Thermal and Morphological Properties of Poly(L-Lactic Acid)/Poly(D-Lactic Acid)-B-Polycaprolactone Diblock Copolymer Blends

Electron Beam-Induced Compatibilization of PLA/PBAT Blends in Presence of Epoxidized Soybean Oil

Blending of polymers can enhance performance of plastics and can give the opportunity to broaden the application fields. Especially the brittleness of poly(lactic acid) (PLA) is an issue, that is often addressed by blending it with soft polymers like poly(butylene adipate terephthalate) (PBAT). The immiscibility of those two polymers leads to limited properties of the blend. This study aimed to examine the application of electron-beam treatment with the implementation of a compatibilizing agent. PLA and PBAT were compounded with the addition of epoxidized soybean oil (ESBO) in different ratios and extruded into flat films. These were treated with electron beams at irradiation doses ranging from 12.5 to 100 kGy. The films thus produced were characterized by differential scanning calorimetry, size exclusion chromatography, scanning electron microscopy and tensile testing. A significant change in the glass transition temperatures of the blend partners was observed, as well as a substantial increase in elongation at break, even in PLA-rich compositions. These findings indicate improved compatibilization. Furthermore, the use of epoxidized soybean oil showed a changed extraction behavior of PBAT, indicating a formed binding to PLA. The results show that electron-beam treatment can significantly improve the compatibility between different polymers in blends, leading to enhanced mechanical and thermal properties.

Anisotropicity and flexibility in trilayered microfibrous substrates promote heart valve leaflet tissue engineering

Heart valve leaflet substrates with native trilayer and anisotropic structures are crucial for successful heart valve tissue engineering. In this study, we used the electrospinning technique to produce trilayer microfibrous leaflet substrates using two biocompatible and biodegradable polymers-poly (L-lactic acid) (PLLA) and polycaprolactone (PCL), separately. Different polymer concentrations for each layer were applied to bring a high degree of mechanical and structural anisotropy to the substrates. PCL leaflet substrates exhibited lower unidirectional tensile properties than PLLA leaflet substrates. However, the PLLA substrates exhibited a lower flexural modulus than the PCL substrates. These substrates were seeded with porcine valvular interstitial cells (PVICs) and cultured for one month in static conditions. Both substrates exhibited cellular adhesion and proliferation, resulting in the production of tissue-engineered constructs. The PLLA tissue-engineered constructs had more cellular growth than the PCL tissue-engineered constructs. The PLLA substrates showed higher hydrophilicity, lower crystallinity, and more significant anisotropy than PCL substrates, which may have enhanced their interactions with PVICs. Analysis of gene expression showed higherα-smooth muscle actin and collagen type 1 expression in PLLA tissue-engineered constructs than in PCL tissue-engineered constructs. The differences in anisotropic and flexural properties may have accounted for the different cellular behaviors in these two individual polymer substrates.