Component Relaxation Times in Entangled Binary Blends of Linear Chains: Reptation/CLF along Partially or Fully Dilated Tube
Component Relaxation Times in Entangled Binary Blends of Linear Chains: Reptation/CLF along Partially or Fully Dilated Tube
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DOI：
10.1021/ma4018795
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发表时间：
2013-11
期刊：
影响因子：
5.5
通讯作者：
H. Watanabe;Yumi Matsumiya;E. Ruymbeke
中科院分区：
文献类型：
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作者：
H. Watanabe;Yumi Matsumiya;E. Ruymbeke
最近的介电分析表明，单分散本体中的缠结线性顺式聚异戊二烯（PI）链在末端弛豫状态下表现出沿部分扩张的管的沿着蠕动/轮廓长度波动（CLF），其中管的直径由沿链骨架的约束释放（CR）激活的张力平衡沿着确定（Matsumiya等人，Macromolecules 2013，46，6067）。关于这一发现，我们重新研究了具有各种组分分子量和体积分数的线性PI共混物中组分的介电和粘弹性终端弛豫时间，Mi和Mi i（对于短组分和长组分，i = 1和2）。在具有M2 <$M1和大的<$2（>长-长缠结开始的临界体积分数<$2e）的缠结共混物中，长链的弛豫时间τ2，B随着<$2的减小而减小，但在具有相同<$2的溶液中保持显著大于相同长链的τ2，soln。这一结果表明，CR激活的张力平衡延迟的爬行/CLF运动的长链在这样的共混物。一个简单的“解决方案模型”考虑到这种延迟由于CR松弛的短-长纠缠制定。利用CR弛豫时间τdil-2的数据，稀释长链的CR（具有π 2 π 2 e）非常好。然而，这个模型不能适用于M2和M1分离得很窄的情况，并且短-长纠缠在长链弛豫的时间尺度上相当大地存在。对于这种情况，一个“混合模型”被制定为考虑自洽的，虽然在一个近似的方式，CR松弛的所有种类的纠缠（短-短，短-长，长-短，和长-长纠缠），从而模仿耦合松弛的长链和短链。由该模型导出的组分弛豫时间（再次基于τdil-2，CR数据）令人惊讶地接近数据，不仅对于具有窄分离的M2和M1的PI/PI共混物，而且对于具有M2和M1的那些也是如此（后者也用解决方案模型令人满意地描述），这表明在末端松弛状态中组分的蠕动/CLF发生在沿着部分扩张的管，其直径由CR活化的张力平衡确定。此外，“共混物模型”对于具有各种M2/M1比的聚苯乙烯共混物的文献数据也是令人满意的。这些结果证明了共混物中CR活化张力平衡的重要性，这与单分散本体的发现一致。
Recent dielectric analysis suggested that entangled linear cis-polyisoprene (PI) chains in monodisperse bulk exhibit, in the terminal relaxation regime, reptation/contour length fluctuation (CLF) along a partially dilated tube with its diameter being determined by the constraint release (CR) activated tension equilibration along the chain backbone (Matsumiya et al. Macromolecules 2013, 46, 6067). In relation to this finding, we re-examined the dielectric and viscoelastic terminal relaxation times of components in linear PI blends having various component molecular weights and volume fractions, Mi and υi (i = 1 and 2 for the short and long components). In entangling blends with M2 ≫ M1 and large υ2 (>critical volume fraction υ2e for the onset of long−long entanglement), the relaxation time τ2,b of the long chain decreases with decreasing υ2 but stayed considerably larger than τ2,soln of the same long chain in a solution having the same υ2. This result suggested that the CR-activated tension equilibration retards the reptation/CLF motion of the long chain in such blends. A simple “solution model” considering this retardation due to the CR relaxation of short−long entanglements was formulated. Utilizing data for the CR relaxation time τdil‑2,CR of dilute long chains (with υ2 υ2e very well. Nevertheless, this model could not apply to the cases where M2 and M1 are rather narrowly separated and the short−long entanglements considerably survive in the time scale of the long chain relaxation. For this case, a “blend model” was formulated to consider self-consistently, though in an approximate way, the CR relaxation of all species of entanglements (short−short, short−long, long−short, and long−long entanglements) thereby mimicking coupled relaxation of the long and short chains. The component relaxation times deduced from this model (again on the basis of the τdil‑2,CR data) were surprisingly close to the data, not only for the PI/PI blend having narrowly separated M2 and M1 but also for those with M2 ≫ M1 (the latter being described satisfactorily also with the solution model), suggesting that reptation/CLF of the components in the terminal relaxation regime occurs along partially dilated tube with the diameter being determined by the CR-activated tension equilibration. Furthermore, the “blend model” worked satisfactory also for literature data for polystyrene blends having various M2/M1 ratios. These results demonstrate the importance of CR-activated tension equilibration in the blends, which is consistent with the finding for monodisperse bulk.