Molecular orientation in thin films

R. M. Corn and D. A. Higgins, in Molecular Orientation in Thin Films as Probed by Optical... 

Runge AF, Saavedra SS et al (2006) Combination of polarized TIRF and ATR spectroscopies for determination of the second and fourth order parameters of molecular orientation in thin films and construction of an orientation distribution based on the maximum entropy method. J Phys Chem B 110(13) 6721-6731... 

Raman CV, Krishnan KS (1928) A new type of secondary radiation. Nature 121 501-502 Ferraro JR, Nakamoto K (1994) Introductory Raman spectroscopy. Academic, Boston Gouadec G, Coiomban P (2007) Raman spectroscopy of nanomaterials how spectra relate to disorder, particle size and mechanical properties. Prog Cryst Growth Ch 53 1-56 Sourisseau C (2004) Polarization measurements in macro- and micro- Raman spectroscopies molecular orientations in thin films and azo-dye containing polymer systems. ChemRev 104 3851-3891 Rayleigh L (1879) Phil Mag 8 261... 

Infrared ER spectrometry has no mechanism of intensity enhancement, in contrast to other methods such as RA spectrometry to be described in Chapter 10 and surface-enhanced infrared absorption (SEIRA), mentioned in Chapter 13. Nonetheless, infrared ER spectrometry provides a unique technique for utilizing s- and p-polarized radiations for obtaining information governed by the surface selection rule on the transition dipoles of molecular vibrations. Theoretical analysis of the information obtained by this technique has the possibility for elucidating molecular orientations in thin films on dielectric substrates and molecular interactions in a wide variety of materials, including liquid crystals. 

In order to evaluate quantitatively the molecular orientation in thin LB films, several attempts have been made by using infrared reflection-absorption (RA) technique [1,2]. Recently, we have proposed a useful and convenient method combining infrared... 

On the basis of these experimental results and discussion, we tried to establish a convenient and useful method for quantitative evaluation of the molecular orientation in thin LB films using FT-IR transmission and RA spectra. Here, we assume a uniaxial orientation of the transition moment with an angle < > around the normal axis, Z, to the LB film surface i. e. the XY plane (Figure 8). In this case, the ratio of the absorbance of a particular band in the transmission spectrum, AT, to that of the same band in the RA spectrum, AR, is given by... 

Hasegawa, T., Umemura, J. and Takenaka, T. (1993) Infrared external reflection study of molecular orientation in thin Langmuir-Blodgett films. J. Phys. Chem., 97, 9009-9012. 

The main objective in the blown film process is to prodnce a thin film with a imiform gauge, and good optical and mechanical properties. Because the film produced can be very thin, it is important to avoid the presence of defects snch as gels and contaminants. More importantly, in order to obtain good mechanical properties it is advantageons to have molecular orientation in the film that is more or less equal in both directions (machine and transverse). Without this balance in orientation the mechanical properties of the film conld be affected and low tear resistance can be observed in the machine direction. 

Sometimes the hazy optical properties of polypropylene are a detriment to its use in thin films. To address this problem, as well as to improve physical properties and reduce material costs, we can orient the molecular chains by stretching the polymer film after it has left the extrusion die. There are two methods of orienting films, film blowing, shown in Fig. 11.6, and tentering, shown in Fig, 19.6. 

Phthalocyanines (Pc) are attractive materials for their potential functions including the semiconductive behaviours in addition to the thermal and chemical stabilities. In particular, control of orientation of the Pc macrocycles in thin films is expected to provide novel molecular electronic devices. Previously, we have found that copper tetrakis(butoxycarbonyl) Pc is oriented nearly perpendicular to the surface and also the dipping direction in the LB films [46], while octa-alkyl Pc derivatives [H2Pc(R)8, CuPc(R)a R = CnH2n+i. n=7,9,11] take the orientation with Pc macrocycles nearly parallel to the plane of films deposited by the horizontal lifting method to form a non-alternating X-type film [47], as illustrated schematically in... 

Because chromophores orientation is important for creating anisotropy and optical nonlinearities, intensive studies have been performed to understand induced molecular orientation and relaxation processes in polymers. To gain further insight into the physics of thin polymer films and the effects of molecular orientation in solid polymers, studies at high pressure could be beneficial. Pressure as a thermodynamic parameter is widely used to study... 

Molecular Orientation Dependence of the Ionization Energy of Pentacene in Thin Films... 

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