Showing papers in "Macromolecules in 1980"

Brownian Dynamics Study of Polymer Conformational Transitions

Abstract: Conformational transitions of a macromolecule have been studied by computer simulation of the Brownian dynamics of a polymer chain. An activation energy equal to about one barrier height has been found. However, there is a great deal of cooperativity of transitions especially between bonds which are second nearest neighbors.

Determination of the Polymer-Polymer Interaction Parameter for the Polystyrene-Polybutadiene Pair

Abstract: : The light scattering technique was utilized to measure the phase separation temperatures (cloud points) of mixtures containing a polystyrene and a polybutadiene of various molecular weights and also of mixtures containing a polystyrene and a random or block copolymer of styrene and butadiene. The data was analyzed to obtain the polymer-polymer interaction parameter for the styrene-butadiene pair as a function of temperature and concentration. The value of the parameter deduced from the homopolymer mixtures agrees well with that obtained from the mixtures containing a copolymer. The polymer-polymer interaction parameter thus evaluated was compared with a theoretical expression derived on the basis of the Flory equation-of-state theory. The effect of the free volume disparity between the two components was found to play a relatively minor role in determining the interaction parameter when the two polymers lack any specific interactions which would make them mutually miscible. (Author)