149

Original Research Paper

J. Jpn. Soc. Colour Mater., 94〔6〕，149–157（2021）

Interfacial Molecular Motion and Chemical Characteristicsof Polymer Jointed to Metal by Chemical Bonding
Xueliang Deng＊,＊＊, Jing Sang＊,†, Sumio A isawa＊, Katsuhito Mori＊＊ and Hidetoshi Hirahara＊＊Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University,

4-3-5 Ueda, Morioka, Iwate 020-8551, Japan＊＊Sulfur Chemical Institute, 210, Collabo MIU, 4-3-5 Ueda, Morioka, Iwate 020-0066, Japan†Corresponding Author, E-mail: sangjing@iwate-u.ac.jp(Received April 9, 2021; Accepted May 21, 2021 )Abstract
The adhesion of metals and polymers has wide industrial applications; interface bonding and adhesion mechanisms are essential
for determining the final properties of polymer composites. A triazine-based silane coupling agent was used to treat aluminum andpolydimethylsiloxane (PDMS) to form metal–polymer interface bonds through chemical bonding. Bonding strength tests, swelling
experiments, rubber curing degree measurements, and dynamic viscoelastic analyses were performed on Al/PDMS samples of different
thicknesses to investigate the molecular motion of the formed Al/PDMS interface. The influence of the PDMS thickness on the molecularmotion of joint was studied. The bonded Al/PDMS interface had a higher degree of cooperation of molecular motion corresponding to stressrelaxation than that of unbonded rubber, whose molecules restrain molecular motility. Swelling experiments revealed that only a specificthickness of the PDMS can chemically bond with Al, and below this thickness, the solvent, toluene, cannot penetrate the bonding interface.
This study provides basic insights about metal–polymer interface mechanisms at a molecular level.
Key-words: Silicon rubber, Chemical bonding interface, Direct adhesion, Swelling, DMA, Molecular motion

1．Introduction
Interfaces between metals and crosslinked polymers playa significant role in many fields such as splicing, assemblyand coating, plastic metallization, microelectronics, microsystem technology, and nanotechnology 1 - 3 ). Achieving
a high polymer/metal adhesion strength is an ongoingchallenge, especially in the harsh environments of manytechnical applications. Moreover, all organic coatings applied
to metals such as steel, zinc-coated steel, aluminum, andmagnesium require strong interfacial adhesion strengths towithstand severe forming operations and prolonged exposure
to corrosive environments 4,5 ). For example, the most basicanti-corrosion performance criterion for metals is to meet therequirements for ensuring normal operations in water, air,salt water, and organic solvents 6,7 ). However, many organic
coatings lose their adherence to the metal substrate due toproblems such as swelling of the polymer or gas blistering
caused by corrosion in a humid or solvent environment 8,9 ).
The basic conditions that the metal surface needs towithstand to confirm the anti-corrosion effect of the organic
coating, the mechanism by which molecules of the organic【Figures and illustrations】Figures and illustrations published in black andwhite in the journal can be seen in color at our public website「J-STAGE」.
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－1－layer move when water or solvent molecules penetrate theinterface, the reason why the interface between the metal andorganic layer affects the bonding force and durability, and theeffects of anti-corrosion properties are all questions that need
to be answered through research.
Molecular chain mobility is important in determining theinterfacial strength, durability, and corrosion resistance ofcomposite materials formed by dissimilar material bonding(for example, a bond between a metal and polymer) 10,11 ).
There have been many studies on the interactions
between metals and organic materials 12-14 ): the interface
characteristics of metals and organic materials 15 - 18 ) ,direct combinations of metals and organic materials,
and the applications of composite materials 19 - 22 ). The
combination of a metal and organic molecules is based on
the thermodynamic concept of adhesion at the molecularlevel, which is used to study and explain the phenomenonof interfacial bonding 4 ). The ideal state of the combinationis the integration of the different materials, which is key
to ensure the various properties of the composite material.
Recently, research using non-destructive methods, suchas ultrasonic and electromagnetic testing, as well as
thermography, to evaluate adhesion interfacial properties has
been reported 23,24 ). However, it is difficult to perform a nondestructive analysis of molecular motion for the bonding
interface after integration 25 ). The molecular motion of the© 2021 Journal of the Japan Society of Colour Material