Linear Rheological Response of a Series of Densely Branched Brush Polymers

详细信息    查看全文

• 作者：Miao Hu ; Yan Xia ; Gregory B. McKenna ; Julia A. Kornfield ; Robert H. Grubbs
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：September 13, 2011
• 年：2011
• 卷：44
• 期：17
• 页码：6935-6943
• 全文大小：1087K
• 年卷期：v.44,no.17(September 13, 2011)
• ISSN：1520-5835

文摘

We have examined the linear rheological responses of a series of well-defined, dense, regularly branched brush polymers. These narrow molecular weight distribution brush polymers had polynorobornene backbones with degrees of polymerization (DP) of 200, 400, and 800 and polylactide side chains with molecular weight of 1.4 kDa, 4.4 kDa, and 8.7 kDa. The master curves for these brush polymers were obtained by time temperature superposition (TTS) of the dynamic moduli over the range from the glassy region to the terminal flow region. Similar to other long chain branched polymers, these densely branched brush polymers show a sequence of relaxation. Subsequent to the glassy relaxation, two different relaxation processes can be observed for samples with the high molecular weight (4.4 and 8.7 kDa) side chains, corresponding to the relaxation of the side chains and the brush polymer backbone. Influenced by the large volume fraction of high molecular weight side chains, these brush polymers are unentangled. The lowest plateau observed in the dynamic response is not the rubbery entanglement plateau but is instead associated with the steady state recoverable compliance. Side chain properties affect the rheological responses of these densely branched brush polymers and determine their glassy behaviors.