Polymerization-induced aggregate images of phenol–formaldehyde monolayers and its electrical properties

Abstract

Amphiphilic phenols, o-, m- and p-hexadecoxyphenol ( o-, m- and p-HP), were synthesized by the reaction of catechol, resorcinol, and hydroquinone, respectively, with 1-iodohexadecane. Monolayers of the HPs were spread on aqueous subphases and on aqueous 1% formaldehyde subphases. The surface pressure–area isotherms revealed characteristic monolayer behaviors according to the structural isomers. The optical images of the HPs monolayers were observed by Brewster angle microscopy (BAM). Any noticeable morphology of o-, m-, and p-HP domains at a surface pressure lower than collapse was not observed by BAM. However, very different images were monitored according to the structural isomers when the surface pressure reached near the collapse point. The scanning Maxwell-stress microscopy results showed characteristic aggregates morphology, which can be correlated with the BAM images. The network patterns are supposed to give a clue to understanding the microscopic morphology of the phenolic resins. Electrical properties for phenol–formaldehyde LB films deposited from the pure water (PW) and 1% aqueous formaldehyde (1AF), and heat-treated 1AF LB films (H1AF) have investigated such as conductivity, dielectric constant and activation energy. The value of conductivity, dielectric constant and activation energy obtained by temperature dependence of p-HP LB films was as follows: PW>1AF>H1AF. We have provided evidence for the high insulating performance of the phenol–formaldehyde thin films by the LB method.