Polyelectrolyte Behavior of an Interpolyelectrolyte Complex Formed in Aqueous Solution of a Charged Dendrimer and Sodium Poly(l-glutamate)

Abstract

The binding of the protonated fourth generation poly(amido amine) dendrimer as a guest polyelectrolyte (GPE) to the anionic homopolyelectrolyte poly(l-glutamic acid) sodium salt as a host polyelectrolyte (HPE) has been investigated by potentiometric and turbidimetric titration in aqueous 0.25 M NaCl solutions. The polyelectrolyte behaviors of interpolyelectrolyte complex (IPEC)-forming mixtures were compared with those of hypothetically noninteracting individual polyelectrolytes (PEs) at different stoichiometric ratios, Φ, of GPE to HPE. From the overall degree of protonation, β, at a given pH and Φ, the degree of conversion, ϑ(pH), of oppositely charged groups to ion pairs with released counterions has been calculated, as well as the thermodynamic dissociation constant, K D, of an ion pair in the IPEC. A high cooperativity of the binding of the ammonium groups of the GPE to the HPE is concluded from the strong linear increase in the pK D with ϑ. As soon as the GPE becomes partly charged below pH 11, both ϑ and the turbidity, which are proportional to the molecular weight, increase linearly with the decreasing pH, showing that the initial increase in ϑ is due to an increased number of bound GPEs. From the increase in ϑ to well above 0.5, it is likely that the linear HPE penetrates partly into the interior shells of the dendrimer GPE.

Bioinspired control of colloidal silica in vitro by dual polymeric assemblies of zwitterionic phosphomethylated chitosan and polycations or polyanions

“…In contrast, literature reports show that small molecules with functional groups possessing cationic charge, such as proline, lysine, aspartate and serine, exert some, albeit minor, catalytic effect on silicic acid condensation [97]. Amine-terminated PAMAM dendrimers at low dosages (40 ppm is the optimum) stabilize silicic acid, but at the same time, due to their cationic charge from protonated surface amine groups at pH 7 [98,99], interact with anionic colloidal silica particles (originating from the inability of the dendrimer to achieve quantitative inhibition) to form PAMAM-SiO 2 composite precipitates. The propensity of the dendrimeric inhibitor to be entrapped within the silica 3D matrix is alleviated by addition of anionic polyelectrolytes (e.g.…”

Spectroelectrochemical analysis of ion-transfer and adsorption of the PAMAM dendrimer at a polarized liquid|liquid interface

“…2a). The pK a of G4 PAMAM dendrimer was reported as 9.20 (pK a,2 ) for 64-terminal amino groups in the periphery moiety and 6.65 (pK a,1 ) for 62-tertiary amines as branch points [18]. At pH 0.9, thus, G4 PAMAM dendrimers exist as the cationic species in the aqueous phase because of the protonation of terminal amino groups and tertiary amines.…”

Fluorescence emission from PAMAM and PPI dendrimers

“…The significant influence on the fluorescence properties of experimental factors (pH, temperature, time, concentration, and oxidation) has been studied. The variation of solution pH is especially noticeable because of protonation of amine groups (pK of primary amine = 9.20; pK of tertiary amine = 6.65) [38] as well as deprotonation of carboxylic acid groups. Moreover, the fluorescence lifetime has been discussed in relation to the formation of the fluorescence-emitting moieties in PAMAM dendrimers at varying pH or temperature.…”