Infrared spectra evaluation of syndiotactic polystyrene by dynamic infrared linear dichroism spectra and static difference spectra

Abstract

SUMMARY Uniaxially drawn syndiotactic polystyrene (sPS) in various modifications has been analyzed by static difference polarization spectra and DIRLD (dynamic infrared linear dichroism) spectra during mechanical stretching. Both, derivative bipolar bands and monopolar bands, are observed as a hint to submolecular changes induced by the applied external strain. The lineshape features in the dynamic in-phase spectra are described on the basis of frequency shifts and absorption amplitude variations during the stretching cycle. The conformationally sensitive vibrational modes are most sensitive to the external perturbation. The different responses of the conformationally insensitive vibrational modes to the external perturbation are discussed.

Interpretation of the Structure of Poly(Ethylene Terephthalate) by Dynamic FT-IR Spectra

“…For oriented PET, the in-phase spectrum has m uch stronger intensity than the quadrature one, which has also been obser ved in the studies of other polymers and implies that the movement of the functional groups is nearly synchronous with the applied strain. 7,10,12 Such a difference between in-phase and quadrature spectra decreases in the case of unoriented PET; this m eans that, under our conditions, the unoriented ® lm responds in a more viscous fashion than the oriented one.…”

“…The dynamic in-phase signals of oriented PET may be classi® ed into two kinds of bands according to the line shape features: monopolar band and bipolar band, which have been discussed by com paring the difference between two static absorbance spectra at m aximum and minimum positions of a stretching cycle. 7,10,12 When the stress causes only a wavenumber shift of this vibrational mode, a symmetric bipolar band appears in the dynamic in-phase spectrum. The m onopolar band is obser ved when the amplitude is being modulated.…”

Infrared Spectroscopy

“…Overlapping bands were resolved, and the hydrogen-bonded regions were more sensitive to the applied perturbation. In the investigations of uniaxially drawn polystyrene (39) in different crystalline forms, the dynamic response varied according to the conformation of the chains: trans-planar or helix.…”

A Faster Approach to Infrared Rheo-Optics Using a Planar Array Infrared Spectrograph

“…Among those probes, infrared spectroscopy is a tool of choice because it can simultaneously provide molecular information about the conformation and orientation of the different components of the system. 2 Infrared rheo-optics have been applied to study a wide range of samples, including homopolymers, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] polymer blends, 3,18,19 copolymers, [20][21][22][23][24][25][26][27] and biopolymers. 15,28 Marcott and coworkers first developed infrared rheo-optics using a dispersive infrared spectrometer 3,8,16,17,19,29 but, because of their multiplex advantage and high signal-to-noise ratio performance, Fourier transform infrared spectrometers (FT-IR) in the stepscan [13][14][15][16]18 or the asynchronous sampling modes 7,23,24 have now become standard instrumentation for infrared studies.…”