Semi-Interpenetrating Polymer Networks with Predefined Architecture for Metal Ion Fluorescence Monitoring.

Kyriakos Christodoulou,Theodora Krasia-Christoforou,Mariliz Achilleos,Christiana Polydorou,Epameinondas Leontidis

doi:10.3390/polym8120411

Abstract

The development of new synthetic approaches for the preparation of efficient 3D luminescent chemosensors for transition metal ions receives considerable attention nowadays, owing to the key role of the latter as elements in biological systems and their harmful environmental effects when present in aquatic media. In this work, we describe an easy and versatile synthetic methodology that leads to the generation of nonconjugated 3D luminescent semi-interpenetrating amphiphilic networks (semi-IPN) with structure-defined characteristics. More precisely, the synthesis involves the encapsulation of well-defined poly(9-anthrylmethyl methacrylate) (pAnMMA) (hydrophobic, luminescent) linear polymer chains within a covalent poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) hydrophilic polymer network, derived via the 1,2-bis-(2-iodoethoxy)ethane (BIEE)-induced crosslinking process of well-defined pDMAEMA linear chains. Characterization of their fluorescence properties demonstrated that these materials act as strong blue emitters when exposed to UV irradiation. This, combined with the presence of the metal-binding tertiary amino functionalities of the pDMAEMA segments, allowed for their applicability as sorbents and fluorescence chemosensors for transition metal ions (Fe3+, Cu2+) in solution via a chelation-enhanced fluorescence-quenching effect promoted within the semi-IPN network architecture. Ethylenediaminetetraacetic acid (EDTA)-induced metal ion desorption and thus material recyclability has been also demonstrated.

Highlights

The development of luminescent chemosensors for transition metal ions has attracted considerable attention in the last years given their high importance in biological systems [1], and their harmful environmental effects when they are present in high concentrations in aquatic media [2,3]
Giving further credence to the BIEE-crosslinking approach as an alternative to synthetically demanding and multistep controlled polymerization processes, in the present study we report on the synthesis of 3D structure-defined emissive amphiphilic semi-IPN, consisting of BIEE-crosslinked poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) segments and embedded hydrophobic and nonconjugated/fluorescent poly(9-anthrylmethyl methacrylate) linear chains both prepared by reversible addition–fragmentation chain transfer (RAFT)-controlled radical polymerization
The synthetic methodology followed for the preparation of structure-defined, BIEE-crosslinked fluorescent semi-IPN polymer networks was based on our recent publication [57]

Summary

Introduction

The development of luminescent chemosensors for transition metal ions has attracted considerable attention in the last years given their high importance in biological systems [1], and their harmful environmental effects when they are present in high concentrations in aquatic media [2,3]. A few research groups have been working on the synthesis of fluorescent semi-interpenetrating network (semi-IPN) architectures The latter are 3D polymer structures consisting of secondary linear polymer. Polymers 2016, 8, 411 chains that are interlaced—but not covalently bonded—with a primary polymer network [21,22,23,24] In this limited number of existing reports, the fluorescent component is either a conjugated conductive polymer [25,26,27,28], fluorescent nanoparticles such as carbon nanodots and quantum dots (QDs) [29,30,31], or fluorescent dyes dispersed within or covalently linked to the polymer matrix [32,33,34,35]. The abovementioned materials have several disadvantages including: (a) low structural stability and robustness in the presence of chemical and physical impacts [36,37,38,39,40]; (b) possible leaching and relatively high probability of aggregation-induced fluorescence quenching of the physically entrapped organic dyes [41]; and (c) agglomeration phenomena of the fluorescent nanoparticles such as carbon nanodots resulting in inferior fluorescence properties due to self-quenching [42]

Methods

Results

Conclusion