Entanglement in blends of monodisperse star and linear polystyrenes. 1. Dilute blends

Abstract

Viscoelastic properties of binary blends composed of narrow molecular weight distribution (MWD) 4-arm star polystyrenes (2-chain) of molecular weight (MW) M2 and narrow MWD linear polystyrenes (1-chain) of Ml were examined and compared with binary blends of narrow MWD linear polystyrenes of M2 and M1. In these blends, the volume fraction 4z of the 2-chain was kept small so that the 2-chains were entangling only with the matrix 1-chains but not with themselves. When the MW of the components of these dilute blends were such that M, < Ml << M,, with M, being the characteristic MW, the star 2-chain exhibited Rouse-Ham-like relaxation modes with the (weight average) relaxation time proportional to 42OMl3MZ2 and the compliance proportional to 4z-1M,0M2 Similar behavior was also found in the dilute blends of linear chains.These results suggest that the star as well as the high-MW linear (2-) chain in the dilute blend with Mz >> Ml > M, may relax as the surrounding 1-chains diffuse away so that the 1-2 entanglement has become ineffective.In the framework of the generalized tube model, this relaxation mechanism corresponds to the tube renewal mode. The limiting ratio of M2/Ml, for which these power laws are valid, is smaller for the star/linear chain blends than that for the linear chain blends. This is because the intrinsic relaxation time of the star 2-chain of M, is longer than that of the linear 2-chain of the same M2, observed in the bulk states. Thus, the star 2-chain exhibits the Rouse-Ham modes more easily than the corresponding linear 2-chain in the same matrix 1-chains.

Dielectric Relaxation of Type-A Polymers in Melts and Solutions

“…[11] These results demonstrate a difference in the CR effects on the dielectric and viscoelastic mode distributions, the latter becoming significantly narrower on suppression of CR. [37,100,101] This difference in the CR effects reflects the difference between the local correlation and orientation functions explained in Section 1.6. Figure 19 shows a ratio of the dielectric s 1 of various PI probes to the viscoelastic ps G P m of the PB matrices.…”

“…Appendix C1) and the viscoelastic mode distribution is close (but not identical) to the model prediction. [37,100,101,103,104] With increasing M 1 A [2M 2 M e 2 ] 1/3 , the mode distribution becomes narrower and ps G P pr becomes more weakly dependent on M 1 ; [37,100,101] the probe relaxation is no longer dominated by CR.…”

“…[31] dilute probes in the CR regime (M 2 M e 2 /M 1 3 F 0.5) are well described by this CR model. [37,100,101,103,104] However, the reptation and Rouse-CR models do not accurately describe detailed dynamic features of the probe, as noted from differences between the model eigenfunctions DF 0 p (n) ={ ffiffi ffi 2 p /pp}{cos (pp/2) -cos (ppn/ N)} (thick solid curves in Figure 22) and the observed DF p . Thus the actual CR relaxation proceeds via nonRouse dynamics, and the relaxation in absence of CR (in high-M matrices) is not the pure reptation relaxation.…”

Viscoelastic Relaxation of Linear Polyisoprenes: Examination of Constraint Release Mechanism

“…This type of motion of the tube and the probe therein is referred to as the constraint release (CR). [1][2][3][4] For binary blends of polystyrenes (PS) composed of dilute probes entangled only with matrix chains, the CR dynamics of the probe has been extensively examined through viscoelastic 2,[5][6][7][8][9] and diffusion [12][13][14] experiments. These experiments revealed that the probe exhibits pure CR dynamics only when the entangling matrix chains are much shorter than the probe and that the terminal CR relaxation occurs through a Rouse-like mechanism characterized by the experiments examining not only the τ CR values but also the viscoelastic mode distribution suggest that α is close to 3.…”

“…(2) is written in terms of the relaxation spectrum H 2,B (τ ) of the probe in the blend as 2,6,8,9) Thus, τ 2,B evaluated with Eq. (3) is identical to the secondmoment average relaxation time <τ 2 > defined in terms of…”