黑皂膜的光谱学研究

由溴化十六烷基三甲铵(CTAB)和甲基橙(MO)的混合溶液制成了含染料分子甲基橙的黑皂膜(BSF)。用电子吸收和FT-IR光谱考察了成膜的动态过程。水核厚度随溶液中甲基橙浓度增加而交薄,由普通型BSF最终交为Newton型BSF。脂链CH_2伸缩振动及甲基橙π—π~*吸收特征表明,两类BSF中CTAB的聚集态均为取向的液晶态,而MO在两类膜中亦具有相同的聚集形态和取向特征。以单轴取向模型建立了分子取向角与偏振Raman强度间的关系。由偏振Raman实验结果计算出MO在两类BSF中以相同的倾角(约80°)嵌在单分子膜壁上。     

二维凝聚体系中单轴承向分子的偏振Raman散射强度

分析子薄膜体系几种常用测量坐标下的偏振Raman散射强度表达式，发现当测量坐标与膜坐标重叠时，各种偏振Raman散射强度只需用膜坐标中的Raman散射活性来表达，如果这两个坐标不重叠，需进一步求出膜坐标中Raman张量元二次交叉项的平均值，本文给出了单轴唯一角取向模型这了些二次交叉项的平均值表达式及取向分布模型下膜坐禁中所有Raman张量元二次项平均值。     

二维凝聚体系中单轴取向分子的偏振Raman散射强度

分析了薄膜体系几种常用测量坐标下的偏振Raman散射强度表达式,发现当测量坐标与膜坐标重叠对,各种偏振Raman散射强度只需用膜坐标中的Raman散射活性来表达。如果这两个坐标不重叠,需进一步求出膜坐标中Raman张量元二次交叉项的平均值。本文给出了单轴唯一角取向模型下这些二次交叉项的平均值表达式及取向分布模型下膜坐标中所有Raman张量元二次项平均值。     

含染料分子黑皂膜的共振Raman光谱

以染料分子BY为酸、碱性探针,研究了含BY的BSF,BY的CTAB胶束溶液和BY水溶液三种微环境,在不同pH条件下的共振Raman光谱。结果表明,束缚于BSF夹心界面和胶束界面的BY,具有类似的光谱变化,但BSF在很大的pH范围内(中-碱性),以酸式和碱式结构共存为特点。进一步研究发现,BSF夹心水核相的pH,对体相pH的变化,表现出相对稳定的新功能。     

界面单分子膜的共振Raman光谱及分子取向分布

基于长链分子在界面单分子膜中的单轴取向性,建立了以分布函数描述的取向分布模型。籍此对含偶氮苯的长链两亲性分子的界面单分子膜的共振Raman光谱观测结果进行了理论分析。利用偏振Raman强度值计算得到序参数和,并进一步给出了分子取向分布的图象。结果表明,取向分布随吸附量增加而改变,在不同的界面间显示出有意义的差别。文中还从分子取向变化的角度,讨论了二维凝聚态的性质,从而对这类界面体系获得更深刻的认识。     

由激光诱导荧光方法探测光碎片分子取向的理论研究

采用密度矩阵方法,推导了从激光诱导荧光(LIF)强度中抽出光碎片取向参数的表达式.光碎片的取向由分子态多极矩描述.用于解离母分子和激发碎片分子的激光均为线偏振光,而探测荧光为非偏振光.激光诱导荧光强度是光碎片分子初始态多极矩、线强度因子和解离-激发几何因子的函数.光碎片的取向参数可以由测量荧光偏振比和计算动力学因子而获得.     

利用和频振动光谱研究空气/短链脂肪酸界面的分子取向

利用和频振动光谱(SFG-VS)方法检测了5种短链脂肪酸分子(乙酸、丙酸、正丁酸、正戊酸及正己酸)在空气/纯液体界面的结构, 得到了3种偏振组合(ssp, ppp, sps)下的和频振动光谱. 通过偏振选择定则对各个谱峰进行了指认和分析, 同时计算出空气/纯脂肪酸液体界面上脂肪酸分子的甲基取向角. 对比发现, 从丙酸到己酸, 分子甲基基团的界面取向角随碳链的增长略有增大. 并对其机理进行了分析.     

用偏振红外光谱表征经单轴和双轴拉伸的PET薄膜

用偏振红外光谱方法研究了拉伸速率和不同拉伸方式,包括单轴拉伸、双轴同时拉伸和双轴依次拉伸等,对PET薄膜取向的影响。对由不同拉伸方式制得的反式结构含量和密度均基本相同的试样进行比较得出:单轴拉伸试样中分子链相对拉伸方向的轴取向程度最高,分子链在薄膜平面内的取向分布亦最不均匀;双轴拉伸试样中分子平面(苯环面)相对薄膜平面有明显的平面取向,而单轴拉伸试样中分子平面和薄膜平面基本上无共平面趋势。在所用的实验条件下,拉伸速率对取向程度几乎没有影响。     

红外光谱结合线阵列检测技术研究聚合物分散液晶膜分子取向

采用偏振红外光谱和变温红外光谱研究聚合物分散液晶膜中液晶分子取向随外加电场及温度的变化.利用线阵列检测技术表征了聚合物与液晶界面处的成分分布.结果表明,线阵列检测技术能够快速而直观地给出成分分布图,通过该成分分布图可以解释PDLC在温度场作用下分子取向的变化.     

