Morphology Development in Polymer Fibers undergoing Solvent/Non‐solvent Exchange

Abstract

The solvent/non-solvent interchange across the fiber surface affects the morphology of the fiber in various ways. In this paper, simulations have been performed to elucidate the diverse morphologies obtained during spinning of polymer fibers under the presence of a non-solvent. The proposed model deals with a ternary system derived from Cahn-Hilliard equation, alternatively known as Time Dependent Ginzburg Landau-TDGL model B equation, involving the spatio-temporal evolution of concentration order parameter. Depending on the coexistence region of the ternary phase diagram, various fiber morphologies including concentric bands, internal microfibrillar structures, and porous structures were discerned. It may be inferred that the formation of the aforementioned diverse morphologies is a direct consequence of the initial conditions of the starting mixtures in a manner governed by the relative rates of solvent/non-solvent exchange and the dynamics of phase separation.

Modeling and Simulation of a Ternary System for Macromolecular Microsphere Composite Hydrogels

“…the energy of the interface i, cf. [13,14,39]. However, since the MMC hydrogel has a well-defined network structure, we have to the reticular free energy density f [φ 1 , φ 2 ] in order to replace the Flory-Huggins free energy of mixing.…”

Comparative Studies on the Solvent Quality and Atmosphere Humidity for Electrospinning of Nanoporous Polyetherimide Fibers

“…For instance, due to the need for high surface area in some specific areas such as catalytic systems, sensing materials, membranes in solar cells, filtration, hydrogen storage systems, protective clothing and recently oil absorption, ,,,, the mechanism of porosity evolution within electrospun fibers is of significant and commercial interest which has been able to attract great attention. In literature mechanisms envisaged to formation of pores during electrospinning process could be classified in six main categories: (1) Rapid solvent drying and breath figure formation which can be considered when volatile solvents are employed to prepare electrospinning solutions or polymer–solvent binary system shows an upper critical solution temperature (UCST) phase diagram, ,,,− (2) temperature-induced phase separation (TIPS), (3) nonsolvent-induced phase separation (NIPS), − (4) vapor-induced phase separation (VIPS), ,,,− ,, (5) polymer–polymer phase separation, in which electrospinning is performed with a solution composed of two miscible polymers and followed by leaching process to selectively remove one of components, and (6) interaction of Lewis acid with the Lewis base and subsequent removal of Lewis acid component …”

“…It was demonstrated by Pai et al 17 that morphology of polystyrene electrospun fibers is determined as a direct consequence of competition between VIPS and two other processes, that is, buckling instability and solvent drying. Evolution of morphologies in electrospun fibers as a result of VIPS mechanism was theoretically investigated by Dayal and Kyu 33 in the framework of Cahn−Hilliard equation. They showed it is possible to postulate different morphologies for electrospun fibers regarding the location of concentration of electrospinning solution on nonsolvent/solvent/polymer ternary phase diagram.…”

Formation of Ordered Patterns in Electroresponsive Polymer Ionic Liquid Blends

“…The expressions of chemical potentials, afford the calculation of flux of A and B as follows: [ 53 ] $$\begin{eqnarray} {\bm J}_A = \ - {M}_{AA}{\bm\nabla} ({\mu }_A - \ {\mu }_P) + {M}_{AB}{\bm\nabla} ({\mu }_B - \ {\mu }_P)\end{eqnarray}$$ $$\begin{eqnarray} {\bm J}_B = - {M}_{BB}{\bm\nabla} ({\mu }_B - {\mu }_P) + {M}_{AB}{\bm\nabla} ({\mu }_A - {\mu }_P)\end{eqnarray}$$where $${\mu }_i\ = \mu _i^{eq}\ + \mu _i^{neq} + \mu _i^{el}\ ( {i\ = \ A,\ B,P} )$$ is the total chemical potential and M ij is the Onsager kinetic coefficient or mobility coefficient given in terms of bare Onsager kinetic coefficient of component i , M 0, ii , as [ 53,59 ] …”