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. 2023 Dec 30;16(1):128.
doi: 10.3390/polym16010128.

A Novel Approach for Glycero-(9,10-trioxolane)-Trialeate Incorporation into Poly(lactic acid)/Poly(ɛ-caprolactone) Blends for Biomedicine and Packaging

Olga V Alexeeva  1 , Anatoliy A Olkhov  1   2   3 , Marina L Konstantinova  1 , Vyacheslav V Podmasterev  1 , Tuyara V Petrova  2 , Levon Yu Martirosyan  1 , Olga K Karyagina  1 , Sergey S Kozlov  1 , Sergey M Lomakin  1   2 , Ilya V Tretyakov  2 , Valentina Siracusa  4 , Alexey L Iordanskii  2
Affiliations

A Novel Approach for Glycero-(9,10-trioxolane)-Trialeate Incorporation into Poly(lactic acid)/Poly(ɛ-caprolactone) Blends for Biomedicine and Packaging

Olga V Alexeeva et al. Polymers (Basel). .

Abstract

The product of ozonolysis, glycero-(9,10-trioxolane)-trioleate (ozonide of oleic acid triglyceride, [OTOA]), was incorporated into polylactic acid/polycaprolactone (PLA/PCL) blend films in the amount of 1, 5, 10, 20, 30 and 40% w/w. The morphological, mechanical, thermal and antibacterial properties of the biodegradable PLA/PCL films after the OTOA addition were studied. According to DSC and XRD data, the degree of crystallinity of the PLA/PCL + OTOA films showed a general decreasing trend with an increase in OTOA content. Thus, a significant decrease from 34.0% for the reference PLA/PCL film to 15.7% for the PLA/PCL + 40% OTOA film was established using DSC. Observed results could be explained by the plasticizing effect of OTOA. On the other hand, the PLA/PCL film with 20% OTOA does not follow this trend, showing an increase in crystallinity both via DSC (20.3%) and XRD (34.6%). OTOA molecules, acting as a plasticizer, reduce the entropic barrier for nuclei formation, leading to large number of PLA spherulites in the plasticized PLA/PCL matrix. In addition, OTOA molecules could decrease the local melt viscosity at the vicinity of the growing lamellae, leading to faster crystal growth. Morphological analysis showed that the structure of the films with an OTOA concentration above 20% drastically changed. Specifically, an interface between the PLA/PCL matrix and OTOA was formed, thereby forming a capsule with the embedded antibacterial agent. The moisture permeability of the resulting PLA/PCL + OTOA films decreased due to the formation of uniformly distributed hydrophobic amorphous zones that prevented water penetration. This architecture affects the tensile characteristics of the films: strength decreases to 5.6 MPa, elastic modulus E by 40%. The behavior of film elasticity is associated with the redistribution of amorphous regions in the matrix. Additionally, PLA/PCL + OTOA films with 20, 30 and 40% of OTOA showed good antibacterial properties on Pseudomonas aeruginosa, Raoultella terrigena (Klebsiella terrigena) and Agrobacterium tumefaciens, making the developed films potentially promising materials for wound-dressing applications.

Keywords: PLA/PCL blend films; antibacterial activity; ozonide; polycaprolactone; polylactic acid.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Chemical structure of PLA (a), PCL (b) and OTOA (c).
Figure 2
Figure 2
FTIR spectra of pristine PLA, PCL and PLA/PCL films (a), close-up view of FTIR spectra at 1650–1850 cm−1 interval (b).
Figure 3
Figure 3
FTIR spectra of pristine PLA/PCL film, PLA/PCL + OTOA films and pure OTOA: (a) Close-up view of FTIR spectra at 2700–3200 cm−1 interval, (b) FTIR spectra at 1675–1825 cm−1 wavenumber region.
Figure 4
Figure 4
(a) DSC heat flow curves of PLA and PLA/PCL films; (b) DSC thermograms for the samples of pristine PLA/PCL (1), PLA/PCL + 1% (2), + 5% (3), + 10% (4), + 20% (5), + 30% (6), + 40% OTOA (7), respectively.
Figure 5
Figure 5
DSC heat flow curves of PCL and PCL + OTOA 35% films.
Figure 6
Figure 6
Deconvolution of the overlapping exo- and endothermic peaks in the DSC thermograms for PLA/PCL + OTOA films with 10–40% OTOA content.
Figure 7
Figure 7
XRD patterns of PLA, PCL and PLA/PCL films (a); XRD patterns of PLA/PCL + OTOA film samples with 0–40% OTOA (b).
Figure 8
Figure 8
Microphotographs of the pristine PLA, PCL, PLA/PCL and PLA/PCL + OTOA film samples (10–40% OTOA), obtained with an optical microscope (a–g).
Figure 9
Figure 9
Elastic modulus (blue), tensile strength (black), and relative elongation at break (green) for reference PLA/PCL and PLA/PCL + OTOA (0–40%) film samples.
Figure 10
Figure 10
(a) Water contact angle for PLA/PCL films with variable OTOA content; (b) sorption capacity (Q) of PLA/PCL films with variable OTOA content; (c) weight loss versus time data from a water vapor permeability experiment.
Figure 11
Figure 11
Comparison of antibacterial activities on Pseudomonas aeruginosa for: ref PLA/PCL film and the 100% OTOA (a); ref PLA/PCL film and the PLA/PCL films with 20% (b), 30% (c) and 40% (d) OTOA, respectively.
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