Reversibly pH-Responsive Nanoporous Layer-by-Layer Microtubes

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Chemistry

Background:

• Layer-by-layer (LbL) assembly is a versatile technique for fabricating multilayered materials.
• Microtubes offer unique structural properties for various applications.
• Controlling nanoporosity is crucial for material functionality.

Purpose of the Study:

• To develop nanoporous layer-by-layer (LbL) microtubes using PAH and PAA.
• To investigate the influence of pH, treatment time, and layer number on nanopore formation.
• To characterize the resulting asymmetric porous structure.

Main Methods:

• LbL deposition of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) within porous templates.
• Postassembly acid treatment to induce nanopore formation.
• Systematic variation of solution pH, treatment duration, and number of deposited layers.

Main Results:

• Nanoporous structure formation was optimized at pH 1.8.
• A complete nanoporous transition was achieved in just 5 minutes.
• The pore formation process was found to be reversible.
• An asymmetric porous structure was observed, with a rough inner surface and a smoother outer surface with isolated pores.

Conclusions:

• PAH/PAA LbL microtubes can be controllably fabricated with a tunable nanoporous structure.
• Acid treatment is an effective method for generating nanoporosity in LbL assemblies.
• The asymmetric nature of the porous structure offers potential for directional transport or filtration applications.