掺杂光敏分子对环氧树脂光定向材料的性能影响

分别将肉桂酸和对正辛氧基肉桂酸进行酰氯化,与环氧树脂先驱聚合物(BP-AN)发生官能化反应,合成以肉桂酸酯和对正辛氧基肉桂酸酯为侧基的两种感光高分子(BP-AN-H和BP-AN-C8),然后合成了两种感光分子,对苯二酚双肉桂酸酯和对苯二酚双对正辛氧基肉桂酸酯,利用1H-NMR、FTIR进行了表征.最后将对应感光高分子与感光分子按不同比例掺杂,利用线性偏振光聚合(LPP)技术制备光定向层,组装成液晶盒.在偏光显微镜下观察液晶盒的定向效果,并测定其透过率-旋转角曲线.发现在一定的掺杂比例以下,增大掺杂感光分子的比例能够提高体系的定向效果,而且掺杂对苯二酚双对正辛氧基肉桂酸酯对定向能力的提高效果更为明显.     

侧链胆甾液晶聚合物及弹性体的液晶性能研究

把胆甾液晶单体 4 烯丙氧基苯甲酸胆甾醇酯 (Mch)分别和向列液晶单体 4 烯丙氧基苯甲酰氧基 4′ 甲氧基苯 (Mn) ,向列液晶交联剂 2 叔丁基对苯二酚双 [4 (6 丙烯酰氧基己氧基 )苯甲酸酯 ](Mnc)接枝到聚硅氧烷链上 ,得到系列侧链液晶聚合物Pn 系列和液晶弹性体Pe 系列 .通过热分析、偏光显微分析和X 射线分析等手段分别研究了向列液晶单体和向列液晶交联剂对含同一胆甾液晶基元聚合物的影响 .结果表明 ,向列液晶单体的摩尔百分比在 80 %以下 ,液晶聚合物Pn 系列为胆甾型液晶 ,在研究的范围内 ,液晶弹性体Pe 系列也为胆甾型液晶 ,Pn 系列和Pe 系列都具有较宽的液晶相范围 ,热分解温度均在 2 80℃以上 .     

硝基苯甲酸在水-乙醇混合溶剂中的电离热力学

用流动混合微量热计测定了25℃时三个硝基苯甲酸在水-乙醇[0-80%(v/v)]混合溶剂中的电离焓。引用文献ΔG1^0的插值结果, 计算了硝基苯甲酸在相同溶剂中电离过程的熵变。根据溶质在混合溶剂中的迁移焓特征, 分析讨论了硝基苯甲酸在水-乙醇混合溶剂中电离焓的变化趋势。认为邻硝基苯甲酸电离焓的特殊性, 可能与基团的空间位阻使阴离子的负电荷高度定域有关。     

单体结构对聚合物稳定胆甾相液晶形貌及光电性能的影响

采用紫外光聚合诱导相分离法制备聚合物稳定胆甾相液晶(PSCT),研究了单体4,4′-二[6-(丙烯酰氧基)己氧基]联苯(BAB6)、2-甲基-1,4-二[4-(3-丙烯酰氧基己氧基)苯甲酸基]对苯二酚(HCM-009)、2-甲基-1,4-二[4-(3-丙烯酰氧基丙氧基)苯甲酸基]对苯二酚(LCM)对常黑和常白模式PSCT光电性能的影响。结果表明:BAB6不具备液晶性,与液晶的相容性差,形成的聚合物网络疏松,网孔较大;HCM-009和LCM均具有液晶性,能很好地溶于液晶中。BAB6、HCM-009、LCM 3种单体形成的聚合物网络对液晶分子的锚定作用依次增强,常黑模式PSCT的阈值(饱和)电压减小,下降时间变长,迟滞宽度变大;而常白模式PSCT的驱动电压增大,响应速率变快。     

