Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering (MSBME)

Degree Level

Graduate

Department

Biomedical Engineering

Advisor/Mentor

Qian, Xianghong

Committee Member

Wickramasinghe, S. Ranil

Second Committee Member

Wolchok, Jeffrey C.

Third Committee Member

Millett, Paul C.

Keywords

Dissipative Particle Dynamics (DPD); membrane filtration; N-methyl-2-pyrrolidone (NMP); polyethersulfone (PES); polymer science; simulation

Abstract

Dissipative particle dynamics (DPD), a coarse grain simulation method, was applied to the membrane formation process of non-solvent induced phase separation (NIPS) to gain further insight on the mechanism of certain variables and how they affect the final morphology. NIPS involves two solutions, an organic polymer dissolved in an organic solvent colloquially called the dope and an aqueous coagulation bath, brought into contact with one another. The solvents then mix, causing the polymer to fall out of solution as an asymmetric membrane with a dense surface layer and a more open subsurface layer in response to the decreasing solubility. Polyethersulfone (PES), a common industrial choice we have previously studied, was utilized as the polymer with N-methyl-2-pyrrolidone (NMP) as the organic solvent and water as the coagulation bath. In this study, our previous model construction was altered in several ways. Firstly, the simulation area was enlarged, allowing for a better sampling of subsurface behavior. Secondly, polymer chain length was increased to bring it more in line with the high molecular weight of industrially common polymers, with our experimental systems ranging from 100 to 200 monomers. Lastly, polyvinylpyrrolidone (PVP) was introduced as an additive to the polymer solution in concentrations varying from 1 to 10% by volume of the dope. PVP is a common polymer additive utilized in industry to produce larger pores, a result that was successfully replicated. We also investigated the effects of adding solvent to the coagulation bath as well as the effects of adding water to the polymer solution.

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