一种光响应性热敏聚合物的合成及性能表征

合成了偶氮单体2-[4-(4′-乙氧基苯基偶氮)苯氧基]乙基丙烯酸酯(EAPEA),利用核磁共振、傅立叶红外和元素分析法对其分子结构进行了表征.利用该单体与异丙基丙烯酰胺共聚得到一种对温度和光敏感的共聚物.共聚物中少量的EAPEA单元能够显著降低聚异丙基丙烯酰胺(PNIPA)的相转变温度.当EAPEA的摩尔含量为2.94%时,相转变温度从PNIPA均聚物的31.8℃下降为22.0℃.在波长为365nm的紫外光照射下,共聚物中的偶氮基团能够从反式构型转变为顺式构型.在紫外光下照30s后,EAPEA摩尔含量为0.98%的聚{异丙基丙烯酰胺-共-2-[4-(4′-乙氧基苯基偶氮)苯氧基]乙基丙烯酸酯}的相转变温度从27.2℃上升到29.3℃.     

DTA中升温速率及样品热导率对T_g测量值影响的模拟研究

就不同升温速率和实际样品的不同热导率对差热分析 (DTA)中高分子材料的玻璃化转变曲线的影响进行了MonteCarlo模拟研究 ,发现当所有样品刚完成玻璃化转变时 ,在Tg 曲线中该特征点要低于Tg 的转变中点。转变中点所对应的样品温度肯定要高于实际的玻璃化转变温度。如果以玻璃化转变曲线的转变中点所对应的样品温度作为该材料的玻璃化转变温度 ,那么 ,升温速率越快、样品的热导率越小 ,所测得的玻璃化转变温度就越大 ,反之亦然。DTA测得的玻璃化转变温度与升温速率间有很好的线性依赖关系 ,但与样品热导率间的关系是非线性的     

二氧化碳-氧化环己烯的共聚反应

由CO2 -氧化环己烯 (CHO)配位催化共聚制得高Tg 的脂肪族聚环己基撑碳酸酯 ,并用IR、NMR和DSC等进行了表征 ,用TG对聚合物的热稳定性进行了分析。加入异氰酸苯酯有提高产物特性粘数的作用。     

丙三醇浓溶液玻璃化转变与结构松弛参数DSC分析

In order to examine the effects of water contents and heating/cooling rates on the glass transition and the structure relaxation parameters of glycerol/water mixtures, five aqueous solutions (60%, 70%, 80%, 90% and 100%) were investigated using the differential scanning calorimetry. Four scanning rates (10, 15, 20, 25 K/min) were used to obtain the glass transition parameters. The fitting results of plasticization constants indicated that Gordon-Taylor relationship could not be used effectively without considering scanning rates and that point on calorimetric step was chosen as the glass transition temperature. The specific heat changes during glass transition processes were relative not only to water content but also to heating rates. With the increasing of water contents in glycerol aqueous solutions, the structure relaxation activation energies and dynamic fragilities were decreased. Since the thermodynamic fragilities were increased with the increasing of water content, so the dynamic fragility and thermodynamic fragility were changed inversely if the water contents were changed in glycerol/water mixtures.     

玻璃化液体中构型熵与展宽弛豫函数关系的研究

The relationship between the transport properties and thermodynamic properties in glass forming liquids was investigated. The configurational entropy of Adam-Gibbs theory on cooperatively rearranging regions and the theoretic function derived from extremal value model were used to propose a brief that non-exponential stretched exponent in KWW form relaxation function is equal to the relative configurational entropy of cooperatively rearranging region in liquids, and is inversely proportional to the critical number of molecules occurring configurational transformation in a cooperatively rearranging region. Therefore, the new physical significance on glassy configuration is imposed on the stretched exponent, and theoretical developments and empirical correlations between the structural relaxation and configurational entropy are established. Further, an improved expression of β(T) was proposed to eliminate the deviation of the fit by using Vogel-Fulcher-Tammann equation from viscosity data at higher temperatures, which conforms well over 200 K temperature range. The improvement on β(T) is correspondent to the improvement on the difference in thermal capacities between isobaric and isochoric processes.     

邻甲酚醛环氧树脂/聚氨酯互穿聚合物网络的形态与性能

邻甲酚醛环氧树脂/聚氨酯互穿聚合物网络的形态与性能;互穿聚合物网络; 邻甲酚醛环氧树脂; 聚氨酯; 力学性能; 玻璃化转变温度     

超支化聚醚的支化度对玻璃化转变温度的影响

聚合物的分子结构对聚合物性能影响很大.支化度不同的同种聚合物,必须通过不同的催化体系合成,很难得到既具有相近分子量又具有不同支化度的系列聚合物样品,因此对聚合物性能与支化度的依赖关系的研究报道不多.     

超导体YBa2Cu3O7-δ的摩擦学特性研究

采用溶胶-凝胶法制备YBa2Cu3O7-δ和Ag/YBa2Cu3O7-δ超导材料,并分析其相组成及结构,用SFT-4000型高真空超低温摩擦磨损试验机对其从室温至液氮温度范围内的摩擦学特性进行评价.结果表明：在室温条件下,YBa2Cu3O7-δ与不锈钢盘对摩时的摩擦系数在0.50左右,当温度降到超导转变温度以下时,其摩擦系数急剧降低至0.13,最后稳定在0.20以下.添加Ag可以改善YBa2Cu3O7-δ的常温摩擦磨损性能,Ag/YBa2Cu3O7-δ复合材料的摩擦系数低且非常平稳,其中10%Ag/YBa2Cu3O7-δ的摩擦系数为0.20,磨损率为8.96×10-5mm3/（N.m）,Ag/YBa2Cu3O7-δ的磨损机制为YBa2Cu3O7-δ硬基底承载与软金属Ag转移膜的润滑作用.     

Fabrication of rhenium Josephson junctions

Rhenium is a superconductor with a relatively weak tendency to oxidize, which is advantageous in superconducting quantum circuit and qubit applications. In this work, Re/A1-A1Ox/Re Josephson tunnel junctions were fabricated using a selective film-etching process similar to that developed in Nb trilayer technology. The Re films had a superconducting transition temperature of 4.8 K and a transition width of 0.2 K. The junctions were found to be highly reproducible using the fabrication process and their characteristics had good quality with a low leakage current and showed a superconducting gap of 0.55 meV.     

超支化聚缩水甘油的合成及性能

以三羟甲基丙烷为引发剂、缩水甘油(2,3-环氧-1-丙醇)为单体、无水N-甲基吡咯烷酮(NMP)为溶剂,采用阴离子开环聚合、一步法制备了超支化聚缩水甘油(hPG)。通过调控单体与引发剂的物质的量之比,成功合成了3种不同数均分子量的hPG;通过核磁共振氢谱、凝胶渗透色谱、傅里叶红外光谱等表征了hPG的支化结构、分子量及分布、化学官能团;采用差示扫描量热仪、热重分析仪、粒径-电位分析仪等分析了hPG的玻璃化转变温度(T_g)、热降解温度(T_d)及热稳定性和溶液性质等参数。结果表明,溶剂NMP的引入有利于hPG数均分子量的快速增加和单分散性的提升;hPG的T_g和T_d随着数均分子量的增加略有增加。