SYNTHESIS AND PROPERTIES OF POLYSTYRENE／LAPONITE NANOCOMPOSITES

Exfoliated polystyrene (PS)/laponite nanocomposites were prepared successfully. The characteristic doo1 diffraction peak of organo-laponite disappeared in the XRD patterns of nanocomposites, indicating that the laponite layers were exfoliated and the ordered crystal structure of laponite was destroyed because of the styrene polymerization. TEM observations showed that the exfoliated laponite primary particles were dispersed randomly in the PS matrix with lateral dimensions from 1 nm to 10 rim. SEM results showed that the PS/laponite nanocomposite particles were almost monodispersed spheres with the size of about 120 rim. Because of the interaction between PS and laponite nanolayers, the nanocomposites exhibited higher thermal stability and glass transition temperature when compared to pure PS.     

Thermally stimulated depolarization currents of tactic polymethyl methacrylates and their mixtures

Summary Thermally stimulated depolarization currents (TSDC) of atactic (a), syndiotactic (s) and isotactic (i) PMMA and mixtures ofs- andi-PMMA were measured. In pure tactic PMMA, TSDC peak was obtained at a temperature corresponding to the glass transition temperature of each PMMA. TSDC of mixtures isolated as precipitates from 1/1 and 1/2 (i/sweight ratio) mixed solutions showed a peak which can be attributed to the glass transition temperature of the stereocomplex. TSDC of original l/1 mixture showed two peaks which are ascribed to the glass transition temperature of residual i-PMMA and the stereocomplex. The results suggests that stereocomplex formation occurs ini/s weight ratio of 1/2 independent of the way of preparation.With 9 figures and 1 table     

Superoxes,high temperature universal phases in (GC)2

Most of the common classes of organic compounds chromatograph normally on Superoxes. There is no tailing or adverse effect from excessively different activity different activity coefficients. Superoxes are therefore universal phases for gas chromatography. This is also expressed by a wide useful temperature range from ～50° to ～300°. High MW Superox-4 has a MAOT about 20° higher than the lower MW Superox-0.1. Several applications illustrating the versatility of Superox phases in (GC)² are presented.     

4-氯酚在TiO2纳米膜上光催化降解及反应动力学特征

氯酚(ＣＰ)化合物被广泛应用于木材防腐、金属防锈及杀虫剂等,因其毒性大、难降解,对环境造成严重污染[1,2]。目前用于ＣＰ的光催化降解的ＴｉＯ2粉体悬浮体系,催化剂不易回收利用。本文采用Ｓｏｌ Ｇｅｌ法制备的负载型ＴｉＯ2纳米粒子膜作为光催化剂,对4 ＣＰ进行了降解实验研究。同时应用ＸＲＤ法表征了不同实验条件下薄膜中ＴｉＯ2的晶相结构和粒度,考察了不同层数ＴｉＯ2膜的光催化活性,并对4 ＣＰ的降解条件及反应动力学特征进行了探讨。1　实验部分1.1　玻璃负载ＴｉＯ2膜的制备与表征[3-5]按照钛酸四丁酯∶无水乙醇∶水=3∶12∶…     

The preparation of thick-film glass capillary columns

A detailed method for the routine preparation of glass capillary columns is presented. The method consists of coating a glass tube with quartz powder prior to pulling the tube into a capillary. The inner surface of the capillary consists of an even distribution of quartz particles fused to the walls. This surface has been found readily deactivated by standard procedures and ideal for the preparation of thick-film glass capillary columns. The method has been thoroughly tested in two independent laboratories to ensure that the procedures described are reproducible.     

The ground-state energy of the ±J sping glass. A comparison of various biologically motivated algorithms

We compare various evlutionary strategies to determine the ground-state energy of the ±J spin glass. We show that the choice of different evolution laws is less important than a suitable treatment of the free spins of the system At least one combination of these strategies does not give the correct results, but the ground states of the other different strategies coincide. Therefore we are able to extrapolate the infinit-size ground-state energy for the square lattice to –1.401±0.0015 and for the simple cubic lattice to –1.786±0.004.     

Temperature- and hydration-dependence of molecular mobility in seeds

Broad-band ac dielectric relaxation spectroscopy (DRS) and various techniques of thermally stimulated currents (TSC) have been used to investigate molecular mobility in cereal and legume seeds, over wide ranges of water content and temperature. We focused our interest on the detailed study of the interactions between water and seed constituents. The results are quantitatively discussed, using various concepts dictated by the experimental techniques employed and in relation to the protein and carbohydrate contents of the seeds. In addition, the glass transition in the seeds, freezing and melting of water, and the protonic conduction process have been studied in some detail.Financial support through the Greek Ministry of Industry, Energy and Technology (Secretariat of Research and Technology), the Czech Ministry of Education, Youth and Sport (Dept. of International Scientific and Technological Cooperation), and the Empirikos Foundation is gratefully acknowledged.     

稀土磷酸盐发光材料的微波合成

稀土磷酸盐发光材料的微波合成徐文国，田一光，刘淼，刘海堂，方光华，庞文琴（吉林大学化学系，环境科学系，长春，１３００２３）关键词微波合成，稀土磷酸盐，微晶玻璃，玻璃态，发光材料稀土磷酸盐发光材料的研究是当前材料科学的热门研究课题。它们一般通过高温固相...     

Prediction of the retention indices of methyl pyridines and pyrazines in capillary gas chromatography based on the non-linear additivity of the sorption energy

Summary Methylbenzenes, pyridines and pyrazines were investigated on fused-silica and glass capillary columns coated with SE-30 and PEG-40M/KF liquid phases, at two temperatures, 80° and 110°C. The contribution of the methylene groups to the partial molar free sorption energy was determined for methylpyridines and pyrazines. Equations are proposed for the calculation of the retention indices of methyl pyridines and pyrazines. These equations are based on the ortho- and α-effects of the methyl groups. The predicted indices have been experimentally tested for six dimethyl- and trimethylpyridines, and four methylpyrazines. Good accuracy of the calculation permits to use this method for the identification of methylpyridines and pyrazines in complex mixtures. Enlarged text of the paper presented at the Eighth International Symposium on Capillary Chromatography, Riva del Garda, Italy, May 19–21, 1987.     

Characterization of OV-1/FFAP-mixture coated glass capillary columns used for the separation of free fatty acids

As an alternative to acid pretreated UCON and FFAP capillaries for the analysis of wide-boiling free fatty acid mixtures, OV-1 : FFAP phase mixtures were used on high-temperature silylated inert glass capillary columns. The HETP-carrier gas velocity curves, peak asymmetry factors, coating efficiency, gas phase and stationary phase contributions to the mass transfer resistance were determined for various OV-1 : FFAP ratios. Mixed-phase capillaries showed optimum performance at a 2 : 1 OV-1 : FFAP ratio. The thermal and long-term stability of OV-1-stabilized FFAP columns surpassed those of the UCON and pure FFAP reference column used.