QSPR Modeling of Gibbs Free Energy of Organic Compounds by Weighting of Nearest Neighboring Codes

We examine the encoding of chemical structure of organic compounds by Labeled Hydrogen-Filled Graphs (LHFGs). Quantitative Structure-Property Relationships (QSPR) for a representative set of 150 organic molecules have been derived by means of the optimization of correlation weights of local invariants of the LHFGs. We have tested as local invariants Morgan extended connectivity of zero- and first order, numbers of path of length 2 (P2) and valence shells of distance of 2 (S2) associated with each atom in the molecular structure, and the Nearest Neighboring Codes (NNC). The best statistical characteristics for the Gibbs free energy has been obtained for the NNC weighting. Statistical parameters corresponding to this model are the following n = 100, r² = 0.9974, s = 5.136 kJ/mol, F = 38319 (training set); n = 50, r² = 0.9990, s = 3.405 kJ/mol, F = 48717 (test set). Some possible further developments are pointed out.     

Characteristics of Interactions in the Pectin–Chitosan System

Interpolymeric complexes have been obtained from citric pectin and chitosan, the latter synthesized from crab chitin. The composition and structure of complexes obtained from different ratios of the components were studied by IR spectroscopy, rheological investigation of gel structure, and mathematical modelling of system properties. Rheological investigation of the processes involved in the formation of interpolymeric complexes with gel structures from citric pectin and chitosan was conducted in moderately concentrated solutions containing different ratios of the components. It was shown that the toughness of the gel structures was determined by the ratio of the amounts of the heterogeneous polymers. The toughest product (τ=121.4 Pa) was obtained by use of equimolar quantities of pectin and chitosan. With deviation of the composition of the mixture from equimolar the toughness of the gel decreased. It is proposed that the polyelectrolyte pectin–chitosan complex with a network structure is formed at the expense of electrostatic interaction between positively charged amino groups at C-2 of the chitosan pyranose ring and negatively charged carboxyl groups at the C-5 of the pectin pyranose ring.     

Eu~(3+)掺杂方钠石荧光材料的合成及发光特性

采用水热反应及后期热处理工艺合成了Eu3+掺杂方钠石结构的荧光材料Na8Al6Si6O24(OH)2·(H2O/NO3)2∶Eu3+。SEM图像显示,所合成的样品由一些长棒状和不规则多面体结构组成,平均粒径约为0.6μm和2μm。样品在394 nm(对应于Eu3+离子的7F0→5L6跃迁)激发下发出单色性较好的红色荧光,相应的色坐标值为(0.613 6,0.337 7),色纯度为85.5%,量子效率为0.36。随着Eu3+掺杂摩尔分数的增大,样品的红色荧光增强。当Eu3+摩尔分数超过7%时发生部分相变现象。发光热猝灭研究发现,样品的相对亮度和红色比在37~100℃内比较稳定。     

Unusual Kinetics in Aqueous Heterophase Polymerizations

The heterogeneous nature of aqueous heterophase polymerizations is the base for an easy route to unique block copolymers, for the development of new and more effective polymerization strategies, and the abilities to unique studies of radical polymerization kinetics. Thermo-sensitive double hydrophilic block copolymers and micro- or nano-gel particles of poly(N-isopropyl acrylamide) as thermo-responsible block and charged or uncharged hydrophilic polymers can easily be prepared if the polymerization of N-isopropyl acrylamide is started with the corresponding polymeric radicals. The application of extremely fast microwave heating allows the development of highly effective pulsed thermal polymerization strategies and the production of polymers with desired molecular weight distributions over wide ranges. 2,2′-azobisisobutyronitrile simultaneously initiates the polymerization in both the monomer and the aqueous phase and leads, even under surfactant-free conditions, to stable latex particles.