# Synthesis and Self‐Assembly of Pore‐Forming Three‐Arm Amphiphilic Block Copolymers

## TL;DR

This paper describes the synthesis of a three-arm block copolymer that self-assembles into porous structures, useful for materials like absorbers and coatings.

## Contribution

A novel two-step synthesis of an amphiphilic three-arm block copolymer and its self-assembly into porous structures is presented.

## Key findings

- Porous structures are formed via self-assembly and SNIPS protocol.
- SEM and AFM reveal complex surface and swelling characteristics.
- PHEMA-rich copolymers show non-regular lamellar microphases confirmed by TEM and SAXS.

## Abstract

The synthesis of an amphiphilic three‐arm block copolymer (AB)3‐BCP, which consists of poly(methyl methacrylate) (PMMA) and poly(butyl methacrylate) (PBMA) in the hydrophobic inner block, is reported. The hydrophilic block segment is based on poly(2‐hydroxyethyl methacrylate) (PHEMA) originating from 2‐(trimethylsiloxyl)ethyl methacrylate (HEMA‐TMS). The preparation is carried out in two steps using a core‐first approach. Using atom transfer radical polymerization (ATRP) as a controlled polymerization technique, three (AB)3‐BPCs with HEMA contents of 15 to 38 mol−1 % are prepared, applying different reaction conditions. Porous structures are generated from these BCPs by applying a self‐assembly and nonsolvent‐induced phase separation (SNIPS) protocol. Complex surface structures are observed using scanning electron microscopy (SEM). Bulk morphologies are investigated for a better understanding of the underlying self‐assembly. For PHEMA‐rich (AB)3‐BCPs, non‐regular lamellar microphases are observed in transmission electron microscopy (TEM) and confirmed by small‐angle X‐ray scattering (SAXS). The porous structures and their expected swelling characteristics are analyzed using atomic force microscopy (AFM) in air and water. Time‐resolved measurements in water indicate a rapid swelling after immersion into the water bath. The present study paves the way for exciting porous materials based on the herein synthesized amphiphilic three‐arm block copolymers useful for applications as absorber materials and coatings.

A novel two‐step synthesis of an amphiphilic three‐arm block copolymer and self‐assembly and its tendency to pore formation is presented. Self‐assembly in the bulk state is investigated using TEM and SAXS. Pore formation following a SNIPS protocol is studied using SEM. The porous structures are further investigated via AFM in air and water.