Abstract
Recently, we reported the synthesis of two new dimeric cucurbit[6]uril compounds (1 and 2). Herein, we describe the ability of compound 1 to undergo supramolecular polymerisation when combined with polyethylene glycol (PEG) derived divalent guests 3MW (MW = 300, 1000, 3350, 10,000). Interestingly, we find that the shorter PEG-derived guests 3300, 31000 and 33350 lead to low degrees of oligomerisation based on the diffusion coefficients obtained by diffusion-ordered spectroscopy measurements. In contrast, when 1 was combined with the longest PEG-derived guest 310,000, we observed the formation of a supramolecular polymer with a degree of oligomerisation of at least 36. We observe that the supramolecular polymer 1n·(310,000)n undergoes a slow decrease in its degree of oligomerisation to 22 over the course of 14 days controlled by the slow dissociation rate constant of the hexanediammonium unit of 310,000 from the CB[6]-sized cavity of 1.
Acknowledgements
The authors thank the National Science Foundation (CHE-1110911 to L.I.), the Department of Education (P200A090105, GAANN fellowship to J.B.W.) and the University of Maryland (University Fellowship to J.B.W.) for financial support.
Notes
1. For the molecular weights of 3MW we used the average molecular weight of the PEG oligomer minus two OH groups plus the weight of the two +H3N(CH2)6NH2 + arms; MW(3300) = 500, MW(31000) = 1200, MW(33350) = 3550, MW(31000) = 10,200.