Stretchable and recoverable acrylate-based pressure sensitive adhesives with high adhesion performance, optical clarity, and metal corrosion resistance

Abstract

In the era of the Internet of Things, digital displays play a critical role in human-machine interfaces. In particular, displays applied to contemporary devices such as flexible smart watches and foldable/rollable electronics underline the need for pertinent materials and device technologies to fulfill their designed functions. However, despite the technical advancements of electronic components such as stretchable/flexible electrodes and flexible backplanes, their proper assembly remains a challenge. Herein, we report the compositional effect of acrylic acid (AA) on the physical properties of as-synthesized pressure sensitive adhesives (PSAs), especially on their adhesion performance in terms of wettability and peel adhesion. Accordingly, an empirical criterion for intimate wetting is proposed based on the storage modulus of the PSAs. In this study, the PSA with the best adhesion performance was evaluated for its viscoelastic properties and suitability for specific applications. The results demonstrated the strain-dependent conformational recovery of the adhesive; the implementation of the prestrain strategy enables rapid strain reversibility at 25% of the total strain. Furthermore, the AA-incorporated PSAs exhibited remarkable metal corrosion resistance as well as high optical clarity. Thus, this fundamental study of stretchable PSAs can provide useful guidance for the development of advanced PSAs that can be used in a wide range of applications involving display devices.

Entanglement density, macromolecular orientation, and their effect on elastic strain recovery of polyolefin films

“…For amorphous polymers, entropic restoring forces are generated by the progressive macromolecular chain orientation in the stretching direction leading to an entropy decrease in the system. [8][9][10] Thus, limiting the entropy change by chain orientation in the future stretching direction induced during the process is one way to tune the elastic recovery. Orientation and bi-orientation have been performed on a biaxial stretcher (see stretching mode, thickness, and achieved draw ratio in Tables 9-11).…”

“…Less stress relaxation leads to higher elasticity. 9 Increasing the Me favors stress relaxation by increasing the friction phenomena between the chains during stretching.…”

“…Amorphous chains are gradually oriented in the stretching direction, and this macromolecular orientation generates entropic restoring forces. [8][9][10] This force increases as long as the deformation goes until it reaches extensibility limit of the chains, which leads to chain breakage or disentanglements. Regarding crystalline phase, lamellae are gradually reoriented in the stretching direction until they are finally transformed into highly oriented fibrils, and this is called fibrillation phenomenon.…”

“…10 Restoring forces are directly linked to the change in entropy, which in turn depends on the molecular structure and chain length as expressed by thermodynamics of rubber elasticity. 9 The highest entropy state of a macromolecular chain is encountered in its coiled state, when the distance between chain ends is very small compared to the total chain length. 8 During the deformation process, the chain ends are gradually separated.…”

Highly Stretchable, Soft, and Clear Viscoelastic Film with Good Recoverability for Flexible Display

“…Acrylic PSAs have been widely used in display, electronics, and automobile industries due to their good optical properties, high weathering resistance, robust adhesion, and facile modification. − Additionally, acrylic polymers can be conveniently prepared by radical polymerization, which is commonly practiced in industry . Acrylic CVF for flexible displays has been previously reported. ,− For example, Park et al . designed rigid-flexible nanoparticles composed of a rigid core and an elastic reactive coil shell, forming linkages with a matrix polymer chain and thereby improving recovery with high adhesion strength.…”