Optically clear simulataneous interpenetrating polymer networks based on poly(ethylene glycol) diacrylate and epoxy. II. Kinetic study

Simultaneous interpenetrating polymer networks (SINs) based on diglycidyl ether of bis-phenol A (DGEBA) and poly(ethylene glycol) diacrylate (PEGDA) in weight ratios of 100/0, 50/50, and 0/100 were blended and cured simultaneously by using benzoyl peroxide (BPO) and m-xylenediamine (MXDA) as curing agents. A kinetic study during SIN formation was carried out at 45, 55, 63, and 70°C. Concentration changes for both the epoxide and C?C bond were monitored with FTIR. A rate expression for DGEBA cure kinetics was established with a model reaction of phenyl glycidyl ether (PGE) and benzylamine. Experimental results revealed that lower rate constants and higher activation energy for the SIN were found, compared with those for the constituent DGEBA and PEGDA network formation. A model of network interlock was proposed to account for this phenomenon. During simultaneous cure of DGEBA and PEGDA, the interlock (mutual entanglement) between DGEBA and PEGDA networks provided a sterically hindered environment, which subsequently increased the activation energy and reduced cure rates for both DGEBA and PEGDA. © 1993 John Wiley & Sons, Inc.     

液晶聚合物网络研究进展

综述了液晶聚合物网络的新进展。包括液晶热固体、液晶弹性体和液晶互穿网络。介绍了各种网络的合成、主要性能和应用前景。     

人工神经网络及其在分析化学中的应用

人工神经网络是一种新兴的计算方法，有着广阔的发展前途，目前在分析化学领域已经有了多方面的应用。本文简要介绍了人工神经网络的原理及其在分析化学中的应用。     

Open spaces and molecular motions of polyether-based network polymers probed by positron annihilation

The lifetimes of positrons have been measured for network polymers based on polyethers. From the temperature dependence of the lifetime of ortho-positronium (o-Ps), τ₃, for the network polymer of poly(ethylene oxide-co-propylene oxide) [P(EO/PO)], an onset temperature for limited local motions of molecules, T_γ, and the glass transition temperature, T_g, were determined to be 57 and 201 K, respectively. For the network polymer of poly[EO-co-2-(2-methoxyethoxy)ethyl glycidyl ether] [P(EO/MEEGE)], T_γ and T_g were determined to be 57 and 185 K, respectively. For both specimens, above 270 K, the observed linear temperature dependence of τ₃ was attributed to the thermal expansion of open spaces in a liquid state. In the temperature range between T_γ and 270 K, for the P(EO/MEEGE) network, τ₃ was longer and its intensity was smaller than those for the P(EO/PO) network. These results were attributed to the increase in the size of open spaces for the P(EO/MEEGE) network polymer and the blocking of these regions by motions of side chains and chain ends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1919–1925, 1998     

Supermolecular structures and flow birefringence in polymer solutions

Experimental studies of supermolecular structures and localized flow birefringence in solutions of high-molecular weight polymer are described. Advantage is taken of poly(ethylene oxide) and polyisobutylene. Supermolecular structures are examined with the aid of optical microscopy using freeze-dried samples of the polymer solutions. Birefringence is investigated that arises in planar elongational flow in a cross-slot cell. Flow velocities at which the onset of the localized birefringence occurs are determined. Then these velocities are correlated with viscoelastic characteristics of the solutions. The presence of a liquid-crystalline fibrillar network in the polymer solutions exhibiting flow birefringence is ascertained. The fibrils are birefringent objects. The fibrils are birefringent objects. The localized birefringence phenomenon is explained in term of the orientation of the fibrils in elongational flow. It has been shown that the onset of localized birefringence occurs at a critical Weissenberg number, the value of which is close to unity.     

ANN原子参数法预报合金相晶型及晶格常数

运用人工神经网络方法，以二元合金组成元素的电子结构为基本特征，对二元合金相晶型作了区分，进一步对其晶格常数作了预报，结果令人满意。     

Synthesis,structure and dielectric properties of a novel Gd coordination polymer based on 2-（ pyridin-4-yl ）- 1H-i midazole-4,B -dicarboxylate

A new Gd coordination polymer based on 2-（pyridin-4-yl）-I H-imidazole-4,5-dicarboxylate （H3PIDC） has been synthesized under hydrothermal conditions, formulated as {[Gd3（HPIDC）3（PIDC）（H2O）4].3H2O}n （1）. The compound crystallizes in the monoclinic system, space group C2/c with a=20.951（7）, b = 9.515（3）, c = 27.483（10） A,β= 106.176（6）°, Z = 4, V= 5262（3） A3, C40 H45 Gd3 N12 O30, Dc = 2.071 g/cm3, Mr=1645.63, λ （MoKa）=0.71073A, μ=3.846mm-1, F（000）=3204, the final R=0.0390 and wR= 0.1332. Complex 1 is a two-dimensional MOF built up from T-shaped 3-connected HPIDC2 , PIDC3 and 4-connected metal nodes. Dielectric constant of complex 1 was measured at different frequencies with temperature variation.     

人工神经网络法用于高效毛细管电泳分离条件优化的研究

把人工神经网络（ＡＮＮ）法应用于高效毛细管电泳（ＨＰＣＥ）分离条件的优化，给出了反向传播（ＢＰ）的ＡＮＮ模型的具体算法。用正交试验法同时考察了缓冲溶液组成、浓度、ｐＨ值和有机添加剂浓度等实验因素对ＨＰＣＥ分离合成色素和防腐剂的影响，采用误差反向传播方法建立了有效的ＡＮＮ预测模型，预测最佳分离条件，获得了满意的分离结果。     

互穿网络型二阶非线性光学极化聚合物

报导了二阶非线性光学材料含对硝基苯偶氮苯烷基胺发色基团的聚氨酯和聚丙烯酸酯的互窗网络聚合物的合成和极化工艺，考察了微观形态，用电致色变法测定了其极化膜发色基团的取向度及取向的热稳定性，其二阶非线性光学系数ｘ＾（２）可达１０＾－７ｅｓｕ量级。该互穿网络聚合物极化膜有良好的光学性质和优异的热稳定性，在１２０℃温度下序参数可长期保持稳定。