Synthesis and characterisation of regioselective cellulose derivatives The typical regioselective cellulose derivatives 3 mono O alkyl cellulose samples bearing two different ether moieties namely methyl ethyl methyl n propyl and ethyl n propyl were synthesized applying protecting group technique. The NMR spectra of the peracetylated products revealed the regioselectivity of the alkylation as well as the degree of substitution of both alkyl moieties. The number average degree of polymerization (DPn) calculated from size exclusion chromatography decreases from DPn 117 (starting cellulose Avicel PH 101) to DPn range of 20 50 due to the multi step synthesis. It could be demonstrated that the lower critical solution temperature (LCST) is influenced by the degree of substitution of both alkyl groups. For example LCST values between 33 and 58°C were measured for aqueous solutions of 3 mono O ethyl n propyl cellulose. On the contrary the solution behaviour of a mixture of 3 mono O ethyl and 3 mono O propyl cellulose e. g. was controlled by the derivative with the lowest LCST.