热致型液晶聚合物的等温和非等温晶化动力学

利用等温和非等温方法详细研究了芳香族聚酯──热致型聚合物对，对’－联苯二甲酸二辛酯的结晶相和液晶相形成机理，并计算了相变过程中的表面自由能与温度系数，研究结果表明：从介晶相开始的结晶过程是二维异相成核、三维线性增长的，而从各向同性液相开始的液晶相形成过程则是二维异相成核二维线性增长的．对两个晶化过程的表面自由能的研究表明，该聚合物液晶相形成过程的相转变表面自由能比结晶过程小得多，预示了它将具有更大的晶化速率．研究还发现，该聚合物的液晶相形成过程具有比结晶过程大得多的温度敏感性．     

O-(4-喹唑啉)羟肟酸硫代酯(酰胺)类化合物的合成及生物活性

用差示扫描量热分析研究了间规聚苯乙烯（ｓＰＳ）的非等温结晶及其动力学，并分别用Ｏｚａｗａ和Ｊｅｚｉｏｒｎｙ两种方法来处理ｓＰＳ的非等温结晶数据．结果表明，在２５～４０℃／ｍｉｎ的冷却速率范围内，ｓＰＳ的半结晶时间随冷却速率增大而呈指数式下降，ｓＰＳ非等温结晶过程遵循Ｏｚａｗａ动力学方程，但不符合Ｊｅｚｉｏｒｎｙ方法中的Ａｖｒａｍｉ动力学方程．所得到的ｓＰＳ非等温结晶Ａｖｒａｍｉ指数ｎ在３６～４１之间，高于等温结晶时的ｎ值     

聚氧化乙烯梳状聚合物共混物的非等温结晶动力学

用ＤＳＣ方法对乙烯基甲醚／马来酸酐交替共聚物多缩乙二醇酯（ＣＢＰ） 聚氧化乙烯（ＰＥＯ）共混体系的非等温结晶动力学进行了研究，用Ｍａｎｄｅｌｋｅｒｎ、Ｚ Ｊ（Ｚｉａｂｉｋｉ Ｊｅｚｉｏｒｎｙ）、Ｏｚａｗａ和对Ｏｚａｗａ方法的一种修正方法对该体系进行了处理．结果表明：得到了一种既没有结晶又有较多ＥＯ单元含量的共混物，ＣＢＰ对ＰＥＯ的结晶有抑制作用．Ａｖｒａｍｉ指数随冷却速率的加快在３８～５７之间波动．Ｍａｎｄｅｌｋｅｒｎ方法求得的结晶动力学参数Ｚｃ随冷却速率的增加而增加，共混物的Ｇｃ值不随冷却速率的变化而变化，随ＰＥＯ含量增加而减少，处理结果表明而Ｚ Ｊ理论能较好地解释本体系的非等温结晶过程和机理．     

一个判别液晶聚合物状态的新方法

伴随液晶相转变而产生的转变焓、转变熵可提供有关各相的结构、状态及有序度等信息.本文从动力学、热力学角度分析了液晶聚合物从各向同性熔体冷却时系统的热熵变化,建立了液晶聚合物升降温过程中的热熵图,提出了定量判断液晶聚合物从各向同性熔体冷却后所处状态的新方法.     

甲基纤维素/二氯乙酸液晶溶液的相转变

本文研究了甲基纤维素/二氯乙酸液晶溶液液晶相与各向同性相之间相互转变的过程。在连续升温过程中,由于液晶相内部有序度的非均一性,升温速率对液晶相织构随温度的变化有较大的影响。在等温相转变过程中,无论是从各向同性态转变为液晶态,还是其逆过程,从液晶态转变为各向同性态,相转变曲线均具有指数方程特征。利用与 Avrami 方程相似的指数方程进行处理,在从各向同性态转变为液晶态时,指数 n 大部分约为1。但液晶相向各向同性相在低于 Tc 时的相转变中,n 均小于1。相转变速率受溶液浓度和温度的影响。在质量分数为0.259的浓度时,液晶相向各向同性相的转变在低于 Tc 时39.5℃进行得最快。     

