Nanostructures of Cellulose Acetate Phthalate Obtained by Electrospinning from 2‑Methoxyethanol-Containing Solvent Systems: Morphological Aspects, Thermal Behavior, and Antimicrobial Activity

Cellulose acetate phthalate (CAP) is well-known and largely used as a pharmaceutical excipient for enteric coating of tablets and capsules. Recent literature has proved that this polymer exhibits antimicrobial and antiviral properties when it is used as a micronized powder. Nanostructures of CAP are also prepared, and their potential for antimicrobial and technological applications is recently reported. In the present work, we are focused on synthesis and characterization of CAP nanofibers and powders by electrospinning/electrospraying from solutions in solvent mixtures containing 2-methoxyethanol. The morphologies of the obtained nanostructures are investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses and discussed in comparison with those previously reported for products obtained in 2-methoxyethanol alone. Thermal properties of CAP nanostructured as powders and fibers are studied in comparison with those of CAP films using thermogravimetric (TG), Fourier transform infrared (FTIR), and mass spectrometry. TG analysis reveals that CAP nanoproducts exhibit an apparent lower stability than CAP films. Further investigations of both residual polymer and the evolved degradation gas products evidence the presence of phthalic anhydride as a main degradation product in the initial stage of the process. In the case of nanostructures of CAP, due to their high porosity and very high specific surface areas, this degradation product is easier and continuously eliminated during the thermal treatment. This behavior explains their apparent lower thermal stability as compared with that of the films where the diffusion of phthalic anhydride proceeds slowly and therefore the weight loss of the sample is delayed. The paper also reports preliminary results of antimicrobial activities of the investigated products against Escherichia coli and Staphylococcus aureus.