Branch-Induced Heterogeneous Chain Motion in Precision Polyolefins

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• 作者：Lucas Caire da Silva ; Robert Graf ; Clifford R. Bowers ; Kenneth B. Wagener
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：December 22, 2015
• 年：2015
• 卷：48
• 期：24
• 页码：8858-8866
• 全文大小：434K
• ISSN：1520-5835

文摘

The effect of branching on the chain dynamics of model branched polyethylene was studied by solid state ²H and ¹³C NMR. Methyl branched polyethylene models with branches at every 15th (PE15) and 21st (PE21) chain carbon were synthesized with deuterons placed either at the carbon alpha to the branching point or in the middle of the chain between branches. Line shape analysis of the temperature-dependent ²H spectra revealed that the distribution of motional amplitudes in the solid state is homogeneous along the crystalline chain but heterogeneous in the less constrained amorphous phase. The ¹³C and ²H longitudinal spin relaxation data obtained at different positions along the chain are explained in terms of the segmental dynamics as a function of branch incorporation into the crystals. A detailed analysis of the chain dynamics in the conformationally disordered phase exhibited in PE15 is also provided.