原位红外光谱研究间规聚丙烯介晶相的相转变行为

聚合物的介晶相作为一种介于结晶和无定形之间的有序态结构[1],其相转变行为对于理解结晶过程具有重要的意义。间规聚丙烯(sPP)是一种典型的多晶型聚合物,不同的晶型中分子链采取不同的构象[2]。基于红外光谱对分子链构象的敏感性,本工作采用原位红外光谱研究了sPP介晶相在连续升温过程中的微观结构变化。通过对拉伸后的sPP薄膜进行应力松弛得到了高介晶相含量的sPP薄膜。红外光谱研究结果表明,介晶相在升温过程中经历了多次相转变过程。在20~40℃之间,介晶相和少量结晶完善程度低的formⅡ晶体发生部分熔融;在40~90℃范围内,未熔融的介晶相转变为formⅠ/Ⅱ,且在70~90℃之间,还存在formⅠ/Ⅱ的完善和无定形相向formⅠ/Ⅱ的转变,即无定形相的冷结晶过程。当温度高于90℃时,formⅠ/Ⅱ开始发生熔融。     

1-羟基-5-十二烷氧基-萘LB膜结构和取向的光谱研究

用红外透射,反射光谱及紫外可见吸收光谱方法研究了１－羟基－５－十二烷基－萘ＬＢ膜及溶液状态下的结构,分子取向。研究结果表明分子在溶液中主要是以单体形式存在;在ＬＢ膜中是以聚集体形式存在。     

红外光谱法研究液态邻位取代的苯甲酸类衍生物的氢键行为

用红外光谱法研究了高温下熔融态的邻位取代苯甲酸衍生物的氢键行为。邻卤(F,Cl,Br,I)苯甲酸在固态时以羧基二聚体形式存在,熔融后二聚体部分解聚,仍有部分分子以二聚体形式存在。固态和液态邻乙氧基苯甲酸的红外吸收无明显差异,表明两者均为分子内氢键的结构。固态邻甲氧基苯甲酸以羧基二聚体形式存在,其熔融后二聚体全部解聚形成了分子内氢键,即甲氧基的氧与羧基的氢形成了氢键。     

四新戊氧基酞菁锌旋涂膜的吸收光谱的温度特性

在玻璃基片上制备了四新戊氧基酞菁锌的旋涂膜,通过测定该薄膜在不同温度退火后的吸收光谱和Ｘ射线衍射谱图,研究了酞菁分子聚集体在薄膜中的变化。随着温度的升高,单体逐渐转变为聚集体;当温度升高到４００℃时,聚集体重又向单体转变,同时还伴随有体系内非晶→晶相→非晶的相变。     

西佛碱型液晶化合物相变过程中分子排列方式变化的拉曼光谱研究

用变温拉曼光谱对相变过程的研究表明,液晶化合物的初始晶态与熔融后缓慢降温得到的晶态并不吻合,两个状态下分子尾链的构象及刚性核部分的构象不同导致分子的聚集状态不同。西佛碱型液晶化合物VO10相变过程中,在晶态到液晶态相转变过程中,烷氧基尾链链内构象发生突变,同时有序性降低,刚性核部分两个苯环之间的二面角在相变点时发生明显变化,二面角加大。     

二乙胺四氯合铜相变的FTIR和2D-COS分析

具有热致变色性能的化合物二乙胺四氯合铜[(C_2H_5)2NH_2]_2CuCl_4在52℃附近发生从绿色变为黄色的热致变色现象。本文采用傅里叶变换红外光谱(FTIR)和二维相关性分析(2D-COS)研究在加热和冷却过程中相转变过程中有机部分的铵离子和乙基所起的作用。随着温度的升高,分子中产生N—H…Cl氢键的强度减弱和烷基链的热扰动两种作用。2D-COS分析表明N—H…Cl氢键首先对温度升高有反应,可能作为[CuCl_4]~(2-)阴离子结构变化的主导驱动力。     

锰硅化物的固相反应生长研究

报道了利用固相反应方法在单晶Si(100)衬底上制备锰硅化物薄膜.实验发现,样品在固相反应过程中经历了两种相转变,即反应温度为450℃时形成了立方相MnSi,达到550℃时形成了四方相MnSi1.73.随着反应温度的提高,薄膜呈现取向生长.利用四探针法对固相反应过程中化合物薄层方块电阻的原位测量表明,立方相开始形成的温度约为410℃,由立方相向四方相转变的起始温度约为530℃.红外透过谱测量得到了不同结构相的红外吸收特征峰.     

