在新看到的Early View版的Angew. Chem. Int. Ed.上看到一篇Highlights文章，有感，就给作者发了个email。以下是我email的内容和他的回复。
Prof. Craig,
I have read your recently published Highlight article on ionic network materials. The paper from which you started your discussion (JACS 130:9648) described two networks that, in the view point of polymer gels, both have an average molecular weight between crosslinks of only ~1500. The materials in the works by D. W. Armstrong et al have lower values of chain lengths. That’s why it is so interesting that the material can show “polymer-like” behavior in the apparently solid state, without sufficient “configuration number” available molecularly. The dramatic effect of changing the anion from flexible EDTA4- to rigid H2tp4- on the moduli is also interesting. You have proposed a series questions in the end of your Highlight article, among which I think the most straightforward is how “polymer-like” this class of materials are, and where the “polymer-like” behaviors come from. Even in the classic field of polymer physics, the current molecular theories still cannot provide prudent and confident comfirmation of the origins and dynamics of the bulk properties, though rheology has pratically established various generally accepted criteria for describing and understanding chain dynamics and networks. More rheological study on ionic liquid materials may possibly set them inside the framework of and provide new tests on currently gelation and gel theories, with their structural uniqueness and accuracy compared with the high molecular weight polymer counterparts.
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Cheers,
Andrew Sun
Thanks, Andrew. I completely agree. Although the authors of the original paper discuss their results in the context of supramolecular polymer networks, it is not clear that this will prove to be the most appropriate framework for discussing their properties, but the empirical results are potentially useful and interesting on their own. Frankly, of it all the fact that the solid-like porphyrin-based materials are reported to have some elasticity is the observation I would have been least likely to expect, although the authors provide fairly limited characterization of those materials.
I like very much your statement that “current molecular theories cannot provide…confident confirmation of the origins and dynamics of the bulk properties”, and I actually think that there are wonderful opportunities created by these supramolecular approaches to polymer science, because they offer the opportunity for very specific control of very specific macromolecular dynamics and therefore to test some theories of polymer physics. While these ionic systems are interesting, however, it is not clear to me that they are easily suited to such a pursuit. My sense is that the multi-body interactions inherent in densely coulombic systems create quite a complex situation that is not easily deconvolved.
Best,
SC