A poly(amido-amine), PAA, bearing β-CD units in the side chain was synthesized by a polyaddition reaction of 1,4-bis-acryloyl-piperazine with 6-monodeoxy-6-monoamino-β-cyclodextrin (β-CD-NH2). Unlike the simple β-CD-NH2 with a greater basicity constant (log K = 8.60), the polymer revealed an unusual polyelectrolyte behaviour with a lower basicity constant (log K° = 6.29) of the tertiary nitrogen atom, that is strongly dependent on the degree of protonation α of the whole macromolecule. It follows the modified Henderson-Hasselbalch equation with n = 1.75, in a wide α-range. The greater (-46.1 kJ/mol) and the lower (-27.6 kJ/mol) enthalpy (ΔH°) changes of the compounds were in line with the protonation of a primary or a tertiary nitrogen atom. The calorimetric data suggested that the PAA protonation destroyed a packing structure formed by two rigid β-CD side chains interacting head-to-head. The UV spectrophotometric data showed that the PAA exhibits affinity towards the l-ascorbic acid at low pH (pH 2.46) with an isosbestic point at 241 nm and a slight blue shift of the maximum absorption of the ascorbic acid (244 nm) on PAA additions. © 2009 Springer Science+Business Media B.V.
Casolaro, M., Staltari, L., Anselmi, C., Mendichi, R., Bernini, A. (2010). The protonation Thermodynamics of Cyclodextrin-containing Polymers for Drug Inclusion. JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY, 67(1-2), 141-151 [10.1007/s 10847-009-9690-y].
The protonation Thermodynamics of Cyclodextrin-containing Polymers for Drug Inclusion
CASOLARO M.;ANSELMI C.;BERNINI A.
2010-01-01
Abstract
A poly(amido-amine), PAA, bearing β-CD units in the side chain was synthesized by a polyaddition reaction of 1,4-bis-acryloyl-piperazine with 6-monodeoxy-6-monoamino-β-cyclodextrin (β-CD-NH2). Unlike the simple β-CD-NH2 with a greater basicity constant (log K = 8.60), the polymer revealed an unusual polyelectrolyte behaviour with a lower basicity constant (log K° = 6.29) of the tertiary nitrogen atom, that is strongly dependent on the degree of protonation α of the whole macromolecule. It follows the modified Henderson-Hasselbalch equation with n = 1.75, in a wide α-range. The greater (-46.1 kJ/mol) and the lower (-27.6 kJ/mol) enthalpy (ΔH°) changes of the compounds were in line with the protonation of a primary or a tertiary nitrogen atom. The calorimetric data suggested that the PAA protonation destroyed a packing structure formed by two rigid β-CD side chains interacting head-to-head. The UV spectrophotometric data showed that the PAA exhibits affinity towards the l-ascorbic acid at low pH (pH 2.46) with an isosbestic point at 241 nm and a slight blue shift of the maximum absorption of the ascorbic acid (244 nm) on PAA additions. © 2009 Springer Science+Business Media B.V.File | Dimensione | Formato | |
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https://hdl.handle.net/11365/3107
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