スチレン-ブタジエン共重合体の希薄トルエン溶液の粘弾性

抄録

Studies have been made of the dynamic viscoelastic properties of copolymers of styrene (S) and butadiene (B) in toluene (good solvent for both components) at 30.0°C. The polymers were prepared by the "living polymer" method with the same monomer feed ratio of S 61mol % and B 39mol %. The two were block copolymers with three sequences of B-S-B (BSB 1101) and S-B-S (SBS 1102), and the one was a random copolymer (SB 1103). The complex rigidities and the steady shear viscosities were measured by means of torsional crystals at the frequencies of 19.6kc, 39.2kc or 40.15kc, and 117.7kc, and a Ubbelohde dilution type viscometer respectively. The intrinsic rigidities and the generalized limiting relaxation times were obtained by extrapolation to zero concentration.
The dimensionless functions of intrinsic rigidities were plotted logarithmically against the generalized angular frequencies together with the theoretical curves of Rouse (free-draining case) and Zimm (non-draining case). In these plots, the experimental points lie between the Rouse and the Zimm theory for the two block copolymers and closely on the Zimm theory for the random copolymer. It means that the random copolymer is nearly non-draining, and the block ones are partial-draining; BSB 1101 seems to exhibit the stronger draining effect than SBS 1102 in toluene at 30.0°C. Since the draining effects correlate with the volume expansion, it may be suggested that the random copolymer has more compact conformation than the block sorts in such good solvent as toluene.