Farrington PJ, Hawker CJ, Fréchet JMJ, Mackay ME
Department of Chemical Engineering, The University of Queensland 4072, Australia, IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, California 95120-6099, and Department of Chemistry, University of California, Berkeley, California 94720.
Macromolecules. 1998 Jul 28;31(15):5043-50. doi: 10.1021/ma970198g.
The zero shear melt viscosity, eta0, for a variety of dendritic poly(benzyl ether) macromolecules has been measured. The viscosity of low generation dendrimers exhibits a strong molecular mass, M, dependence, yet, direct proportionality between eta0 and M is observed at higher generations. The viscosity scales with M for mono- and tridendrons rather than generation number. Hypercore dendrimers continue this scaling although the viscosity is slightly greater. A large deviation from the master curve for the mono- and tridendrons is found for an end-substituted monodendron. The viscosity for the end-substituted monodendron is also much more temperature dependent than virgin dendrimers, and it is concluded that end groups have a much larger effect on the viscosity than the core. Reexamination of literature data for intrinsic viscosity and glass transition temperature is performed, and these quantities also scale with molecular mass. Comparison with free volume theory indicates that the theory is extremely robust although some question of its validity is made when applied to dendrimers.
已测量了多种树枝状聚（苄基醚）大分子的零剪切熔体粘度η0。低代数树枝状聚合物的粘度表现出对分子量M的强烈依赖性，然而，在较高代数时观察到η0与M之间存在直接比例关系。单端基和三端基树枝状分子的粘度随M而不是代数变化。超核树枝状聚合物延续了这种比例关系，尽管其粘度略高。对于端基取代的单端基树枝状分子，发现其与单端基和三端基树枝状分子的主曲线有很大偏差。端基取代的单端基树枝状分子的粘度也比原始树枝状聚合物对温度的依赖性大得多，并且得出结论，端基对粘度的影响比核心大得多。对特性粘度和玻璃化转变温度的文献数据进行了重新审视，这些量也随分子量变化。与自由体积理论的比较表明，该理论非常可靠，尽管将其应用于树枝状聚合物时其有效性存在一些问题。
