Raman polarization measurements of atactic polystyrene (APS) films were recorded after uniaxial stretching. Twelve different polarization directions were observed by varying the direction and polarization of the laser and scattered radiation. The polarization behavior of several vibration modes were shown clearly in the Raman spectra. On the basis of these polarization properties and previous vibrational studies of model compounds of polystyrene as well as of monosubstituted benzene derivatives, a reassignment of some of the vibrational modes of APS is made and discussed.

Infrared measurements of the dichroic ratio of atactic polystyrene absorption bands provide a valuable method of determination of the overall orientation of chains as well as the particular orientation of the trans conformational segments. The orientation process produces the alignment of the chains as well as an increase in the amount of trans conformational segments. A linear relationship is observed between birefringence and dichroic ratio for the absorption bands characteristic of overall orientation. A value of 35° ± 3° is obtained for the angle between the normal to the plane of the benzene ring and the chain axis from both infrared and birefringence determinations.

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SynopsisInteresting polyimide materials, possessing good mechanical and thermal properties, are obtained by homopolymerization or reaction of 4,4'-bis(maleimidodipheny1methane) with a diamine. Fourier transform infrared spectroscopy has been used to characterize the crosslinking of such materials using maleimide and amine absorption bands. Amine group reaction on double bonds is readily achieved and appears to be insensitive to the temperature of curing. On the other hand, the decrease of maleimide double bonds is strongly dependent on the reaction temperature. The residual amount of double bonds present in the cured material is a function of the temperature: a linear relationship holds between residual double bond concentration vs. curing temperature. The general behavior during crosslinking of this kind of polyimide was related to glass transition temperature changes.