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The uniform structure of cellulose, combined with its hydrophilicity, biocompatibility, chirality, and structure-forming capacity, as well as its broad synthetic potential, make the design of cellulose-based advanced materials a challenge for polysaccharide research. The synthesis of new cellulose products with regiocontrolled pattern of functionalization and of well defined supramolecular nanoscale architectures is a highlight in recent cellulose chemistry. The present feature will discuss regioselective functionalization of cellulose and cellulose derivatives with respect to reactivity of the polymer depending on molecular and supramolecular structure. Experimental examples of functionalization via ester intermediates of controlled stability as well as via protecting or activating ether groups are described and the efficiency of the reaction routes and procedures is evaluated. Moreover, problems and progress in techniques of product analysis and structure-property relationships as well as potential applications of regioselectively functionalized cellulosics are presented together with a discussion of possible future developments in cellulose chemistry. Acta Polymer., 48,277-297 0 VCH Verlagsgesellschaft mbH, D-6945 1 Weinheim 1997 0323-7648/97/0808-0277$17.50+.50/0 ' 278 Klemm, Heinze, Philipp, Wagenknecht Acta Polymer., 48,277-297 (1997) Fig. 5. Electron microscopic pictures (TEM) of typical cellulose samples: acotton linters, b -spruce sulfite pulp (from Fink et al.