单体结构对聚合物稳定胆甾相液晶形貌及光电性能的影响

采用紫外光聚合诱导相分离法制备聚合物稳定胆甾相液晶(PSCT),研究了单体4,4′-二[6-(丙烯酰氧基)己氧基]联苯(BAB6)、2-甲基-1,4-二[4-(3-丙烯酰氧基已氧基)苯甲酸基]对苯二酚(HCM-009)、2-甲基-1,4-二[4-(3-丙烯酰氧基丙氧基)苯甲酸基]对苯二酚(LCM)对常黑和常白模式PSCT光电性能的影响。结果表明:BAB6不具备液晶性,与液晶的相容性差,形成的聚合物网络疏松,网孔较大;HCM-009和LCM均具有液晶性,能很好地溶于液晶中。BAB6、HCM-009、LCM 3种单体形成的聚合物网络对液晶分子的锚定作用依次增强,常黑模式PSCT的闲值(饱和)电压减小,下降时间变长,迟滞宽度变大;而常白模式PSCT的驱动电压增大,响应速率变快。     

硝基苯甲酸酯水解反应单电子转移机理的证据: ESR和自旋捕获的研究

对-硝基苯甲酸甲酯(1), 对-硝基苯甲酸正丁酯(2), 对-硝基苯甲酸叔丁酯(3), 对-硝基苯甲酸苄酯(4), 对-硝基苯甲酸苯酯(5), 对-硝基苯甲酸(对-硝基)苯酯(6), 间-硝基苯甲酸甲酯(7), 间-硝基苯甲酸乙酯(8), 间-硝基苯甲酸苯酯(9)和3,5-二硝基苯甲酸甲酯(10)与氢氧化钾在二甲亚砜中反应, 反应产物分别为相应的对-硝基苯甲酸和间-硝基苯甲酸。反应液用ESR检测, 得到1-10自由基负离子的ESR谱。用自旋捕获技术证明反应过程中有OH自由基生成, 自由基捕获剂亚硝基叔丁烷(TNB), 苯基叔丁基硝酮(PBN)和氧气使产物硝基苯甲酸的产率降低, 结果表明, 1-10与KOH与DMSO中反应存在单电子转移机理。     

硝基苯甲酸酯水解反应单电子转移机理的证据: ESR和自旋捕获的研究

对-硝基苯甲酸甲酯(1),对-硝基苯甲酸正丁酯(2),对-硝基苯甲酸叔丁酯(3),对-硝基苯甲酸苄酯(4),对-硝基苯甲酸苯酯(5),对-硝基苯甲酸(对-硝基)苯酯(6),间-硝基苯甲酸甲酯(7),间-硝基苯甲酸乙酯(8),间-硝基苯甲酸苯酯(9)和3,5-二硝基苯甲酸甲酯(10)与氢氧化钾在二甲亚砜中反应,反应产物分别为相应的对-硝基苯甲酸和间-硝基苯甲酸.反应液用 ESR 检测,得到1—10自由基负离子的 ESR 谱.用自旋捕获技术证明反应过程中有·OH 自由基生成.自由基捕获剂亚硝基叔丁烷(TNB),苯基叔丁基硝酮(PBN)和氧气使产物硝基苯甲酸的产率降低.结果表明,1—10与 KOH 在 DMSO 中反应存在单电子转移机理.     

气液色谱法测定双-(4,6-二异丙基水杨酸)合铜(Ⅱ)与脂肪胺和醇加合反应的热力学性质

用气液色谱法,在不同的温度下,测定了以α-甲基萘作为固定液时,路易斯碱脂肪胺和醇的溶解平衡常数K_R~0,以及它们与作为路易斯酸的过渡金属配合物双-(4,6-二异丙基水杨酸)合铜(Ⅱ)相互作用的表观分配常数K_R和加合反应的平衡常数K_1。再根据热力学公式: 进一步求出了加合反应的焓变ΔH和熵变ΔS。     