锰硅化物的固相反应生长研究

报道了利用固相反应方法在单晶Si(100)衬底上制备锰硅化物薄膜.实验发现,样品在固相反应过程中经历了两种相转变,即反应温度为450℃时形成了立方相MnSi,达到550℃时形成了四方相MnSi173.随着反应温度的提高,薄膜呈现取向生长.利用四探针法对固相反应过程中化合物薄层方块电阻的原位测量表明,立方相开始形成的温度约为410℃,由立方相向四方相转变的起始温度约为530℃.红外透过谱测量得到了不同结构相的红外吸收特征峰     

萃金体系第三相的产生及其谱学研究

利用^198Au示踪法研究了十四烷基二甲基苄基氯化铵从碱性氰化液中萃取金第三相的产生过程，同时用傅里叶变换红外光谱（FTIR），核磁共振（NMR），激光光散射（DLS）等方法分析了第三相形成后上下两有机相的微观结构，结果表明，随着有机相中金浓度的增大，有机相中有纳米级的聚集体形成；当金浓度继续增大时，有机相分为上下两相，有机相中的金，磷酸三丁酯（TBP）和水主要集中在下层，下层有机相有明显的水特征吸收峰，TBP的P=O伸缩振动向低频移动，核磁共振（^31P-NMR)的化学位移明显移向高场；用激光光散射技术测定了两有机相中聚集体的大小。     

N-十六烷基聚对苯二甲酰对苯二胺的红外光谱研究

以聚对苯二甲酰对苯二胺(PPTA)和1-溴正十六烷为原料,利用N-烷基化方法合成了N-十六烷基聚对苯二甲酰对苯二胺(PPTAC16),并采用DSC和FTIR方法进行了详细研究。DSC结果表明PPTAC16存在侧链结晶行为,但侧链结晶的完善程度低于正十六烷烃的结晶。红外光谱结果表明,烷基侧链结晶中亚甲基堆积的有序度低于正十六烷烃晶体,亚甲基的构象中存在相当数量的旁式构象。变温红外光谱结果表明随着温度的升高,亚甲基的伸缩振动谱带和变角振动谱带的峰位发生突变,说明侧链结晶的熔融;该结果与DSC测试结果一致。另外,伴随着十六烷基侧链结晶的熔融,PPTAC16的主链发生了一种不可逆的变化,且熔融后的烷基侧链所处的状态与液态十六烷烃存在差别。     

Thermal and dielectric studies of self-assembly systems formed by hydroquinone and alkyloxy benzoic acids

Self-assembly systems formed by hydroquinone and alkyloxy benzoic acids are isolated and characterized. Hydroquinone formed double hydrogen bonds with p-n-alkyloxy benzoic acids. Various hydrogen bonded complexes have been synthesized with hydroquinone and pentyloxy to dodecyloxy benzoic acid, respectively. FTIR studies confirm the hydrogen bond formation in the complex. Polarizing Optical Microscopic (POM) studies revealed the textural information while the transition and enthalpy values are experimentally deduced from Differential Scanning Calorimetry (DSC) studies. Phase diagram has been constructed from the POM and DSC data. The members of the present homologous complexes are characterized by POM, DSC, optical tilt angle and dielectric studies. Odd-even effect has been evinced in enthalpy values and transition temperatures corresponding to the isotropic to nematic phase transition. Optical tilt angle in Smectic C phase data has been fitted to a power law and it has been observed that the temperature variation of the tilt angle follows Mean Field theory prediction. Results of Fourier Transform Infrared Spectra (FTIR), POM, DSC, tilt angle and dielectric studies are discussed.     

