Long-term hydrolytic and enzymatic degradation profiles of poly(ε-caprolactone) (PCL) networks were obtained. The hydrolytic degradation studies were performed in water and phosphate buffer solution (PBS) for 65 weeks. In this case, the degradation rate of PCL networks was faster than previous results in the literature on linear PCL, reaching a weight loss of around 20% in 60 weeks after immersing the samples either in water or PBS conditions. The enzymatic degradation rate in Pseudomonas Lipase for 14 weeks was also studied, with the conclusion being that the degradation profile of PCL networks is lower than for linear PCL, also reaching a 20% weight loss. The weight lost, degree of swelling, and calorimetric and mechanical properties as a function of degradation time were obtained. Furthermore, the morphological changes in the samples were studied carefully through electron microscopy and crystal size through X-ray diffraction. The changes in some properties over the degradation period such as crystallinity, crystal size and Young's modulus were smaller in the case of enzymatic studies, highlighting differences in the degradation mechanism in the two studies, hydrolytic and enzymatic.

a b s t r a c tThe present paper studies the effect of pH on hydrolytic degradation of Poly(ε-caprolactone) (PCL) Degradation of the films was performed at 37 C in 2.5 M NaOH solution (pH 13) and 2.5 M HCl solution (pH 1). Weight loss, degree of swelling, molecular weight, and calorimetric and mechanical properties were obtained as a function of degradation time. Morphological changes in the samples were carefully studied through electron microscopy. At the start of the process the degradation rate of PCL films at pH 13 was faster than at pH 1. In the latter case, there was an induction period of around 300 h with no changes in weight loss or swelling rate, but there were drastic changes in molecular weight and crystallinity. The changes in some properties throughout the degradation period, such as crystallinity, molecular weight and Young's modulus were lower in degradations at higher pH, highlighting differences in the degradation mechanism of alkaline and acid hydrolysis. Along with visual inspection of the degraded samples, this suggests a surface degradation at pH 13, whereas bulk degradation may occur at pH 1.

A study was carried out to determine the effects of graphene oxide (GO) filler on the properties of poly(ε-caprolactone) (PCL) films. A series of nanocomposites were prepared, incorporating different graphene oxide filler contents (0.1, 0.2, and 0.5 wt%) by the solution mixing method, and an in-depth study was made of the morphological changes, crystallization, infrared absorbance, molecular weight, thermal properties, and biocompatibility as a function of GO content to determine their suitability for use in biomedical applications. The infrared absorbance showed the existence of intermolecular hydrogen bonds between the PCL’s carbonyl groups and the GO’s hydrogen-donating groups, which is in line with the apparent reduction in molecular weight at higher GO contents, indicated by the results of the gel permeation chromatography (GPC), and the thermal property analysis. Polarized optical microscopy (POM) showed that GO acts as a nucleating point for PCL crystals, increasing crystallinity and crystallization temperature. The biological properties of the composites studied indicate that adding only 0.1 wt% of GO can improve cellular viability and that the composite shows promise for use in biomedical applications.

Alkaline hydrolysis of a polycaprolactone (PCL) network obtained by photopolymerization of a PCL macromer was investigated. The PCL macromer was obtained by the reaction of PCL diol with methacrylic anhydride. Degradation of PCL network is much faster than linear PCL; the weight loss rate is approximately constant until it reaches around 70%, which happens after approximately 60 h in PCL network and 600 h in linear PCL. Calorimetric results show no changes in crystallinity throughout degradation, suggesting that it takes place in the crystalline and amorphous phases simultaneously. Scanning electron microscopy microphotographs indicate that degradation is produced by a different erosion mechanism in both kinds of samples. The more hydrophilic network PCL would follow a bulk-erosion mechanism, whereas linear PCL would follow a surface-erosion mechanism. Mechanical testing of degraded samples shows a decline in mechanical properties due to changes in sample porosity as a consequence of the degradation process.

Poly(ε-caprolactone) (PCL) based composites containing different graphene oxide (GO) contents (0.1, 0.2 and 0.5 wt%) were produced by the solution mixing method followed by compression molding and enzymatically degraded in a pH 7.4 phosphate buffer solution containing Pseudomonas lipase at 37 °C. Morphological changes, molecular weight, calorimetric and mechanical properties were analyzed according to graphene oxide content. The study of tensile properties showed that the composites increased their Young’s modulus, while tensile strength and elongation at break decreased to significantly less than that of neat PCL. PCL composite crystallinity was evaluated by differential scanning calorimetry (DSC). It was found that incorporating GO can reduce nucleation activity as well as crystallization rates, from 67.6% for neat PCL to 50.6% for a composite with 0.5 wt% GO content. For enzymatic degradation, the weight loss data showed that incorporating GO into the PCL significantly altered enzymatic degradation. The presence of GO did not alter PCL’s hydrolysis mechanism, but did slow down composite enzymatic degradation in proportion to the percentage of filler content.