Sustainable
polymers from renewable resources are classified as
biobased polymers. Poly(lactic acid) (PLA) is one of the most common
biobased polymers applied in the biodegradable plastic industry as
a feasible substitute of petrochemical-derived products. Cardanol
oil (CA), a renewable resource and relatively low-cost side product
of the cashew agro-industry, combined with neat PLA permitted the
preparation of plasticized PLA/CA films by means of hot melt extrusion
processes. Looking at packaging applications of the functional biobased
PLA/CA films, chemical, mechanical, thermal, antioxidant, and barrier
properties were studied. Thermal analysis revealed that the PLA glass-transition
temperature decreased with the increasing content of CA, indicating
that CA worked as a plasticizer for PLA. The presence of CA increased
the oxygen transmission through the PLA/CA films; consequently, the
permeability values were always appreciably higher for plasticized
films. Nevertheless, the CA-plasticized PLA films showed good barrier
properties similar to packaging materials commonly used in the food
industry today. Release studies from PLA/CA films were carried out
in four food simulants (physiological saline solution, ethanol, acetic
acid, and isooctane) through spectrophotometric measurements and revealed
the release effects only in simulants for fatty foods. Radical scavenging
assays indicated the elevated antioxidant activity of CA-incorporated
films compared to neat PLA.
A straight synthetic route to fabricate hybrid nanocomposite films of well-dispersed CdS nanocrystals (NCs) in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) is reported. A soluble cadmium complex [Cd(SBz)2]2·MI, obtained by incorporating a Lewis base (1-methylimidazole, MI) on the cadmium bis(benzyl)thiol, is used as starting reagent in an in situ thermolytic process. CdS NCs with spherical shape nucleate and grow well below 200°C in a relatively short time (30 min). Photoluminescence spectroscopy measurements performed on CdS/MEH-PPV nanocomposites show that CdS photoluminescence peaks are totally quenched inside MEH-PPV, if compared to CdS/PMMA nanocomposites, as expected due to overlapping of the polymer absorption and CdS emission spectra. The CdS NCs are well-dispersed in size and homogeneously distributed within MEH-PPV matrix as proved by transmission electron microscopy. Nanocomposites with different precursor/polymer weight ratios were prepared in the range from 1:4 to 4:1. Highly dense materials, without NCs clustering, were obtained for a weight/weight ratio of 2:3 between precursor and polymer, making these nanocomposites particularly suitable for optoelectronic and solar energy conversion applications.
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