Two-Layer Structure of Microcapsule Membrane as Predicted from Electrophoretic Studies.

Area of Science:

• Polymer Chemistry
• Materials Science
• Colloid Science

Background:

• Hydrophilic gel microcapsules are crucial for various applications.
• Understanding membrane composition is key to controlling microcapsule properties.

Purpose of the Study:

• To synthesize and characterize four types of hydrophilic gel microcapsules with distinct membrane compositions.
• To investigate the effect of membrane composition and PEGylation on microcapsule surface properties and swellability.

Main Methods:

• Interfacial polymerization using N,N-dimethylacrylamide (DMAAm), 4-aminomethylstyrene (AmSt), and N,N-dimethylaminopropylacrylamide (DMAPAA) based copolymers.
• Synthesis of PEGylated copolymers via copolymerization with alpha-acryloxy-omega-methoxy-poly(ethylene glycol) (a-PEG).
• Electrophoretic mobility measurements to analyze microcapsule membrane structure and charge distribution.

Main Results:

• Microcapsule membranes exhibit a two-sublayer structure with differing charge densities and softness.
• The outer sublayer is negatively charged, and the inner sublayer is positively charged.
• PEGylation reduced outer sublayer charge density and increased surface layer softness, without affecting the inner sublayer.
• Asymmetrical membrane structure leads to non-uniform charge distribution, influencing swellability with medium permittivity.

Conclusions:

• The study successfully prepared and characterized novel hydrophilic gel microcapsules.
• Membrane composition, particularly PEGylation, significantly alters surface properties and swellability.
• The asymmetrical charge distribution in microcapsule membranes is a critical factor in their swelling behavior.