Using Dynamic Bonds to Enhance the Mechanical Performance: From Microscopic Molecular Interactions to Macroscopic Properties
作者：Zhang, C.; Yang, Z.J.; Duong, N.T.; Li, X.H.; Nishiyama, Y.; Wu, Q.; Zhang, R.C.*; Sun, P.C.*
關鍵字：crosslinked polymer; dynamic bonds, 2-ureido-4[1H]-pyrimidinone; solid-state NMR
論文來源：期刊
具體來源：Macromolecules, 2019, in press
發表時間：2019年
Polymeric materials combining good mechanical performances with
self-healing ability and malleability have attracted dramatic attention, but it
still remains a challenge until now for the facile fabrication of such
high-performance materials, not to mention the atomic-level characterization
for understanding the molecular origin of the macroscopic properties. Herein,
we proposed a facile strategy to fabricate a dual-crosslinked poly(n-butyl
acrylate) polymer material, in which the self-complementary quadruple hydrogen
bonding interactions between 2-ureido-4[1H]-pyrimidinone (UPy) dimers
were utilized as the dynamic sacrificial crosslinkages, and thus to enhance the
mechanical strength and toughness. The hydrogen bonding interactions between
UPy dimers in such synthetic crosslinked polymer material were revealed in
detail by selective saturation double-quantum (DQ) solid-state NMR spectroscopy
under ultrafast magic-angle-spinning (MAS) beyond 60 kHz. In the meantime, the
self-healing capability and recyclability were achieved by utilizing dynamic
fast boronic ester transesterification at an elevated temperature. A novel symmetrical
diboronic ester crosslinker was developed and employed to enhance the probability
of bornoic ester transesterification at an elevated temperature. The boronic ester transesterification was verified on
a small molecular model and polymer materials by solution 1H NMR
spectroscopy and swelling experiments, respectively, and the crosslinking
structure of polymer materials was addressed by low-field proton
multiple-quantum NMR spectroscopy and T2 relaxometry. Overall, it is well
demonstrated that a combination of diboronic ester bonds and UPy dimers as the chemical and physical crosslinkage, respectively, can impart
the rubbery materials with enhanced mechanical stiffness and toughness, good healing
and recycling efficiency, and elucidation of the structure-property relationship
here can further provide piercing insights into the development of
high-performance polymer materials.