Natural polymers and green methodologies: a never ending source of novel sustainable and functional materials

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Physicochemical surface properties of bacterial cellulose/polymethacrylate nanocomposites: an approach by inverse gas chromatography

Publication . Faria, Marisa; Vilela, Carla; Silvestre, Armando J.D.; Deepa, Bhanumathyamma; Resnik, Matic; Freire, Carmen S. R.; Cordeiro, Nereida

Nanocomposites of poly(glycidyl methacrylate) and bacterial cellulose (BC), or poly(poly(ethylene glycol) methacrylate) and BC were produced via the in-situ polymerization of methacrylic monomers, inside the BC 3D network. The nanocomposites surface properties were evaluated by inverse gas chromatography (IGC). The dispersive component of surface energy (γsd) varied between 35.64 - 83.05 mJ m-2 at 25 °C. The surface of the different nanocomposites has a predominant basic character (Kb/Ka = 4.20-4.31). Higher specific interactions with polar probes were found for the nanocomposite bearing pendant epoxide groups, that apart from the low surface area (SBET = 0.83 m2 g-1) and monolayer capacity (nm = 2.18 μmol g-1), exhibits a high value of γsd (88.19 mJ m-2 at 20 °C). These results confirm the potential of IGC to differentiate between nanocomposites with different surface functional groups and to predict their potential interactions with living tissues, body fluids and other materials.

2019Journal article

Open access

Poly(glycidyl methacrylate)/bacterial cellulose nanocomposites: preparation, characterization and post-modification

Publication . Faria, Marisa; Vilela, Carla; Mohammadkazemi, Faranak; Silvestre, Armando J.D.; Freire, Carmen S. R.; Cordeiro, Nereida

Nanocomposites composed of poly(glycidyl methacrylate) (PGMA) and bacterial cellulose (BC) were prepared by the in-situ free radical polymerization of glycidyl methacrylate (GMA) inside the BC network. The resulting nanocomposites were characterized in terms of structure, morphology, water-uptake capacity, thermal stability and viscoelastic properties. The three-dimensional structure of BC endowed the nanocomposites with good thermal stability (up to 270 °C) and viscoelastic properties (minimum storage modulus = 80 MPa at 200 °C). In addition, the water-uptake and crystallinity decreased with the increasing content of the hydrophobic and amorphous PGMA matrix. These nanocomposites were then submitted to post-modification via acid-catalysed hydrolysis to convert the hydrophobic PGMA into the hydrophilic poly(glyceryl methacrylate) (PGOHMA) counterpart, which increased the hydrophilicity of the nanocomposites and consequently improved their water-uptake capacity. Besides, the post-modified nanocomposites maintained a good thermal stability (up to 250 °C), viscoelastic properties (minimum storage modulus = 171 MPa at 200 °C) and porous structure. In view of these results, the PGMA/BC nanocomposites can be used as functional hydrophobic nanocomposites for post-modification reactions, whereas the PGOHMA/BC nanocomposites might have potential for biomedical applications requiring hydrophilic, swellable and biocompatible materials.

2019Journal article

Open access

Profiling of lipophilic and phenolic phytochemicals of four cultivars from cherimoya (Annona cherimola Mill.)

Publication . Santos, Sónia A. O.; Vilela, Carla; Camacho, João F.; Cordeiro, Nereida; Gouveia, Manuela; Freire, Carmen S. R.; Silvestre, Armando J.D.

The lipophilic and phenolic extractives of the ripe mesocarp of four cherimoya cultivars ('Perry Vidal', 'Mateus I', 'Mateus III' and 'Funchal') from Madeira Island, were studied for the first time. The predominant lipophilic compounds are kaurene diterpenes (42.2-59.6%), fatty acids (18.0-35.6%) and sterols (9.6-23.7%). Kaur-16-en-19-oic acid is the major lipophilic component of all cultivars accounting between 554 and 1350mgkg(-1) of dry material. The studied fruits also contain a high variety of flavan-3-ols, including galloylated and non-galloylated compounds. Five phenolic compounds were identified for the first time: catechin, (epi)catechin-(epi)gallocatechin, (epi)gallocatechin, (epi)afzelechin-(epi)catechin and procyanidin tetramer. 'Mateus I' and 'Mateus III' cultivars present the highest content of phenolic compounds (6299 and 9603mgkg(-1) of dry weight, respectively). These results support the use of this fruit as a rich source of health-promoting components, with the capacity to prevent or delay the progress of oxidative-stress related disorders.

2016Journal article

Open access