Complex phase behavior and state of miscibility in Poly(ethylene glycol)/Poly(l‐lactide‐co‐ε‐caprolactone) Blends

Abstract

A miscibility and phase behavior study was conducted on poly(ethylene glycol) (PEG)/poly(L-lactide-e-caprolactone) (PLA-co-CL) blends. A single glass transition evolution was determined by differential scanning calorimetry initially suggesting a miscible system; however, the unusual T g bias and subsequent morphological study conducted by polarized light optical microscopy (PLOM) and atomic force microscopy (AFM) evidenced a phase separated system for the whole range of blend compositions. PEG spherulites were found in all blends except for the PEG/PLA-co-CL 20/80 composition, with no interference of the comonomer in the melting point of PEG (T m 5 64 C) and only a small one in crystallinity fraction (X c 5 80% vs. 70%). However, a clear continuous decrease in PEG spherulites growth rate (G) with increasing PLA-co-CL content was determined in the blends isothermally crystallized at 37 C, G being 37 mm/min for the neat PEG and 12 mm/min for the 20 wt % PLA-co-CL blend. The kinetics interference in crystal growth rate of PEG suggests a diluting effect of the PLA-co-CL in the blends; further, PLOM and AFM provided unequivocal evidence of the interfering effect of PLA-co-CL on PEG crystal morphology, demonstrating imperfect crystallization in blends with interfibrillar location of the diluting amorphous component. Significantly, AFM images provided also evidence of amorphous phase separation between PEG and PLA-co-CL. A true T g vs. composition diagram is proposed on the basis of the AFM analysis for phase separated PEG/PLA-co-CL blends revealing the existence of a second PLA-co-CL rich phase. According to the partial miscibility established by AFM analysis, PEG and PLA-co-CL rich phases, depending on blend composition, contain respectively an amount of the minority component leading to a system presenting, for every composition, two T g 's that are different of those of pure components.

Interactions in blends of dendronized polymeric nanocomposites with some common drugs

“…AFM was used to analyze the morphologies of the PEAM and blends as another complementary technique for determining the compatibility between the components and to verify that interactions occur during the blending process.…”

Interaction of dendronized polymeric nanocomposites with isomeric cyclohexanediols

“…UV‐vis is a powerful tool for detecting interactions among two or more components in a mixture. Any displacements or diminution of the bands corresponding to the constituents of the blend provide information about the interaction of the molecules involved in the system . Figure shows a compilation of the absorption profiles for PEAM/CHD blends with different compositions.…”

“…AFM was used to analyze the morphologies of the PEAM and blends, as another complementary technique for determining the compatibility between the components, and to gain further insight into the interactions involved in the blending process.…”

Striking Dispersion of Recrystallized Poly(ethylene glycol)-Poly(lactic acid) Solvent-Casting Blend

“…Among numerous modifiers that have been researched, the excellent biocompatibility, biodegradability, non-toxicity and chain flexibility make the Polyethylene Glycol (PEG) a good choice for the modification for PLA, in either chemical way (e.g. the PLA-PEG block polymer) [5] or physical way (the blend mixture) [6][7][8][9][10][11][12]. Usually the PEG is used as the plasticizer to improve the mechanical properties of PLA [9,12].…”

“…Usually the PEG is used as the plasticizer to improve the mechanical properties of PLA [9,12]. The phase miscibility, stability, and thermal properties of PEG-PLA materials have also been intensively investigated [8,11,13,14].…”