Phosphonium-Containing ABA Triblock Copolymers: Controlled Free Radical Polymerization of Phosphonium Ionic Liquids

Abstract

Phosphonium ion-containing acrylate triblock (ABA) copolymers were synthesized using nitroxide mediated radical polymerization. The polymerization of styrenic phosphonium-containing ionic liquid monomers using a difunctional alkoxyamine initiator, DEPN2, afforded an ABA triblock copolymer with an n-butyl acrylate soft center block (DP ∼ 400) and symmetric phosphonium-containing external reinforcing blocks (DP < 30). Two phosphonium monomers with different alkyl substituent lengths enabled an investigation of the effects of ionic aggregation of phosphonium cations on the physical properties of ABA block copolymer ionomers. Subsequently, the thermomechanical properties and morphologies of these materials were compared to a noncharged triblock copolymer analogue with neutral polystyrene external blocks. Shortening the alkyl substituents on the phosphonium cation enhanced the hydrophilicity of tributyl-4-vinylbenzyl phosphonium chloride (BPCl) relative to trioctyl-4-vinylbenzyl phosphonium chloride (OPCl). In both cases, phosphonium cations promoted microphase-separation and thermoplastic elastomer performance for the OPCl- and BPCl-containing triblock copolymers compared to a less well-defined, microphase segregated morphology for the styrene analogue. Dynamic mechanical analysis (DMA) of phosphonium-containing triblock copolymers exhibited well-defined rubbery plateau regions, whereas the plateau was shortened for the nonionic analogue. The solid state morphologies of the block copolymers were studied using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), and both techniques revealed phase separation at the nanoscale. DMA studies indicated that phosphonium aggregation governed flow activation energies.

Ionic polymers based on quaternized polysulfones: hydrodynamic properties of polymer mixtures in solution

“…Therefore, blending of functionalized polysulfones with other synthetic polymers has wide applications, as a versatile method to tailor materials for specific uses [13] and for further developments in biomedical applications. In this respect, in the present study, polyvinyl alcohol (PVA) and cellulose acetate phthalate (CAP) were selected for their excellent physical properties, including high hydrophilicity, flexibility, film-forming ability, emulsifying capacity, dispersing power, tensile strength, adhesive or bonding properties, and very good physical and chemical stabilities [14,15].…”

Densely quaternized anion exchange membranes synthesized from Ullmann coupling extension of ionic segments for vanadium redox flow batteries

“…It should be noted that the FT-IR spectra for OMPFEK-20, Br-OMPFEK-20, and QA-OMPFEK-20 are nearly identical. This may be due to the low absorption intensity and the peak overlap of the new C-Br and C-N bonds with other functionalities on the OMPFEK backbones [32,39].…”

Phosphonium polymers for gene delivery

“…Nitroxide-mediated polymerisation (NMP) was successfully utilised by Long and coworkers to synthesise a family of phosphonium-containing ABA triblock copolymers, where the number of ionic repeating units as well as the length of the hydrophobic alkyl substituents on the phosphonium cation were systematically varied. 50 Polymerisation from a (DEPN-terminated poly(n-butyl acrylate) difunctional nitroxide initiator of (tributyl-4-vinylbenzyl phosphonium chloride or trioctyl-4-vinylbenzyl phosphonium chloride monomers at 125°C in DMF afforded the desired ABA block copolymers ( Figure 7). These materials were assessed for their potential to be incorporated in alkaline fuel cell membranes and for melt processing, by analysing their thermal and thermo-mechanical properties as well as self-assembly properties, by employing differential scanning calorimetry, glass transition measurements, dynamic mechanical analysis and TEM.…”