磷酸-氨水蒸沉γ晶型聚酰胺6的热行为研究

尼龙6是一种多晶型的半结晶高聚物。实验采用蒸沉法制备出尼龙6,首先通过XRD和FTIR的手段进行表征,与采用沸水处理的尼龙6样品表征结果对比,确定其为γ晶型,然后在130～211℃的温度范围内进行热处理,通过DSC研究其在低于熔点热处理时的整个热行为变化过程,并运用FTIR观察其在不同条件下热处理发生的晶型变化。发现蒸沉法制备的γ晶型尼龙6随着热处理温度的升高,整体结晶完善度以及晶片厚度随着处理温度的升高而增加。而且在这个过程中,样品厚度不同的晶片在不同温度下发生了γ晶型向α晶型的转化,最终在接近熔点(211℃)热处理时,样品变为以α晶型为主。     

氢键诱导液晶的DSC和变温红外光谱研究

制备了两个分别基于4,4’-联吡啶(BPy)和丙基反式环己基苯甲酸(PCBA)以及BPy和丙基反式双环己基甲酸(PCCA)的氢键液晶复合物(PCBA-BPy和PCCA-BPy),结合使用偏光显微镜(POM),用差示扫描量热(DSC)和变温傅里叶变换红外光谱对它们的中间相性能和分子间氢键的热稳定性进行了表征。结果表明,这两个氢键复合物都具有由于分子间氢键作用而导致的近晶相,但它们中存在的氢键作用却不相同,在PCBA-BPy中,温度变化时,发生氢键结合的羰基的吸收峰的位置仅在发生晶型转变时有突变,而在PCCA-BPy中,温度变化时,其羰基的吸收峰的位置则基本不发生突变。另外,当温度高于它们的清亮点时,这两个氢键液晶复合物的分子间氢键都发生部分分解。     

Optical modulation in nematic phase of halogen substituted hydrogen bonded liquid crystals

A series of halogen-substituted hydrogen-bonded liquid crystalline complexes have been designed and synthesised. A successful attempt has been made to form complementary hydrogen bonding between the dodecyloxy benzoic acid (12BAO) and halogen-substituted benzoic acids and the physical properties exhibited by the individual complexes are studied. The complexes obtained are analysed by polarising optical microscope (POM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and dielectric studies. The formation of complementary hydrogen bond is confirmed through FTIR spectra. An interesting feature of this series is the observation of a field-induced transition (FiT) in nematic phase. Another interesting phenomenon is the observation of a new smectic X phase (worm-like texture) in all the synthesised complexes. Dielectric relaxation studies in the smectic C phase of these hydrogen bonded complexes along with the Arrhenius and the Cole–Cole plots are discussed. Optical tilt angle in smectic C phase and the corresponding fitted data analysis concur with the Mean field theory prediction.     

TiO2光催化剂的光谱研究

采用sol-gel法制备了纳米TiO2光催化剂,运用FTIR,FT－Ranam,DSR等光谱技术对催化剂进行了表征,以光催化解油酸作为模型反应考察光催化活性。实验结果表明,催化剂的烧结温度对催化剂的晶相结构、半导体能带结构、光吸收性能及光催化活性均产生显著的影响,当烧结温度为400℃时,TiO2光催化剂具有最好的表观吸光度,最大的吸收带边,以及最佳的光催化活性。     

Crystal melting processes of propylene carbonate and 1,3-propanediol investigated by the reed-vibration mechanical spectroscopy for liquids

The melting of crystals is one of the most common and general phase transition phenomena.However, the mechanism of crystal melting is not well understood, and more experimental measurements and explorations are still needed.The mechanical spectra of propylene carbonate and 1,3-propanediol during the crystal melting processes are measured by the reed vibration mechanical spectroscopy for liquids(RMS-L) for the first time.The experimental results show that as the temperature increases, the real part of the complex Young modulus first decreases slowly, and then quickly drops to zero;meanwhile, its imaginary part increases slowly at first, then goes up and drops quickly to zero, showing a peak of internal friction.Preliminary analyses indicate that both the real and imaginary parts can present some characteristics of the melting process, such as the transition from the disconnected liquid regions to the connected liquid regions, that from the connected crystal regions to the disconnected crystal regions, and so on.In addition, the results show that the melting rate per unit volume of crystalline phase versus temperature satisfies the Arrhenius relation at the initial stage of melting, and deviates from this relation as the temperature increases to a certain value.Therefore, the RMS-L will provide an effective supplement for the further study of melting.     

