Metastable liquid-liquid and solid-liquid phase boundaries in polymer-solvent-nonsolvent systems

Witte, P. van de; Dijkstra, Pieter J.; Berg, J.W.A. van den; Feijén, Jan

doi:10.1002/(sici)1099-0488(19970415)35:5<763::aid-polb4>3.0.co;2-n

Cited by 31 publications

(21 citation statements)

References 11 publications

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“…PEG was selected as the water extractable porogen to make the porous PLGA microspheres [17]. Figure 1 shows the morphological change of PLGA microspheres from a non-porous to an open cellular porous structure with increasing weight ratio of PEG/PLGA.…”

Section: Resultssupporting

confidence: 93%

Preparation of “Open/closed” pores of PLGA-microsphere for controlled release of protein drug

et al. 2018

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Poly(D,L-lactic-co-glycolic acid) has been extensively used as a controlled release carrier for drug delivery due to its good biocompatibility, biodegradability, and mechanical strength. In this study, porous PLGA microspheres were fabricated by an emulsion-solvent evaporation technique using poly ethylene glycol (PEG) as an extractable porogen and loaded with protein (lysozyme) by suspending them in protein solution. For controlled release of protein, porous microspheres containing lysozyme were treated with water-miscible solvents in aqueous phase for production of pore-closed microspheres. The surface morphology of microspheres were investigated using scanning electron microscopy (SEM) for confirmation of its porous microstructure structure. Protein property after release was observed by enzymatic activity assay. The pore-closing process resulted in nonporous microspheres which exhibited sustained release patterns over an extended period.

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Section: Resultssupporting

confidence: 93%

Preparation of “Open/closed” pores of PLGA-microsphere for controlled release of protein drug

et al. 2018

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“…One has to also consider the combination of liquid-solid and liquid-liquid phase equilibria when a crystallizable polymer is used. [5][6][7] Polysulfone (PSF) and polyethersulfone (PES) are important as polymer membrane materials because of their chemical resistance, mechanical strength, thermal stability, and transport properties. 8,9 There are several reports on experimental phase diagrams in ternary mixtures of PSF/solvent/nonsolvent 10 -14 and PES/ solvent/nonsolvent.…”

Section: Introductionmentioning

confidence: 99%

Liquid-liquid phase separation in polysulfone/polyethersulfone/N-methyl-2- pyrrolidone/water quaternary system

Baik¹,

Kim²,

Lee³

et al. 1999

J. Appl. Polym. Sci.

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To construct a phase diagram of the polysulfone (PSF)/polyethersulfone (PES)/N-methyl-2-pyrrolidone (NMP)/water quaternary system, cloud point measurements were carried out by a titration method. The miscible region in the PSF/PES/ NMP/water quaternary system was narrow compared to the PSF/NMP/water and PES/NMP/water ternary systems. The binary interaction parameters between PSF and PES were estimated by water sorption experiments. The calculated phase diagram based on the Flory-Huggins theory fit the experimental cloud points well. In addition to the usual polymer-liquid phase separation, polymer-polymer phase separation, which resulted in a PSF-rich phase and a PES-rich phase, was observed with the addition of a small amount of nonsolvent. The boundary separating these two modes of phase separation could be well described and predicted from the calculated phase diagrams with the estimated binary interaction parameters of the components.

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“…On the other hand, S-L demixing happens in higher polymer and nonsolvent concentration which originates from more favorable interaction of NMP/PVDF rather than DMF/PVDF and decreased g 23 for NMP compared to DMF. This is consistent with theoretical calculations of Witt et al [70].…”

Section: Ternary Phase Diagramsmentioning

confidence: 84%

Interplay of liquid-liquid and solid-liquid phase separation mechanisms in porosity and polymorphism evolution within poly(vinylidene fluoride) nanofibers

2015

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Porosity and polymorphism evolution within poly(vinylidene fluoride) (PVDF) nanofibers is discussed in relation to interplay of liquid-liquid (L-L) and solid-liquid (S-L) phase separation mechanisms. To this end, poly(vinylidene fluoride) (PVDF) solutions composed of nonvolatile solvents, dimethylformamide (DMF) and N-methylpyrrolidone (NMP), are subjected to electrospinning under environmental conditions of constant temperature (T=20 o C) and different levels of relative humidity (RH) ranging from 20 to 80 %. It is demonstrated that bead appearance, fiber diameter, porosity formation and polymorphism evolution is strongly affected by L-L phase inversion. Increasing RH as well as size of L-L miscibility gap in the ternary phase diagram of nonsolvent (water)/solvent (DMF or NMP)/polymer (PVDF) reduces time required to induce L-L demixing as verified by calculated mass transfer pathways. Therefore, bead-free fibers of larger diameters are expected, meanwhile, growth of β-phase crystals is suppressed. This is why fibers electrospun from DMF-based solution contain less β-phase crystals at high values of RH. In contrast, for solutions composed of NMP, jet stretching due to whipping instability plays pivotal role to form fiber structure as a result of delayed L-L demixing with respect to S-L demixing at high RH, 80 %. Furthermore, retarded L-L demixing in NMP-based systems destabilizes fiber formation at low humid environment which can be enhanced by addition a volatile solvent such as acetone. Additionally, more evidence for increment of β-phase formation with increasing working distance (w.d.) at constant RH is provided.

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Metastable liquid-liquid and solid-liquid phase boundaries in polymer-solvent-nonsolvent systems

Cited by 31 publications

References 11 publications

Preparation of “Open/closed” pores of PLGA-microsphere for controlled release of protein drug

Preparation of “Open/closed” pores of PLGA-microsphere for controlled release of protein drug

Liquid-liquid phase separation in polysulfone/polyethersulfone/N-methyl-2- pyrrolidone/water quaternary system

Interplay of liquid-liquid and solid-liquid phase separation mechanisms in porosity and polymorphism evolution within poly(vinylidene fluoride) nanofibers

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