In situ formation of PLA-grafted alkoxysilanes for toughening a biodegradable PLA stereocomplex thin film

Abstract

Poly(lactide) (PLA) has received tremendous attention recently from researchers and industrialists due to its ability to solve environmental problems related to plastic pollution. However, PLA's brittleness, poor thermal stability, low elongation at break, and poor melt processing prevent its use in a broader spectrum of applications. Herein, we produced a very tough and thermally more stable PLA stereocomplex by simply mixing PLA with organoalkoxysilane. The stereocomplex PLA/silane (sc-PLA-silane) composite was prepared by simple mixing of three types of organoalkoxysilanes in sc-PLA followed by in situ formation of a silane-based rubbery core with a cross-linked PLA shell. Mechanical and thermal properties were improved by stereocomplexation of PLA with a small amount (1-5 wt%) of PLA-grafted silanes. The addition of organoalkoxysilane with different functional groups resulted in a plasticizer of rubbery silica-PLA core-shell gel through in situ condensation and grafting of long PLA chains at the interface between the stereocomplex and silane particles. The results revealed that the toughness of sc-PLA was improved dramatically with only a small addition (only 2.5%) of 3-(triethoxysilyl)propyl isocyanate (ICPTES). The morphology and mechanical and thermal properties of the toughened stereocomplex films were characterized. The results revealed that elongation at break was increased from 16% to 120%, while other mechanical properties such as tensile strength and modulus were retained. Surface analysis confirmed that this toughness was achieved by formation of a silica-PLA core-shell gel. The mechanical properties of PLA were improved without any significant reduction in modulus and tensile strength using this simple methodology. environmental pollution. 5,6 Nevertheless, the brittleness of PLA is a main hindrance, along with thermal limitations. 7-10 PLA is an optically isomeric polymer, having D(+) and L(À) stereoisomers. The polymers made from L and D forms considerably differ in thermal properties. Thermal properties, such as thermal stability and glass, crystallization, and melt transitions, can be modied using stereoselective polymerization and by blending D and L in different proportions. 11 The mechanical properties of PLA can also be improved by stereocomplexation. 12-14 Stereocomplexed PLA is a suitable polymeric material for certain applications such as drug carriers, wound dressing, biomedical implants, and scaffolds for tissue engineering. 15,16 PLLA and PDLA have optical activity due to their chiral structures. The melting temperatures (T m ) of PLLA and PDLA do not exceed 180 C. However, T m drops quickly, and the crystallization capacity decreases sharply with a decrease in optical purity. 12,17 The low thermal stability limits thermal processes like injection molding and extrusion. 18 However, the melting temperature can be increased from 180 C to about 230 C through stereocomplexation of PLLA and PDLA. 18,19 PLA is an inherently brittle polymer, which has 4-7% elongation at break;Preparation of...

Stereochemistry Determines Immune Cellular Responses to Polylactide Implants

“…With ATR-FTIR spectroscopy, the α helix (wavenumber 921 cm −1 ) which is characteristic of PLLA and PDLA is transformed into a more compact β helix (wavenumber 908 cm−1) in stereocomplex PLA (Fig. S1B, C) 28 . Using a bioenergetic model we had developed and optimized 6 , we degraded the different types of PLA to obtain breakdown products over 12 days (d), also referred to as extracts in complete (serum containing) medium.…”

Stereochemistry Determines Immune Cellular Responses to Polylactide Implants

“…PLA stereocomplexation was confirmed using an IRAffinity-1 spectrophotometer (Shimadzu) where the changes in the conformation of PLA chains could be observed using ATR-FTIR spectroscopy as previously described. 28…”

Preparation of the Heterogeneous Saponified Poly(Vinyl Alcohol)/Poly(Methyl Methacrylate–Methallyl Alcohol) Blend Film

“…On the other hand, saponified films showed higher T g than unsaponified films, consistent with the E′ results and their similar tendencies. However, the addition of PMMA slightly decreased the T g of PVAc for all blend ratios and may be due to the conversion of PMMA to P(MMA-MAA) in which more hydrogen bonding occurred between the hydroxyl group, which is responsible for the decrease in T g by increasing the elasticity of the polymer matrix [ 56 ].…”