We study the effect of interfiber adhesion on the mechanical behavior of crosslinked ran dom fiber networks in two dimensions. To this end, we consider networks with connectiv ity number, z , below, at, and above the isostaticity limit of the structure without adhesion, z c . Fibers store energy in the axial and bending deformation mode and the crosslinks are of freely rotating type. Adhesive forces lead to fiber bundling and to a reduction of the total volume of the network. The degree of shrinkage is determined as a function of the strength of adhesion and network parameters. The mechanical response of these struc tures is further studied in uniaxial tension and compression. The stressstrain curves of networks without interfiber adhesion exhibit an initial linear regime, followed by strain stiffening in tension and strain softening and strain localization in compression. In pres ence of adhesion, the response becomes more complex. The initial linear regime persists, with the effective modulus decreasing and increasing with increasing adhesion in cases with z > z c and z < z c , respectively. The strain range of the linear regime increases signif icantly with increasing adhesion. Networks with z > z c subjected to tension strainstiffen at rates that depend on the adhesion strength, but eventually enter a large strain/stress regime in which the response is independent of this parameter. Networks with z < z c are stabilized by adhesion in the unloaded state. Beyond the initial linear regime their tangent modulus gradually decreases, only to increase again at large strains. Adhesive interactions lead to similar effects in compression. Specifically, in the z > z c case, increasing the adhe sion strength reduces the linear elastic modulus and significantly increases the range of the linear regime, delaying strain localization. This first investigation of the mechanics of crosslinked random networks with interfiber adhesion opens the door to the design of soft materials with novel properties.
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Elasticity of SlideRing Gels
Slidering gels are polymer networks with crosslinks that can slide along the chains. In contrast to conventional unentangled networks with crosslinks fixed along the chains, the slidering networks are strainsoftening and distribute tension much more uniformly between their strands due to the socalled “pulley effect”. The sliding of crosslinks also reduces the elastic modulus in comparison with the modulus of conventional networks with the same number density of crosslinks and elastic strands. We develop a singlechain model to account for the redistribution of monomers between network strands of a primary chain. This model takes into account both the pulley effect and fluctuations in the number of monomers per network strand. The pulley effect leads to modulus reduction and uniform tension redistribution between network strands, while fluctuations in the number of strand monomers dominate the strainsoftening, the magnitude of which decreases upon network swelling and increases upon deswelling.
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 Award ID(s):
 2116298
 NSFPAR ID:
 10400542
 Date Published:
 Journal Name:
 ACS Macro Letters
 Volume:
 12
 ISSN:
 21611653
 Page Range / eLocation ID:
 362 to 368
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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