Swelling, Elasticity and Spatial Inhomogeneity of Poly(N,N‐dimethylacrylamide) Hydrogels Formed at Various Polymer Concentrations

Abstract

Summary: The equilibrium swelling degree, modulus of elasticity and the spatial inhomogeneity of poly(N,N‐dimethylacrylamide) (PDMAAm) hydrogels were investigated over the entire range of the initial monomer concentration. The degree of dilution of the networks after their preparation was denoted by ν, the volume fraction of crosslinked polymer after the gel preparation. The linear swelling ratio of the gels increased linearly with increasing ν. Depending on the value of ν, three different gel regimes were observed: (1) For ν < 0.3, increasing ν decreases the extent of cyclization during crosslinking so that the effective crosslink density of gels increases with rising ν. (2) For 0.3 < ν < 0.7, increasing ν reduces the accessibility of the pendant vinyl groups during crosslinking due to steric hindrance at high polymer concentrations. As a result, the effective crosslink density of gels decreases with increasing ν. (3) For ν > 0.7, the modulus of elasticity increases sharply with increasing ν due to the increasing extent of chain entanglements in this high concentration regime. Static light scattering measurements on the gels show that the degree of spatial gel inhomogeneity in PDMAAm gels attains a maximum value at ν = 0.06. The appearance of a maximum as well as the ν‐dependence of scattered light intensities from gels was successfully reproduced by the theory proposed by Panyukov and Rabin.Effective crosslink density νe of the hydrogels shown as a function of ν.magnified imageEffective crosslink density νe of the hydrogels shown as a function of ν.

Unusual swelling behavior of polymer–clay nanocomposite hydrogels

“…For the following calculations, we set A ¼ 1. Further, assuming the conversion of the monomer to the crosslinked polymer is complete, using the polymer densities 1.35 g/ml for both PAAm and PNIPA [14], 1.21 g/ml for PDMA [16], n 0 2 was calculated as 0.037, 0.037, and 0.041, respectively. The polymer volume fraction relates to V rel by n 2 ¼ n 0 2 =V rel .…”

Thermosensitive Poly[(2‐(diethylamino)ethyl methacrylate)‐co‐(N,N‐dimethylacrylamide)] Cryogels Prepared by a Two‐Step Polymerization Method

“…Gundogan et al showed that increasing monomer concentration caused the polymer chains to entangle so that the network formed in a concentrated solution can swell less than that formed in a dilute solution. [22] Therefore, the swelling ratios of the 22C0 cryogels are lower than those of the 22C45 cryogels at the same time interval.…”

Influence of Discrete and Continuous Culture Conditions on Human Mesenchymal Stem Cell Lineage Choice in RGD Concentration Gradient Hydrogels

“…V 2 , the volume fraction of cross-linked polymer, was determined by the following equation. 35 $$V_2={false(1+false(q_{\mathrm{f}}-1false)\rho /dfalse)}^{-1}$$where q f is the mass of the swollen hydrogel divided by the mass of the freeze-dried hydrogel. The density of the solvent (alpha minimum essential media), d , is assumed to be 0.997 g/mL.…”