Polystyrene Microstructured Foams Formed by Thermally Induced Phase Separation from Cyclohexanol Solution

Abstract

The thermally induced phase separation can be used to prepare materials of various microstructured morphologies that define their applications. In this work, foams formed from a polystyrene‐cyclohexanol solution are prepared, characterized, and modeled. To obtain a reliable thermodynamic description, cloud points are determined by an in‐house fabricated thermooptical device. The Flory–Huggins lattice model combined with Hansen solubility theory is employed as input to the Cahn–Hilliard model of phase separation dynamics. The previously reported model is extended by incorporating polar interactions. The resulting experimental and predicted morphologies are compared and good prediction capabilities of the model regarding the resulting morphology and its characteristics are obtained. The experimental and modeling work extends the knowledge of the mechanism and the kinetics of foam morphology evolution for thermal and sound insulation applications.

The Effect of Conductive Heat Transfer on the Morphology Formation in Polymer Solutions Undergoing Thermally Induced Phase Separation

“…The model that was employed to describe the thermodynamics of phase separation through spinodal decomposition was the Flory-Huggins theory, which is capable of describing the thermodynamics of phase separation in polymer solutions very successfully [ 16 ]. Although Flory-Hugging’s theory has some limitations, it is a very effective theory in the phase equilibrium investigations [ 1 , 6 , 8 , 15 , 20 , 44 ]. The free energy of mixing of the homogenous system in the Flory-Huggins theory is defined as [ 64 ]: where T is the temperature, v is the volume of the cell or segment of the polymer, is Flory’s interaction parameter, k B is the Boltzmann’s constant, N 1 and N 2 are the degrees of polymerization of the solvent and the polymer, respectively.…”

“…The thermally induced phase separation process (TIPS) is one of the principal methods of producing numerous functional polymeric materials that are widely employed in industrial applications, such as membranes, microcellular foams, thermally reversible porous gels, and polymer-dispersed liquid crystals [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. During the TIPS process, the quality of the solvent decreases through an instantaneous quench in systems with an upper critical solution temperature (UCST) or an immediate jump in temperature in systems with a lower critical solution temperature (LCST) [ 4 , 9 , 10 , 11 , 12 , 13 , 14 ].…”

“…An electrical field, a temperature gradient, a shear flow, a chemical reaction, or a concentration gradient can all be employed to create anisotropy [ 2 , 17 , 18 , 42 , 43 , 44 ]. A deep understanding of the impact of these techniques to induce anisotropy leads to in-depth knowledge of the fabrication of functional polymeric materials with desired morphologies, and mechanical, optical, and thermal properties [ 2 , 6 , 45 , 46 , 47 , 48 ].…”

Uniform macroporous amidoximated polyacrylonitrile monoliths for gallium recovery from Bayer liquor

“…29 It has been reported that multiple monoliths used in different fields have been successfully synthesized by TIPS. [30][31][32][33] By changing fabrication parameters, such as polymer concentration and mass, cooling temperature, and the composition of mixed solvents, it is easy to control the pore structure of porous materials. 34 For example, with the polymer concentration increases, a transformation of morphologies from beads to bi-continuous and cellular can be observed.…”

“…In this case, the growth of a polymer‐poor phase will result in a cellular structure after diluent extraction 29 . It has been reported that multiple monoliths used in different fields have been successfully synthesized by TIPS 30–33 . By changing fabrication parameters, such as polymer concentration and mass, cooling temperature, and the composition of mixed solvents, it is easy to control the pore structure of porous materials 34 .…”