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

Macroporous polymers of pure meta-divinylbenzene (meta-DVB) and pure para-d ivinylbenzene (para-DVB) have been prepared in the presence of toluene and 2-EHA as pore forming agents. The formation of the pore structure has been studied during the polymerization by pore-size distribution measurements, t ogether with determination of the specific surface area from nitrogen sorpt ion isotherms using the BET treatment. In addition, the morphology and text ure have been characterized by SEM during the polymerization process. Large differences in the pore-size distribution among all the polymer samples ar e found. The polymers prepared in toluene as porogen have a pore-size distr ibution, which mainly consists of small pores, while large pores appear wit h 2-EHA as porogen. In the presence of 2-EHA, a major change in the pore-si ze distribution is also observed when the monomer is shifted from para-DVB to meta-DVB, leading to a bimodal distribution. The texture characterizatio n by SEM shows details and discriminates the samples in consistency with wh at may be expected from pore-size distribution measurements. (C) 1999 John Wiley & Sons, Inc.