Tuning the Johari-Goldstein β-Relaxation and Its Separation from α-Relaxation of Poly(n-alkyl methacrylate)s by Small Molecule-bridged Hydrogen Bonds  

作　　者：Yuan-Biao Liu Gao-Peng Shi Guo-Zhang Wu 

机构地区：[1]Shanghai Key Laboratory of Advanced Polymeric Materials,School of Materials Science&Engineering,East China University of Science&Technology,Shanghai 200237,China

出　　处：《Chinese Journal of Polymer Science》2021年第11期1459-1469,共11页高分子科学（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Nos.51873063 and 51373053)。

摘　　要：Introducing small molecule-bridged hydrogen bonds(HBs)between polymer chains has been reported to effectively reduce the interchain cooperativity despite of strengthening the intermolecular interaction.Here,a systematic investigation on tuning the Johari-Goldsteinβ(βJG)relaxation by adding various low-molecular-weight phenols in poly(n-alkyl methacrylate)s is carried out to further clarify the anomalous dynamics.Given these small molecules capable of coupling the motion with pendent groups of host polymers due to forming at least two HBs per molecule,poly(n-alkyl methacrylate)mixtures exhibit rich dynamic changes in theβJG-properties andα,βJG separations.An increased loading of phenols with a small size and strong inter-HB strength(Δυi)clearly benefits for significant retardation and suppression of theβJG-relaxation,narrows theα,βJG separation and converges theβJG-peak with theα-peak,which demonstrates the alleviation of inter-chain topological constraints.However,small molecules with a relatively big size and weakΔυi are found to amplify the magnitude of theα,βJG separation of poly(butyl methacrylate),even though experimental results of changes inα-dispersion and dynamic fragility confirm a reduction of the coupling factor n in all of these hybrids.The counterintuitive phenomenon suggests that the crossover time tc in the Coupling Model is no longer a universal quantity if the inter-chain interaction of polymers is strengthened by HBs.These compelling findings shed vital insights into the HBinduced anomalous dynamics,and provide essential guidance for tailoring theβJG behavior and designing glassy polymeric materials.

关 键 词：Johari-Goldsteinβ-relaxation Hydrogen bond Glass transition Poly(n-alkyl methacrylate) Small molecule 

分 类 号：TQ317[化学工程—高聚物工业] O641.3[理学—物理化学]