesquioxane (PMSQ) pyrolysed at different temperature under flowing nitrogen were investigated by means of FT-IR and X-ray photoelectron spectroscopy. Two temperature domains correspond to important changes in the chemical composition of PMSQ. The former (T-p < 500 &DEG;C) is related to the transition from regular structure to irregular structure and the latter (T-p > 500 degreesC) is associated with the organic-inorgnic transition.

Changes of the composition and structure of various samples of polymethylsilsesquioxane (PMSQ), pyrolyzed at different temperatures under flowing nitrogen, were investigated using thermogravimetric analysis, Raman and Fourier transform infrared spectroscopies, X-ray photoelectron spectroscopy, elemental analysis, scanning electron microscopy, and transmission electron microscopy. The center of the Si2p peak could be used to estimate the extent of the pyrolysis of PMSQ. Two temperature domains correspond to important changes in the chemical composition of PMSQ. The former (T-p < 500degreesC) is related to the conversion from a regular structure to an irregular structure and the latter (T-p > 500degreesC) is associated with the organic-ceramic conversion. During the latter pyrolysis, flowing of the molten bulk occurred and then a final solid structure was obtained. The main product of PMSQ, pyrolyzed at 900degreesC, is silica, as well as some amount of silicon oxycarbide and traces of amorphous carbon. Based on the above analysis and observation, a conversion process from polysilsesquioxane to a ceramic is proposed. (C) 2002 Wiley Periodicals, Inc.

Exfoliated polyurethane/montmorillonite nanocomposites with both high elongation at break and high tensile strength were studied by dynamic-infrared spectroscopy (dynamic-IR). The results show that crystallization induced by additional stress is impeded by the nano-layered organo montmorillonite.

The microstructure of bulk YBCO processed by the powder melting process using a submicrometre Y2BaCuO5 precursor in combination with the addition of CeO2 was characterized by scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy. The mean diameter of the Y2BaCuO5 precursor was less than 500 nm. As a result, the mean diameter of the Y2BaCuO5 particles entrapped in the textured bulk YBCO is about 500 nm. Two types of Y2BaCuO5 were found within the bulk YBCO: one with one or two nanometric Y2O3 cores; the other, however, has no cores. The refinement mechanism for Y2BaCuO5 particles related to the employment of a submicrometre Y2BaCuO5 precursor and the minor addition of CeO2 is discussed. In addition, a high density of twins with an average spacing of about 60-80 nm was observed. Moreover, a twin domain boundary structure where domains with different orientation twins meet one another was found. The formation mechanisms for this high density of twins and the twin domain boundary structure are also discussed.

国防航空工业的发展需求高性能陶瓷,尤其是纳米陶瓷.聚有机硅倍半氧烷可作为前躯体,通过热解制备陶瓷.该方法操作简便,易于控制.本文综述了国外有关聚有机硅倍半氧烷热解理论与应用研究近况,并对这一领域的发展进行了展望.

Well-defined polystyrene (PS)-b-poly(ethylene oxide) (PEO)-b-PS triblock copolymers were synthesized by atom-transfer radical polymerization (ATRP), using C—X-end-group PEO as macroinitiators. The triblock copolymers were characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The experimental results showed that the polymerization was controlled/living. It was found that when the number-average molecular weight of the macroinititors increased from 2000 to 10,000, the molecular weight distribution of the triblock copolymers decreased roughly from 1.49 to 1.07 and the rate of polymerization became much slower. The possible polymerization mechanism is discussed. According to the Cu content measured with atomic absorption spectrometry, the removal of catalysts, with CHCl3 as the solvent and kaolin as the in situ absorption agent, was effective. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2882–2888, 2000

Polytetrahydrofuran monomethacrylate (MA-PTHF) macromonomer was prepared by cationic ring-opening polymerization(CROP) of tetrahydrofuran (THF) using boron trifloride etherate (BF3 · OEt2) as initiator and epichlorohydrin (ECH) as promoter. Two kinds of transfer agents were used: methacrylic acid (represented as TA1), and a mixture of methacrylic acid and sodium methacrylate (represented as TA2). The effects of polymerization conditions on molecular weight and molecular weight distribution of macromonomers were studied in this article, when the composition of reactants was kept constant. Under the same conditions, the molecular weight of macromonomer using TA2 is lower than that using TA1, which indicates that TA2 is more active than TA1. The molecular weight of MA-PTHF macromonomer varies with the polymerization time before transfer agents were added (T1), but molecular weight distribution remains constant. When T1 is limited in 30 min, the apparent number-average molecular weight of MA-PTHF increases significantly with the increase of T1, and ranges from 5000 to 18,000. Hence, the molecular weight of MA-PTHF macromonomer can be controlled by varying T1. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 810–815, 2000

由单螺杆挤出机制备了聚氯乙烯(PVC)/梯形聚苯基倍半硅氧烷(PPSQ)(100/0、95/5、90/10、85/15、80/20)机械共混物.通过扫描电镜(SEM)观察了该共混物的相结构,富PPSQ相形成的球状颗粒较均匀地分散于PVC的连续相中.PVC/PPSQ共混物的流动温度(Tf)均低于纯PVC的Tf,而它们的玻璃化转变温度(Tg)略高于纯PVC的Tg,随PPSQ含量的增加,PVC/PPSQ共混物的Tf 移向低温,更易塑化.经PPSQ改性后的PVC的表观粘度随温度变化敏感性增加.加入少量PPSQ 后,可有效地改善PVC的流动性.

综述了近20年来在选择性溶剂中嵌段聚合物缔合行为的研究进展 ,探讨了胶束结构、表征方法及胶束形成的热力学、动力学和流体力学。

The possible molecule conformation of a new type of polymer surfactant at air/solid interface, acrylamide-poly(oxyethylene alkyl ether)acrylate-anionic monomer random copolymers, was studied by X-ray photoelectron spectroscopy in detail. By means of changing the detection angle, group composition at surface layer in thickness of 0 ∼ 2.5 nm can be obtained. The results show that the surface activity of the copolymers related closely with the conformation of the groups of the copolymers. The hydrophobic backbone of the copolymer plays the most important role in enhancing surface activity. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2297–2302, 1999

The effect of temperature on the hydrodynamic behavior of a poly(styrene-butadiene-styrene) (SBS) micelles in butanone was studied by dynamic light scattering. Dynamic light scattering experiments were performed to measure the apparent hydrodynamic radii (R h) of the micelles at the temperature 27-60°C. The scattered light of a polarized He-Ne laser was measured at 90° and collected on a Brookhaven BI-9000 AT correlator.

The hydrodynamic behavior of poly(styrene - butadiene - styrene) (SBS) triblock copolymer solutions in tetrahydrofuran (THF) and butanone were studied by viscosity method. Viscosity measurements were made in Ubbelohde viscometer placed in a thermostatistically controlled bath with a precision of ±0.1°C. Measurements of block copolymer solutions were carried out within the polymer concentration range from (2-5) × 10 -3g·cm -3. The data were evaluated according to Huggins and Kraemer equations.