Isobornyl and Isocamphyl Photostabilizers in Poly(lactic acid)-Based Electrospun Fibers.

In this work, electrospun polylactide fibers with new photostabilizing additives, 4-methyl-2,6-diisobornylphenol (DIBP) and N-isocamphylaniline (NICA), have been tested under the influence of UV-C radiation (254 nm). The changes in the polymers' chemical structure under UV-C radiation were revealed through the increase in absorption in the 3600-3100 cm-1 region in regard to the FTIR spectra. In the samples that were irradiated for 1 h, the stabilizing effect of the photoprotectors became most noticeable as the difference in the content of the hydroxyl groups in stabilized and the pure PLA reached a maximum. The TG-DSC method revealed that the most sensitive indicator of the irradiation effect was the glass transition temperature (Tg), which persisted after 2 h of irradiation when using photostabilizers and their combinations. The PLA/DIBP(1) and PLA/NICA(1) samples showed the best results in protecting PLA from UV-C radiation based on the Tg values; although, the mixture of DIBP and NICA was not as effective. The chemical structure of the photostabilized PLA samples was studied using NMR, GPC, and Py-GC/MS analysis. The electrospun polylactide fibers were mechanically tested and the effects of the electrospun samples on cell viability were studied.

Tailoring Photoprotection of Polylactide with New Isobornyl Derivatives of Phenol and Aniline.

This article is devoted to the development of new photostabilizers for polylactide (PLA), a polymer that is an environmentally friendly alternative to polymers and is based on fossil raw materials. We have elucidated the role of the reaction center of two potential PLA photoprotectors: N-isobornylaniline and 2-isobornylphenol, in reactions occurring in a polymer matrix under the action of UV-C radiation. PLA samples with the photostabilizers were irradiated under a wavelength of 253.7 nm for 4, 8 and 12 h. The effectiveness of the photostabilizers was evaluated based on FTIR spectrometric data, 1H and 13C NMR, scanning electron microscopy and simultaneous thermal analysis (TG-DSC). Both stabilizers led to the protection of ester bonds between monomer units of PLA. However, 2-isobornylphenol proved to be more effective at a concentration of 0.05 wt.%, while the optimal concentration of N-isobornylaniline was 0.5 wt.% by weight. TG-DSC showed that the addition of N-isobornylaniline led to an increase in PLA resistance to thermal decomposition; the temperature of the onset of weight loss increased by 2.8 °C at 0.05 wt.% and by 8.1 °C at 0.5 wt.% of N-isobornylaniline. The photoprotector 2-isobornylphenol, on the contrary, reduced the thermal stability of PLA.