Intermacromolecular Complexation Between Poly(Methacrylic Acid) Hydrogels and Poly(Ethylene Glycol)

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Abstract
The interaction of poly(methacrylic acid) (PMAA) hydrogels with poly(ethylene glycol) (PEG) has been investigated by means of FT-IR spectroscopy and refractometry. It has been shown that PEG molecules penetrate a swollen PMAA network and form intermacromolecular complexes (IMCs) with PMAA. The kinetics data indicate that the decrease of the chain length of PEG macromolecules results in the lowering of the rate of PEG diffusion in the gel. The dissociation constants K and the composition θ of PMAA gel-PEG complexes have been determined. It was found that the stability of IMCs as well as the equilibrium fraction of PEG in the IMC lower sharply with a decrease of molecular weight of PEG. The complexation causes a contraction of the PMAA gel in neutral medium and the collapse of the gel in acid medium. It was found that at an excess of PMAA with respect to PEG, the complex forms essentially in the outer layer of the gel.