Degree

Doctor of Philosophy (PhD)

Department

Chemistry

Document Type

Dissertation

Abstract

Polymer- and membrane-based nanoparticles are widely used in applications ranging from medicine to materials science. Among these systems, short-chain diblock copolymer vesicles occupy an intermediate regime between biologically relevant lipid vesicles and long-chain polymersomes. Their membrane thickness and properties approach those of lipid membranes while retaining the synthetic tunability of polymer-based systems. Exploiting this regime requires understanding how the structure and dynamics of these vesicles respond to external influences and to changes in molecular architecture.

To provide context for the characterization of the short-chain diblock copolymer vesicle, the influence of perturbations on a thin membrane is considered. Such perturbations may arise during sample preparation, from interactions between vesicles, or from molecules incorporated into the membrane. The development of and application of an automatic extruder revealed pressure applied during extrusion most directly determines vesicle size. The influence of colloidal interactions was found to exert little impact on osmotic pressure-related structural behavior. Finally, a light-driven molecular motor was incorporated into a thin-membrane polymer vesicle its rotational frequency within the membrane without affecting vesicle structure.

Next, the influence of molecular architecture on short-chain diblock copolymer vesicles was investigated. In these vesicles, changes in molecular weight may affect structure and dynamics while they do not in high-molecular-weight systems. Small-angle neutron scattering, neutron spin echo spectroscopy, and quasielastic neutron scattering were used to characterize vesicles formed from two block copolymers with different hydrophobic block lengths across multiple time- and length scales. The membranes were found to possess thicknesses and bending rigidities slightly larger than those of lipid vesicles, while the polymer dynamics were consistent with melt-like polymeric behavior.

Finally, an excursus examines solid nanoparticles prepared from high molecular weight cyclic poly(3-hydroxybutyrate). This comparison highlights the distinct structural and dynamical behavior arising from the absence of a membrane interface.

Together, these studies investigate how membrane- and polymer-based nanoparticles respond to applied perturbations and molecular architecture. The results situate short-chain diblock copolymer vesicles as versatile, tunable platforms whose membrane properties approach those of biologically relevant lipid systems while they retain the synthetic tunability of polymeric systems.

Date

8-12-2026

Committee Chair

Gerald J. Schneider

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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