No abstract

The physical and morphological properties of heterogeneous mixtures of polystyrene with styrene: butadiene copolymers were determined. A mechanism of ultimate failure is proposed which permits the qualitative rationalization of the effects of copolymer composition, structure, and concentration upon certain physical properties of the mixture.

The Flory‐Wall expressions for the fraction of substituents remaining on a vinyl copolymer, when substituents are removed at random from adjacent 1,3 positions, are extended to the case of nonrandom copolymerization. A copolymer composition equation is derived for the case in which the type of monomer preceding the active freeradical chain end affects the propagation reaction. The distribution of lengths of sequences in copolymers is discussed.

The response of a viscoelastic fluid to a shearing stress varying sinusoidally with time can be described in terms of a complex dynamic viscosity. The real part of the complex viscosity thus obtained from dynamic measurements is observed to decrease with increasing frequency of the deformation in much the same way that the apparent viscosity of the material diminishes with increasing rate of shear in a steady flow test. Also, the dynamic and steady state viscosities approach the same limiting value as frequency and shear rate, respectively, approach zero. Therefore, it is natural to speculate on analogies between the role of frequency in dynamic tests and that of shear rate in steady flow measurements and to seek correlations between dynamic and steady state measures of viscosity.

Using the copolymer composition equation, the critical constants α and β are determined for the systems styrene–2,5‐dichlorostyrene, styrene–methyl acrylate, styrene–diethyl maleate, and styrene–diethyl chloromaleate.