This article describes detailed structure-property relationships of 5 regioselectively methylated celluloses and 10 diblock cellulose derivatives with regioselective functionalization patterns: methyl 2,3,6-tri-O- (1, 236MC), methyl 2,3-di-O- (2, 23MC), methyl 2,6-di-O- (3, 26MC), methyl 3-O- (4, 3MC), methyl 6-O-methyl-cellulosides (5, 6MC), methyl beta-D-glucopyranosyl-(1 -> 4)-2,3,6-tri-O-methyl- (6, G-236MC), methyl beta-D-glucopyranosyl (1 -> 4)-2,3-di-O-methyl- (7, G-23MC), methyl beta-D-glucopyranosyl-(1 -> 4)-2,6-di-O-methyl- (8, G-26MC), methyl beta-D-glucopyranosyl-(1 -> 4)-3-O-methyl- (9, G-3MC), methyl beta-D-glucopyranosyl-(1 -> 4)-6-O-methyl- (10, G-6MC), methyl beta-D-glucopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 4)-2,3,6-tri-O-methyl- (11, GG-236MC), methyl beta-D-glucopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 4)-2,3-di-O-methyl- (12, GG-23MC), methyl beta-D-glucopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 4)-2,6-di-O-methyl- (13, GG-26MC), methyl beta-D-glucopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 4)-3-O-methyl- (14, GG-3MC), and methyl beta-D-glucopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 4)-6-O-methyl-cellulosides (15, GG-6MC). Surface tension, differential scanning calorimetry, fluorescence, and dynamic light scattering measurements of aqueous solutions of compounds 1-15 revealed that there was no relationship between aggregation behaviors and gel formation, gelation occurred only when the hydrophobic environments formed by hydrophobic interactions between the sequences of 2,3,6-tri-O-methyl-glucopyranosyl units upon heating. The diblock structure consisting of cellobiosyl block and approx. ten 2,3,6-tri-O-methyl-glucopyranosyl units was of crucial importance for thermoreversible gelation of methylcellulose. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1539-1546, 2011