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|Title:||The protonation Thermodynamics of Cyclodextrin-containing Polymers for Drug Inclusion.||Authors:||Casolaro, Mario
|Keywords:||Cyclodextrin-containing polymers; Poly(amido-amine)s; L-ascorbic acid; Protonation thermodynamics; Molecular modelling||Issue Date:||2010||Project:||None||Journal:||JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY||Abstract:||
A poly(amido-amine), PAA, bearing b-CDunits in the side chain was synthesized by a polyadditionreaction of 1,4-bis-acryloyl-piperazine with 6-monodeoxy-6-monoamino-b-cyclodextrin (b-CD-NH2). Unlike thesimple b-CD-NH2 with a greater basicity constant(log K = 8.60), the polymer revealed an unusual polyelectrolytebehaviour with a lower basicity constant(log K = 6.29) of the tertiary nitrogen atom, that isstrongly dependent on the degree of protonation a of thewhole macromolecule. It follows the modified Henderson–Hasselbalch equation with n = 1.75, in a wide a-range.The greater (-46.1 kJ/mol) and the lower (-27.6 kJ/mol)enthalpy (DH) changes of the compounds were in linewith the protonation of a primary or a tertiary nitrogenatom. The calorimetric data suggested that the PAA protonationdestroyed a packing structure formed by two rigidb-CD side chains interacting head-to-head. The UV spectrophotometricdata showed that the PAA exhibits affinitytowards the L-ascorbic acid at low pH (pH 2.46) with anisosbestic point at 241 nm and a slight blue shift of themaximum absorption of the ascorbic acid (244 nm) onPAA additions.
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