Abstract
This work considers the development of an easy and scalable approach to change the features of poly(l-lactide) (PLLA) films, which is based on the application of a surface treatment with an amino-functionalized polyhedral oligomeric silsesquioxane (POSS). Indeed, the developed approach is based on the potential reactivity of POSS amino group towards the polymer functionalities to produce an aminolysis reaction, which should promote the direct grafting of the silsesquioxane molecules on the polymer surface. Neat and treated films were studied by infrared spectroscopy and X-ray photoelectron spectroscopy, which proved the effectiveness of POSS grafting. Moreover, scanning electron microscopy measurements demonstrated the homogeneous distribution of Si on the film surface treated with the silsesquioxane. The influence of the film treatment on the surface wettability was evidenced by contact angle measurements. These findings demonstrated a relevant enhancement of the surface hydrophobicity, which increase turned out to depend on the conditions applied, as it increased by increasing the reaction temperature and the contact time. Finally, in order to evaluate the stability of neat and of the treated PLLA films the surface morphology of the samples treated with pH 7.4 buffer at 50 °C was studied.
Highlights
Polylactide (PLA), a biodegradable polyester, is one of the most interesting and sustainable substitutes of polymers from fossil resources [1]
The polymer film is exposed to a solution of polyhedral oligomeric silsesquioxane (POSS) to obtain a heterogenous reaction on the polymer surface. Both the neat and treated films were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FE-SEM), Differential Scanning Calorimetry (DSC), ThermoGravimetric Analysis (TGA) and contact angle measurements, while the hydrolytic degradation was followed by monitoring the film morphology over time
Despite no strict correlation between the intensity of the above signals with contact time and the temperature was found, in the case of the samples exposed to the silesquioxane for a lower tc, namely PLLA_POSS_4_40 and PLLA_POSS_4_60, the band at 1600 cm−1 is barely visible
Summary
Polylactide (PLA), a biodegradable polyester, is one of the most interesting and sustainable substitutes of polymers from fossil resources [1]. The above approaches were found to affect the polymer degradation, several drawbacks have to be taken into account for their use, including the change of the polymer features such as the transparency and the dispersibility of the additives In this light, the development of easy approaches, using mild conditions, capable of enhancing the hydrolysis resistance of the polymer without affecting the bulk properties is a crucial issue for extending PLA exploitation. It is worth underling that the surface of PLA film was mainly modified by using plasma [9,10] and gas phase treatment [11] These methods were applied to enhance the PLA surface hydrophilicity, which modification turned out to increase the polymer hydrolytic degradation [8,9,10,11]. Both the neat and treated films were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FE-SEM), Differential Scanning Calorimetry (DSC), ThermoGravimetric Analysis (TGA) and contact angle measurements, while the hydrolytic degradation was followed by monitoring the film morphology over time
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