茂金属间规立构聚丙烯结晶动力学研究

用ＤＳＣ和密度法对茂金属间规立构聚丙烯（ｓＰＰ）样品进行了等温和非等温结晶动力学研究．测得平衡熔点Ｔ０ｍ为１５８℃,平衡熔融热焓ΔＨ０ｍ为３７ｋＪ／ｍｏｌ,侧表面自由能σ＝５２ｅｒｇ／ｃｍ２,折叠链表面自由能σｅ＝６９ｅｒｇ／ｃｍ２,链堆砌功ｑ＝３３７５ｋＪ／ｍｏｌ．对非等温结晶过程研究表明,由熔体结晶的ｓＰＰ具有非均相成核,三维球状生长机理．成核与生长活化能ΔＥ＝７３１ＫＪ／ｍｏｌ     

热致液晶共聚酯对聚丙烯结晶的诱导作用

用差示扫描量热法和光学解偏振法研究了热致液晶性芳香共聚酯与聚丙烯共混物的等温和非多温结晶行为.结果表明,这一热致液晶聚合物对聚丙烯结晶有诱导成核和加速作用.当共聚酯含量在2-5％之间时,聚丙烯的结晶速率最快.偏光显微镜的观察揭示出在聚丙烯熔体中原位形成的液晶聚合物微纤诱导了聚丙烯横穿晶的形成.     

热致液晶性纤维素衍生物HECA的非等温相转变动力学

本文利用DSC研究了羟乙基纤维素醋酸酯在不同降温速率下的非等温相转变动力学。发现利用改进的Avrami方程来处理得到其指数n接近于1,表明液晶相是在无热成核以后呈一维方式生长的。相转变速率常数随温度的升高而减小。相转变的半周期t_1/2比大多数高聚物结晶过程的半周期要短,并且随温度的升高而变长。相转变速率最快时的温度随着降温速率的增加而向低温方向位移。同时,在一定降温速率范围内降温速率增加,动力学相转变能力增强。有利于液晶相的形成。     

偶氮苯为探针的液晶聚合物聚集形态研究

利用紫外-可见光谱,对比研究了尾挂侧链液晶聚合物和腰挂侧链液晶聚合物在结晶相和液晶相转变过程中的液晶基元取向情况.研究表明,石英基材表面倾向于诱导偶氮液晶基元垂直于基材排列;观察到了在液晶态尾挂侧链液晶聚合物和腰挂侧链液晶聚合物的不同取向行为.在室温下重新结晶数天后,腰挂液晶聚合物的紫外可见光谱缓慢回复.     

烷基取代聚噻吩的非等温结晶动力学

根据ＤＳＣ测得的数值,采用Ｊｅｚｉｏｒｎｙ ,Вороховский和由作者实验室提出的一种新方法研究了十二烷基取代聚噻吩（Ｐ３ＤＤＴ） 和十八烷基取代聚噻吩（Ｐ３ＯＤＴ） 的非等温结晶过程,并应用Ｋｉｓｓｉｎｇｅｒ 法求取其结晶表观活化能ΔＥ,探讨了不同烷基取代基团对结晶过程的影响．Ｐ３ＤＤＴ 应用Ｊｅｚｉｏｒｎｙ 和Вороховский法描述时在结晶后期均发生偏离现象,而作者提出的新方法描述时则得到较好的线性关系．求得Ｐ３ＤＤＴ 的ΔＥ 为１８４－７９ｋＪ／ｍｏｌ,Ｐ３ＯＤＴ 的ΔＥ 为２４６－９３ｋＪ／ｍｏｌ,比较结晶表观活化能数值可知,Ｐ３ＤＤＴ 比Ｐ３ＯＤＴ 更易结晶．     

Photochemistry of peroxoborates: borate inhibition of the photodecomposition of hydrogen peroxide

