Poly(N-isopropylacrylamide)-based semi-interpenetrating polymer networks for tissue engineering applications. Effects of linear poly(acrylic acid) chains on rheology

Abstract

Semi-interpenetrating polymer networks (semi-IPNs), comprised of poly(N-isopropylacrylamide-co-acrylic acid) (p(NIPAAm-co-AAc)) hydrogels and linear p(AAc) chains, were synthesized, and the effects of the p(AAc) chains on semi-IPN rheology were examined. Oscillatory shear rheometry studies were performed and the rheological data were analyzed as a function of temperature, frequency, and p(AAc) chain amount (weight average molecular weight (M _w ) 4.5 × 10⁵ g/mol). At 22^°C, the semi-IPNs, as well as control p(NIPAAm-co-AAc) hydrogels, demonstrated rheological data that were representative of soft, loosely cross-linked solids. Furthermore, only the highest p(AAc) chain amount tested affected the rigidity of the p(NIPAAm-co-AAc)-based semi-IPNs, as compared to the p(NIPAAm-co-AAc) hydrogels. At 37^°C, the complex shear moduli (G ^∗) demonstrated by the p(NIPAAm-co-AAc)-based semi-IPNs were significantly greater than G ^∗ exhibited by the p(NIPAAm-co-AAc) hydrogels, and the semi-IPN G ^∗ values significantly increased with increasing p(AAc) chain amount. These results can be used to develop p(NIPAAm)-based semi-IPNs with tailored mechanical properties that may function as scaffolds in tissue engineering initiatives.

Keywords:

• SEMI-IPN
• N-ISOPROPYLACRYLAMIDE
• RHEOLOGY
• OSCILLATORY SHEAR RHEOMETRY
• ACRYLIC ACID