CHAIN SHORTENING IN POLYMETHYLENE LIQUIDS

The longitudinal accordion motion of polymethylene chains has been studied for n=5-36 liquids and solids via laser-vibrational scattering. Unlike the fully extended, trans chains of the solids, the abundance of the trans conformation in the liquids is vanishingly small for n≥9, in favor of chain shortened forms. This is indicated by the variation of the primary accordion mode frequencies, which approach a limiting value. A gradual intensity dimunition and broadening of the primary longitudinal band, accompanied by an increase of continuum intensity, with increasing n, indicates an approach towards conformational randomness.