Study of polyfunctional carboxyl telechelic microspheres

Abstract

The effects of the hydroxyl group and the carboxyl group on the polymerization of e-caprolactone (CL) were investigated. The results indicate that the carboxyl group does not initiate the polymerization of CL, but can accelerate the polymerization of CL, which is initiated by the hydroxyl group. Thus, a series of polyfunctional carboxyl telechelic microspheres (PCTMs) with different lengths and number of oligocaprolactone telechelic branch chains, which are capped with two (or three) carboxyl groups at one of these telechelic chains' extremities, were prepared by hydroxy acid (dl-malic acid or citric acid)-initiated polymerization of CL. These PCTMs are water-swellable, spherical, and porous and have both higher total carboxyl amounts and higher telechelic carboxyl ratios than those of the monofunctional carboxyl telechelic microspheres (MCTMs). Their static ion-exchange capacities also increased by increasing the telechelic carboxyl ratios and almost corresponded to the total carboxyl amounts. The intermediate products were characterized by acid–base titration, hydroxyl value titration, ultraviolet, infrared, as well as 1H- and 13C-nuclear magnetic resonance analyses, respectively. The morphology of the PCTMs were characterized by scanning electron microscopy technology. Some of the physical and chemical parameters of the PCTMs are also described. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 667–676, 1999