Study of polyfunctional carboxyl telechelic microspheres

The effects of the hydroxyl group and the carboxyl group on the polymerizat ion of epsilon-caprolactone (CL) were investigated. The results indicate th at the carboxyl group does not initiate the polymerization of CL, but can a ccelerate the polymerization of CL, which is initiated by the hydroxyl grou p. 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 thes e telechelic chains' extremities, were prepared by hydroxy acid (DL-malic a cid or citric acid)-initiated polymerization of CL. These PCTMs are water-s wellable, spherical, and porous and have both higher total carboxyl amounts and higher telechelic carboxyl ratios than those of the monofunctional car boxyl telechelic microspheres (MCTMs). Their static ion-exchange capacities also increased by increasing the telechelic carboxyl ratios and almost cor responded to the total carboxyl amounts. The intermediate products were cha racterized by acid-base titration, hydroxyl value titration, ultraviolet, i nfrared, as well as H-1- and C-13-nuclear magnetic resonance analyses, resp ectively. The morphology of the PCTMs were characterized by scanning electr on microscopy technology. Some of the physical and chemical parameters of t he PCTMs are also described. (C) 1999 John Wiley & Sons, Inc.