A High-Adhesion Polymer Gel for Polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) is valued for its low dielectric constant and loss tangent but has low surface free energy (SFE), hindering adhesion to other materials. Our group developed a copolymer gel, poly(2-(diethylamino)ethyl methacrylate-co-dodecyl acrylate) (P(DEAE-co-DA)), with exceptional adhesion to PTFE. Gel sheets were synthesized via photo-radical bulk polymerization, alongside homopolymer gels poly(2-(diethylamino)ethyl methacrylate) (PDEAE) and poly(dodecyl acrylate) (PDA) for comparison. These were assessed using 90° peel tests, contact angle measurements, and oscillatory frequency sweep tests. The 90° peel tests revealed that P(DEAE-co-DA) exhibited 4–6 times higher peel strength than PDEAE and PDA. SFE was highest for PDEAE, followed by P(DEAE-co-DA), PTFE, and PDA. Theoretical adhesive work (Wa) to PTFE was 48.41 mJ/m² for PDEAE, 44.99 mJ/m² for P(DEAE-co-DA), and 36.51 mJ/m² for PDA, suggesting PDEAE’s superior adhesion. However, experimental peel tests showed P(DEAE-co-DA) had the highest peel strength. To explore this discrepancy, oscillatory frequency sweep tests measured storage modulus, loss modulus, Tanδ, relaxation time (τ), and activation energy (Ea). P(DEAE-co-DA) displayed higher Tanδ, shorter τ, and a significantly lower Ea (8.03 kJ/mol) compared to PDEAE (49.7 kJ/mol) and PDA (15.9 kJ/mol). This low Ea enhances chain mobility, enabling side chains to align with the PTFE surface, strengthening van der Waals interactions. The superior peel strength of P(DEAE-co-DA) primarily stems from enhanced viscoelastic energy dissipation, explaining its outstanding adhesion despite a lower theoretical Wa.