Aggregation Phenomena in Aqueous Solutions of Uncharged Star Polymers with a Porphyrin Core

Abstract

Uncharged star polymers having a porphyrin core and four poly(ethylene glycol)methyl ether (PEGME) arms have been synthesized and investigated (through the study of the structural and dynamical properties) as a function of the molecular mass of the arms, in different thermodynamic conditions. Molecules with short PEGME arms are insoluble in water, whereas in the presence of long PEGME chains, the star polymers are water-soluble; for the intermediate length of the arms, the building up of large rigid monodisperse aggregates, driven by the diffusion limit aggregation mechanism, has been observed by means of static and dynamic light scattering. These aggregated systems, whose sizes are modulated by changing the pH and triggered by the chain flexibility, can be well described in terms of the DLVO interparticle potential in the frame of the colloidal theory.

Water‐soluble star polymers with a phthalocyanine as the core and poly(ethylene glycol) chains as branches

“…This was consistent with the presence of a smaller number of aggregates (ca. half, with the consideration that the absorbance and aggregate size were the same) in aqueous solution; this was probably due to a stronger steric hindrance of PEGME 750 chains (each corresponding to about 16 ethylenoxyl repetitive units) in the face‐to‐face stacking phenomenon 21…”

Lamellar self-assembly of a porphyrin derivative possessing poly(ethylene oxide) methyl ether and the formation of a silica–porphyrin hybrid with tetraethoxysilane

“…In order to investigate the selfassembled structure, a thin film was used in this study. Micali et al reported the aggregation of PEO-TPP in water, confirmed by various light scattering techniques, though the assembled structure of porphyrin rings was unfortunately not discussed [42].…”

“…On the other hand, PEO-TPP is only able to utilize the amphiphilicity and p-p interaction for the self-assembly in the formation of hybrids, which result in weaker interactions between PEO-TPP than that of the phthalocyanine derivative. Another reason for the lacking of a periodicity between porphyrin rings is the electrostatic repulsion between porphyrin dications [42]. These differences should suppress the ordered arrangement of the porphyrin rings in PEO-TPP-SiO 2 hybrid.…”

“…Aida et al reported the synthesis and cofacial selfassembly of a porphyrin derivative with poly(ethylene oxide) chains terminated with OH groups [40]. Mineo et al also reported the synthesis of PEO-TPPs with various PEO chain length [41], and the aggregation of the PEO-TPP in water was investigated [42][43][44]. A poly(ethylene oxide) chain is a hydrophilic part of nonionic surfactants used conventionally for the preparation of mesostructured materials, and such a chain was grafted onto the outside of a porphyrin core, which makes the derivative amphiphilic.…”

Uncharged Water‐Soluble Metal‐Bis‐Porphyrins Like Molecular Tweezers for Amino Acids

“…Molecular aggregation of these compounds in aqueous solutions [22,23] and modification of their spectroscopic properties (NMR, UV-vis and circular dichroism (CD) in correspondence with the porphyrin Soret band) upon treatment with aliphatic and aromatic a-L-AAs, oligopeptides and/or proteins have been studied. [24,25] In the present work, a similar synthetic procedure was adopted to prepare uncharged water-soluble bisporphyrins I whose use as molecular receptor of AAs has also been studied.…”