Tunable elasticity and thermodynamic parameters of hydroxypropyl methacrylate‐based gels with varying extents of monomer concentration: Statistical mechanics treatments of physical observations

Abstract

The present article reports the scaling laws relating the preparation conditions with the equilibrium swelling degree and the crosslinking density of a new family of hydroxyl functional hydrogels (Hgs) prepared by free radical crosslinking polymerization of hydroxypropyl methacrylate (HPMA) in aqueous solution with tetraethylene glycol dimethacrylate (TEGDMA) as crosslinker. For comparison of physical properties, chemical and mechanical stability, HPMA cryogels (Cgs) were also prepared using the cryotropic gelation technique by conducting the gelation reactions at subzero temperatures. The measurements of the equilibrium swelling degree and the elastic properties of poly(hydroxypropyl methacrylate) (PHPMA) gel samples having different initial monomer concentration were treated according to the scaling theory to explain the rubbery behavior of the resulting Hgs. The obtained scaling relation between the reduced modulus and the swelling degree Gr≈(Veq)−1.48 indicated limiting chain extensibility which is neglected in the Flory–Rehner theory. The effective crosslink density and polymer–solvent interaction parameter of PHPMA Hgs were used to interpret the observed deviation. Results showed that the properties of PHPMA Hgs and Cgs can be controlled by varying the HPMA and TEGDMA content. Increase of total monomer concentrations causes a pronounced decrease in the equilibrium swelling degree, and an increase in the elastic response of PHPMA Hgs and Cgs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45889.

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