Bulk Structure and Rheological Properties of Poly (macromonomer)s Associate with Multibranched Structure of High Branch Density

用平行板流变仪测定了多支化聚苯乙烯的动态剪切模量随频率和温度的变化，研究了聚合物分子的多支化结构对流变性能的影响。多支化聚苯乙烯是ω-甲基丙烯酰氧基乙基聚苯乙烯大分子单体（MA-PSt）的聚（大分子单体）和MA-PSt与甲基丙烯酸甲酯（MMA）单体的统计共聚物。在相同条件下，还测量了线性聚苯乙烯的动态剪切模量以进行比较。聚（大分子单体）的储能动态剪切模量G'的主曲线没有显示所谓的平台区，并且G'从玻璃化转变区的边缘到末端区逐渐减小。在该区域中，损耗模量G”总是大于G '。在分支密度较小的共聚物中，平台区变得明显。这些结果表明，由于高分支密度的多支化结构，在聚（大分子单体）体系中，分子间的链缠结受到限制。支化聚合物的成膜性质如脆性与流变性质的结果一致，因此，可以归因于不存在分子间链缠结。

Dynamic shear moduli of multibranched polystyrenes were measured as functions of frequency and temperature using a parallel-plate rheometer to investigate the effect of the multibranched structure of polymer molecules on the rheological properties. The multibranched polystyrenes are poly(macromonomer)s of omega-methacryloyloxyethyl polystyrene macromonomers (MA-PSt)s and statistical copolymers of the MA-PSt with methyl methacrylate (MMA) monomer. The dynamic shear moduli of a linear polystyrene were also measured under the same conditions for comparison. The master curve of the storage dynamic shear modulus G' for the poly(macro-monomer)s did not show the so-called plateau region and the G' gradually decreased from the edge of the glass transition region to the terminal zone. In this region, the loss modulus G" was always larger than G'. The plateau region became clear in the copolymers with less branch density. These results indicate that the intermolecular chain entanglement is restricted in the poly(macromonomer) system due to the multibranched structure of high branch density. Film forming properties of the branched polymers such as brittleness are consistent with the results of rheological properties, thus, can be ascribed to the absence of the intermolecular chain entanglement.