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Study of phase separation in blends of semi-flexible and flexible coil polymers
A series of semi-flexible, wholly-aromatic, para-linked polyamides were synthesized at Polaroid Corporation for various optical applications. These polymers were unique in the fact that they exhibited rodlike nature and were soluble in common solvents as well. This unique property was found to be due to the presence of 2,2$\sp\prime$-disubstituted biphenyl group in the backbone of these materials. Blends of one of these polymers(PolymerI) and flexible poly(4-vinyl pyridine) were prepared by using solution blending and semi-interpenetrating network (SIN) formation methods. Both the methods of blends preparation gave rise to completely transparent and clear films over a wide range of composition of polymerI. The blends were characterized by thermal, spectroscopic, microscopic and scattering techniques. The amorphous nature of polymerI with no detectable glass transition temperature and small electron density and refractive index difference between two polymers precluded the attempts to get any quantitative information on the size of the phases in the blends. The Fourier-Transform infra-red results showed that there were hydrogen bonding interactions between two polymers. A second blend system containing another para-linked polyamide (PolymerII) was studied to obtain information about phase morphology. The flexible polymer used was poly(N-vinylpyrollidone). This system also gave rise to completely transparent films. The FTIR results indicated that there were hydrogen bonding interactions between the two polymers. Light scattering and cloud point measurements were able to detect the phase separation in the system. The light scattering measurements and the theoretical model used to analyze the results did not match very well. The reason for this was believed to be due to mixed composition of the phase separated regimes. The compositions of the phases were measured by comparing the turbidity values obtained from the theoretical model and the UV-transmittance measurements. It was found that composition of one of the phases had to be around 72/28(polymer1/polymer2) to account for the experimentally observed transmittace value. This led to the belief that even the phase separated regimes probably contained both polymers and the final refractive index difference between the phases was not large enough to give rise to cloudy films. TEM results confirmed the presence of phase separation in the system.
Sethumadhavan, Murali, "Study of phase separation in blends of semi-flexible and flexible coil polymers" (1996). Doctoral Dissertations Available from Proquest. AAI9619436.