**4. Conclusions**

EOs are well known for their antimicrobial properties, being suitable as food preservatives. However, to ensure their long-term effect, which is controlled by their volatility, it may be necessary to encapsulate them in, for instance, porous materials. The present study evaluated the complexation of eugenol EO on MCM-41 to be thereafter incorporated into PHBV biopolymers by electrospinning. The resultant electrospun mats were annealed below the biopolymer melting point to generate continuous films. The thermal analysis performed on the films showed that the incorporation of MCM-41 with eugenol induced certain plasticization on PHBV as well as a reduction in crystallinity. Interestingly, the incorporation of MCM-41 with eugenol up to 10 wt.-% had a relatively low influence on the thermal stability of the PHBV films. During the mechanical analysis, it was observed that the mechanical strength of the PHBV films was increased while the ductility was only slightly reduced after the incorporation of MCM-41 with eugenol. The barrier properties were also enhanced due to the presence of the eugenol-containing nanofillers and were optimal around contents of 15 wt.-%. Finally, the antimicrobial activity against *S. aureus* and *E. coli* was studied in both an open and closed system to better represent the real conditions in packaging applications. The electrospun biopolymer films showed antibacterial activity after 15 days, being higher (as expected) in the ones that were studied

in the closed system, which was ascribed to the accumulation of eugenol in the system's headspace. For all this, the films developed can be regarded as a sustainable material to be used in the form of interlayers or coatings for active food packaging applications.

**Author Contributions:** Conceptualization was devised by J.M.L., A.B., R.M.-M.; Methodology, J.M.L., B.M.-R. and S.T.-G.; A.B. and R.M.-M. synthesized and provided the nanoparticles and eugenol; B.M.-R. prepared the films and carry out most of the characterization; L.C. conducted the mechanical measurements; B.M.-R. and K.J.F-L carried out the antimicrobial experiments; Writing-Original Draft Preparation was performed by B.M.-R.; Writing-Review & Editing, S.T.-G.; Supervision, S.T.-G. and J.M.L.; Project Administration, J.M.L.; S.T.-G. and J.M.L. designed the work, supervised the execution and interpretation of all experiments and carried out the final version of the manuscript.

**Funding:** This research was supported by the Ministry of Science, Innovation, and Universities (MICIU) program numbers AGL2015-63855-C2-1-R and MAT2015-64139-C4-1-R, by the Generalitat Valenciana (GVA) PROMETEO/2018/024 program, and by the EU H2020 projects YPACK (reference number 773872) and ResUrbis (reference number 730349).

**Acknowledgments:** B.M.-R. and S.T.-G. acknowledge MICIU for her FPI gran<sup>t</sup> (BES-2016-077972) and his Juan de la Cierva - Incorporación contract (IJCI-2016-29675), respectively. K.J.F-L. also acknowledges GVA for her Santiago Grisolia gran<sup>t</sup> (GRISOLIAP/2017/101). A.B. would also like to thank GVA (POSTD/2014/016) and MICIU for her Juan de la Cierva - Incorporación contract (IJCI-2014-21534). The authors also thank the Joint Unit in Polymers Technology between IATA–CSIC and PIMA-Universitat Jaume I.

**Conflicts of Interest:** The authors declare no conflict of interest.
