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Neste trabalho foi realizada a síntese e a caracterização de copolímeros dibloco formados pelo poli(estireno)-b-poli(γ-benzil-L-glutamato) (PS-b-PBLG). O bloco de PS foi sintetizado via polimerização aniônica, enquanto o bloco de PBLG foi sintetizado via polimerização por abertura de anel. Os homopolímeros e copolímeros foram caracterizados por meio de técnicas clássicas de ressonância magnética nuclear de próton e carbono (RMN 1H e 13C), cromatografia de permeação em gel (GPC) e análise térmica (calorimetria de varredura diferencial (DSC) e termogravimetria (TG)). A caracterização em solução foi realizada utilizando-se a técnica de espalhamento de luz estático (SLS). Na análise de SLS foram determinados parâmetros como a massa molar ponderal média (Mwm), o segundo coeficiente virial (A2) e a concentração crítica (C*) para os homopolímeros puros e para o copolímero PS100-b-PBLG330. http://dx.doi.org/10.18226/23185279.v2iss1p31, The synthesis and characterization of diblock copolymers formed by poly(styrene) and poly(γ-benzyl-L-glutamate) (PBLG) were studied. The PS and PBLG blocks were obtained by anionic and open ring polymerization, respectively. The homopolymers and copolymers were characterized by classical techniques such as nuclear magnetic resonance of proton and carbon (1H and 13C NMR), gel permeation chromatography (GPC) and thermal analysis (differential scanning calorimetry (DSC) and thermogravimetry (TGA)). The characterization in solution was performed using static light scattering (SLS). In the analysis by SLS, parameters such as average molar mass (Mwm), second virial coefficient (A2) and critical concentration (C*) for the pure homopolymers and the copolymer PS100-b-PBLG330 were determined. http://dx.doi.org/10.18226/23185279.v2iss1p31

Strawberry is a non-climacteric fruit with a very short postharvest shelf-life. Loss of quality in this fruit is mostly due to its relatively high metabolic activity and sensitivity to fungal decay, meanly grey mold (Botrytis cinerea). In this study, the ability of gelatin coatings containing cellulose nanocrystals (CNC) to extend the shelf-life of strawberry fruit (Fragaria ananassa) over 8 days were studied. The filmogenic solution was obtained by the hydration of 5 g of gelatin (GEL) in 100 mL of distillated water containing different amounts of CNC dispersion (10 mg CNC/g of GEL or 50 mg of CNC/g of GEL) for 1 hour at room temperature. After this period, the solution was heated to 70 ºC and maintained at this temperature for 10 minutes. The plasticizer (glycerol) (10g/100g of the GEL) was then added with constant, gentle stirring in order to avoid forming air bubbles and also to avoid gelatin denaturation until complete homogenization. Strawberries (purchased at the local market) were immersed in the filmogenic solution for 1 minute and after coated were dried at 15 ºC by 24 hours. The strawberries were then kept under refrigeration and characterized in terms of their properties (weight loss, ascorbic acid content, titratable acidity, water content). The results have shown that samples covered with GEL/CNC had a significant improvement in its shelflife. For instance, for the control sample (without coating) the weight loss after 8 days of storage was around 65%, while covered samples loss in the range of 31-36%. Edible coating was also effective in the retention of ascorbic acid (AA) in the strawberries, while control sample presented a fast decay in the AA content, covered samples showed a slow decay in the AA concentration. Moreover, the use of GEL/CNC edible coating had an antimicrobial effect in the fruits, Postprint (published version)

Polylactic acid (PLA) has been larger used in biomedical field due to its low toxicity and biodegradability. The aim of this study was to produce PLLA nanocomposites, by melt extrusion, containing Halloysite nanotubes (HNT) and/or titanium dioxide (TiO2) nanoparticles. Immediately after drying, PLLA was mechanically homogenized with the nanofillers and then melt blended using a single screw extruder (L/D = 30) at a speed of 110 rpm, with three heating zones in which the following temperatures were maintained: 150, 150 and 160ºC (AX Plásticos model AX14 LD30). The film samples were obtained by compression molding in a press with a temperature profile of 235 ± 5ºC for 2.5 min, after pressing, films were cooled up to room temperature. The mechanical tests were performed according to ASTM D882-09 and the water vapor permeability (WVP) was measured according to ASTM E-96, in triplicate. The tensile properties indicated that the modulus was improved with increased TiO2 content up to 1g/100g PLLA. The Young's modulus (YM) of the PLA was increased from 3047 MPa to 3222 MPa with the addition of 1g TiO2/100g PLLA. The tensile strength (TS) of films increases with the TiO2 content. In both cases, the YM and TS are achieved at the 1% content of TiO2 and is due to the reinforcing effect of nanoparticles. Pristine PLA showed a strain at break (SB) of 3.56%, while the SB of nanocomposites were significant lower, for instance the SB of composite containing 7.5 g HNT/100g PLLA was around 1.90 %. The WVP of samples was increased by increasing the nano filler content. It should be expected that an increase of nanofiller content would decrease the mass transfer of water molecules throughout the samples due to the increase in the way water molecules will have to cross to permeate the material. However, this was not observed. Therefore, this result can be explained considering the molecular structure of both fillers, which contain several hydroxyl groups in the surface, making the end ma, Postprint (published version)