The UV absorbance and photochemical decomposition kinetics of hydrogen peroxide in borate/boric acid buffers were investigated as a function of pH, total peroxide concentration, and total boron concentration. At higher pH borate/boric acid inhibits the photodecomposition of hydrogen peroxide (molar absorptivity and quantum yield of H(2)O(2) and HO(2) (-), (19.0+/-0.3) M(-1) cm(-1) and 1, and (237+/-7) M(-1) cm(-1) and 0.8+/-0.1, respectively). The results are consistent with the equilibrium formation of the anions monoperoxoborate, K(BOOH)=[H(+)][HOOB(OH)(3) (-)]/([B(OH)(3)][H(2)O(2)]), 2.0 x 10(-8), R. Pizer, C. Tihal, Inorg. Chem. 1987, 26, 3639-3642, and monoperoxodiborate, K(BOOB)=[BOOB(2-)]/([B(OH)(4) (-)][HOOB(OH)(3) (-)]), 1.0+/-0.3 or 4.3+/-0.9, depending upon the conditions, with molar absorptivity, (19+/-1) M(-1) cm(-1) and (86+/-15) M(-1) cm(-1), respectively, and respective quantum yields, 1.1+/-0.1 and 0.04+/-0.04. The low quantum yield of monoperoxodiborate is discussed in terms of the slower diffusion apart of incipient (.)OB(OH)(3) (-) radicals than may be possible for (.)OH radicals, or a possible oxygen-bridged cyclic structure of the monoperoxodiborate.     

NMR study of hydroxy protons of di- and trimannosides, substructures of Man-9

The chemical shifts, temperature coefficients and inter-residual rotating-frame Overhauser effect (ROE)s for the hydroxy protons of some alpha-(1,2)-, alpha-(1,3)- and alpha-(1,6)-linked di- and trimannosides have been measured for samples in 85% H2O/15% acetone-d6 solution. These mannosides, Manalpha(1-->2)ManalphaOMe (1) Manalpha(1-->3)ManalphaOMe (2), Manalpha(1-->6)ManalphaOMe (3), Manalpha(1-->2)Manalpha(1-->2)ManalphaOMe (4), Manalpha(1-->2)Manalpha(1-->3)ManalphaOMe (5), Manalpha(1-->2)Manalpha(1-->6)ManalphaOMe (6) and Manalpha(1-->3)[Manalpha1-->6]ManalphaOMe (7), are substructures of the N-glycan Man-9.The NMR data show that the hydration of each individual hydroxyl group in the di- and trisaccharides is very similar to the hydration of the corresponding hydroxyl in the monomeric methyl alpha-D-mannoside. No hydrogen-bond interactions were found to stabilize the conformations of the alpha-(1,2)- and alpha-(1,6)-linkages and the chemical shifts for the hydroxy proton resonances of the alpha-(1,6)-linkage indicated high-conformational flexibility. For the alpha-(1,3)-linkage, however, the downfield shift for the signal of O(2)H of the 3-substituted residue together with the ROE between this proton and H5' on the next residue suggest some weak inter-residue interactions.     

Fractional sublimation of some metal chelates of thenoyltrifluoroacetone

Studies on the fractional sublimation of various metal β-diketone chelates have been extended to include the chelates of thenoyltrifluoroacetone (TTA). Many of the common metal chelates were found to be stable, to sublime readily, and to form well-defined zones in the vacuum fractional sublimator. Of the 17 chelates reported only those of manganese (II) and iron(II) were not volatile. The chelates of UO₂(II), Zr(IV), Pb(II), and Cr(III) partially decomposed during sublimation and their recovery was incomplete. The recovery of the sublimed chelates of Ni(II), Mg(II), Al(III), Pd(II), Co(II), Cu(II). Fe(III), Tl(III), Zn(II) and Be(II) ranged from 87 to 100%, with most recoveries being quantitative. The sublimation recrystallization zone temperatures of the various chelates are compared to those of the metal acetylacetonates and the benzoyltrifluoroacetonates; in general, the metal chelates of TTA sublime more readily than those of benzoyltrifluoroacetone but are potentially less useful for fractional sublimation separations than the corresponding metal acetylacetonates. Even so, a quantitative separation of iron(III) from Ni(II), Al(III), Mn(II), and Fe(II) is proposed that depends upon the fractional sublimation of the TTA chelates.     

