Entanglement Locking in the Unique Elasticity of Polydimethylsiloxane Rubbers. Issue 10 (13th April 2020)

• Record Type: Journal Article
• Authors: Villani, Vincenzo; Lavallata, Vito
• Is Part Of: Macromolecular chemistry and physics. Volume 221:Issue 10(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-04-13
• Subjects: dynamic‐mechanical analysis -- polydimethylsiloxane -- polymer viscoelasticity -- rubber blends -- rubber elasticity theory; Polymers -- Periodicals; Polymerization -- Periodicals; Synthetic products -- Periodicals; Macromolecules -- Periodicals; 547.7
• DOI: 10.1002/macp.201900497
• Languages: English
• ISSNs: 1022-1352

Abstract

Abstract: The viscoelasticity behavior of the polydimethylsiloxane (PDMS) rubber blends of high molecular weight polymers modified by low molecular weight agents is studied in compression mode by stress–strain curves, the creep and step‐strain, and dynamic‐mechanical experiments. The strain spectra highlight the dynamics of active chains at high frequencies and of dangling ends in the low frequencies field. At low deformation, the blending agent enhances the elastic properties by increasing the density of the active chains in the rubber network, in agreement with the classical theories of elasticity. At high deformation, in analogy with the rheological studies on similar liquid blends, the Entanglement Locking model is proposed: the short chains of the blending agent are adsorbed on entanglement sites of long dangling chains, giving effective crosslinks via high entropy dynamics. In this way, the long‐term entanglement locking enhances the density of active chains and elastic behavior. At high deformation, the entanglement locking model enriches the rubber elasticity theories according to the tube network model and Mooney–Rivlin equation. The models herein and the possibility they offer for improving rubber viscoelasticity are valuable for the development of polymer physics and technology. Abstract : The entanglement locking mechanism of polydimethylsiloxane (PDMS) rubber network is investigated. The random‐coils of free short chain are adsorbed on entanglement sites of dangling chains. Many‐body dynamics stabilize effective crosslinks, increasing the density of active chains and the entropy of the network. The arrows in the image indicate the chaotic dynamics among the isodimensional coils interacting in an incompatible way.