Hydrolytic Degradation of Double Crystalline PPDX-b-PCL Diblock Copolymers

• Published in: Macromolecular chemistry and physics Vol. 206; no. 9; pp. 903 - 914
• Main Authors: Albuerne, Julio, Marquez, Leni, Müller, Alejandro J., Raquez, Jean-Marie, Degée, Philippe, Dubois, Philippe
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 09.05.2005; WILEY‐VCH Verlag; Wiley
• Subjects: Applied sciences; block copolymers; Chemical reactions and properties; Degradation; DSC; Exact sciences and technology; hydrolytic degradation; Organic polymers; Physicochemistry of polymers; poly(p-dioxanone); poly(ε-caprolactone); Biodegradation; block copolymers; Lactone copolymer; Film; poly(p-dioxanone); Experimental study; In vitro; Hydrolysis; Caprolactone copolymer; hydrolytic degradation; poly(ε-caprolactone); DSC; Diblock copolymer; Reaction mechanism; Liquid solid reaction; Kinetics; Aliphatic copolymer
• ISSN: 1022-1352; 1521-3935
• DOI: 10.1002/macp.200400524

The degradation behavior of the diblock copolymers PPDX‐b‐PCL was studied under in vitro conditions, in samples with high PPDX content. Molded films were immersed in phosphate buffer solution at pH = 7.4 and 37 °C for 9 months. The samples were periodically extracted, dried and evaluated by weighing, SEC, 1H NMR, DSC, and POM. The results point out that an increase in PCL content reduced the weight loss in the diblock copolymers. 1H NMR and DSC analysis showed that degradation occurred almost exclusively in the PPDX block during the first 9 months of hydrolysis. POM results for the diblock copolymer with high PPDX content (77%) indicated the presence of some typical homo‐PPDX spherulites in the 0.8 months degraded sample when no weight loss was detected. This result demonstrated that random chain scission during the early stages of degradation can produce homo‐PPDX chains that cannot be dissolved in the hydrolysis medium because their molecular weight is still too high. It was found that a small increase in PCL content in the diblock copolymers produced a synergistic increase in the PPDX block degradation stability. This is a direct result of the inter‐digitized lamellar morphology present in the copolymers where PCL and PPDX lamellae are alternated within mixed spherulites. In view of its much higher resistance to hydrolysis, the PCL lamellae offer a barrier‐type protection to the PPDX within the copolymer. A schematic morphological model is proposed to explain the observed changes during the different degradation stages encountered by the diblock copolymers. Proposed scheme for the hydrolytic degradation process of PPDX‐b‐PCL diblock copolymers.