Development of acrylate-based elastic pressure sensitive adhesives via photopolymerization

Abstract

Since the development of the 5G network, wireless and user-oriented electronics are rapidly emerging. In response to demands for wearable devices and packaging of electronic devices, the connections between electronic elements are required to satisfy several specific functions like flexibility or thermal conductivity. However, commercial PSAs show poor flexibility with low adhesion performance, and none of them are designed to possess thermal conductivity for application in electronic devices. Therefore, developing advanced functional pressure sensitive adhesives is critical for the commercialization of electronics. Herein, UV curable acrylate-based PSAs are synthesized containing various acrylate monomers and inorganic fillers. In this study, acrylate-based PSAs are synthesized using 2-carboxyethyl acrylate (CEA) as a functional monomer. The synthesized PSAs exhibit strong peel adhesion with great flexibility and also show adequate transmittance to be used as an optically clear adhesive. The flexibility of synthesized PSAs is evaluated by the stress-relaxation, strain recovery, and repetitive cycle tests. In order to achieve elastic characteristics in the PSAs, a pre-straining strategy is introduced for rapid restoration, and the 10% pre-strained film exhibited instantaneous strain recovery. The pre-strained PSAs can withstand 100 cycles of repetitive bending and stretching test. Furthermore, to grant thermal conductivity in PSAs, hexagonal boron nitride (h-BN) is implemented in the PSAs composite. The peel adhesion of PSAs was measured with different inorganic filler contents. Physical properties and thermal conductivity were evaluated in detail. The PSAs containing h-BN reveal adequate thermal conductivity to utilize in electronic devices. Consequently, the acrylate-based PSAs are successfully synthesized via photopolymerization. The synthesized PSAs can provide elastic behavior for flexible electronics. The adhesive and physical properties of PSAs are improved by adding functional monomer (CEA) and inorganic filler (h-BN). Thus, the CEA-incorporated PSAs can be utilized in a wide range of industries, including assembly of stretchable displays/epidermal devices and temperature control of electronic.