Supercoiling transformation of chemical gels

Abstract

The swelling/deswelling behavior of chemical gels has been an unsolved problem disputed over for a long time. The Obukhov-Rubinstein-Colby model depicts the influence that swelling/deswelling has on elasticity, but its physical picture is too complicated to be sufficiently validated by experiment. In this study, we use molecular dynamics simulation to verify the validity of the molecular picture of network strands predicted by the Obukhov-Rubinstein-Colby model. We conclude that the physical picture of the Obukhov-Rubinstein-Colby model is reasonable, and furthermore the simulation can reveal the details of conformational changes in network strands during the supercoiling transformation. Our findings not only reveal the validity, but also give a better understanding of the dynamics of the swelling/deswelling behavior of chemical gels.

Swelling and Tensile Properties of Tetra‐Polyethylene glycol via Coarse‐Grained Molecular Models

“…We observed two main regimes of power‐law dependence of E m on (semidilute and concentrated regime, with and , respectively) for our simulated realistic networks and ideal diamond networks, with a crossover value of φ c ≈ 0.5. Asai et al further suggested a dilute regime with and our limited results for would appear to approach such a scaling as shown in Figures and . The crossover behavior around ≈ 0.5 is similar to that observed in experimental studies, with experimental exponent of 0.58 [0.51] for 10k [20k] gels in the semidilute regime, and exponent of 1.1 [1.2] for 10k[20k] gels in the concentrated regime.…”

“…[17] However, to make meaningful comparisons of Young's moduli from experimental and simulated gels at intermediate degrees of swelling φ m which are below φ s , it is convenient to normalize φ m relative to the maximum swelling ratio of simulation and experiment, so that we will use the normalized swelling degree: Figures 8 and 9 for the 10k and 20k gels, respectively (details of stress-strain relations for these gels are shown in Figures S10 and S11 φ , respectively) for our simulated realistic networks and ideal diamond networks, with a crossover ˆm φ value of φ c ≈ 0.5. Asai et al [67] further suggested a dilute regime with Em m 0.33 φ and our limited results for ˆ0 .1 m φ < would appear to approach such a scaling as shown in Figures 8 and 9. The crossover behavior around ˆm φ ≈ 0.5 is similar to that observed in experimental studies, [17,68] with experimental exponent of 0.58 [0.51] for 10k [20k] gels in the semidilute regime, and exponent of 1.1 [1.2] for 10k[20k] gels in the concentrated regime.…”

Scaling Theory of Swelling and Deswelling of Polymer Networks

“…The entanglement crossover upon deswelling was detected by experiments and simulations on end-linked networks of tetra-PEG. − The simulation results by Asai et al are in good agreements with the function describing the crossover between the unentangled regime (U, eq ) and the entangled deswollen regime (ED, eq ) (see Figure b). The polymer volume fraction at the entanglement crossover is estimated to be ϕ e = 0.46 by fitting eq to the simulation data . This estimate is close to the value ϕ e ≈ 0.4 obtained by using eq S22′ in the Supporting Information with N x = 100 and N em = 30.…”

The Swelling of Poly(Isopropylacrylamide) Near the θ Temperature: A Comparison between Linear and Cross‐Linked Chains

“…The models introduced in Section 1 have been applied to macroscopic gel systems with varying degree of agreement between experiment/simulations and theory . Experimental tests often focus on the scaling exponents for various quantities (equilibrium swelling, bulk modulus, etc.)…”

“…between experiment/simulations and theory. [50][51][52][53][54][55][56][57][58][59][60][61] Experimental tests often focus on the scaling exponents for various quantities (equilibrium swelling, bulk modulus, etc.) with degree of crosslinking ( f ) or the volume fraction of the gel at the preparation state (φ 0 ).…”