Understanding the surface properties of polybenzoxazines: Interaction of polybenzoxazine model compounds with metal ions and water

Abstract

The structure of polybenzoxazines (and their properties) is mainly defined by the existence of intra-and intermolecular hydrogen bonds. The effect of different substituents present in the phenolic ring of polybenzoxazines can modulate these intermolecular forces and the interaction with other materials, such as metals. To extend this knowledge, a series of structure-controlled polybenzoxazines and polybenzoxazine model compounds have been synthesized. The interactions with different metal ions have been investigated using UV-vis and NMR analysis. Association constants have been estimated by UV-vis titration method and the effect of the presence of different substituents in the aromatic ring has been established. Water contact angles have also been measured. The different techniques give us information about the inner hydrogen bonding structure. Cyano group, present as substituent in polybenzoxazine compounds, acts as an additional coordination point towards metal ions and water. Our findings should allow modulating the adhesion and other surface properties of the benzoxazine-derived polymers by playing with the properties of the substituents and their structure (phenoxy/phenolic).

Application of Benzoxazine‐Based Dimers, Oligomers, and Polymers as Chelating Agents

“…However, it was observed that the CH 2  groups signal shifts downfield when the metal ions were added. This was attributed to “the reduction of electron density of the methylene group as a result of the coordination of the metal ion with the dimer” which is consistent with the structure presented in Scheme c. Moreover, in the case of Zn 2+ , a broad peak was detected, while the splitting of the CH 2  signal was observed when Cu 2+ and Al 3+ were utilized.…”

“…The spatial conformation of polybenzoxazines is key for the polybenzoxazine capability of acting as a ligand to metal ions due to the presence of intramolecular hydrogen bonding. In 2016, Shen et al . studied the influence of the spatial conformation over the interaction between polybenzoxazines and metal ions by synthesizing a significant number of dimers with aliphatic and aromatic amines as well as with electron donating and withdrawing substituents in the phenolic portions (see Scheme ).…”

“…Possible structures of BNZ dimers a) and b) exhibiting intramolecular hydrogen bonding, and c) interacting with a cation. Adapted with permission . Copyright 2016, Wiley Periodicals, Inc.…”

“… 1 H‐NMR spectra of 1a, 1a‐CuCl 2 , 1a‐AlCl 3 , and 1a‐ZnCl 2 in methanol‐d 4 with a 1:1 ratio. Adapted with permission . Copyright 2016, Wiley Periodicals, Inc.…”

“…The interaction between the dimer and the metal ions was evaluated through two parameters, the association constant ( K a ), defined as the equilibrium constant for Scheme , and the stoichiometric ratio ( n ). In the cited work, the results were presented only for ZnCl 2 salt, although the same experiments were carried out utilizing CuCl 2 , AlCl 3 , and FeCl 3 .…”