In this work, we use constant load indentation and cantilever peel of polymer films to measure relaxation events due to the chemical modification of a buried interface. Hydroxypropyl cellulose films on four different chemical interfaces were produced, and the viscoelastic compliance and fracture strength of each interface was measured. Polymer compliance of films having strong interfacial interactions with the substrate, as measured by cantilever peel, exhibited equivalent compliance to bulk measurements when modeled as a thin film with a perfectly bonded interface. On weaker interfaces, larger contact areas led to this model calculating significantly higher compliances than expected, which we attribute to debonding events at the interface. These additional relaxations at the buried interface were strongly dependent on the extent the substrate surface moieties could hydrogen bond with the hydroxyl groups present on the polymer chain. These deviations caused by debonding events accumulated over time, with a predicted compliance up to 250 percent greater than expected if the interface was perfectly bonded. By modifying the polymer-substrate interface, the strength and durability of different chemical interactions at the interface can be studied and used to design robust interfacial interactions for improved performance.
Pub Type: Journals
adhesion, creep, hydrogen bonding, polymer, coatings, films, durability