Molecular dynamic simulation study on structure of water in crosslinked poly(N-isopropylacrylamide) hydrogels

Tönsing, Thorsten; Oldiges, Christian

doi:10.1039/b109281m

Cited by 43 publications

(38 citation statements)

References 23 publications

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“…Tönsing and Oldiges [43] were in 2001 presumably first who studied structure of water around PNiPAAm oligomers composed of 15, 23, and 33 units combined with 2, 3, and 4 crosslinker molecules at three temperatures of 285, 300, and 325 K. They used the GROMOS force field for the polymer and the SPC/E water model. Initial equilibration of 200 ps followed by a production run of 250 ps revealed preferential presence of the water hydrogens around the oxygen atoms of PNiPAAm and of the water oxygens around the hydrogen of the N-H group of the polymer.…”

Section: Poly(n-isopropyl Acrylamide)mentioning

confidence: 99%

Molecular Simulations of Hydrogels

Košovan

Richter

Holm

2013

Intelligent Hydrogels

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Section: Poly(n-isopropyl Acrylamide)mentioning

confidence: 99%

Molecular Simulations of Hydrogels

Košovan

Richter

Holm

2013

Intelligent Hydrogels

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“…The statistical mechanical aspects of the SN were introduced in the early 1940s, [22][23][24][25][26] and MD simulations focusing on water in SN hydrogels, [27][28][29][30][31] no theoretically investigated have yet been reported for DN hydrogels.…”

Section: Introductionmentioning

confidence: 99%

Mechanical and Transport Properties of the Poly(ethylene oxide)−Poly(acrylic acid) Double Network Hydrogel from Molecular Dynamic Simulations

2007

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We used atomistic molecular dynamics (MD) simulations to investigate the mechanical and transport properties of the PEO-PAA double network (DN) hydrogel with 76 wt % water content. By analyzing the pair correlation functions for polymer-water pairs and for ion-water pairs and the solvent accessible surface area, we found that the solvation of polymer and ion in the DN hydrogel is enhanced in comparison with both PEO and PAA single network (SN) hydrogels. The effective mesh size of this DN hydrogel is smaller than that of the SN hydrogels with the same water content and the same molecular weight between the cross-linking points (M c ). Applying uniaxial extensions, we obtained the stress-strain curves for the hydrogels. This shows that the DN hydrogel has a sudden increase of stress above ∼100% strain, much higher than the sum of the stresses of the two SN hydrogels at the same strain. This arises because PEO has a smaller M c value than PAA, so that the PEO in the DN reaches fully stretched out at 100% strain that corresponds to 260% strain in the PEO SN (beyond this point, the bond stretching and the angle bending increase dramatically). We also calculated the diffusion coefficients of solutes such as D-glucose and ascorbic acid in the hydrogels, where we find that the diffusion coefficients of those solutes in the DN hydrogel are 60% of that in the PEO SN and 40% of that in the PAA SN due to its smaller effective mesh size.

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“…Most notably Ball and Edwards 59 60 added corrections to the free energy terms from existing network and solution theories, yet there has been little effort in understanding the molecular level cues that lead to the viscoelastic properties of these systems, not to mention the inherent difficulties in experimentally characterizing them at the microstructural scale. More recently, molecular dynamics (MD) simulations have contributed new ideas on the role of water in these systems [61][62][63][64] and some 44 54 65 66 have ventured further into elucidating the molecular origins of enhanced mechanical toughness through the formation of double interpenetrating networks (DN). In particular, Gong and co-workers have proposed that the improved mechanical response is in part from entanglement between the two polymeric constituents and a dissipation of deformation energy within softer regions of the material, 67 although the molecular nature of these mechanisms remain largely unknown.…”

Section: Motivationmentioning

confidence: 99%

First-Principles Based Approaches to Nano-Mechanical and Biomimetic Characterization of Polymer-Based Hydrogel Networks for Cartilage Scaffold-Supported Therapies

Jaramillo-Botero¹,

Blanco²,

Li³

et al. 2010

Jnl of Comp & Theo Nano

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Atomistic-level molecular dynamics (MD) is used to investigate the thermodynamical and mechanical properties of candidate polymer-based hydrogel networks for tissue scaffold-support therapies that serve a predominantly biomechanical function, in particular articular cartilage. The MD uses force field parameters based on quantum mechanical calculations (including atomic charges and torsional potential energy curves). We provide first principles estimates of the entropic and enthalpic contributions to elastic response, cohesive energies, viscosities, and stress-strain characteristics for relevant single and double network hydrogel compositions of poly(acrylamide)-PAAm and poly(2-acrylamido-2-methylpropanesulfonic acid)-PAMPS, aimed at the functional bio-engineering of artificial tissue with high dynamic load requirements (>10's of MPa even at >90 wt-% water contents).Our results indicate the existence of covalent cross-linking mechanisms taking place during the synthesis of interpenetrating double network hydrogels at critical crosslink concentrations and as a function of starter monomer concentrations and degree of polymerization. Furthermore, percolation thresholds estimated from single chain statistics of acrylamide polymers are consistent with experimentally measured gel points and help explain the precipitous loss of the high fracture energy in double network hydrogels at low crosslink densities; favoring this mechanism, over others presented in the literature (e.g., entanglement, hydrogen bonding), as the origin of enhanced toughness for interpenetrating double network hydrogels. These findings are useful for steering experimental efforts towards systematic optimization of the bio-mimetic response of polymer-based scaffolds for tissue engineering.

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Molecular dynamic simulation study on structure of water in crosslinked poly(N-isopropylacrylamide) hydrogels

Cited by 43 publications

References 23 publications

Molecular Simulations of Hydrogels

Molecular Simulations of Hydrogels

Mechanical and Transport Properties of the Poly(ethylene oxide)−Poly(acrylic acid) Double Network Hydrogel from Molecular Dynamic Simulations

First-Principles Based Approaches to Nano-Mechanical and Biomimetic Characterization of Polymer-Based Hydrogel Networks for Cartilage Scaffold-Supported Therapies

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