具有超支化结构的聚醚型脂肪族聚氨酯弹性体的合成与表征及力学性能研究

用聚四氢呋喃醚二醇、端羟基超支化聚酯(HB-20)、异佛尔酮二异氰酸酯和1,4-丁二醇,合成了含有超支化结构的聚醚型脂肪族聚氨酯(PU)弹性体.通过Flory-Rehner公式计算了体系的交联密度;用FT-IR、WAXD和DSC表征了超支化PU的氢键化程度和形态.实验结果表明,在PU弹性体中引入少量的HB-20,能提高氨基甲酸酯羰基的氢键化程度和软硬段间的微相分离程度,从而显著提高材料的拉伸强度.由于氢键化程度和交联密度双重效应的影响,含6 wt%HB-20的聚醚型PU与不含HB-20的PU相比拉伸强度提高了2倍多,达到37.9 MPa,断裂伸长率仍高达414%.     

CH3＋HNCO反应机理的理论研究

在6-311＋＋G**基组水平上,采用UMP2方法对自由基CH3与HNCO反应机理进行了研究，全参数优化了反应通道上各驻点的几何构型.结果表明, 自由基CH3与HNCO分子间反应有三条反应通道,第一为CH3与HNCO分子间经过生成一个稳定化能为4.56 kJ•mol－1的含氢键的分子复合物M后，经过渡态TS生成另一个产物复合物M′，然后分解为甲烷和NCO自由基；第二是CH3与HNCO分子间通过生成稳定反式中间体trans-int，其经过渡态trans-ts分解成产物CH3NH和CO；第三是CH3与HNCO分子间通过生成稳定顺式中间体cis-int，其经过渡态cis-ts分解成产物CH3NH和CO.比较三条反应通道的反应活化能，表明CH3与HNCO反应较易生成CH4＋NCO.     

Hydrogen-bonded Intramolecular Charge Transfer Excited State of Dimethylaminobenzophenone using Time Dependent Density FunctionalTheory

Density functional theory and time-dependent density-functional theory have been used to investigate the photophysical properties and relaxation dynamics of dimethylaminobenzophe-none (DMABP) and its hydrogen-bonded DMABP-MeOH dimer. It is found that, in non-polar aprotic solvent, the transitions from S₀ to S₁ and S₂ states of DMABP have both n→π^* and π→π^* characters, with the locally excited feature mainly located on the C=O group and the partial CT one characterized by electron transfer mainly from the dimethylaminophenyl group to the C=O group. But when the intermolecular hydrogen bond C=O…H-O is formed, the highly polar intramolecular charge transfer character switches over to the first excited state of DMABP-MeOH dimer and the energy difference between the two low-lying electronically excited states increases. To gain insight into the relaxation dynamics of DMABP and DMABP-MeOH dimer in the excited state, the potential energy curves for con-formational relaxation are calculated. The formation of twisted intramolecular charge trans-fer state via diffusive twisting motion of the dimethylamino/dimethylaminophenyl groups is found to be the major relaxation process. In addition, the decay of the S1 state of DMABP-MeOH dimer to the ground state, through nonradiative intermolecular hydrogen bond stretching vibrations, is facilitated by the formation of the hydrogen bond between DMABP and alcohols.     

拉曼光谱方法研究疏水作用对四甲基脲氢键形成的影响

测得了四甲基脲(TMU)与水,甲醇和乙醇及N,N-二甲基甲酰胺(DMF)与水二元体系的拉曼光谱,分析二元溶液混合体系中羰基伸缩振动的频移随体积比变化的规律,从光谱的变化中可以得出羰基频移经历两个阶段： 首先,羰基伸缩振动随体系中氢键受体体积比的增加向低波数方向移动;其次,当二元混合体系中体积比超过一个临界值后,羰基伸缩振动振动频率不变,变化的仅仅是相对强度。通过分析临界体积比可以得出TMU与水相互作用中水是以较大缔合分子形式存在;而TMU与甲醇、乙醇,DMF与水相互作用中是以单分子或小的缔合分子形式存在的。     

可天宁印迹聚合物分子识别特性的光谱与XPS研究

以可天宁(COT)为模板分子,甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯为交联剂,合成了一种新型的分子印迹聚合物。采用紫外光谱、X射线光电子能谱、红外光谱和1H NMR波谱研究了印迹聚合物的结合位点和识别机理。结果表明,该聚合物通过协同氢键作用形成1∶2型配合物,专一地结合可天宁分子。MAA分子羧基上的氢原子是氢键的质子给予体;COT分子吡啶环上的氮原子以及羰基上的氧原子是质子的接受体,是与MAA形成氢键作用的选择性识别位点。