Designing Protective Film Adhesives with Low Peel Strength by Controlling Alkyl Side Chain Length in Polyacrylate Resins

A series of polyacrylate-based pressure-sensitive adhesives (PSAs) intended for application in protective films were synthesized using various alkyl acrylates with differing alkyl side-chain lengths to examine the influence of side-chain length on the structural and adhesive properties. The PSA synthesized from dodecyl acrylate (PSA-C12) demonstrated an optimal balance characterized by low 180° peel strength (<5 gf/25 mm) on glass and steel substrates, reduced initial tack, strong shear holding power, excellent resistance to hygrothermal aging, and excellent reusability. Notably, all PSA samples exhibited high optical transparency (>90% transmittance in the visible spectrum) and low haze (<3%), satisfying a critical requirement for screen protection applications. The markedly decreased peel strength observed in PSA-C12 sample, relative to PSAs derived from alkyl acrylates with shorter side chains, was mechanistically elucidated. The extended dodecyl side chains in PSA-C12 sample not only intrinsically reduced the bulk polarity but also preferentially migrated to the surface, effectively shielding the ester groups as corroborated by swelling tests, surface energy measurements, and X-ray photoelectron spectroscopy analysis. This phenomenon substantially diminished the peel strength by attenuating interfacial interactions with substrates. This study offers a definitive strategy for the design of removable protective film PSAs through the modulation of alkyl side-chain length in alkyl acrylates.