Young's modulus of plasma‐polymerized allylamine films using micromechanical cantilever sensor and laser‐based surface acoustic wave techniques

• Published in: Plasma processes and polymers 2018-09, Vol.15 (9), p.n/a
• Main Authors: Toda, Masaya, Miyake, Koji, Chu, Li‐Qiang, Zakerin, Marjan, Förch, Renate, Berger, Rüdiger, Itakura, Akiko N.
• Format: Article
• Language: English
• Subjects: Acoustic properties; cantilever sensing; humidity sensor; Mechanical properties; Modulus of elasticity; plasma polymerization; Polymerization; Surface acoustic waves; Thin films; Young's modulus of ultra‐thin films
• ISSN: 1612-8850; 1612-8869
• DOI: 10.1002/ppap.201800083

Mechanical properties of ultra‐thin organic films are fundamentally important in coating applications. Micromechanical cantilever sensor (MCS) and laser‐based surface acoustic wave (LA‐SAW) techniques were both used to measure Young's moduli (E) of plasma polymerized films at different humidities (H). For plasma polymerized allylamine (ppAA) films deposited at 5 W and 90 W, E of 1400 ± 350 MPa and 110 ± 20 MPa at H between 10 and 40%, and 1070 ± 250 MPa and 32 ± 10 MPa at H between 70 and 80% were measured. The LA‐SAW technique revealed E lower than 60% of that measured by MCS. The difference suggested either an enhanced swelling at the air interface or a gradient of cross‐linking density. The mechanical properties of plasma polymerized allylamine (ppAA) films that swell in humidity are discussed in this work. The micromechanical cantilever sensor (MCS) and the laser‐based surface acoustic wave (LA‐SAW) techniques allow measuring Young's moduli of thin ppAA films. The calculated Young's moduli indicate a crosslinking gradient in ppAA films, and a lower crosslinking density at the air interface.