Phase behavior of polylactides in solvent (SINGLEBOND) Nonsolvent mixtures

Abstract

Isothermal phase diagrams for the semicrystalline poly‐L‐lactide (PLLA) and the amorphous poly‐DL‐lactide (PDLLA) in combination with several solvent–nonsolvent combinations (dioxane/water, dioxane/methanol, chloroform/methanol, and NMP/water) have been determined. The locations of the liquid–liquid miscibility gap, the solid–liquid miscibility gap and the vitrification boundary in the isothermal phase diagrams at 25°C were identified. The liquid–liquid miscibility gap for the systems with PLLA was located in the same composition range as the corresponding systems with PDLLA. For the systems containing PLLA solid–liquid demixing was thermodynamically preferred over liquid–liquid demixing. Attempts were made to correlate the experimental findings with predictions on the basis of the Flory‐Huggins theory for ternary solutions using interaction parameters derived from independent experiments. Qualitative agreement was found between the theoretical predictions and the experimentally obtained liquid–liquid miscibility gap. No good agreement was found for the solid–liquid miscibility gap. © 1996 John Wiley & Sons, Inc.

On the calculation of free energy of mixing for aqueous polymer solutions with group-contribution models

“…Table 1 Free-volume percentage calculated via Eqs. (13) and (15). Kannan et al [11] pointed out that volume and surface parameters R k and Q k of H 2 O group used in UNIFAC are different from the corresponding van der Waals values (see Table 2).…”

“…(13) and (15). The experimental value of water free volume reported in Elbro et al [12], 36% (although the authors do not supply precise information about the origin of this value), is larger than the one computed, 22%.…”

“…The primary objective of this work is the test of groupcontribution models capabilities to predict the phase behaviour of ternary polymer solutions, particularly the (poly-L-lactide-acid [PLLA])-dioxane-water system, for which only few information are available on the phase behavior as a function of temperature and composition [5,13]. However, this ternary solution was extensively used to obtain porous scaffold via phase separation techniques in a certain range of temperatures and compositions [6,9,14,15].…”

Scaffold design and characterisation for osteochondral tissue regeneration

“…Dioxane increases microporosity through an increase in micropore dimensions. This effect is due to the fact that more molecules of solvent diffuse among the polymer chains as the solvent content increases (169)(170). The limit of the micropores formation seems to be achieved at 20% of polymer content for the 1:1 scaffolds and at 18% of polymer content for the 1:1.25 scaffolds.…”

Bacterial cellulose nanowhiskers to enhance the properties of plastics and bioplastics of interest in food packaging

“…where the parameters for PLA in chloroform at 25ºC are α=0.79 and Κ= 1.33·10 -3 ml/g (Van De Witte et al, 1996).…”