Influence of polymerizable surfactants on the adhesion performance and water resistance of water-based acrylic pressure-sensitive adhesives (PSAs)

Abstract

The behavior of different polymerizable surfactants was investigated to improve the water-resistance of pressure-sensitive adhesives (PSAs) based on acrylic acid (AA) and n-butyl acrylate (n-BA). Differences in the adhesion properties were found according to the chemical structure and the critical micelle concentration of the polymerizable surfactant, especially when compared to the nonpolymerizable reference surfactant (Dowfax 2A1). The polymerizable surfactants with a branched structure resulted in more gel content and higher glass transition temperature in the adhesive. In general, the peel resistance and tack properties decreased with the use of polymerizable surfactants in the PSA formula. However, increased shear resistance was observed with respect to the PSA adhesive synthesized with the reference surfactant. Furthermore, the adhesives made with higher molecular weight polymerizable surfactants resulted in higher shear elastic modulus, shear strength, and deformation energy than the rest of the PSA adhesives. On the other hand, as expected, all the polymerizable surfactants studied contributed to the improved water resistance of the PSA compared to the reference PSA prepared with a conventional surfactant. The covalent bond formed between the polymer and the surfactant limited the migration of the surfactant towards the air-film interface thus reducing the formation of water entry pathways. The polymerizable surfactants with linear molecular structure showed the best water resistance performance.

The Effect of Macromonomer Surfactant Microstructure on Aqueous Polymer Dispersion and Derived Polymer Film Properties

“…The surfactants used in emulsion polymerization not only control the colloidal stability of the particles in the polymer dispersion (i.e., the latex) but their composition and microstructure (block copolymers, branched copolymers, polymer brushes) can also have a large influence on the physical properties of the latex and the final polymer film (or coating). ,− In general, most used surfactants are not covalently bound to the colloidal particles and can diffuse from the particles into the environment or from the bulk to the film surface (and potentially desorb). This is especially undesirable in the case of biomedical applications, but also more generally, this may negatively affect the polymer film properties, such as adhesion, surface polarity, smoothness, and gloss. − To prevent desorption of surfactants from the particle surfaces or migration from the bulk polymer film (and potential leaching into the environment), reactive surfactants, which are chemically bound to the polymer particles, can be used, − and those containing propenyl end-groups are promising candidates. − Methacrylic oligomers containing these end-groups (see Scheme ) are readily prepared via catalytic chain transfer polymerization (CCTP), − and their application in emulsion polymerization has been described previously. ,,− Amphiphilic block macromonomers can be obtained by chain extension via sulfur-free reversible addition–fragmentation chain transfer ,− or used directly in an emulsion polymerization to form in situ amphiphilic copolymers, in a mechanism similar to what is commonly known as polymerization-induced self-assembly. ,− In an earlier work, we synthesized macromonomers via CCTP, which were successfully used as reactive surfactants in an emulsion polymerization. − These macromonomers were composed of methacrylic acid (MAA) and methyl methacrylate (MMA), butyl methacrylate (BMA), lauryl methacrylate (LMA), or butyl acrylate (BA) and used in the emulsion polymerization of methyl methacrylate and/or butyl ac...…”