Abstract
Slide-ring (SR) gels, a new type of gels that have cross-links moving along the chains, are known to have unique mechanical characteristics. In the case of biaxial deformations, it has been experimentally shown that the stress–strain (S–S) relationships of SR gels can be well described by the neo-Hookean (NH) model. This behavior is quite different from that of conventional chemical gels, where the S–S curves deviate from the NH model. To understand the molecular mechanism of such peculiar elastic properties of SR gels, we studied the effects of movable cross-links by using molecular simulations and theoretical analysis. We calculate the S–S relationships in biaxial deformation for two types of models: slip model, where the cross-links can slide along chains representing SR gels, and non-slip model, which corresponds to conventional chemical gels. In the theoretical analysis, we calculate the S–S relationships by using the models with the Gaussian and the Langevin chains to investigate the nonlinear stretching effect of the chain in the slip and non-slip models. As a result, we found that the peculiar elastic behaviors of SR gels in biaxial deformations are well explained by the effect of movable cross-links suppressing the nonlinear stretching of the chain.
Highlights
IntroductionGels are classified into two types: chemical gels and physical gels, depending on the strength of the bond energy of cross-links
Gels are, traditionally, classified into two types: chemical gels and physical gels, depending on the strength of the bond energy of cross-links
We explored the influence of sliding cross-links on the elastic properties of SR gels under biaxial deformation computationally and theoretically
Summary
Gels are classified into two types: chemical gels and physical gels, depending on the strength of the bond energy of cross-links. SR gels are prepared by cross-linking polyrotaxane (PR) consisting of many cyclic molecules (cyclodextrin: CD) threaded on a main chain end-capped with bulky groups [2,3]. The figure-of-eight cross-links in SR gel can slide along the chains and act like pulleys to vary the network structure in response to imposed deformation. By this so-called pulley effect, the stress on the network under deformation can be effectively relaxed [4]. The mechanical properties of SR gels are drastically different from those of the conventional chemical gels; a great deal of attention has been given to SR gels from scientific and engineering fields
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