A Novel Ion Extraction Material Using Host-Guest Properties of Oligobenzoxazine Local Structure and Benzoxazine Monomer Molecular Assembly SUWABUN CHIRACHANCHAI, 1 APIRAT LAOBUTHEE, 1 SUTTINUN PHONGTAMRUG, 1 WANIDA SIRIPATANASARAKIT, 1 HATSUO ISHIDA 2 1 The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand 2 The NSF Center for Molecular and Microstructure of Composites (CMMC), Department of Macromolecular Science, Case Western Reserve University, Cleveland, Ohio 44106-7202, USA Received 1 April 1999; accepted 3 June 1999 ABSTRACT: Bisphenol-A based benzoxazine monomer (BA-m) and its oligomer are applied as an ionophore to study by Pedersen’s technique, the ion interaction with alkali and alkaline earth ions. Ion extraction efficiencies are significant when the solubility parameter of the organic phase is close to that of BA-m or the -parameter is 0.34. Ionophore concentration controls the amount of metal ion extraction. Both BA-m and its oligomer show high entrapment efficiency over 70% extraction, for all types of ions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2561–2568, 2000 Key words: benzoxazine; oligobenzoxazine; ionophore; host-guest compound; molec- ular assembly; solubility parameter; c-parameter INTRODUCTION Fine separation is essential in technologies such as separation of isotopes, isomers, and ions, de- contamination of waste water, and other concen- tration processes. Although ion exchange mem- branes are primarily required to separate selec- tively cations from anions and vice versa, separating different ions with the same electrical sign and same charge is also important. At present, there are some difficulties in excluding various ions from the system to obtain ultra high purity substances. To achieve high efficiency of an ion exclusion system, an ion exchange resin has been widely used. Host-guest or inclusion compound is a novel approach to control the ion extraction process on the molecular level via the interaction between host and guest compound. Over the past decade, inclusion compounds have received much atten- tion because the understanding on the molecular recognition of the inclusion phenomenon has grown rapidly. Thus, the inclusion phenomenon is widely studied in many applications, such as in the drug delivery system for the pharmaceutical industry, 1 increasing compound solubility for the food and cosmetic industries, 2 and in synthetic enzyme mimicry, 3–5 including the separation of chemical and ion species. 6 Polybenzoxazine is a class of phenolic material that undergoes ring-opening polymerization. Ning and Ishida 7 reported that benzoxazine resin has a great deal of molecular design flexibility compared with ordinary phenolics. Benzoxazine is synthesized by the Mannich reaction from phe- nol, formaldehyde, and amine. Polyfunctional Correspondence to: H. Ishida. Contract grant sponsors: Royal Thai Government Research Fund and The NSF Center for Molecular and Microstructure of Composites. Journal of Applied Polymer Science, Vol. 77, 2561–2568 (2000) © 2000 John Wiley & Sons, Inc. 2561