# Step-by-Step Analysis of a Copper-Mediated Surface-Initiated Atom-Transfer Radical Polymerization Process for Polyacrylamide Brush Synthesis Through Infrared Spectroscopy and Contact Angle Measurements

## TL;DR

This study improves the reproducibility of making polymer brushes by analyzing each step of a copper-mediated polymerization process using spectroscopy and contact angle measurements.

## Contribution

A systematic step-by-step analysis of Cu0-SI-ATRP for PAM-PB synthesis with simplified steps and reduced variability.

## Key findings

- Ultrasonication improved siloxane and amine group availability with lower APTES concentration.
- BiBB anchoring was insensitive to concentration but benefited from premixing.
- Method A produced more consistent PAM-PBs with reduced variability compared to Method B.

## Abstract

Polymer brushes (PBs) are transformative surface-modifying nanostructures, yet their synthesis via controlled methods like copper-mediated surface-initiated atom-transfer radical polymerization (Cu0-SI-ATRP) faces reproducibility challenges due to a lack of understanding of parameter interdependencies. This study systematically evaluates the Cu0-SI-ATRP process for polyacrylamide brushes (PAM-PBs), aiming to clarify key parameters that influence the synthesis process. This evaluation followed a step-by-step characterization that tracked molecular changes through infrared spectroscopy (IR) and surface development by contact angle (CA) through two different mixing methods: ultrasonic mixing and process simplification (Method A) and following literature-based parameters (Method B). Both methods, consisting of surface activation, 3-aminopropyltriethoxysilane (APTES) deposition, bromoisobutyryl bromide (BiBB) anchoring, and polymerization, were analyzed by varying parameters like concentration, temperature, and time. Results showed ultrasonication during surface activation enhanced siloxane (1139→1115 cm−1) and amine (1531 cm−1) group availability while reducing APTES concentration to 1 Vol% without drying sufficed for BiBB anchoring. BiBB exhibited insensitivity to concentration but benefited from premixing, evidenced by sharp C–Br (~1170 cm−1) and methyl (3000–2800 cm−1) bands. Additionally, it was observed that PAM-PBs improved with Method A, which had reduced variance in polymer fingerprint regions compared to Method B. Adding to the above, CA measurements gave complementary step-by-step information along the modifications of the surface, revealing distinct wettability behaviors between bulk PAM and synthesized PAM-PBs (from 51° to 37°). As such, this work identifies key parameter influence (e.g., mixing, BiBB concentration), simplifies steps (drying omission, lower APTES concentration), and demonstrates a step-by-step, systematic parameter decoupling that reduces variability. In essence, this detailed parameter analysis addresses the PAM-PBs synthesis process with better reproducibility than the previously reported synthesis method and achieves the identification of characteristic behaviors across the step-by-step process without the imperative need for higher-cost characterizations.