Stimuli-Responsive Polyelectrolyte Polymer Brushes Prepared via Atom-Transfer Radical Polymerization

Abstract

We present an account of our research into polyelectrolyte polymer brushes that are capable of acting as stimuli-responsive films. We first detail the synthesis of poly(acrylic acid) polymer brushes using ATRP in a "grafting from" strategy. Significantly, we employed a chemical-free deprotection step that should leave the anchoring ester groups intact. We have demonstrated how these polymer assemblies respond to stimuli such as pH and electrolyte concentration. We have used poly(acrylic acid) polymer brushes for the synthesis of metallic nanoparticles and review this work. We have used XPS, ATR-FTIR, and AFM spectroscopy to show the presence of silver and palladium nanoparticles within polymer brushes. Finally, we report the synthesis of AB diblock polyampholyte polymer brushes that represent an extension of polyelectrolyte polymer brushes.

Swelling Behavior of Multiresponsive Poly(methacrylic acid)‐block‐‐poly(N‐isopropylacrylamide) Brushes Synthesized Using Surface‐Initiated Photoiniferter‐Mediated Photopolymerization

“…This pattern of behavior exhibited by the PMAA brush in response to changes in pH mirrors that observed for weak PEs by other researchers. [20,34] The increase in swollen PMAA layer thickness occurs primarily in the pH-range of 4 < pH < 6, centered at pH $ 5, which is consistent with the reported pKa of PMAA. [50] The swelling results also show that exposure of a dry PMAA brush to the buffer solution at pH ¼ 3, where the PMAA brush is hardly or not ionized, swells the layer $1.5 times its dry-layer thickness.…”

“…[31][32][33] Additionally, because light is the activating agent, SI-PMP is well suited for the direct synthesis of polyelectrolytes (PMAA, in this study), alleviating problems with, for example, catalyst complexation, dissociation, or disproportionation that occurs during ATRP of electrolytic monomers in protic media. [34][35][36][37][38] The response characteristics of the constituent materials used in this study are well known. Because of the weakly ionizable carboxylate groups along the backbone, the degree of dissociation of PMAA can be changed by adjusting the pH and/ or the ionic strength of the solution.…”

“…The effect of pH, ionic strength and valency on the swelling of weak polyacids (PMAA or poly(acrylic acid), for example) has been studied by various groups. [19][20][21]34,[39][40][41] The thickness of these polyacid layers increases with pH, but the thickness may increase or decrease as a function of salt concentration, depending upon whether the counterion concentration outside of the layer is greater or less than that within the brush. [41] However, the swelling response of PMAA brushes to changes in pH and ionic strength at elevated temperatures (higher than room temperature) has not been investigated.…”

Smart Polymers with Special Wettability

“…Taking advantage of electrostatic interactions, ionizable chemical groups are capable of altering hydrophobic volumes along with extending or collapsing polymer chains. [29] Molecular chirality, including L-amino acid-based polymers of poly(N-acryloyl-valine) (PAV, Figure 1c), acts as a novel factor influencing the immune response of organisms against foreign objects via enantioselective interaction. [30] Changes of temperature or pH are not the only option for modulating surface properties.…”

Effect of different ligands on the controlled polymerization of monodisperse polystyrene nanospheres by atom transfer radical polymerization in an aqueous emulsion

“…Control over the polymer molecular weight and its distribution during polymerization has long been a challenge in polymer material research, especially in the applications for medicine release material and as biotechnology materials [3,4]. The advent of atom transfer radical polymerization (ATRP) provides a new way to synthesize polymers with controlled molecular weight [5][6][7]. Numerous well-defined (co)polymers with the desired molecular weight and low polydispersity index (PDI <1.5) [8,9], (co)polymers with complex architectures [10][11][12][13], functional polymers and hybrid materials have been prepared by the ATRP technique [14][15][16].…”