Improvement of Adhesive Properties Through the Segregation of Oligomers and an Investigation of the Mechanism Using SUSH
To design novel high-performance materials using chemical compounds, it is important to address the mesoscale region, up to an order of 106 in the length dimension, between the nanoscale region of molecular structures and the macroscale region in which ac
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Improvement of Adhesive Properties Through the Segregation of Oligomers and an Investigation of the Mechanism Using SUSHI Simulation Hiroshi Sasaki
22.1 Introduction To design novel high-performance materials using chemical compounds, it is important to address the mesoscale region, up to an order of 106 in the length dimension, between the nanoscale region of molecular structures and the macroscale region in which actual material properties are evaluated. From a coarse-grained point of view, a polymer chain can be described as a “very thin and long thread twisting together and rolled into a ball.” Indeed, this description aptly encompasses the distinctive features of a polymer chain. One such feature is “segregation,” which is the bleeding out of small molecules or oligomers, which is defined as low molecular weight (Mn < 10,000) polymer, from the polymer bulk and localization at the interface between the polymer layer and substrate. Segregation seems to be a low cost and effective way of improving the macroscale material performance through the formation of a mesoscale structure. In an adhesion application in which more than two different substrates are joined, it is well known that the interface makes a large contribution to the adhesive performance. By controlling the molecular weight and/or solubility of properly functionalized oligomers, one can concentrate them to an interface through segregation and possibly improve macroscale properties, such as adhesion. Recently developed personal information devices, such as smartphones and tablet personal computers, widely use touch panels. The touch panel component is assembled employing adhesives, including pressure-sensitive adhesives (PSAs), with superior optical properties; these adhesives are called optically clear adhesives (OCAs). The adhesive layer should join parts together firmly while maintaining
H. Sasaki () Toagosei Co. Ltd., Nagoya, Aichi, Japan e-mail: [email protected] © Springer Science+Business Media Singapore 2016 Japan Association for Chemical Innovation, Computer Simulation of Polymeric Materials, DOI 10.1007/978-981-10-0815-3_22
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Fig. 22.1 Touch panel devices and bubbling issue of plastic panels
high optical performance. As the OCA performance is directly linked to usability, manufacturers wish to improve the properties of OCAs. Recent research on cover panels has investigated weight reduction, improvement of the impact resistance and aesthetic design, and the substitution of glass with plastics, such as polycarbonate (PC) and polymethylmethacrylate. Plastic cover panels, however, present a problem in that bubbles often form in an accelerated evaluation under high temperature and humidity. The prevention of bubbling during this process is important for further development of touch screens. Schematic structure of touch panel devices and bubbling issue of plastic panels are summarized in Fig. 22.1. In our previous development of an OCA for plastic panels, we found that the addition of selected oligomers ef
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