Physical and mechanical properties of amphiphilic and adaptative polymer conetworks produced by Atom Transfer Radical Polymerization

Abstract

Model amphiphilic polymer conetworks have been successfully produced by combination of ring-opening polymerization (ROP) of e-caprolactone and atom transfer radical polymerization (ATRP) of amino-functionalized methacrylate monomer. Their swelling properties have been investigated in Millipore ® water as well as in toluene in order to demonstrate the amphiphilic nature of the gel. The control over the cross-linking degree and therefore the conetwork structure was highlighted by swelling experiments and confrontation of the results with the Flory-Rehner relationship. Environmental responsiveness towards pH and temperature was also demonstrated. The presence of the hydrophobic poly(e-caprolactone) (PCL) cross-linkers was found to be beneficial for improving both stiffness and elongation at break of the resulting hydrogels but also for favouring their hydrolytic degradability. Moreover, tensile testing studies performed on two representative hydrogel samples produced by either ATRP or more conventional free-radical polymerization (FRP) allowed to reveal the strong impact of the polymerization mechanism over the mechanical performances of the resulting conetworks. As a result, it came out that ATRP not only produces amphiphilic polymer conetworks with controlled architecture but allows also for significantly enhancing their physico-mechanical properties resulting in much less brittle materials.