# Synthesis and Mechanistic Study of a Copolymer Demulsifier for Dehydration of Water‐in‐Oil Emulsion of Crude Oil

## TL;DR

A new polymer is developed to efficiently separate water from crude oil emulsions, even in salty conditions.

## Contribution

A novel polymeric demulsifier with salt tolerance and a dual mechanism for demulsification is synthesized and characterized.

## Key findings

- The optimal copolymer composition is AM:EHMA:VBS:VP = 1:4:4:1, synthesized at 60 °C for 8 h.
- The demulsifier performs best at 80 °C with 300 mg L−1 concentration and remains effective in high salt environments.
- Mechanistic studies show the demulsifier reduces interfacial film strength and droplet surface charge density.

## Abstract

This study presents the synthesis and characterization of a novel polymeric demulsifier, P(AM‐EHMA‐VBS‐VP), through emulsion polymerization for efficient separation of water‐in‐crude oil emulsions. The synthesis parameters are systematically optimized using orthogonal array design complemented by single‐factor experiments. The demulsification performance is evaluated under simulated field conditions, with particular emphasis on dosage optimization and temperature effects. Comprehensive mechanistic investigations are conducted through dynamic interfacial tension measurements, interfacial dilational rheology analysis, and zeta potential characterization to elucidate the demulsification mechanism and the impact of inorganic salts on demulsification efficiency. The optimized synthesis conditions yield a copolymer with monomer mass ratios of AM:EHMA:VBS:VP = 1:4:4:1, achieved at 60 °C for 8 h with 30% monomer concentration and 0.15% initiator dosage. Optimal demulsification performance is observed at 80 °C with a demulsifier concentration of 300 mg L−1. The synthesized demulsifier demonstrates remarkable salt tolerance, maintaining effectiveness in environments containing up to 30 000 mg L−1 NaCl and 10 000 mg L−1 CaCl2. Mechanistic studies reveal that the demulsifier operates through interfacial adsorption, which simultaneously reduces the mechanical strength of the interfacial film and decreases the surface charge density of emulsion droplets. This dual mechanism effectively compromises the emulsion stability by diminishing both the film's resistance to deformation and the electrostatic repulsion between droplets.

P(AM‐EHMA‐VBS‐VP), a novel polymeric demulsifier, adsorbs at the interface, reduces interfacial modulus, overcomes asphaltene‐inhibited coalescence, and promotes droplet coalescence for effective demulsification.© 2025 WILEY‐VCH GmbH