Styrene‐divinylbenzene copolymers, IV. Structure and texture changes during synthesis

Abstract

Styrenedivinylbenzene macroporous resins were prepared with the same composition (13% DVB), but varying diluent amount of benzyl alcohol. From sample analysis, the copolymerization kinetics concerning both monomer consumption and residual double bond amount were determined. Porous texture and morphology analyses by BET**, BJH***, mercury porosimetry, and scanning electron microscopy were carried out, too. Depending on diluent amount, the final product is classified as inside or outside the macroporous domain. Texture evolution is clearly different for the two classes of products, although their chemical evolutions are almost the same. A qualitative discussion of porous texture formation is presented, based on occurrence of three critical events: gelation, phase separation and molecular overlap. ZUSAMMENFASSUNG:Es wurden makropor6se Styrol-Divinylbenzol-Harze bei gleicher Zusammensetzung (1 3% Divinylbenzol), aber mit variierenden Verdiinnunganteilen von Benzylalkohol, hergestellt. Aus der Analyse der Proben wurde die Copolymerisationskinetik sowohl aufgrund des Monomerverbrauchs als auch des Doppelbindungsanteils bestimmt. Ebenso wurden Porenstruktur-und Morphologieanalysen mittels BET, BJH, Quecksilberporosimetrie und Rasterelektronenmikroskopie durchgefiihrt. In Abhtingigkeit vom Anteil an Verdiinnungsmittel wurde das Endprodukt als innerer oder ilu-Derer makropor0ser Bereich klassifiziert. Die Strukturbildung ist fur die zwei Produktklassen unterschiedlich, obwohl ihre chemische Entstehung nahezu gleich ist. Es wird eine qualitative Diskussion iiber die Bildung der lockeren Struktur gegeben, die auf drei kritischen Erscheinungen beruht: Gelbildung, Phasentrennung und molekulare Uberlappung.

Formation of the porous structure during the polymerization ofmeta-divinylbenzene andpara-divinylbenzene with toluene and 2-ethylhexanoic acid (2-EHA) as porogens

“…3 The decrease in surface area may be related to an infilling process during the polymerization resulting in a decrease in the amount of small and medium-sized pores. 10 Also, in the case of para-DVB in 2-EHA, a rather high surface area is obtained early in the polymerization.…”

“…The porous texture is built up of rather large nuclei (20 -50 nm) and agglomerates but no microspheres. 3,10 Under such conditions, high surface areas in excess of 500 m 2 /g with a narrow distribution of very small pores (100 Å) are obtained. 11 The quality of the solvent medium does not change much during the course of the polymerization.…”

“…2 In another study applying benzyl alcohol as porogen, a broad pore-size distribution was obtained. 10 For high diluent content, a high surface area (100 m 2 /g) was obtained at a low monomer conversion, and it decreased to a rather low value (20 m 2 /g) during the polymerization. This was ascribed to the clustering of microspheres into a big fused mass, where an infilling process had taken place to a large extent.…”

Swelling of porous ethylvinylbenzene–divinylbenzene copolymers and the stability of the pore structure

“…The purified DVB was mixed with EVB to give the various batches of monomer mixtures (22.0-98. 4 w t % of DVB), and in each batch the ratio of DVB isomers (m : p) was close to 1 : 1. Reagent-grade toluene was used as the diluen t .…”

Characterization of crosslinked, macroporous, monosized polymer particles

“…The porous texture is built up of rather large nuclei (20 -50 nm) and their agglomerates, but no microspheres. 3,11 Under such conditions high surface areas in excess of 500 m 2 /g with a narrow distribution of very small pores (100 Å) are obtained. 12 The quality of the solvent medium does not change much during the course of the polymerization.…”