(718g) Static and Dynamic Properties of Biodegradable Poly (antioxidant ?-amino ester) Networks Based On Incorporation of Curcumin Diacrylate

Poly (antioxidant β-amino esters) (PAβAE), which are biodegradable antioxidant polymer hydrogels, have shown promising results in reducing oxidative stress and also improving biocompatibility at the same time [1].  The degradation and resulting antioxidant properties of these biomaterials are closely correlated with the composition and architecture of the networks that are established during polymerization.  In this work, we examine a series of hydrogel networks formed by polymerization of a commercial diacrylate (PEG400DA) and a primary diamine (TTD) in combination with acrylate-functionalized curcumin (i.e., curcumin diacrylate – CDA).  Network structure and thermomechanical response properties were examined by dynamic mechanical analysis and broadband dielectric spectroscopy, as well as controlled swelling measurements.  In addition, the aqueous degradation of these hydrogels was evaluated as a function of composition and polymerization history.  The establishment of fundamental relations between network structure and corresponding response characteristics is crucial to tailoring these materials for desired efficacy as antioxidant therapeutics.

Curcumin diacrylate was synthesized and isolated according to methods described previously [1].  Crosslinked polymer networks were formed by pre-polymerization of 4,7,10-trioxa-1,13-tridecanediamine (TTD) with poly(ethylene glycol) 400 diacrylate (PEG400DA) in anhydrous dichloromethane (DCM) followed by addition of CDA and incubation at 50°C.  The molar ratio of total acrylate to amine (RTAA) was fixed at 1.0 for all polymerizations with diacrylate content varied from 0 to 100% CDA.  The liquid reaction mixture was deposited in an enclosed casting ring, resulting the in the formation of polymer films of thickness 0.1 to 0.3 mm.     

Mechanical properties of the films, and corresponding crosslink density, were assessed via dynamic mechanical analysis as well as equilibrium swelling studies.  In general, increased curcumin content led to an increase in the glass transition temperature of the films and a corresponding decrease in network degradation kinetics.  Broadband dielectric spectroscopy measurements were used to characterize the time-temperature characteristics of the  glass-rubber (α) relaxation, as well as dual sub-glass relaxations (β₁ and β₂) as a function of network composition and preparation history; the observed characteristics were consistent with previous results reported for amorphous UV-crosslinked PEGDA homopolymer networks [2].  The detailed characterizations to be presented will be linked to controlled synthesis strategies for the production of well-defined hydrogels with specific degradation and response properties.

[1] P. P. Wattamwar, D. Biswal, D. B. Cochran, A. C. Lyvers, R. E. Eitel, K. W. Anderson, J. Z. Hilt, T. D. Dziubla, Synthesis and characterization of poly(antioxidant β-amino esters) for controlled release of polyphenolic antioxidants, Acta Biomaterialia, 8 (2012) 2529-2537.

[2] S. Kalakkunnath, D.S. Kalika, H. Lin, R.D. Raharjo, B.D. Freeman, Molecular relaxation in cross-linked poly(ethylene glycol) diacrylate and poly(propylene glycol) diacrylate networks by dielectric spectroscopy, Polymer, 48 (2007) 579-589.