SO2-4/TiO2固体酸的红外和拉曼光谱研究

用ＩＲ、Ｒａｍａｎ光谱研究了ＳＯ＾２－４／ＴｉＯ２固体酸在不同烧温度下的结构、晶相转变和表面酸中心。结果表明,ＳＯ＾２－４与ＴｉＯ２表面的结合为螯合式双配结构。当烧结温度小于５００℃时,ＳＯ＾２－４／ＴｉＯ２样品具有较高的结构稳定性,晶相结构以锐钛矿为主,表面Ｂ酸位数目约是Ｌ酸位数目的２倍,当烧结温度大于５００℃时,随着烧结晶度的升高,表面结合的ＳＯ＾２－４逐渐流失,晶相从锐钛矿转变为金红石,表面Ｂ酸位减少并消失。     

Thermal and Optical Properties of Some Hydrogen-Bonded Liquid Crystal Mixtures

Phase transition properties of the mixtures of hydrogen-bonded nematic liquid crystals (HBLC) 4-hexylbenzoic acid (6BA), 4-(octyloxy)benzoic acid (8OBA), and 4-(decyloxy)benzoic acid (10OBA) have been investigated by means of differential scanning calorimetry (DSC) and polarize optic microscope (POM). The DSC and POM results clearly indicate the existence of smectic and nematic phase transitions in binary mixtures. The phase transition temperature values of 6BA/10OBA mixtures have clearly increased with increasing heating rate. The activation energies were calculated for the phase transitions of 6BA/10OBA liquid crystal (LC) mixture. The optical transmittance of these mixed hydrogen-bonded nematic liquid crystals was investigated in terms of temperature variations through electrooptic methods. The electrooptic experiments indicate that, while low in the nematic phase, the optical transmittance is very high at the nematic-isotropic phase transition. The transmitted light intensity values of 6BA/8OBA mixture are somewhat higher than those of other binary mixtures, 6BA/10OBA and 8OBA/10OBA, a result associated with the different alkyloxy chain lengths.     

Hydrogen bonding and liquid crystallinity of low molar mass and polymeric mesogens containing benzoic acids: a variable temperature Fourier transform infrared spectroscopic study

The phase behaviour and mesomorphism of poly(4-(6-propenoyloxyhexyloxy)benzoic acid) (PPOHBA) and 4-pentyloxybenzoic acid (POBA) is studied using variable-temperature Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction. PPHOBA exhibits a smectic C phase and POBA, a nematic phase. The temperature dependence of the Fermi resonance bands associated with the hydroxyl groups and of the carbonyl stretching region in the FTIR spectra indicates that there is a dynamic equilibrium between monomers and open and closed dimers formed by hydrogen bonding between benzoic acid moieties. The nematic phase observed for POBA is linked to the anisotropic cyclic dimer, while an abrupt increase in the concentration of monomer drives isotropisation. In PPOHBA, hydrogen-bonded supramesogens promote smectic behaviour, while hydrogen-bonded crosslinks stabilise the lamellae. The increased viscosity arising from this dynamic crosslinking is offset by the flexibility of the acrylate backbone and alkyl spacers.     

Induced Smectic X Phase Through Intermolecular Hydrogen-Bonded Liquid Crystals Formed Between Citric Acid and <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">n</Emphasis>-(Octyloxy)Benzoic Acid

Hydrogen-bonded liquid crystal (HBLC) is synthesized from citric acid (CA) and 4-(octyloxy)benzoic acid (8OBA) with different mole ratios. Fourier transform infrared spectroscopy (FT-IR) confirms the presence of hydrogen bond between CA and 8OBA. Nuclear magnetic resonance (NMR) spectroscopic studies validate the intermolecular complementary, cyclic type of hydrogen bond, and molecular environment in the designed HBLC complex. Powder X-ray diffraction analysis reveals the monoclinic nature of liquid crystal complex in solid phase. Liquid crystal parameters such as phase transition temperature and enthalpy values for the corresponding mesogenic phases are investigated using a polarizing optical microscope (POM) and differential scanning calorimetry (DSC). It is observed that the change in chain length and steric hindrance while increasing the mole ratio in HBLC complex induces a new smectic X (Sm X) along with higher-order smectic G (Sm G) phases by quenching of smectic C (Sm C). From the experimental observations, induced Sm X phase has been identified as a finger print texture. Also, Sm G is a multi-colored mosaic texture in 1:1, 1:2, and 1:3 mol ratios. The optical tilt angle, thermal stability factor, and enhanced thermal span width of CA + 8OBA complex are discussed.