VISCOELASTICITY AND IONIC CONDUCTIVITY OF TWO-COMPONENT EPOXY NETWORK CONTAINING LITHIUM PERCHLORATE*

Polymeric solid electrolyte system composed of triglycidyl ether of glycerol (TGEG), diglycidyl ether of polyethylene glycol (DGEPEG)and LiClO_4 salt were synthesized. In this" system the electrolyte has a pecularity that not merely can the LiClO_4 provide ionic carriers, but also catalyze the crosslinking reaction without adding an usual curing agent. The effect of salt content and degree of crosslinking on the viscoelasticity and ionic conductivity were studied. Both WLF and VTF equations were used to treat the experimental data in order to elucidate the mechanism of ionic conduction. It was found that the ionic conductivity of the system is carded out through the segmental motion mechanism. However, the data must be treated with care. For example, in evaluating WLF parameters, the contribution concerned with ionic carrier generation with temperature to the conductivity must be differentiated from that concerned with segmental motion. Besides, the temperature range suitable to WLF equation must also be considered. For VTF equation, it might be inapplicable ff the temperature is too low and close to the glass transition temperature of the specimen. Further study is needed in order to have a quantitative information on the limitation of these equations.     

Arylsulfenylation of 2,3-dialkylindoles; preparation of 3-arylthioindolenines and thermal conversion to an n-sulfenylindole

Reaction of 2,3-dialkylindoles with o-nitrophenylsulfenyl chloride in the presence of triethylamine gives good yields of previously unknown 3-o-nitrophenylsulfenyl-2,3-dialkylindolenines which decompose thermally to give the corresponding 2,3-dialkylindole and N₁-o-nitrophenylsulfenyl indoles.     

New Preparation Methodology of Functionalized Picolines

Under the organomagnesium complex n‐Bu₂CH₃MgLi conditions, picoline compounds provide a new entry to a broad range of polyfunctional picoline derivatives, after reaction with various electrophiles.     

脉冲电流作用下LY12铝合金的微观结构和合金元素分布

研究了在凝固过程中施加脉冲电流对LY12铝合金微观结构和合金元素分布的影响.实验结果表明,在脉冲电流作用下,LY12合金的微观结构发生了明显变化,聚集在晶界和枝晶网的共晶组织大大减少,网络变得不连续,在晶内和晶界附近存在弥散的近似球状的共晶质点.另外,脉冲电流能有效地改善合金中Cu和Mg的成分偏析,其中对Cu在Al合金中的负偏析现象的改善更为显著,使Cu较均匀地分布于整个试样. 关键词： LY12铝合金 脉冲电流 显微结构 偏析     

单组分桥联茂基二异丙胺基钕配合物催化甲基丙烯酸甲酯聚合

催化聚合;茂稀土胺化物;单组分桥联茂基二异丙胺基钕配合物催化甲基丙烯酸甲酯聚合     

化学教学中应如何培养学生的问题意识

当前,中学生问题意识较差,不能发现并提出问题。这种状况不能适应新课程改革的需要。笔者总结自己在化学教学中培养学生问题意识的几种做法：唤醒“问”的意识,使学生想问;营造“问”的氛围,使学生敢问;创设“问”的情境,使学生能问;传授“问”的技巧,使学生会问;教师要正确面对学生的提问。