A novel amphiphilic diblock copolymer having sulfonic acid groups in its hydrophilic chain with poly(diethylsilacyclobutane) as a hydrophobic segment was synthesized by living anionic polymerization followed by treatment with 1,3-propane sultone. The polymer backbone with a degree of polymerization of 18 (hydrophobic):37 (hydrophilic) was synthesized, and three kinds of diblock copolymers with different degrees of sulfonation (R ) 0, 0.50, 0.81) were prepared as sodium salts. The surface tension of aqueous solutions of highly sulfonated polymers as including the R ) 0 (all carboxylic acid) polymer did not decrease with polymer concentration. The solutions did not show foam formation even after vigorous shaking, and almost no adsorption of polymer molecules was observed at the air/water interface by X-ray reflectivity measurement. However, micelle formation with a radius of 140-200 Å was confirmed by dynamic light scattering and small-angle X-ray scattering experiments. Hence, this polymer showed "micelle formation" without "Gibbs monolayer formation" in water. The surface tension decrease in 0.5 M NaCl aqueous solution was also small, but adsorption of polymer was observed by X-ray reflectivity in addition to formation of foam by shaking. The strong ionic character of this novel class of amphiphilic polymer is thought to be the origin of this curious behavior.
The interface adhesion strength of an advanced polymeric low-k material to different metal barriers was quantitatively measured using the four-point bending technique. Different sample configurations were tested in order to find the optimal configuration to study the polymer/barrier interface adhesion strength. The asymmetrical sample configuration with the notch at the film stack side was found to be the most suitable approach to study the adhesion strength of this interface. The effect of bake/cure temperature on the adhesion strength between polymer and barrier was investigated in more detail. Higher cure temperatures resulted in a lower amount of triple C-bonds in the polymer and lower polymer/barrier interface adhesion strength, while no differences in optical and mechanical properties were observed. Moreover, it was found that higher amount of Ta–C bonds formed at the interface improved the polymer/barrier interface adhesion, thereby suggesting that the chemical interaction between the polymer and metal barrier plays a major role in the adhesion performance.
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