Enthalpies of formation of monoderivatives of hydrocarbons: Interaction of polar groups with an alkyl group

Energies of hydrocarbon monoderivatives CH(3)X, C(2)H(5)X, n-C(4)H(9)X, and n-C(5)H(11)X with 16 different substituents X were calculated at the levels B3LYP/6-311+G(d,p) and B3LYP/AUG-cc-pVTZ//B3LYP/6-311+G(d,p). The results were used to test the validity of the additive rule that has served commonly for estimating the enthalpies of formation Delta(f)H(T). The exact additivity corresponds to zero reaction energy DeltaE of the isodesmic reaction, in which the substituent X is transferred from one alkyl group R to another. Additivity is approximately fulfilled for butyl and pentyl derivatives with the differences less than 0.3 kJ mol(-1) (except charged groups X). Methyl derivatives deviated from the additive rule up to 22 kJ mol(-1) for dipolar groups X and 45 kJ mol(-1) for charged group, in agreement with the available experiments and with the anticipation of all suggested empirical schemes. In addition, smaller deviations of ethyl derivatives (3 or 20 kJ mol(-1), respectively) were observed here for the first time. There is no correlation between the deviations of methyl and ethyl derivatives; they are also not related to steric effects, and only partly to polarization. Deviations of methyl derivatives are proportional to the electronegativity of the first atom of the substituent; even when the definition of electronegativity is somewhat questionable, one can say in any case that it is controlled by the first atom.     

Control of helix sense by composition of chiral-achiral copolymers of N-propargylbenzamides

N-Propargylbenzamides 1-7 were polymerized with (nbd)Rh(+)[eta(6)-C(6)H(5)B(-)(C(6)H(5))(3)] to afford polymers with moderate molecular weights (M(n) = 26,000-51,000) in good yields. The (1)H NMR spectra demonstrated that the polymers have fairly stereoregular structures (81-88 % cis). The optically active polymers, poly(1) and poly(2), were proven by their intense CD signals and large optical rotations to adopt a stable helical conformation with an excess of one-handed screw sense when heated in CHCl(3) or toluene. The sign of Cotton effect could be controlled by varying the content in the copolymers of either chiral bulky 1 and achiral nonbulky 3, or chiral nonbulky 2 and achiral bulky 7. The smaller the pendant group in the copolymerization of achiral monomers with 1, the more easily did the preferential helical sense change with the copolymer composition. However, the copolymers of chiral nonbulky 2 and achiral nonbulky 3 did not change the helical sense, irrespective of the composition. The free energy differences between the plus and minus helical states, as well as the excess free energy of the helix reversal, of those chiral-achiral random copolymers were estimated by applying a modified Ising model.     

Constituents of Leaves of Uncaria Hirsuta Haviland

Nine compounds, ursolic acid (1), β-sitosteryl glucoside (2), umbelliferone (3), uncarine-A (4), chlorogenic acid (5), rutin (6), neohesperidin (7), quercitrin (8)and afzelin (9) were isolated and characterized from fresh leaves of Uncaria hirsuta. Their structures were elucidated by spectral methods. Among them, uroslic acid (I) exhibited a cytotoxic principle of this plant.     

Characterization of the transport properties of membranes of uncertain macroscopic structural homogeneity

