Pronounced effects of the densities of threaded rings on the strain-dependent Poisson's ratio of polyrotaxane gels with movable cross-links. Issue 15 (22nd March 2018)

• Record Type: Journal Article
• Authors: Tanaka, Akira; Kato, Kazuaki; Ito, Kohzo; Urayama, Kenji
• Is Part Of: Soft matter. Volume 14:Issue 15(2018)
• Page Start: 2808
• Page End: 2815
• Publication Date: 2018-03-22
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c8sm00257f
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : The density of threaded ring molecules in polyrotaxane (PR) chains influences pronouncedly the equilibrium Poisson's ratio of PR gels where the cross-linked ring molecules are slidable along the network strands. Abstract : The density of threaded ring molecules ( f CD ) in polyrotaxane (PR) chains has pronounced effects on the strain-induced swelling of PR gels where the cross-linked ring molecules are slidable along the network strands. The equilibrium Poisson's ratio ( μ ∞ ), which is a measure of the strain-induced volume change, for the PR gel increases with an increase in elongation ( λ ) at moderate λ but becomes a constant value ( ) at sufficiently large λ . When the modulus exceeds a threshold value ( E c ), the λ dependence of μ ∞ disappears due to the loss of the slidability of the cross-links. The fraction f CD significantly influences the values of and E c . When f CD is sufficiently small (<14%), (≈0.25) agrees with the values of μ ∞ for the classical gels in good solvents. When f CD is high (>25%), varies over a wide range (0.22 < < 0.33) depending on f CD and the cross-link concentration in a complicated way. The modulus E c at f CD = 25% is more than twice as high as that at f CD = 5% due to the finite contribution of the larger amount of uncross-linked ring molecules via combinatorial entropy in the axial polymers. The origin of the markedly small values of μ ∞ (less than 0.1) at small λ is also considered on the basis of the magnitude of the accompanying force reduction caused by the slidable function of the cross-links.