毛细管气相色谱法研究硝基氨基甲苯异构体在SE-30、SE-54中的热力学性质

通过对色谱分离过程的热力学处理,得到了用毛细管色谱法测定溶质在溶剂中的溶解热力学性质的关系式,利用该式测定了硝基氨基甲苯的五种异构体在SE-30,SE-54固定液中的溶解焓和溶解熵,并对结果进行了定性解释。     

毛细管气相色谱法研究硝基氨基甲苯异构体在SE-30、SE-54中的热力学性质

通过对色谱分离过程的热力学处理, 得到了用毛细管色谱法测定溶质在溶剂中的溶解热力学性质的关系式, 利用该式测定了硝基氨基甲苯的五种异构体在SE-30, SE-54固定液中的溶解焓和溶解熵, 并对结果进行了定性解释。     

反相高效液相色谱中溶质保留过程的热力学研究Ⅲ: 熵变及其分量,吸附及解吸附熵变

从理论上推导出了用柱相比和不用柱相比时溶质在反相高效液相色谱保留过程中的总熵变△S~(~P~a~)的两个表达式, 后者亦为计量置换保留模型中线性参数与该过程热力学函数间的定量表达式。△S~(~P~a~)也能够被分成两个独立的分量,吸附熵变△S~(~Ⅰ~,~a~)和解吸附熵变△S~(~Z~,~D~)。依据液相色谱中溶质计量置换保留模型中容量因子与流动相中置换剂活度a~D间的定量关系, 对在不同a~D条件下熔质的总熵变、吸附及解吸附熵变进行了估算, 并用实验测定的总熵变△S~(~P~a~,~e~)与估算总熵变△S~(~P~a~,~c~)进行了比较, 获得了结果的一致性。本文对传统的"吸附伴随着熵减小, 相反, 解吸伴随着熵增大"的定性规律予以定量的说明。     

Changes in thermodynamic quantities upon contact of two solutes in solvent under isochoric and isobaric conditions

The changes in excess thermodynamic quantities upon the contact of two solutes immersed in a solvent are analyzed using the radial-symmetric and three-dimensional versions of the integral equation theory. A simple model mimicking a solute in water is employed. The solute-solute interaction energy is not included in the calculations. Under the isochoric condition, the solute contact always leads to a positive entropy change irrespective of the solute solvophobicity or solvophilicity. The energy change is negative for solvophobic solutes while it is positive for solvophilic ones. Under the isobaric condition, the contact of solvophobic solutes results in system-volume compression but that of solvophilic ones gives rise to expansion. Effects of the compression and expansion on the changes in enthalpy and entropy are enlarged with rising temperature. When the solute solvophobicity is sufficiently high, the entropy change (multiplied by the absolute temperature) can become negative due to the compression, except at low temperatures with the result of an even larger, negative enthalpy change. The expansion in the case of solvophilic solutes leads to a large, positive entropy change accompanied by an even larger, positive enthalpy change. The changes in enthalpy and entropy are strongly dependent on the temperature. However, the changes in enthalpy and entropy are largely cancelled out and the temperature dependency of the free-energy change is much weaker. The authors also discuss possible relevance to the enthalpy-entropy compensation experimentally known for a variety of physicochemical processes in aqueous solution such as protein folding.     

Retention behavior of neutral solutes in pressurized flow-driven capillary electrochromatography using an ODS column

Several alkyl benzenes are separated by pressurized flow-driven capillary electrochromatography using a temperature-controlled capillary column packed with octadecyl siloxane-modified silica gel, and the effect of applied voltage on the retention is investigated. The van't Hoff plot shows good linearity at the column temperature between 305 and 330 K under applications from -6 to +6 kV. The applied voltage causes a relatively large variation in the enthalpy and the entropy of transfer of the solute from the mobile phase to the stationary phase (> 20%). However, the direction of variation in the enthalpy is almost opposite to that in the entropy, both of which might compensate each other. Therefore, the retention factor is not significantly varied (< 4%) by the application of voltage.     

