Orientation of adsorbed polymer in response to shear flow

We report preliminary evidence of shear-induced alignment of polyisoprene adsorbed from CCl₄ solution on to a single solid surface. The experimental technique was Fourier transform infrared spectroscopy, in the mode of attenuated total reflection. The selective augmentation of vibrational modes oriented preferentially along the chain backbone implied chain orientation in the direction of flow. This occurred at low shear rates (about 1 s^-1). The extent of orientation increased with increasing molecular weight, and did not depend on shear rate within the narrow range (0.4-1.6 s^-1) available to us. After cessation of flow, relaxation toward the conformation in the quiescent state was slow.