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Poly (3-hydroxybutyrate) (PHB) is a valuable biopolymer that is produced in industrial quantity but is not widely used in applications due to some drawbacks. The addition of cellulose nanofibers (CNF) as a biofiller in PHB/CNF nanocomposites may improve PHB properties and enlarge its application field. In this work, n-octyltriethoxy silane (OTES), a medium-chain-length alkyl silane, was used to surface chemically modify the CNF (CNF_OTES) to enhance their hydrophobicity and improve their compatibility with PHB. The surface functionalization of CNF and nanodimension were emphasized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, atomic force microscopy, dynamic light scattering, and water contact angle (CA). Surface modification of CNF with OTES led to an increase in thermal stability by 25 °C and more than the doubling of CA. As a result of the higher surface hydrophobicity, the CNF_OTES were more homogeneously dispersed in PHB than unmodified CNF, leading to a PHB nanocomposite with better thermal and mechanical properties. Thus, an increase by 122% of the storage modulus at 25 °C, a slight increase in crystallinity, a better melting processability, and good thermal stability were obtained after reinforcing PHB with CNF_OTES, paving the way for increasing PHB applicability. [ABSTRACT FROM AUTHOR]

The alarming increase in counterfeiting has determined a more intensive application of authentication solutions such as holographic security marks. Polycarbonate or polymethyl methacrylate currently used in the hot embossing process to produce security marks are discarded as non‐biodegradable waste after utilization. For the first time, poly(lactic acid) (PLA) was studied here as a hot‐embossing substrate to imprint a micro‐relief containing diffractive gratings, as a stage in the fabrication of holographic security marks. Four PLA grades, which differ by crystallinity and mechanical properties, were used to define the suitability of PLA for hot embossing. The 3D topography of embossed micro‐relief in PLA plates was investigated by quantitative phase imaging, scanning electron microscopy, and atomic force microscopy (AFM). The analyses showed that a high crystallinity and a low d‐lactide content of PLA render the hot‐embossing process more difficult and decrease the quality of the imprinted micro‐relief. The average height of the micro‐relief and the difference in height values, which were determined by AFM, allowed the ranking of the PLA grades according to the quality of the diffracted image. The possibility of recycling the embossed PLA substrate several times before composting was also demonstrated in this work. The variation of the mechanical properties, thermal stability, melting, and crystallization behaviors after each recycling cycle has shown that PLA can be reprocessed six times without significant damage to the properties. This study demonstrated that PLA can replace petroleum‐based polymers in the fabrication of holographic security marks and its suitability for a plethora of optoelectronics applications. [ABSTRACT FROM AUTHOR]

Nanocellulose (NC) is a valuable material in tissue engineering, wound dressing, and drug delivery, but its lack of antimicrobial activity is a major drawback for these applications. In this work, basil ethanolic extract (BE) and basil seed mucilage (BSM) were used to endow nanocellulose with antibacterial activity. NC/BE and NC/BE/BSM sponges were obtained from nanocellulose suspensions and different amounts of BE and BSM after freeze-drying. Regardless of the BE or BSM content, the sponges started to decompose at a lower temperature due to the presence of highly volatile active compounds in BE. A SEM investigation revealed an opened-cell structure and nanofibrillar morphology for all the sponges, while highly impregnated nanofibers were observed by SEM in NC/BE sponges with higher amounts of BE. A quantitative evaluation of the porous morphology by microcomputer tomography showed that the open porosity of the sponges varied between 70% and 82%, being lower in the sponges with higher BE/BSM content due to the impregnation of cellulose nanofibers with BE/BSM, which led to smaller pores. The addition of BE increased the specific compression strength of the NC/BE sponges, with a higher amount of BE having a stronger effect. A slight inhibition of S. aureus growth was observed in the NC/BE sponges with a higher amount of BE, and no effect was observed in the unmodified NC. In addition, the NC/BE sponge with the highest amount of BE and the best antibacterial effect in the series showed no cytotoxic effect and did not interfere with the normal development of the L929 cell line, similar to the unmodified NC. This work uses a simple, straightforward method to obtain highly porous nanocellulose structures containing antibacterial basil extract for use in biomedical applications. [ABSTRACT FROM AUTHOR]