Triblock Copolymer Solutions Research Articles

Viscous properties of butadiene/styrene triblock copolymer solutions

AbstractViscosities of dilute and concentrated solutions of a styrene‐butadiene‐styrene triblock copolymer in solvents of different thermodynamic quality and at different temperatures were studied. In 1,4‐dioxane (theta solvent for butadiene blocks) the viscosity derived polymer‐polymer interaction parameter has been found to be much smaller than in decalin (theta solvent for styrene blocks) or in tetralin (good solvent for both blocks). The dynamic viscosity and the enthalpy of activation of viscous flow, ΔH, increase much faster for 1,4‐dioxane solutions with increasing concentration than those for decalin or tetralin. The different properties of solutions in different solvents are discussed in terms of the physical structure of the systems.

Hydroxylation of styrene-diene triblock copolymers in solution and on the surface

A study was made of mechanisms of hydroxylation of styrene-diene block copolymers in a wide range of temperature and reagent concentration. The effect of diffusion processes on the rate of hydroxylation of block-copolymer surface was examined. The ratio of rate constants of epoxidation and hydroxylation of polymers was calculated.

Dipole moments of (styrene- p-chlorostyrene) triblock copolymers in solutions

(Styrene- p-chlorostyrene) triblock copolymers of the ABA and BAB types (A—polystyrene; B—poly- p-chlorostyrene) were prepared by anionic polymerization and their conformational behaviours in solutions were studied from measurements of the dipole moments. Two solvents, toluene and cumene, were used for the study; toluene is a good solvent for both polystyrene and poly- p-chlorostyrene whereas cumene is a selective solvent, good for polystyrene but poor for poly- p-chlorostyrene. It was found that the dipole moments of the block copolymers measured in toluene are the same for the ABA and BAB copolymers; in cumene however the dipole moment of the BAB copolymer is smaller than that of the ABA copolymer. The results give an additional support to our previous conclusion that the conformation of the block copolymers in a good solvent such as toluene could be approximated with a pseudo-random coil form; in a selective solvent, however, some anomalies take place in the conformation of the block copolymers, as deduced from intrinsic viscosity, osmotic pressure and light scattering measurements.

Structure formation in macromolecules of triblock copolymers

Solutions of triblock copolymers with various structures have been investigated in selective solvents at low concentrations of the block-copolymers by polarized luminescence. It has been found that, depending on the structure of the copolymer and the selective properties of the solvent, structures of a globular, dumbbell or ring type are formed in the macromolecules of the lock-copolymer.

A light scattering study of some solutions of triblock copolymers

AbstractThree samples of polystyrene‐polybutadiene‐polystyrene block copolymers have been studied by means of the light scattering technique in several solvents. The light scattering measurements indicate the degree of heterogeneity of the samples. Further measurements which were made on the least heterogeneous of the samples in a solvent closely matching the refractive index of the centre block suggest that the two types of polymer are largely separate. In this case the angular intensity variation of the light scattering can be interpreted in terms of the scattering obtained from a “dumb‐bell” configuration.