Rheooptical studies of polydiacetylene solutions

This work describes a rheooptical experiment with the ability to distinguish between orientation and deformation of polymers while quantifying the degree of deformation in shear using a polymeric chromophore. The chromophore used is poly(4-butoxycarbonylmethylurethane)diacetylene, referred to as 4BCMU, which is known to display varying optical properties that are attributed to conformational changes in the polymer backbone. The orientation may be measured by changes in the extinction coefficient both perpendicular and parallel to the shear field. The results obtained for dilute solutions of 4BCMU under shear are explained by an ellipsoidal random coil polymer in the quiescent state orientating in the shear field. In apparent contradiction to earlier theoretical models, no deformation of the polymer is observed within the range of shear fields used in this work. Extant theories have attributed the rheological behavior of polymer solutions to deformation of the spherical random polymer coils under shear.