Elution order in gas chromatography

The retention behavior of a heterogeneous group of solutes has been examined on seven different stationary phases under isothermal and temperature-programmed conditions. Both ΔH_v (enthalpy of solute vaporization from the stationary phase) and ΔS_v (entropy of solute vaporization from the stationary phase) values were determined for each solute – stationary phase combination under isothermal conditions. Both program rate and carrier gas velocity were shown to affect solute elution order. Unless these and other experimental factors discussed are controlled, column equivalency studies based on solute elution order have dubious value.     

Entropy-enthalpy compensations in solutions of dual character molecules with polymeric chromatographic liquid phases

Careful gas chromatographic studies provide thermodynamic data for insights into solution processes in nonvolatile solvents. Using 24 solutes and five stationary phases, several entropy-enthalpy compensation effects in the thermodynamics of solution were identified. Despite solute structure differences, when excess enthalpy and entropy of solutions were examined, entropy-enthalpy compensation effects were found in solvents dominated by single types of interaction: squalane and, to some extent, methoxy poly(ethylene oxide) (PEO). The main reason for the absence of linearity in other solvents is pure solute state interactions in the reference state and the multicharacter nature of solvents. In this study, consideration of solute state interactions was removed through examination of the thermodynamics of transfer between solvent pairs. It was found that solute transfers from squalane to poly[methyl(trifluoropropyl)siloxane] (QF-1) and to poly(methylphenyl) (DC-550) also gave linear relationships. The former system contains a second correlation for ester type solutes. The transfer data for squalane to poly(methylsiloxane) (DC-200) had smaller ranges and were more scattered. The effects of derivatizing groups on the transfer enthalpy and entropy were treated as a summation of hydrocarbon cores with the derivative groups. The group properties of transfer then also show entropy-enthalpy compensation effects. Many solution effects could be explained on the basis of solvent composition and local interactions with solutes.     

Effect of phase ratio on van't Hoff analysis in reversed-phase liquid chromatography,and phase-ratio-independent estimation of transfer enthalpy

In analysis of the thermodynamics of the transfer of a solute from the mobile phase to the stationary phase in reversed-phase liquid chromatography, it is nearly always assumed that the phase ratio is constant. This type of analysis is typically performed by applying a form of the van't Hoff equation, which relates the retention factor to temperature via the enthalpy and entropy of transfer. When non-linear van't Hoff plots are observed, it is often assumed that the enthalpy and entropy of transfer change with temperature. However, when the possibility of a change in the phase ratio is considered, it becomes apparent that non-linear van't Hoff behavior may or may not be due to changes in enthalpy or entropy. In this work, we present mathematical evidence that phase ratio changes, if they occur, can cause deviations from linearity in a van't Hoff plot. We also show that the phase ratio influence can be eliminated by considering the molecular difference between two solutes instead of the solutes themselves. The resulting selectivity van't Hoff plots may be linear, even when the van't Hoff plots of the two solutes are non-linear. In such cases, temperature-dependent phase ratio changes, and not necessarily changes in the transfer enthalpy, may be responsible for the curved van't Hoff plots of the individual solutes. In addition, we present chromatographic evidence that different solutes may "see" different thermodynamic phase ratios. It is clear that the concept of a phase ratio in reversed-phase chromatography is not nearly as well defined as a phase ratio in a bulk system like a liquid-liquid extraction.     

A review of: “Instrumental HPTLC,by W. Bertsch,S. Hara,R. E. Kaiser,and A. Zlatkis,editors, H. Verlag,Heidelberg, West Germany, 1980, 390 pp., cloth bound.”

Abstract

To understand the retention mechanisms involved in reversed-phase micelle chromatography, two models were examined to study the temperature and micelle concentration contribution to the retention process. the first model described the temperature contribution, using the van's Hoff equation, for each of the three equilibria: micelle-to-extra-micelle-mobile-phase, extra-micellar-mobile-phase-to-stationary phase and micelle-to-stationary phase. the second model described the temperature contribution on k' irrespective of the various equilibria involved. It was found that the enthalpy of retention obtained with the second model decreased with increasing micelle concentration. This contradicted a primary assumption in the first model that the equilibrium constants were independent of micelle concentration. No relationship was found between the enthalpy of retention evaluated with either model and the polarity of the partitioned solute molecules. A correlation was found between the entropy of retention and the polarity of these molecules. Fluorescence studies indicated that the micelle solvated molecules were probably located in the core of the micelles which contained other mobile phase components such as 1-propanol and water.     

