Kinetics of Threading α-Cyclodextrin onto Cationic and Zwitterionic Poly(bola-amphiphiles)

The amphiphilic polymers, poly(iminoundecamethylene), poly(( N -methylimino)undecamethylene), poly(( N, N -dimethylammonio)undecamethylene), and poly( (N -methylimino)undecamethylene- N -oxide) were synthesized from nylon-11 by BH 3 reduction of amide groups to amino groups and subsequent methylations. The poly( N -oxide) was obtained by H 2 O 2 oxidation of the polymeric tertiary amine. Since the polymers and their inclusion compounds were water-soluble, threading kinetics of α-cyclodextrin rings onto these polymers could be investigated by 1 H NMR. Kinetics were fitted by an empirical root exponential association function Y = Y ∞ (1 − exp(−sqrt(5.3 t / t 90 ))). The time t 90, necessary to reach 90% completion of the threading process, was taken as a measure of the steric hindrance exerted by the hydrophilic groups along the polymer chain. The vaIues of t 90 decreased by more than 3 orders of magnitude as the diameters of the hydrophilic groups decreased from 5.5 to 4.3 Å.