The present paper confirms and extends previous applications of an original method of time-lag analysis to (concentration-independent) gas permeation through porous pellets produced by uniaxial compaction of fine graphite powder. It is shown that this approach to the study of membrane permeability enables one to (i) detect unambiguously a macroscopic structural inhomogeneity affecting transport across the membrane (often present as an unsuspected artifact of the membrane fabrication process); (ii) determine appropriate average values of the resulting space-dependent diffusion, D(x), and sorption, S(x), coefficients (without recourse to equililibrium sorption measurements); (iii) secure substantial information about the functional form, as well as the degree, of variability of D(x) and S(x); and ultimately (iv) link this information to the underlying membrane structural inhomogeneity. In the present context, the salient underlying structural feature is nonuniform porosity across the membrane, represented by (x), and the link between D(x), S(x) and (x) is provided by the simple dual-mode (intrapore gas-phase + adsorbed-phase) model of sorption and transport in porous media. The effect of increasing overall pellet porosity (_obs) by reducing applied compacting pressure, was specifically studied and found to entail marked enhancement of the degree of structural inhomogeneity without material changes in the functional form of D(x), S(x) and hence of (x). The conclusions drawn from time-lag analysis were shown to be consistent with the observed behavior of apparent diffusion coefficients derived from transient-state sorption or permeation measurements and with the results of dual-mode steady-state permeation analysis. The latter results showed additionally that, for a more complete interpretation of observed transport behavior, the variability across the pellet of the orientation of graphite particles should also be taken into account.     

对苯二胺功能化还原氧化石墨烯的结构和官能团变化

采用一步水热回流法,选取对苯二胺(PPD)对氧化石墨烯(GO)进行还原与改性处理,制备了功能化还原氧化石墨烯(GOP-X).采用傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)及X射线衍射(XRD)等研究了PPD与GO的反应作用类型及结构变化.结果表明,随着PPD与GO质量比的增加,GOP-X层间距(d值)先增大后减小,GOP-X共轭结构逐渐恢复,与溶剂分子作用时,层间距增幅呈减小趋势,并最终趋于恒定.PPD单体与GO反应时存在3种键合类型:(1)GO含氧官能团和PPD分子之间的氢键作用(C—OH…H2N—X);(2)质子化PPD与弱酸性GO带负电位置之间的离子键作用(—COO-H3+N—X);(3)PPD中氨基(NH2)与GO含氧官能团之间形成的共价键作用.与GO中羧基(COOH)的酰胺化反应将先于与环氧基(C—O—C)的亲核取代反应.提出了相应的作用机理.     

Constituents of Flowers of Murraya Paniculata

Three new coumarins, yuehgesin-A (1), -B (2) and -C (3) and 22 compounds—murracarpin (4), mupanidin (5), isomeranzin (6), murralongin (7), scopoletin (10), 7-methoxy-8-(l′-ethoxy-2′-hydroxy-3′-methyl-3′-butenyl)coumarin (11), umbelliferone (12), paniculatin (13), braylin (14), auraptenol (15), meranzin hydrate (16), minumicrolin (17), scopolin (18), caffeine (19), 3,3′,4′,5,5′,6,7-heptamethoxyflavone (20), 4-hy-droxybenzaldebyde (21), p-hydroxybenzoic acid (22), cis- and trans-ferulic acid (23), cis- and transmethyl ferulate (24) and trans-ethylferulate (25)—were isolated and characterized from fresh flowers of Murraya paniculata collected in Taiwan. Their structures were elucidated by spectral methods. The chemotaxonomy of Murraya paniculata is, discussed.     

丁酸氯维地平降解杂质的合成

以4-(2,3-二氯苯基)-1,4-二氢-2,6-二甲基-3,5-吡啶二羧酸(2-氰基乙基)（甲基）酯(5)为起始原料,合成了丁酸氯维地平的5种降解杂质：4-(2,3-二氯苯基)-1,4-二氢-2,6-二甲基-3,5-吡啶二羧酸单甲酯(A), 4-(2,3-二氯苯基)-1,4-二氢-2,6-二甲基-3-吡啶羧酸甲酯(B), 4-(2,3-二氯苯基)-2,6-二甲基-3,5-吡啶二羧酸单甲酯(C), 4-(2,3-二氯苯基)-2,6-二甲基-3,5-吡啶二羧酸（丁酰氧基甲基）（甲基）酯(D)和4-(2,3-二氯苯基)-2,6-二甲基-3-吡啶羧酸甲酯(E)。其中A由5水解制得;B由A脱羧制得;C由5氧化后再经水解制得;D由C和丁酸氯甲酯缩合制得;E由C脱羧制得,化合物结构经¹H NMR和MS（ESI）确证。