Preparation of giant vesicles supporting hindered amine on their shells through photo living radical polymerization-induced self-assembly

Abstract

Microsized giant vesicles supporting a hindered amine on their shells were obtained by the photopolymerization-induced self-assembly of amphiphilic diblock copolymers using the photo nitroxide mediated living radical polymerization (photo NMP) technique. The diblock copolymer consisting of hydrophilic poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate) (PTPMA) and hydrophobic poly(methyl methacrylate-random-2,2,6,6-tetramethyl-4-piperidyl methacrylate), P(MMA-r-TPMA) produced various morphologies depending on the stirring speed during the photo NMP-induced self-assembly, block lengths of the copolymer, and hydrophobicity of the P(MMA-r-TPMA) block chain. A 300-rpm stirring speed during the polymerization provided worm-like vesicles with a long axis of over 100 μm along with small spherical vesicles with a 3-μm diameter. As the stirring speed increased to 600 rpm, the worm-like vesicles changed into spherical vesicles. A further increase in the stirring speed to 900 rpm produced much smaller spherical vesicles. The extension of the block chains also reduced the size of the vesicles. An increase in the hydrophobicity of the hydrophobic block chain varied the morphology of the vesicles. While PTPMA-b-P(MMA-r-TPMA) provided spherical vesicles, PTPMA-b-P(n-propyl methacrylate (PrMA)-r-TPMA) produced deformed vesicles accompanied by a size increase. On the other hand, PTPMA-b-P(n-butyl methacrylate (BuMA)-r-TPMA) produced much smaller vesicles. Furthermore, PTPMA-b-P(MMA-r-BuMA-r-TPMA) (MMA/BuMA = 0.487/0.513) provided a morphology similar to that formed by PTPMA-b-P(PrMA-r-TPMA) due to the negligible difference in the hydrophobic energy between Pr and Me_0.487/Bu_0.513. These observations indicated that the morphology of the vesicles was controlled by manipulating the hydrophobic energy of the hydrophobic block chain.

Graphical Abstract

Keywords:

• 2,2,6,6-tetramethyl-4-piperidyl methacrylate (TPMA)
• photo NMP-induced self-assembly
• amphiphilic diblock copolymers
• giant vesicles
• hydrophobic energy

Additional information

Funding

This work was supported by the JSPS Grant-in-Aid for Scientific Research (Grant Number 18K04863).