星形聚苯乙烯本体粘弹性对结构的依赖性

用应力松弛法研完了一组4—12支链星形聚苯乙烯本体的粘弹性。从应力松弛主曲线测定了零切变粘度η_0、稳态柔量J_e~o和其它流变学参数。结果发现,零切变粘度和最大松弛时间τ_m强烈地依赖于聚合物的分子尺寸,并且可以用无扰特性粘度或折合分子量来描述。η_0和τ_m随支化度增大而增大。实验还直接证实了支链长度相同的星形聚合物的J_e~o与支链数目无关,但是星形聚合物的稳态柔量比具有和支链间分子量相同的线形聚合物的稳态柔量大。

STRUCTURE DEPENDENCE OF VISCOELASTIC PROPERTIES OF STAR-SHAPED POLYSTYRENES IN BULK

The viscoelastic properties of a set of star-shaped polystyrenes with 4-12 arms were studied in bulk by the tensile stress relaxation method. The zero-shear viscosity 0, the steady-state compliance Jc0 and other Theological parameters were determined from the relaxation modulus master curves. It was found that the zero-shear viscosity and the maximum relaxation time rm were strongly dependent on the size of polymeric molecules and could be described with the unperturbed specific viscosity or with the reduced molecular weight, 0 and r1n increased with branch degree. It was directly proved that Jc0 of star polymers, whose arms are of same length, is independent of the number of arms. The Jc0,s of star polymers seem to be greater than those of linear polymers having the same molecular weight as span molecular weight of star.