壳层悬挂β-环糊精单元的两亲性超支化聚合物的分子包合与识别行为

采用紫外分光光度法研究了两种壳层悬挂β-环糊精单元的两亲性超支化聚合物在缓冲溶液(25 ℃, pH=11)中的分子包合与识别行为. 结果表明, 两种聚合物具有来自环糊精单元和两亲性超支化聚合物的双重包合能力, 可分别与水溶性染料分子酚酞(PP)、甲基橙(MO)、有机小分子对硝基苯酚(p-NP)等3种客体分子发生单客体包合效应, 而且其包合能力强于单一的环糊精或两亲性超支化聚合物; 通过客体分子PP和MO证实了这两种聚合物还具有双重识别能力, 可以与PP和MO发生双客体包合效应.     

Determination of the molecular orientation of very thin films on solid substrates: surface liquid crystal layers and rubbed polyimide films

The molecular orientation of very thin films on solid substrates can be determined quantitatively by measuring the polarized infrared (IR) absorption spectra of samples as a function of angle of incidence. The quantitative molecular orientation is derived by fitting the incident angle dependence and the dichroic ratio with theoretical calculations. We applied this method to a technologically important system: liquid crystal (LC)/rubbed polyimide film. To understand the alignment mechanism of LC molecules in contact with rubbed polyimide films, we have quantitatively determined the molecular orientation of rubbed polyimide films and a surface LC layer in contact with a rubbed polyimide film. In this paper two relations are discussed: (1) correlation between the inclination angle of polyimide backbone structures in rubbed films and the pretilt angle of bulk LC in contact with them, and (2) relation among the molecular orientation of a rubbed polyimide film and those of surface and bulk LC layers in contact with it.     

Molecular-level control of the photoluminescence from PPV nanostructured films

The fabrication of varied molecular architectures in layer-by-layer (LbL) films is exploited to control the photoluminescence (PL) of poly(p-phenylene vinylene) (PPV) in an unprecedented way. This was achieved by controlling the F?rster energy transfer between PPV layers (donors) and layers of a commercial azodye, Brilliant Yellow (BY) (acceptors). Energy transfer was controlled by inserting spacer layers of inert polymers between PPV and BY layers and by photoaligning the BY molecules via trans-cis-trans isomerization. The PPV/BY LbL films displayed polarized PL whose intensity could be varied almost continuously by changing the time of photoalignment, which was carried out by impinging a linearly polarized laser light simultaneously to the PL experiments. For PPV/BY films with no spacer layers, PL was completely quenched, but its intensity increased with the number of spacing layers. Further increase in PL was obtained by photoaligning the BY molecules perpendicularly to the PPV molecules. This minimizes energy transfer, since F?rster processes are directional, dipole-dependent resonant transfers. Energy transfer is also controlled by imparting a preferential orientation of the PPV chains on PPV/BY LbL films deposited onto flexible Teflon substrates that may be stretched.     

Polarization dependence of Raman scattering from a thin film involving optical anisotropy theorized for molecular orientation analysis

Polarized Raman scattering from a thin film involving uniaxial optical anisotropy deposited on a dielectric substrate has analytically been theorized. The analyte film is modeled as a three-phase system (air/film/substrate) to calculate the electromagnetic fields of the incident and scattered light propagating across the system with an aid of the transfer matrix method to exactly take the optical anisotropy of the film into account. On the new theory, a methodology for molecular orientation analysis of an extended polymethylene chain in the film is proposed, which is employed for determination of the tilt angles of the chains in single- and five-monolayer Langmuir-Blodgett (LB) films of cadmium stearate deposited on a glass plate. The results agree well with those obtained by infrared spectroscopy, which confirms reliability of the present method.     

有限层Langmuir-Blodgett类晶型薄膜微观结构与超分子结构的小角X-射线散射研究 I: 硬脂酸镉盐膜系

本文应用小角X-射线散射,参考方介石与硬脂酸结晶结构,为硬脂酸镉盐膜系设计了七种可能的分子链模型,在微机上进行拟合研究。结果指出:链倾角Ach～24-27°，与β-硬脂酸结晶相近;碳键角Acc～115°,比正四面体模型有所扩张;链端羧酸镉属离子键结构,而非文献习用的共价键结构;堆砌缺陷d约0.156nm,小于文献值约0.1nm;酸/皂剂量比x=0.8-1.0,因制膜条件变化而不同;界面对链堆砌有明显影响。总之,小角X-射线散射可对超薄L-B薄膜(<10nm)的精细结构进行有效的研究。     

Scanning angle Raman spectroscopy measurements of thin polymer films for thickness and composition analyses