Joint use of cyclodextrin additives in chiral discrimination by reversed-phase high-performance liquid chromatography: temperature effects

The temperature dependence of chiral separations was investigated in combined system of reversed-phase (RP) liquid chromatography using two chiral additives: single or β native cyclodextrins and their permethylated derivatives. The model tested compounds of pharmaceutical interest were: methylphenobarbital, mephenytoin, morsuximide and camphor. Taking the localization of a complexation process as a criterion – the combined system with two selectors has been rationalized as occurring in three stages. The influence of temperature (in narrow range of 20°C) on retention and enantioselectivity was studied in; System I (complexation occurs in the mobile phase), in System II (complexation on the stationary phase) and in System III (complexation in both phases together). In System III (as for System I) it has been found that the model compounds could be classified into three groups based on their retention dependence on temperature: retention decrease with temperature decrease, retention increase with temperature decrease or no influence of temperature on retention. For all the compounds investigated, decrease in temperature increases the selectivity. Standard enthalpy (ΔH⁰) and entropy (ΔS⁰) changes of solute transfer between the mobile and the stationary phase and standard enthalpy (ΔH⁰_CD) and entropy (ΔS⁰_CD) changes of complex formation were also calculated. In Systems I and III, if the complexation in the mobile phase is favored process compared with interaction with the stationary phases (RP or covered by permethylated cyclodextrin), the shortest retention time and the best selectivity is observed at low temperature.     

溶剂化的热力学集团展开理论

把二元溶液的过剩内能（excess energy）分成溶剂-溶剂、溶剂-溶质及溶质-溶质相互作用部分。利用集团展开方法给出了二元溶液在正则系综的配分函数的表达式,利用该表达式得到了溶质的偏摩尔内能(partial molar energy)和偏摩尔熵(partial molar entropy)的表达式。在无限稀溶液情形,过剩偏摩尔内能的溶剂-溶剂部分又称重组织内能（reorganization energy）,它反映了溶质存在时对其周围溶剂分子之间的相互作用能的影响。研究表明,在溶质的粒子数密度相对较大时,溶质分子之间的相互作用将影响过剩偏摩尔内能的溶剂-溶剂部分,对于稀溶液,过剩偏摩尔内能的溶剂-溶剂部分与溶质的摩尔分数成线性关系。对低密度二元溶液,溶质的过剩偏摩尔内能和过剩偏摩尔熵也与溶质的摩尔分数成线性关系。     

Determination of the enthalpy of solute-solvent interaction from the enthalpy of solution: aqueous solutions of erythritol and L-threitol

In this work the enthalpy of the solute-solvent interaction of erythritol and L-threitol in aqueous solution was determined from the values obtained for the enthalpy of solvation. The values for this property were calculated from those determined for the enthalpies of solution and sublimation. To determine the values of the enthalpy of solute-solvent interaction, the solvation process is considered as taking place in three steps: opening a cavity in the solvent to hold the solute molecule, changing the solute conformation when it passes from the gas phase into solution, and interaction between the solute and the solvent molecules. The cavity enthalpy was calculated by the scaled particle theory and the conformational enthalpy change was estimated from the value of this function in the gas phase and in solution. Both terms were determined by DFT calculations. The solvent effect on the solute conformation in solution was estimated using the CPCM solvation model. The importance of the cavity and conformational terms in the interpretation of the enthalpy of solvation is noted. While the cavity term has been used by some authors, the conformational term is considered for the first time. The structural features in aqueous solution of erythritol and L-threitol are discussed.