Preparation and characterization of electropolymerized poly(N‐substituted maleimide‐co‐styrene) coatings on copper substrates

Abstract

SYNOPSISPoly (N-substituted maleimide-co-styrene) copolymer films were electropolymerized onto copper substrates as possible candidates for electronic applications. The N-substituted moieties that were investigated include phenyl, 3-carboxyphenyl, and 4-carboxyphenyl. Uniform coatings of 25 pm or more thickness were successfully applied using each of the three N-substituted maleimides. The thickness was controlled by manipulating the monomer concentration, current density, and reaction time. Not only did the 3-and 4-carboxyphenylmaleimide (CMI) /styrene copolymers have high glass transition temperatures (220°C) and fairly good thermal stability ( -430"C), but they also have rather low dielectric constants (2.55 for 4-CMI/styrene), comparable to those of polyimides. Polymerization of the coatings was observed by in-situ Fourier transform infrared spectroscopy (FTIRS) , using a special cell that made the observation of the polymer structure development possible. It was found by FTIRS that all three monomers, when used with styrene, produced alternating copolymers. 0 1993 John Wiley & Sons, Inc. I NTRO DUCT10 NPolyimides are very important materials in the electronics industry, particularly in the manufacture of flexible printed circuit boards and semiconductor chip devices. A reason for this is that polyimides exhibit superior resistance to chemical and thermal attack and thus withstand the degradative effects of wet-etching and hot-soldering processes.' Conventional methods of applying polymer films, such as spraying, spin-coating, and laminating can be used for polyimides, but these methods are most suitable for applying the films to essentially planar substrates. Electropolymerization is a low current, room temperature, low solvent process that can uniformly coat both planar and complex shapes inexpensively.The polymers produced by electropolymerization increase the cell resistivity, and thus additional ~ * To whom correspondence should be addressed. polymer tends to be formed in any "thin" areas; the result is a rather uniform coating.2 Another important advantage of electropolymerization is its ability to obtain even film thickness over irregular surfaces. The starting monomer solutions are of very low viscosity and can easily wet the metal substrates; and polymerization occurs in the proximity of the metal surface. The resulting adhesion to the metal may be improved due to excellent wetting. It was these considerations that provided the initiative for the work reported in this paper. Adaptation of this method to polyimides could increase their effectiveness significantly. Teng and Mahalingam,3 and Garg, Raff, and S~b r a m a n i a n ,~ have investigated the use of electropolymerization to coat metal electrode surfaces with acrylate polymers. These polymers have relatively low glass-transition temperature and their thermal stability appears too low for many electronic applications, however.Iroh, Bell, and Scola' have electropolymerized poly ( 3-carboxyphenyl maleimide-co-styrene) onto AS-4 graphite fibers from...

Radical polymerization of N-(4-butoxycarbonylphenyl)maleimide, its co-polymerization with methyl methacrylate, styrene and acrylonitrile, and the properties of the resulting polymers

“…The co-polymer of 4-carboxyphenyl maleimide (CPMI) with acrylamide is used as a potential flocculant [31]. Poly(CPMI-ST) co-polymer films were electro-polymerized onto copper substrates as possible candidates for electronic applications [32]. Zhang et al [33,34] reported spontaneous coating of CPMI-ST, CPMI-MMA, CPMI-AN and CPMI-ST-AN systems on metal surfaces such as steel, iron, aluminum, zinc, etc.…”