Scanning angle (SA) Raman spectroscopy was used to measure the thickness and composition of polystyrene films. A sapphire prism was optically coupled to a sapphire substrate on which 6–12% (w/v) polystyrene in toluene was spin coated. Raman spectra were collected as the incident angle of the p-polarized, 785-nm excitation laser was varied from 56 to 70°. These angles span above and below the critical angle for a sapphire/polystyrene interface. The thickness of the polystyrene film was determined using a calibration curve constructed by calculating the integrated optical energy density distribution as a function of incident angle, distance from the prism interface and polymer thickness. The calculations were used to determine the incident angle where waveguide modes are excited within the polymer film, which is the angle with the highest integrated optical energy density. The film thicknesses measured by SA Raman spectroscopy ranged from less than 400 nm to 1.8 μm. The average percent uncertainty in the SA Raman determinations for all films was 4%, and the measurements agreed with those obtained from optical interferometery within the experimental uncertainty for all but two films. For the 1270-nm and 580-nm polystyrene films, the SA Raman measurements overestimated the film thickness by 5 and 18%, respectively. The dependence of the calibration curve on excitation polarization and composition of the polymer and bulk layers was evaluated. This preliminary investigation demonstrates that scanning angle Raman spectroscopy is a versatile method applicable whenever the chemical composition and thickness of interfacial polymer layers needs to be measured.     

聚(ε-己内酯)薄膜结晶形貌及分子取向研究

用匀胶机通过溶液铸膜方法在硅片和铝箔基板上分别制备具有不同厚度的聚(ε-己内酯)(PCL)薄膜. 通过原子力显微镜(AFM)和偏光衰减全反射傅里叶红外光谱(ATR-FTIR)对薄膜中PCL的结晶形貌、 片晶生长方式及分子链取向进行了研究. AFM结果表明, 在200 nm或更厚的薄膜中, PCL主要以侧立(edge-on)片晶的方式生长; 对于厚度小于200 nm的薄膜, PCL片晶更倾向于以平躺(flat-on)的方式生长. 这种片晶生长方式的改变在硅片和铝箔基板上都表现出同样的倾向. 此外, 在15 nm或更薄的薄膜中, PCL结晶由通常的球晶结构变为树枝状晶体. 偏光ATR-FTIR结果表明, 当膜厚小于200 nm时, 薄膜结晶中PCL分子链沿垂直于基板表面方向取向, 并且膜越薄, 取向程度越高, 与AFM的观测结果一致.     

拉伸温度对α’-型聚乳酸结构与性能的影响

α’-晶型聚乳酸(PLA)膜被制备和单轴拉伸.通过凝胶渗透色谱仪(GPC)、全反射红外光谱(ATR-IR)、差示扫描量热仪(DSC),X射线衍射(XRD)及Raman光谱等测试技术研究了拉伸温度梯度变化对α’-晶型PLA膜的分子量及其分布、分子链构象、结晶度、晶型转变和取向行为的影响.在恒定拉伸速度与应变下,拉伸温度对PLA膜的应力-应变曲线,特别是屈服强度、拉伸模量产生了较大的影响,其值随拉伸温度的增加而降低.GPC测试结果表明,在不同的温度下拉伸后,PLA会发生一定程度的降解,分子量降低;ATR-IR,XRD,DSC和Raman光谱测试结果表明,在不同的温度下拉伸后α’-型PLA没有发生晶型的转变,即没有由α’-晶体转变为α-或β-晶体.结果表明PLA的结晶度、分子链取向程度强烈依赖于拉伸温度:当拉伸温度低于100℃时,α’-型PLA膜的结晶度与沿着拉伸方向的变形程度随拉伸温度的增加而增加,分子链的高度取向诱导了PLA结晶;当拉伸温度超过100℃后,PLA的分子链沿着拉伸方向上的有序度与结晶度将降低.     

Structure evolution of α′‐phase poly(lactic acid)

Poly(lactic acid) films consisting of α′‐forms were prepared and uniaxially drawn. The effects of the draw rate at temperatures above the glass transition temperature on chain conformation, degree of crystallinity, and crystalline phase transformation were investigated by a combination of vibrational spectroscopy (infrared and Raman), differential scanning calorimetry, and wide‐angle X‐ray diffraction (WAXD). It was established that the α′‐crystal's phase of poly(lactic acid) films does not transform into either an α or β crystals on uniaxial drawing at a fixed draw ratio of 4. However, the degree of crystallinity was significantly increased on deformation. The structural change as a function of deformation also promotes an increase in the strain‐induced enthalpic relaxation endothermic peak appearing near the glass transition region. While the overall changes in physical properties can be attributed to the changes in the degree of crystallinity as a function of strain rate, polarized Raman spectra, and WAXD clearly illustrated changes and the differences in the amorphous and crystalline orientation as a function of processing conditions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1446–1454, 2011     

Accurate Measurement of Raman Depolarization Ratio in Gaseous CO2

The Raman depolarization ratios of gaseous CO₂ in the spectral range of 1240-1430 cm^-1 are determined with a sensitive photoacoustic Raman spectroscopy, and more accurate data compared to the literature results are presented. The precision of the obtained depolarization ratio is achieved by measuring and fitting the dependence of the PARS signal intensity on the cross angle between the polarizations of two incident laser beams.