Temperature- and Region-Resolved Diffusion Coefficient of Oxygen in PVA-co-PE Copolymer Study using Molecular Probes

Open Access
- Author:
- Fortuna, Ethan
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Bratoljub Milosavljevic, Thesis Supervisor
Ali Borhan, Thesis Honors Advisor - Keywords:
- PVA-co-PE
Copolymer
Diffusion
DSC
Luminescent Probe
Molecular Probe - Abstract:
- Polyethylene is currently a common packaging polymer; however, it has a high diffusion coefficient with oxygen. Lowering the oxygen diffusion coefficient by making a PVA-co-PE copolymer results in an inexpensive, oxygen-impermeable packaging material. The objective of this report is to determine the diffusion coefficient of oxygen in PVA-co-PE copolymer systems as a function of region composition and temperature. To distinguish the oxygen diffusivity in the PE and PVA domains within the copolymer, three molecular probes are used. For the (polar) PVA domains, Ru(bpy)32+ and Methyl Viologen (MV) are used while pyrene is used to study the (non-polar) PE domains. Molecular probe measurements are studied as a function of temperature; the results obtained are analyzed and contextualized using a differential scanning calorimetry (DSC) technique. Pyrene fluorescence quenching by O2 in PVA-co-PE is quantified via a nanosecond laser photolysis setup. The non-polar nature of pyrene allows the independent quantification of non-polar domains. An oxygen diffusion rate is determined from the quenching rate, which is proportional to the oxygen concentration that has reached the sample. Then, the experiment is repeated at various temperatures. Additionally, the experiment is repeated with Ru(bpy)32+ as the fluorophore to obtain the measurement in solely the polar domains. This will allow us to distinguish the diffusion coefficients between regions. Due to the low diffusion coefficient of O2 in PVA domains, MV is used as a molecular probe to determine the diffusion coefficient for the PVA regions, since the absorption spectrum is used to determine the oxygen concentration and, subsequently, the diffusion coefficient of O2 in the PVA domain.