The preparation of functionalized polystyrene-divinylbenzene resins containing functional groups bonded to the polymeric matrix by a long alkyl chain has been accomplished in a two-step procedure from unfunctionalized resins and the acid chloride of a monoalkyl ester of an alkanedioic acid. The procedure is useful for the preparation of spacer-modified polymers of variable crosslinking degrees, including highly crosslinked macroreticular resins such as XAD-4. The high mobility of the chains is revealed by the easy analysis of the polymers by gel-phase C-13-NMR spectroscopy.