SYNTHESIS OF NOVEL POLY(ETHYLENE GLYCOL) DERIVATIVES HAVING PENDANT AMINO-GROUPS AND AGGREGATING BEHAVIOR OF ITS MIXTURE WITH FATTY-ACID INWATER

Novel poly(ethylene glycol) (PEG) derivatives having pendant amino gro ups were prepared by copolymerization of allyl glycidyl ether with eth ylene oxide followed by chemical modification of the double bond side chains. Dropwise addition of the mixture of monomers to the anionic in itiator gave an almost monodisperse (M(w)/M(n) = 1.05) random copolyme r. H-1 NMR spectra showed that addition of 2-aminoethanethiol to the p endant allyl groups of the copolymer was completely carried out in met hanol without catalyst, and an aminated PEG derivative with a definite structure was obtained. Acetylation of the pendant amino groups was r eadily performed by acetic anhydride with triethylamine. A gel permeat ion chromatogram of the acetylated polymer showed a very narrow molecu lar weight distribution (M(w)/M(n) = 1.06) of the polyamine. These cat ionic PEG derivatives make amphiphilic poly-ion complexes with fatty a cids, and then aggregate in water. A fluorescence study using pyrene a s a microenvironment probe revealed Chat: the aminated PEG-lauric acid ion complex could take up the hydrophobic fluorescence probe into the lipophilic field inside, and they also had a critical aggregation con centration at [lauric acid] = 0.7 mM. It is much lower than the critic al micelle concentration of the corresponding fatty acid sodium salts, indicating high stability of the polymer-fatty acid aggregate.