Atmospheric Pressure Plasma-Initiated Chemical Vapor Deposition (AP-PiCVD) of Poly(alkyl acrylates): An Experimental Study

Abstract

A novel atmospheric pressure plasma-initiated chemical vapor deposition (AP-PiCVD) approach toward the growth of conventional polymer layers is characterized and interpreted. A set of three methacrylate monomers (methyl, butyl, and glycidyl methacrylate) were investigated using ultrashort plasma discharges (ca. 100 ns) pulsed at various frequencies, covering a range of duty cycle from 0.1% to 0.000 316%. An unprecedented weight-average molar mass of 94 000 g mol −1 coupled to an outstanding thin film conformality and an excellent chemical functionalities retention was achieved for the best deposition conditions. Insights into the growth mechanisms in AP-PiCVD and their dependence on the monomer's intrinsic properties are provided.

Pulsed plasma initiated chemical vapor deposition (PiCVD) of polymer layers − A kinetic model for the description of gas phase to surface interactions in pulsed plasma discharges

“…Summary of previous experimental data for MMA and GMA‐based thin films grown by AP‐PiCVD on which the present kinetic study relies on, namely (a) the deposition rate according to the discharge frequency, (b) the size distribution by size exclusion chromatography (SEC) of thin films grown at 100 Hz, (c) the surface topography by scanning electron microscopy (SEM) of the thin films grown at 100 and 10 000 Hz, and (d) the matrix‐assisted laser desorption/ionization high‐resolution mass spectra (MALDI‐HRMS) of the thin films grown at 100 Hz…”

“…The prevalence of those proposed reaction pathways is governed by the plasma discharge conditions and gas phase composition. In particular, previous works highlighted that the kinetics of AP‐PiCVD are strongly related to the repetition frequency of the ultra‐short plasma pulses . The present work aims at providing a model to describe and understand the AP‐PiCVD kinetic data.…”

“…High‐resolution mass spectrometry (HRMS) evidenced that the ultra‐short plasma pulses cleave a small number of the vinyl monomer units into defined radical and neutral fragments that are able to either initiate or terminate the polymerization . Subsequently, part of the formed radicals and the vinyl monomers diffuse and adsorb from the vapor phase onto the surface where the free‐radical polymerization occurs . As a result, thin films with an unprecedented degree of polymerization for plasma‐enhanced chemical vapor deposition (PECVD) processes are synthesized .…”

“…This process called atmospheric‐pressure plasma‐initiated chemical vapor deposition (AP‐PiCVD) allowed the simultaneous atmospheric‐pressure synthesis and deposition of true homopolymer layers such as poly(diethylallylphosphate) and poly(glycidyl methacrylate) . The chemical and physical properties of the thin films grown using ultra‐short plasma pulses result from a competition between conventional polymerization reactions (initiation, propagation, and termination) and plasma‐polymerization reactions (fragmentation and recombination) . Such competition is notably expressed by the switch from oxygen integration at low plasma discharges frequencies to the oxygen fragmentation and carbon integration when the frequency of plasma pulses increases .…”

“…Such competition is notably expressed by the switch from oxygen integration at low plasma discharges frequencies to the oxygen fragmentation and carbon integration when the frequency of plasma pulses increases . This transition is accompanied by variations in the morphology of the produced thin films, as a result of a shift from predominant gas phase mechanisms to predominant surface mechanisms . The prevalence of those proposed reaction pathways is governed by the plasma discharge conditions and gas phase composition.…”