Short note Blends as a strategy towards tailored hydrolytic degradation of poly(3-caprolactone-co-D,L-lactide)epoly(ethylene glycol)e poly(3-caprolactone-co-D,L-lactide) co-polymers Hanna Bramfeldt a,b , Pierre Sarazin a,b , Patrick Vermette a,b, * a Laboratoire de Bioinge ´nierie et de Biophysique de l’Universite ´ de Sherbrooke, Department of Chemical Engineering, Universite ´ de Sherbrooke, 2500, blvd de l’Universite ´, Sherbrooke, Quebec J1K 2R1, Canada b Research Centre on Aging, Institut universitaire de ge ´riatrie de Sherbrooke, 1036, rue Belve ´de `re Sud, Sherbrooke, Quebec J1H 4C4, Canada Received 20 December 2007; received in revised form 17 January 2008; accepted 20 January 2008 Available online 1 February 2008 Abstract Binary blends were prepared from poly(3-caprolactone) (PCL), and P(CL-co-D,L-lactic acid)eP(ethylene glycol)eP(CL-co-D,L-lactic acid) co-polymers, where the D,L-LA content in the side chains varied from 0 to 70 mol%. Blend discs were fabricated by melt-molding, and the effect of blend composition on hydrolytic degradation was studied. Variations in medium pH were monitored, and morphological changes were ob- served using scanning electron microscopy. Blending of these co-polymers was found to constitute a simple means by which intermediate rates of water absorption and mass loss were obtained, compared to those observed in pure co-polymer preparations. In one of the blends, prepared from the two components containing 70 or 0 mol% D,L-LA in the side chains and thereby exhibiting large differences in degradation rate, hydrolysis resulted in the formation of a porous material over time. Furthermore, all blend samples maintained their initial shape throughout the study. Such materials may be interesting for further investigations for applications in cellular therapy and controlled release. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: Hydrolytic degradation; Aliphatic co-polymers; PEG; Porous scaffolds; Blends 1. Introduction Polymer blends offer a simple means of combining the properties of two materials to achieve a third. Its simplicity makes it preferable, in some cases, to co-polymerisation, which is laborious and time consuming. In the field of tissue engineering, blending two polymers with different degradation profiles may serve to tune physical and mechanical properties [1], or to achieve a desirable rate of degradation [2]. Parame- ters affecting the controlled degradation of blends, apart from the properties of the components, include the composition, preparation method, compatibility and miscibility of the com- ponents [3,4]. Several blend pairs of biodegradable homo- and co-polymers have been studied, including materials composed of poly(3-caprolactone) (PCL), polyanhydrides, poly(ethylene glycol) (PEG), and poly(D,L-lactic acid) (PDLLA) [1,2,4]. Morphological and thermodynamic analyses of polymer blends have shown that PCL are immiscible but compatible with PEG [2,5] and PDLLA [6], whereas PDLLA and PEG have been reported to be miscible [7]. However, in two co- polymer/homo-polymer blends, random P(CL-co-D,L-LA) co- polymers were found to be partially compatible with PDLLA as well as with the amorphous part of the semi-crystalline PCL [4]. Furthermore, blends of PCL and PEGePCLePLA co- polymers exhibited properties indicative of immiscibility of the PEG blocks with PCL [2]. The mechanism of hydrolytic degradation in large devices fabricated from aliphatic polyesters has been described by * Corresponding author. Laboratoire de Bioinge ´nierie et de Biophysique de l’Universite ´ de Sherbrooke, Department of Chemical Engineering, Universite ´ de Sherbrooke, 2500, boulevard de l’Universite ´, Sherbrooke, Que ´bec J1K 2R1, Canada. Tel.: þ1 819 821 8000x62826; fax: þ1 819 821 7955. E-mail address: patrick.vermette@usherbrooke.ca (P. Vermette). 0141-3910/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymdegradstab.2008.01.023 Available online at www.sciencedirect.com Polymer Degradation and Stability 93 (2008) 877e882 www.elsevier.com/locate/polydegstab