Reversible pH Stimulus-Response Material Based on Amphiphilic Block Polymer Self-Assembly and Its Electrochemical Application

Abstract

Stimulus-responsive microporous solid thin films were successfully fabricated by simple molecular self-assembly via an amphiphilic block polymer, polystryene–b–polyacrylic acid (PS–b–PAA). The solid thin films exhibit different surface morphologies in response to external stimuli, such as environments with different pH values in aqueous solutions. The experiments have successfully applied atomic force microscope (AFM) technology to observe in-situ surface morphological changes. There is a reversible evolution of the microstructures in buffer solutions over a pH range of 2.4–9.2. These observations have been explained by positing that there is no conventional PAA swelling but that the PAA chains in the micropores stretch and contract with changes in the pH of the solution environment. The hydrophobicity of the solid thin film surface was transformed into super-hydrophilicity, as captured by optical contact angle measurements. The stimulus-responsive dynamics of pore sizes was described by a two-stage mechanism. A promising electrochemical application of this film is suggested via combination with an electrochemical impedance technique. This study is aimed at strategies for the functionalization of stimulus-responsive microporous solid thin films with reversible tunable surface morphologies, and exploring new smart materials with switch-on/switch-off behavior.

Synthesis and Characterization of pH and Thermo Dual-Responsive Hydrogels with a Semi-IPN Structure Based on N-Isopropylacrylamide and Itaconamic Acid

“…It can be molded into any form, shape, or size for many potential applications in many fields. In recent times, smart hydrogel has been studied extensively due to its phase transitions in response to external stimulus, including temperature, pH, ionic strength, light, pressure, redox, and electric field [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. The typical smart hydrogel is thermal-responsive hydrogel, which has phase transitions in response to temperature changes, and poly( N -isopropylacrylamide) (pNIPAM) is the most widely investigated.…”

Synthesis and Drug Delivery Application of Thermo- and pH-Sensitive Hydrogels: Poly(β-CD-co-N-Isopropylacrylamide-co-IAM)

“…A smart material is responsive to a physical or chemical act, such as light, heat, electric force, magnetic force, acid–base and so forth [ 1 , 2 , 3 ] and has the potential in biomedical applications such as drug release [ 4 , 5 , 6 , 7 , 8 , 9 ]. The drug release mechanism [ 10 , 11 ] usually includes chemical-responsive (for example glucose or antigen responsive [ 12 ]), light-responsive [ 13 , 14 ], electric-responsive [ 15 ], magnetic responsive [ 8 , 9 ], temperature-responsive or pH-responsive systems.…”

Design of Switchable Enzyme Carriers Based on Stimuli-Responsive Porous Polymer Membranes for Bioapplications

“…Physical stimuli possess several intrinsic advantages over chemical stimili: noncontact, tunable strength, and temporal and spatial resolution, the SR-PPMs undergo either a reversible or irreversible modification because of bonding, hydrophobic, or hydrophilic interactions, leading to changes in structure or self-assembly at large-length scales. Ideal SR-PPMs can be fabricated via functionalization of the film surface or pores wall (Figure ) and LBL-assembling methods to improve the surface hydrophilicity and to tune the surface charge, which is beneficial for enzyme immobilization. − …”