Abstract: The present invention is directed to branched reactive water-soluble polymers comprising at least two polymer arms, such as poly(ethylene glycol), attached to a central aliphatic hydrocarbon core molecule through ether linkages. The branched polymers bear at least one functional group for reacting with a biologically active agent to form a biologically active conjugate. The functional group of the branched polymer can be directly attached to the aliphatic hydrocarbon core or via an intervening linkage, such as a heteroatom, -alkylene-, —O-alkylene-O—, -alkylene-O-alkylene-, -aryl-O—, —O-aryl-, (—O-alkylene-)m, or (-alkylene-O—)m linkage, wherein m is 1-10.

Abstract: Segmented water soluble polymers, containing a higher molecular weight segment linked to a lower molecular weight segment, are described. In one embodiment, the polymer segments are poly(ethylene glycol) segments. The segmented polymers are functionalized and are useful for conjugation to various moieties such as pharmacologically active substances. Also described are conjugates of such polymers and methods of their preparation.