A detailed spectroscopic analysis performed on aqueous solutions of uncharged Star-Polymers, having a porphyrin core andfour poly(ethylene glycol) methoxy terminated arms, at different molecular weight values, by Elastic and Quasi-Elastic Lightscattering and Fourier Transform Infrared absorption (FT-IR) has been reported. The aim of the present work is essentially tocharacterize the structural and dynamical properties of the studied samples by applying different spectroscopic techniqueswhich permit to investigate different features of an unique problem.In particular from the light scattering measurements we showed that the species having higher molecular weight (3600 and8500 Da), have a very low scattered intensity compatible with the presence of the molecules in the monomer form. At thelowest investigated molecular weight (2100 Da) molecules aggregate to form large supramolecular structures. This tendency toaggregate was confirmed by FT-IR measurements performed in the same water solutions at low frequency (200 – 700) cm-1.Also the high frequency region, in the OH stretching vibrational range, (2800 – 3800) cm-1, has been investigated versus themolecular mass of the star-polymer. From the comparison of the IR spectra in the case of star-polymers aqueous solutions withthe absorbance spectrum of bulk water, we showed a destructuring effect for the ‘collective’ band centred at about 3200 cm-1,which is related to the OH stretching of tightly bonded water molecules (tetrahedral water)
Aggregation effects in aqueous solutions of Star-polymers by spectroscopic investigations
MINEO, PLACIDO;
2003-01-01
Abstract
A detailed spectroscopic analysis performed on aqueous solutions of uncharged Star-Polymers, having a porphyrin core andfour poly(ethylene glycol) methoxy terminated arms, at different molecular weight values, by Elastic and Quasi-Elastic Lightscattering and Fourier Transform Infrared absorption (FT-IR) has been reported. The aim of the present work is essentially tocharacterize the structural and dynamical properties of the studied samples by applying different spectroscopic techniqueswhich permit to investigate different features of an unique problem.In particular from the light scattering measurements we showed that the species having higher molecular weight (3600 and8500 Da), have a very low scattered intensity compatible with the presence of the molecules in the monomer form. At thelowest investigated molecular weight (2100 Da) molecules aggregate to form large supramolecular structures. This tendency toaggregate was confirmed by FT-IR measurements performed in the same water solutions at low frequency (200 – 700) cm-1.Also the high frequency region, in the OH stretching vibrational range, (2800 – 3800) cm-1, has been investigated versus themolecular mass of the star-polymer. From the comparison of the IR spectra in the case of star-polymers aqueous solutions withthe absorbance spectrum of bulk water, we showed a destructuring effect for the ‘collective’ band centred at about 3200 cm-1,which is related to the OH stretching of tightly bonded water molecules (tetrahedral water)I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
