Tuning Cross-Link Density in a Physical Hydrogel by Supramolecular Self-Sorting

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• 作者：Marcel M. E. Koenigs ; Asish Pal ; Hamed Mortazavi ; Gajanan M. Pawar ; Cornelis Storm ; Rint P. Sijbesma
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：April 22, 2014
• 年：2014
• 卷：47
• 期：8
• 页码：2712-2717
• 全文大小：352K
• 年卷期：v.47,no.8(April 22, 2014)
• ISSN：1520-5835

文摘

Cross-link density is an important parameter for the macroscopic mechanical properties of hydrogels. Increasing network density leads to an increase in the storage and loss moduli of the gel and can be accomplished by either increasing the concentration of cross-linkers, or by reducing the fraction of mechanically inactive cross-links. Mechanically inactive cross-links consist of loops in the network, which do not contribute to the mechanical properties. Suppression of loop formation is demonstrated in a system of semiflexible supramolecular rods of poly(ethylene glycol)鈥揵is(urea) bolaamphiphiles. Use of a cross-linker which, due to self-sorting of its hydrophobic segments, preferentially connects different rods, increases the modulus of a hydrogel by a factor of 15 compared to a system without self-sorting. By using statistical-mechanical calculations, it is shown that this increase can be explained by the increased tendency of the cross-linkers to form bridges between the semiflexible rods and thus increasing the cross-link density in the supramolecular hydrogel.