Polymacromonomers: Structure and dynamics in nondilute solutions, melts, and mixtures

Polymacromonomers are viewed as a special class of well-characterized branc hed polymers with high density of arms and shape ranging from spherical to nonspherical, depending on the arm functionality and molecular mass. We syn thesized a series of such model systems with polystyrene or poly(methyl met hacrylate) backbone and varying functionality and/or molecular mass of poly styrene arms and investigated their structure and dynamics in nondilute sol utions (well above the overlapping concentration c*) and in the melt. We fo und similarities in their soft ordering and dynamic response with other wel l-known model branched polymers such as multiarm stars, in that cooperative and selfdiffusion or arm relaxation and structural rearrangements control their dynamics in solution or in the melt; respectively. However, the prese nt systems do not follow the scaling laws of stars as a consequence of thei r anisotropy and the larger interpenetration needed to observe the effect o f ordering on the dynamic response. The use of blends consisting of differe nt polymacromonomers essentially enhances the polydispersity, enabling the detection of the self-diffusion mode in analogy to the multiarm stars, as w ell as obtaining a wide range of effective intermediate molecular masses, d epending on composition. The mixtures investigated were miscible at all tim es and exhibited a dynamics dominated by the response of the slower compone nts. These polymers complement the generic physical picture of the dynamics of branched polymers toward the low arm molecular mass.