Ferrocene-Modified Block Copolymers for the Preparation of Smart Porous Membranes.

Sebastian Schöttner,Markus Gallei,Christian Rüttiger,Rimjhim Hossain

doi:10.3390/polym9100491

Sebastian Schöttner, Markus Gallei + Show 2 more

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https://doi.org/10.3390/polym9100491

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Journal: Polymers	Publication Date: Oct 8, 2017
Citations: 21	License type: CC BY 4.0

Affiliation: Technical University of Darmstadt

Abstract

The design of artificially generated channels featuring distinct remote-switchable functionalities is of critical importance for separation, transport control, and water filtration applications. Here, we focus on the preparation of block copolymers (BCPs) consisting of polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) having molar masses in the range of 91 to 124 kg mol−1 with a PHEMA content of 13 to 21 mol %. The BCPs can be conveniently functionalized with redox-active ferrocene moieties by a postmodification protocol for the hydrophilic PHEMA segments. Up to 66 mol % of the hydroxyl functionalities can be efficiently modified with the reversibly redox-responsive units. For the first time, the ferrocene-containing BCPs are shown to form nanoporous integral asymmetric membranes by self-assembly and application of the non-solvent-induced phase separation (SNIPS) process. Open porous structures are evidenced by scanning electron microscopy (SEM) and water flux measurements, while efficient redox-switching capabilities are investigated after chemical oxidation of the ferrocene moieties. As a result, the porous membranes reveal a tremendously increased polarity after oxidation as reflected by contact angle measurements. Additionally, the initial water flux of the ferrocene-containing membranes decreased after oxidizing the ferrocene moieties because of oxidation-induced pore swelling of the membrane.

Highlights

Stimuli-responsive membranes attract enormous attention because of their excellent control over permeability, selectivity, and absorption capabilities stimulated by external triggers [1,2,3,4].The elaborated design of synthetic channels resulting in transport control is of critical importance for instance in separation and filtration applications
We reported on the preparation of the amphiphilic block copolymer polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) for the formation of integral asymmetric porous membranes featuring a high water flux [47]
This paper presented the fabrication of redox-responsive integral asymmetric membranes, which were obtained by the functionalization of the amphiphilic block copolymer polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) with redox-responsive moieties based on ferrocene

Summary

Introduction

Stimuli-responsive membranes attract enormous attention because of their excellent control over permeability, selectivity, and absorption capabilities stimulated by external triggers [1,2,3,4].The elaborated design of synthetic channels resulting in transport control is of critical importance for instance in separation and filtration applications. Stimuli-responsive membranes attract enormous attention because of their excellent control over permeability, selectivity, and absorption capabilities stimulated by external triggers [1,2,3,4]. Stimuli-responsive polymer materials attracted enormous attention for a range of recent polymer-based applications [5,6,7]. This type of polymers feature certain chemical functionalities, which can be addressed by external triggers such as the presence of solvent, change of temperature, variation of pH, by light, redox reagents, or electrical or magnetic fields [8,9,10,11]. The ferrocene/ferrocenium redox couple in metallopolymers has attracted significant interest due to the unique capability of (electro)chemical switching between hydrophobic ferrocene and comparably hydrophilic ferrocenium moieties [17,18,19,20,21,22,23,24]

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