Controlled allylation of polyelectrolytes: a deep insight into chemical aspects and their applicability as building blocks for robust multilayer coatings

Abstract

Polyelectrolytes (PEs) bearing easily derivatizable functions for possible post-modification under mild conditions can find a broad range of applications in various fields. The present paper describes the successful controlled side-chain allylation of two types of PEs: polyamine-based polycations, i.e. poly(allylamine hydrochloride) (PAH) and branched polyethyleneimine (PEI), and strong polyanions, i.e. poly(sodium vinyl sulfonate) (PVS) and poly(sodium 4-styrene sulfonate) (PSS). PSS has been largely investigated in the literature, while PVS is much less commonly explored. The allylation of each type presents its own drawback, i.e. heterogeneous reaction in the case of strong polyanions and instability of partially protonated allylated polyamine products. Nevertheless, all encountered difficulties could be solved and thoroughly elucidated by different experimental tests. This partial allyl-functionalization does not affect the electrolytic properties of the newly allylated PEs, as evidenced by the effective construction of two series of polyelectrolyte multilayer (PEM) films, namely PEI-ene (PSS-ene/PAH-ene)4 and PEI-ene (PVS-ene/PAH-ene)4, the latter being one of the rare examples developed in the literature. The presence of allyl groups on the PE side-chains allows for the stabilization of the resulting PEM films via thiol-ene photo-crosslinking in the presence of a water-soluble dithiol crosslinker. In order to fix permanently the resulting crosslinked PEM films on substrates, the covalent crosslinking occurs not only between different C=C bonds on PE layers but also with those present on substrates preliminarily functionalized with allyl groups via sulfur–gold chemistry. The robustness of both resulting crosslinked PEM films under strongly basic solution (pH 14) is validated by Quartz Crystal Microbalance (QCM) measurements. The versatility and effectiveness of the present approach is expected to find potential applications in different scientific and technological fields.

Photoinduced synthesis of antibacterial hydrogel from aqueous photoinitiating system

“…50 %, in order to:(i) increase the proportion of tertiary ammonium ion in the final allylated product since this type of ammonium ion has been known to exhibit higher antibacterial properties than the secondary or primary amines and (ii) increase the number of double bonds in the final product which would enable to prepare highly robust antibacterial films according to the increasing number of possible crosslinking. 1 H NMR analysis of the allylated PEI-HCl confirms the presence of allylic groups[53,54] whose 1 H NMR signals (Figure S1) appear at 5.4-5.9 ppm (m, 1.5H, -CH=CH2 ), and 4.0 ppm (1H, -CH2-CH=CH2) and13 C NMR signals (Figure S2)125.0-129.0 ppm (-CH=CH2) and 56 ppm (-CH2-CH=CH2). This side-chain allyl functionalization was further confirmed by FTIR analysis(Figure S3), especially by the appearance of a strong band (doublet) between 950 and 990 cm -1 attributed to out-of plane bending of allylic protons.…”