There have been significant interests in recent years for incorporating dynamic bonds into polymer materials for achieving multiple functionalities,such as self-healing,recycling,stimuli-responsiveness,and so on.Nevertheless,the impact of dynamic bonds on the polymer dynamics is actually less explored.In this study,we investigate a self-healing solid-liquid elastomer(SLE),which is a dual-crosslinked network made by coupling a permanently crosslinked polydimethylsiloxane(PDMS)network with polyborosiloxane(PBS)via abundant dynamic boron/oxygen dative bonds.Proton double-quantum(DQ)NMR reveals that the crosslinking degree is reduced while the structural heterogeneity of network is enhanced with increasing PBS content,i.e.,increasing the content of dynamic boron/oxygen dative bonds.Rheological experiments clearly reveal two chain relaxation modes in the SLE samples with a characteristic relaxation time of around 2.1 s and 11.8 s,corresponding to the relaxation of coupled PBS and PDMS chains,respectively.The master curves obtained from variable-temperature frequency-dependent rheological experiments also reveal enhanced heterogeneity of chain relaxation with increasing PBS content.Finally,the impact of boron/oxygen dative bonds on the Rouse dynamics is further revealed by fast-field-cycling(FFC)NMR experiments,where the spin-lattice relaxation rate(R,)of all SLE samples follows the same power law of R1(ω)∝ ω-0.33.Nevertheless,the incorporation of PBS did slightly increase the energy barrier of Rouse dynamics.Our study well demonstrates a combined use of rheology and solid-state NMR spectroscopy can provide piercing insights into the interplay of crosslinking structures and dynamics of polymer materials.

Hao Wang;Wan-Su Peng;Qi Wu;Yan Zhao;Shi-Tai Wang;Yi Yang;Jin-Rong Wu;Xiao-Liang Wang;Rong-Chun Zhang

South China Advanced Institute for Soft Matter Science and Technology(AISMST),School of Emergent Soft Matter,South China University of Technology,Guangzhou 510640,China;Key Laboratory of High-Performance Polymer Materials and Technology of Ministry of Education,Department of Polymer Science and Engineering,School of Chemistry and Chemical Engineering,Nanjing University,Nanjing 210093,China;State Key Laboratory of Polymer Materials Engineering,College of Polymer Science and Engineering,Sichuan University,Chengdu 610065,China;Suzhou Niumag Analytical Instrument Corporation,Suzhou 215151,China;Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices,South China University of Technology,Guangzhou 510640,China

高分子科学（英文版）

[1]Hao Wang;Wan-Su Peng;Qi Wu;Yan Zhao;Shi-Tai Wang;Yi Yang;Jin-Rong Wu;Xiao-Liang Wang;Rong-Chun Zhang-.Interplay of Crosslinking Structures and Segmental Dynamics in Solid-Liquid Elastomers)[J].高分子科学（英文版）,2022(10):1297-1306

Crosslinking,Elastomers,polyborosiloxane,Rouse

Interplay,Structures,Segmental,Dynamics,Solid,Liquid,There,have,been,significant,interests,recent,years,incorporating,bonds,into,polymer,materials,achieving,multiple,functionalities,such,self,healing,recycling,stimuli,responsiveness,Nevertheless,impact,dynamics,actually,explored,this,study,investigate,solid,liquid,elastomer,SLE,which,dual,crosslinked,network,made,by,coupling,permanently,polydimethylsiloxane,PDMS,PBS,via,abundant,boron,oxygen,dative,Proton,double,quantum,DQ,NMR,reveals,that,crosslinking,degree,reduced,while,structural,heterogeneity,enhanced,increasing,content,Rheological,experiments,clearly,relaxation,modes,samples,characteristic,around,corresponding,coupled,chains,respectively,master,curves,obtained,from,variable,temperature,frequency,dependent,rheological,also,Finally,further,revealed,fast,field,FFC,where,spin,lattice,follows,same,power,law,R1,incorporation,did,slightly,increase,energy,barrier,Our,well,demonstrates,combined,rheology,state,spectroscopy,provide,piercing,insights,interplay,structures

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