Adhesion of Two Physically Contacting Planar Substrates Coated with Layer-by-Layer Assembled Films

Abstract

Adhesives composed of synthetic and low-cost molecules that are based on simple chemical principles are attractive because of their versatility. In this article, we report adhesion between two planar substrates coated with layer-by-layer (LbL) assembled films of cationic poly(diallyldimethylammonium chloride) (PDDA) and anionic poly(sodium styrenesulfonate) (PSS) and perform lap shear measurements of the adhered substrates. Films prepared on the substrates functioned as adhesives when one substrate coated with the PDDA-surface film contacted the other surface coated with the PSS-surface film under adequate pressure in the presence of water droplets, suggesting that two films adhered on the basis of polyion complex formation. Observations suggested that the adhesives failed at the substrate-film interface rather than at the bulk films. The adhesion was compared between film-coated substrates and noncoated ones. Confocal laser scanning microscopic observation of adhesives composed of fluorescently labeled poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) revealed that the labeled PAH assembled on one substrate was well dispersed, even in a nonlabeled film assembled on another substrate. It was therefore confirmed that after adhesion in the presence of the water component, the polyelectrolytes became intermixed between the glassy films, resulting in changes in the adhesive structure at the substrate-film interface.

Macroscopic Supramolecular Assembly through Electrostatic Interactions Based on a Flexible Spacing Coating

“…As summarized in Figure 3b, the interactive force can further increase by almost fivefold with the increased interaction time to 10 min, during which the growing rate of the forces gradually slows down. This result indicates the time-consuming reconfiguration process of the polyelectrolytes in the MSA process and also corresponds well with the results of most reports [19,20,25,26] that long time pressing of rigid substrates such as silicon wafers can achieve adhesion.…”

“…The challenge mainly lies in the limited motility of the surface moieties even though long‐ranged forces; for example, electrostatic interaction is applied as the driving force. Serizawa and co‐workers reported that to achieve the assembly of 2 mm scaled silicon wafers modified with oppositely charged polyelectrolytes, extra human intervention of mechanical compressing for as long as 60 min was required for the realization of electrostatic interaction …”

“…Serizawa and co-workers reported that to achieve the assembly of 2 mm scaled silicon wafers modified with oppositely charged polyelectrolytes, extra human intervention of mechanical compressing for as long as 60 min was required for the realization of electrostatic interaction. [19] According to our previous report, [2] we have proposed a concept of flexible spacing coating to compensate the rigidity of the substrates. Herein, we applied this concept and introduced a composite multilayer onto rigid materials before introducing interactive moieties and demonstrated electrostatic-interactiondriven MSA of millimeter-scaled rigid building blocks of polydimethylsiloxane (PDMS).…”

Water‐Enabled Self‐Healing of Polyelectrolyte Multilayer Coatings

“…In this way, the damage to the (bPEI10.5/PAA3)*30 coating is repaired. A previous study showed that two substrates coated with PEM films adhere strongly in the presence of water; this demonstrates the strong tendency of polyelectrolytes to interdiffuse at the contacted interface 15. In contrast, the (bPEI6.5/PAA3)*300 coating, with a higher ionic cross‐linking density, is slightly swollen by water, and cannot flow long distances to repair damage.…”

Novel method to measure the shear strength of exfoliated montmorillonite/polymer nanocomposite films

“…The shear strength of polymer nanocomposite films is usually measured by the lap shear test method because it is simple for testing 17–22. However, their failure is often a combination of interfacial and cohesive failures 23.…”