Styrene–divinylbenzene copolymers. II. The conservation of porosity in styrene–divinylbenzene copolymer matrices and derived ion‐exchange resins

Abstract

SynopsisThe collapse of pores in styrenedivinylbenzene copolymers and corresponding ion-exchange resins was studied during the removal of solvating liquids. The process can be followed in a most simple way by measuring the volume of the bead-shaped copolymers upon drying. Other parameters observed during drying were the apparent density and incidently the internal surface. The collapse of pores is considered to be a result of cohesional forces when solvated polymer chains are approaching each other by loss of solvent. The effect will thus be more pronounced in gel-type networks than in porous ones. In porous networks, the effect will be stronger in smaller pores than in larger ones. It is shown that crosslinks, increasing the rigidity of the structures, will favor the conservation of porosity. In ion-exchange resins the pore stability is best when the material is in its lowest state of hydration. Generally, the collapse of pores is a reversible process. The collapsed material can in most cases be reswollen by the proper choice of solvent.

Water uptake, transport and structure characterization in poly(ethylene glycol) diacrylate hydrogels

“…2(a). The collapse of the porous structure is ascribed to cohesion forces when the polymer chains approach one another due to the loss of solvent during drying, and these forces are apparently not completely overcome upon rehydration, so the film does not return to its original (i.e., before drying) morphology [37,38]. However, for the samples without PIPS (e.g., 50/50 PEGDA/H 2 O), there is no observed structure difference in the material before and after drying and rehydration (cf., Fig.…”

Synthesis and simple method of estimating macroporosity of methyl methacrylate–divinylbenzene copolymer beads

“…The proposed method will not be applicable if this copolymer is synthesized by some other procedure, e.g., if the porosity is generated by using some template, or when some polymer is employed as diluent,6 or when some sublimable solid is employed as diluent 25. Furthermore, a fraction of the porosity of the copolymer may be temporarily lost during some post processing conditions 26, 27. Therefore, the proposed method should be applied under the very experimental conditions given in this study, which off course are the most often used experimental conditions in practice.…”

Ion‐exchange resins. III. Functionalization–morphology correlations in the synthesis of some macroporous, strong basic anion exchangers and uranium‐sorption properties evaluation

“…It has been already demonstrated that the morphological changes, which occur by removing 2EH from the macroporous S–DVB copolymers by azeotropic distillation with water, are reversible, the collapsed network being completely re‐expanded in a proper solvent (e.g., toluene), and the real porosity was evidenced after the removal of the good solvent with methanol 38. Such behavior also has been observed for other systems 9, 11, 14, 17, 21. This shows that the whole pore structure of these copolymers is memorized by the copolymer network,20, 23 and a good flexibility of the internuclear chains, which could be a very useful characteristic in the synthesis of some macroporous SBAEs with a high osmotic resistance.…”

“…After the first systematic studies on styrene–divinylbenzene (S–DVB) networks having a permanent porous structure in the dry state,1–9 the correlation between the synthesis conditions and the copolymer morphology has been extensively investigated 10–23. Their uses are connected with a large variety of separation processes having a great interest in industry and science.…”