Molecular dynamics simulation for salinity resistance prediction of cationic terpolymers at high temperature

Abstract

Based on the prediction by molecular dynamics simulation of the behaviour of polymers in brine with monovalent and bivalent metal ions at ${160}^{\circ }$C, ionic terpolymers featuring acrylamide, vinyl pyrrolidone and an ionic part in their structure were synthesized and evaluated. From molecular simulation, and introducing a novel relative compaction index of polymers, the affinity of terpolymers to a highly concentrated brine is determined. For an equivalent number of repetitive monomeric units (20), terpolymers with cationic effective charge, $\mathrm{P}({\mathrm{AM}}_{14}\text{-}{\mathrm{VP}}_4\text{-}{\mathrm{VEtIm}}_2^{+})$ and $\mathrm{P}({\mathrm{AM}}_{12}\text{-}{\mathrm{VP}}_4\text{-}{\mathrm{VEtIm}}_4^{+})$, presented a relative compaction index, $p_r=1.34$ and 1.33 respectively, while a tetrapolymer with negative effective charge, $\mathrm{P}({\mathrm{AM}}_7\text{-}{\mathrm{AA}}_7^{-}\text{-}{\mathrm{VP}}_4\text{-}{\mathrm{VBtMA}}_2^{+})$, displayed the highest value of $p_r=1.41$. The highest value is similar to the value of $p_r=1.72$ shown by anionic terpolymer, $\mathrm{P}({\mathrm{AM}}_8\text{-}{\mathrm{VP}}_6\text{-}{\mathrm{AMPS}}_6^{-})$, which is commercially available. The radial distribution function of salt ions around the polymers is related to the polymer resistance to salt. This property was correlated with experimental evidences, and let to conclude why the $\mathrm{AMPS}$-type commercial terpolymer Superpusher SAV 225, with a negative charge, lost its viscosity by 57% in 7 days while one of the synthesized cationic terpolymers decreased its viscosity by 40% after 28 days of brine exposure at ${160}^{\circ }$C.

GRAPHICAL ABSTRACT

Keywords:

• Terpolymer
• ionic liquid
• acrylamide
• brine
• molecular dynamics simulation

Acknowledgments

Thanks are also due to Dr. Alejandro Ortega-Rodríguez and M. Eng. Norma A. García-Muñoz for their precious help.

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

Natalya Victorovna Likhanova http://orcid.org/0000-0003-4152-0953

Diego Guzmán-Lucero http://orcid.org/0000-0001-8113-7364

Jorge Froylan Palomeque-Santiago http://orcid.org/0000-0003-3857-589X

Felipe de Jesús Guevara-Rodríguez http://orcid.org/0000-0001-7162-1937

Additional information

Funding

The authors acknowledge the Instituto Mexicano del Petróleo (IMP) for the support provided through the grant D.61072.