Correlation of swelling and crosslinking density with the composition of the reacting mixture employed in radical crosslinking copolymerization

Abstract

This article reports the scaling laws relating the synthesis conditions with the crosslinking density (νe) and swelling degree (S) of poly(N‐vinylimidazole) hydrogels (PVI) prepared by radical crosslinking copolymerization in aqueous solution, with N,N′‐methylene bisacrylamide (BA) as crosslinker. Multiple linear regression of νe versus BA concentration ([BA]) and total comonomers concentration (CT) in double log scale render the scaling law νe ∼ C italicT0.81 × [BA]1.04 as comparable to that predicted by the model of polymer network with pendant vinyl groups (νe ∼ CT × [BA]), and showing inverse dependence on CT to that expected, following from stoichiometry, for an ideal network (νe ∼ 2[BA]/CT). S scales with νe through a solvent‐dependent exponent ranging from −0.46 to −0.54, only slightly over the value predicted by the Flory–Rehner theory (−0.6) or the blob's model by de Gennes (−0.5 to −0.8). Finally, the scaling law of S with the composition of the reacting mixture is also solvent‐dependent and it seems to result not only from the dependence of νe on CT and [BA] but also from that of v2r, the polymer volume fraction in the reference state, and χ, the polymer–solvent interaction parameter. Models used seem to overestimate the contribution of entanglements to the effective crosslinking density of PVI. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 263–269, 2007

Discrimination of the roles of crosslinking density and morphology in the swelling behavior of crosslinked polymers: Poly(N‐vinylimidazole) hydrogels

“…It was previously shown 11,[15][16][17] that, in accordance with the model of polymer network with pendant vinyl groups proposed by Tanaka, 15 all the samples synthesized with the same C T Â [BA] have the same crosslinking density…”

“…The affine model and gaussian chains were considered for P el . 22,24,31 Equation (5), with 16 v ¼ 0.496 þ 0.308v 2 , affords the m e (S) values plotted in Figure 5 for PVI swollen in deionized water.…”

“…16,17 These m e (PV) values are also depicted in Figure 5 together with m e (IN), the stoichiometric crosslinking density of an ideal polymer network without defects…”

“…The experimental results of hydrogel samples obtained at almost total conversion, support the prediction of the model by Tanaka, which means that some vinyl groups of the crosslinker remain unreacted, even after total incorporation of the monomers to the polymer network. 11,[15][16][17] The PVI samples employed in this work were synthesized with C T and c xl values varying in a broad range, with the constraint that their product is the same for any sample. In this way, their crosslinking density is expected to be the same.…”

Influence of gel preparation concentration on statistical mechanics of poly(dialkylaminoethyl methacrylate) gels on the basis of scaling concept: Toward tunable elasticity and thermomechanical parameters

“…To present a quantitative description for the dependence of crosslinking density on the gel preparation concentration, the scaling predictions for poly(N‐vinylimidazole) hydrogels were evaluated by Pacios and coworkers. The scaling exponent 1.04 has been determined for the concentration dependence of the crosslinking density …”