Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Chemistry and Biochemistry

Thesis Sponsor/Dissertation Chair/Project Chair

Jaclyn Catalano

Committee Member

Nina Goodey

Committee Member

Glen O'Neil

Abstract

Oil-based paints composed of drying oils and lead-containing pigments undergo complex chemical transformations during curing that influence long-term stability and degradation. Despite centuries of use, the molecular mechanisms governing oxidative polymerization and additive incorporation in lead white oil paint systems remain incompletely understood. This study investigates the role of methyl linoleate, a monoester analog of linoleic acid, in the curing and degradation pathways of lead carbonate and linseed oil paint films. A deep focus was placed on determining whether methyl linoleate becomes chemically integrated into the developing polymeric network or remains as an extractable and unbound component, as this distinction directly informs how additive-like molecules influence network formation, long-term stability, and degradation behavior in oil-based paint systems. Paint films were prepared using basic lead carbonate pigment combined with either raw or boiled linseed oil and varying proportions of methyl linoleate (0-50% of total binder mass). Samples were then placed in a 40°C oven to simulate accelerated aging. Chemical changes were monitored using Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (¹H NMR), and gas chromatography--mas spectrometry (GC-MS). Solvent extraction experiments using dichloromethane (DCM) and dimethyl sulfoxide (DMSO) were conducted to assess component extractability and matrix integrity. FTIR analysis revealed time-dependent shifts in carbonyl stretching bands and reductions in alkene-associated absorptions are indicative of oxidative crosslinking and ester transformation. Difference in curing behavior between raw and boiled linseed oil systems was observed, with boiled oil films exhibiting slightly greater yellowing, wrinkling, and structural fragility. Solvent extraction with DCM resulted in significant matrix degradation, particularly in boiled oil samples, suggesting differences in crosslink density and polymer stability. Proton NMR and GC-MS analysis of extracts provided insight into the presence or loss of methyl linoleate after curing. These findings contribute to a closer understanding of additive and binder interactions in lead white oil paint systems and clarify how ester-modified components influence oxidative polymerization and solvent susceptibility. These findings provide insight into how small unsaturated additives participate in oxidative polymerization and influence matrix integrity, with direct implications for predicting solvent sensitivity, degradation pathways, and lead soap formation in historical oil paintings, as well as informing conservation strategies and the design of modern oil-based coatings.

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