# Hydrophobic Modification of Polyacrylamides with Oligo(Lactide): A Comparative Study in Two Solvent Systems

## TL;DR

This study compares how two solvent systems affect the properties of hydrophobically modified polyacrylamides, which are useful in oil recovery.

## Contribution

A comparative analysis of hydrophobic modification of polyacrylamides in two solvent systems using oligo(lactide) macromonomers.

## Key findings

- Copolymers in tetrahydrofuran/water showed higher incorporation efficiency but lower molar mass.
- Methanol/water copolymers exhibited better rheological performance with higher dynamic viscosities.
- Hydrophobic interactions were found to be the main factor in viscosity enhancement.

## Abstract

The control and modification of polyacrylamide viscosity
through
the incorporation of hydrophobic monomers have gained considerable
attention due to their cost-effectiveness and potential use in enhanced
oil recovery. Hydrophobically modified polyacrylamide copolymers containing
oligo­(lactide) macromonomers were synthesized by free radical polymerization
in two solvent mixtures: methanol/water and tetrahydrofuran/water.
A macromonomer with five repeating units was incorporated at 2, 5,
and 10 mol %, as determined by proton nuclear magnetic resonance.
Copolymers obtained in tetrahydrofuran/water showed higher incorporation
efficiency but lower molar mass than those synthesized in methanol/water,
according to size-exclusion chromatography. The latter presented better
rheological performance, with higher dynamic viscosities in aqueous
solution. Although molar mass affected the results, hydrophobic interactions
proved to be the main factor in viscosity enhancement, as homopolymers
displayed inferior behavior.