Effect of HPAM hydrolysis degree on catanionic mixtures of DTAB/HPAM: A coarse-grained molecular dynamic simulation

• Published in: Computational materials science 2018-10, Vol.153, p.134-140
• Main Authors: Hu, Songqing, Zhu, Qianqian, Wang, Pei, Wang, Hongbing, Li, Chunling, Sun, Shuangqing
• Format: Article
• Language: English
• Subjects: Molecular dynamics simulation; Polyacrylamide; Self-assembly; Surfactant-polymer mixtures
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2018.06.016

[Display omitted] •The self-assembly of DTAB and HPAM was investigated by CG MD simulation.•Sphere-to-rod transition of aggregate was obtained as DTAB concentration increased.•Increasing the HPAM hydrolysis degree promoted the morphological transition.•Promoting transition was due to electrostatic attraction and flexibility of HPAM. Self-assembly of polymer and surfactant mixtures has attracted great interests because of its potential applications, ranging from tertiary oil recovery to drug delivery. However, the mechanism by which the hydrolysis degree of polymers promotes morphology transition is still experimentally challenging. In this study, self-assembly of the cationic surfactant dodecyltrimethylammonium bromide (DTAB) and anionic polyelectrolyte partially hydrolyzed polyacrylamide (HPAM) mixture was investigated by coarse-grained molecular dynamics (CG MD) simulation. In the polymer-surfactant mixtures, a sphere-to-rod transition of aggregates was obtained with the increasing concentration of DTAB. The increase of HPAM hydrolysis degree can promote the morphological transition from spherical into rod-like aggregates. Our simulation revealed that the flexibility of HPAM chain and the electrostatic attraction between DTAB headgroups (N(CH3)3+) and HPAM carboxylate ions (COO−) exerted a crucial role in promoting the morphological transition of aggregates. These simulation results brought to light the molecular-level information of sphere-to-rod transitions in polymer-surfactant aggregates. This work is expected to trigger further studies on morphology transition of polymer-surfactant mixtures.