Enzymatic Hydrolysis of Poly (Caprolactone) and its Blend with Styrene–Butadiene–Styrene (40% PCL/60% SBS)

Abstract

In this study, we aim to evaluate the effect of enzymatic hydrolysis on aliphatic polyester and on its shape memory blend. Therefore, the hydrolysis of poly (ɛ-caprolactone) (PCL) and of its shape memory polymer (SMP) blend [40% PCL/60% styrene–butadiene–styrene (SBS)] in a solution containing an Amano lipase from pseudomonas fluorescence and a phosphate buffered saline (PBS), is achieved. An appropriate characterization helps to better understand the behaviour of these polymers. So, the properties of these materials prior and after hydrolytic degradation are investigated. When they are submitted to enzymatic hydrolysis, the physico-chemical and mechanical properties of PCL and its blend (PCL/SBS) change. PCL undergoes a significant decrease in weight during enzymatic hydrolysis. Yet, blending PCL with SBS considerably reduces its degradation rate in terms of weight drop, compared with pure PCL. The enzymatic hydrolysis causes chains splitting, which rises their mobility and facilitates their reorientation. Consequently, for PCL and its blend, the degree of crystallinity Xc rises during hydrolytic degradation, which confirms that the amorphous regions of PCL are more susceptible to hydrolysis. Besides, this continuous rise in crystallinity causes the augmentation of PCL and its blend melting, crystallization and glass transition temperatures. Moreover, the PCL brittleness increases, and the blend ductility decreases with the enzymatic hydrolysis time. For both, PCL and its blend, the young modulus displays two opposite effects; it goes up due the growth of crystallinity, but at the end of hydrolysis, its value goes down because of weight loss.