Insights into the Protonation State and Counterion Interactions of Linear Polyethyleneimine Materials.
7 affiliations
- 1Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Ciudad Autónoma de Buenos Aires 1113, Argentina.
- 2CONICET-Universidad de Buenos Aires, Instituto de Química y Fisicoquímica Biológicas (IQUIFIB), Ciudad Autónoma de Buenos Aires 1113, Argentina .
- 3ONICET-Universidad de Buenos Aires, Instituto de Química y Metabolismo del Fármaco (IQUIMEFA-UBA-CONICET), Ciudad Autónoma de Buenos Aires 1113, Argentina.
- 4Centro de Investigaciones en Bionanociencias (CIBION - CONICET), Polo Científico Tecnológico, Ciudad Autónoma de Buenos Aires 1425, Argentina.
- 5Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, Córdoba 5000, Argentina.
- 6Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Física Enrique Gaviola (IFEG), Córdoba 5000, Argentina.
- 7Comisión Nacional de Energía Atómica, San Martín, Buenos Aires 1650, Argentina.
Abstract
Polyethyleneimine (PEI) polymers are widely used in the synthesis of nanoparticles, hydrogels and composite materials for biotechnological and environmental applications. However, the solid-state structural organization of linear PEI (L-PEI) materials, and how it is influenced by molecular weight, protonation state and counterion type, have not yet been comprehensively studied. In this work, solid-state nuclear magnetic resonance (ss-NMR), X-ray powder diffraction (XRD), small-angle X-ray scattering (SAXS) and time-domain NMR (TD-NMR) experiments were combined with theoretical calculations to analyze the local chemical environments, crystalline and nanoscale organization, and molecular mobility of L-PEI materials with different molecular weights. The analyzed materials were the free base (PEI·FB), the hydrochloride (PEI·HCl), the trifluoroacetate (PEI·TFA), and the sulfate-containing forms of L-PEI (PEI·Na₂SO₄ and PEI·H₂SO₄), as well as an intermediate protonation state obtained by the heterogeneous treatment with HCl-saturated isopropanol. Proton, ¹³C or ¹⁵N ss-NMR studies evidenced different chemical environments associated with changes in protonation state and counterion identity. Furthermore, XRD and SAXS showed that these variables, together with molecular weight and sample preparation conditions, influenced the crystalline arrangement and characteristic nanoscale organization of the polymer chains. Moreover, TD-NMR revealed the presence of three dynamically distinct proton populations, assigned to rigid, interfacial, and mobile domains, whose relative contributions and relaxation behavior varied among the PEI materials. Finally, high-resolution magic-angle spinning (HRMAS) NMR experiments were used to study different PEI-gel materials and films as well as the crosslinking of protonated PEI and sulfate ions.
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BibTeX
@article{byrne2026insights,
title = {{Insights into the Protonation State and Counterion Interactions of Linear Polyethyleneimine Materials.}},
author = {Agustín J Byrne and Daniel Vladimir and Yamila Garro-Linck and Guillermo J Copello and Ayelén F Crespi and Daniel Vega and Mariela Bollini and Paula G Franco and Juan M Lázaro-Martínez},
journal = {Gels (Basel, Switzerland)},
year = {2026},
month = oct,
doi = {10.3390/gels12100912},
url = {https://europepmc.org/article/MED/42929946},
note = {CC BY},
}
RIS
TY - JOUR
TI - Insights into the Protonation State and Counterion Interactions of Linear Polyethyleneimine Materials.
AU - Agustín J Byrne
AU - Daniel Vladimir
AU - Yamila Garro-Linck
AU - Guillermo J Copello
AU - Ayelén F Crespi
AU - Daniel Vega
AU - Mariela Bollini
AU - Paula G Franco
AU - Juan M Lázaro-Martínez
PY - 2026
DA - 2026/10/10
JO - Gels (Basel, Switzerland)
DO - 10.3390/gels12100912
UR - https://europepmc.org/article/MED/42929946
AB - Polyethyleneimine (PEI) polymers are widely used in the synthesis of nanoparticles, hydrogels and composite materials for biotechnological and environmental applications. However, the solid-state structural organization of linear PEI (L-PEI) materials, and how it is influenced by molecular weight, protonation state and counterion type, have not yet been comprehensively studied. In this work, solid-state nuclear magnetic resonance (ss-NMR), X-ray powder diffraction (XRD), small-angle X-ray scattering (SAXS) and time-domain NMR (TD-NMR) experiments were combined with theoretical calculations to analyze the local chemical environments, crystalline and nanoscale organization, and molecular mobility of L-PEI materials with different molecular weights. The analyzed materials were the free base (PEI·FB), the hydrochloride (PEI·HCl), the trifluoroacetate (PEI·TFA), and the sulfate-containing forms of L-PEI (PEI·Na₂SO₄ and PEI·H₂SO₄), as well as an intermediate protonation state obtained by the heterogeneous treatment with HCl-saturated isopropanol. Proton, ¹³C or ¹⁵N ss-NMR studies evidenced different chemical environments associated with changes in protonation state and counterion identity. Furthermore, XRD and SAXS showed that these variables, together with molecular weight and sample preparation conditions, influenced the crystalline arrangement and characteristic nanoscale organization of the polymer chains. Moreover, TD-NMR revealed the presence of three dynamically distinct proton populations, assigned to rigid, interfacial, and mobile domains, whose relative contributions and relaxation behavior varied among the PEI materials. Finally, high-resolution magic-angle spinning (HRMAS) NMR experiments were used to study different PEI-gel materials and films as well as the crosslinking of protonated PEI and sulfate ions.
SN - 2310-2861
ER -