Hydrolytic degradation of double crystalline PPDX-b-PCL diblock copolymers

被引:26
作者
Albuerne, J
Marquez, L
Müller, AJ
Raquez, JM
Degée, P
Dubois, P
机构
[1] Univ Simon Bolivar, Dept Ciencia Mat, Grp Polimeros USB, Caracas 1080 A, Venezuela
[2] Univ Mons, Lab Polymer & Composite Mat, B-7000 Mons, Belgium
关键词
block copolymers; DSC; hydrolytic degradation; poly(epsilon-caprolactone); poly(p-dioxanone);
D O I
10.1002/macp.200400524
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
The degradation behaviour 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 degrees C for 9 months. The samples were periodically extracted, dried and evaluated by weighing, SEC H-1 NMR, DSC, and POM. The results point out that an increase in PCL content reduced the weight loss in the diblock polymers. H-1 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 synergistics 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.
引用
收藏
页码:903 / 914
页数:12
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