Healable Luminescent Self-Assembly Supramolecular Metallogels Possessing Lanthanide (Eu/Tb) Dependent Rheological and Morphological Properties

Herein we present
the use of lanthanide directed self-assembly
formation (Ln­(III) = Eu­(III), Tb­(III)) in the generation of luminescent
supramolecular polymers, that when swelled with methanol give rise
to self-healing supramolecular gels. These were analyzed by using
luminescent and 1H NMR titrations studies, allowing for
the identification of the various species involved in the subsequent
Ln­(III)-gel formation. These highly luminescent gels could be mixed
to give a variety of luminescent colors depending on their Eu­(III):Tb­(III)
stoichiometric ratios. Imaging and rheological studies showed that
these gels prepared using only Eu­(III) or only Tb­(III) have different
morphological and rheological properties, that are also different
from those determined upon forming gels by mixing of Eu­(III) and Tb­(III)
gels. Hence, our results demonstrate for the first time the crucial
role the lanthanide ions play in the supramolecular polymerization
process, which is in principle a host–guest interaction, and
consequently in the self-healing properties of the corresponding gels,
which are dictated by the same host–guest interactions.

本文报道了利用镧系三价离子（lanthanide(III)，缩写为Ln(III)，涵盖铕(III) Eu(III)与铽(III) Tb(III)）定向自组装过程构建发光超分子聚合物 (luminescent supramolecular polymers) 的方法。该类聚合物经甲醇溶胀后可形成具备自修复 (self-healing) 性能的超分子凝胶。研究人员通过发光光谱与氢核磁共振 (1H NMR) 滴定实验对该体系进行表征，借此得以明确Ln(III)基凝胶形成过程中涉及的各类中间物种。通过调控Eu(III)与Tb(III)的化学计量比，可将此类高发光凝胶混合得到多种发光色彩。成像与流变学研究表明，仅使用Eu(III)或仅使用Tb(III)制备的凝胶具有迥异的形貌与流变学特性，且与通过混合Eu(III)与Tb(III)凝胶所制备的凝胶的性能亦存在显著差异。因此，本研究首次证实了镧系三价离子在本质上属于主客体相互作用 (host–guest interaction) 的超分子聚合过程中所发挥的关键作用，并进一步明确了由相同主客体相互作用主导的对应凝胶的自修复性能机制。