Low-pressure plasma treated polycarbonate and polymethyl methacrylate (PMMA) sheets with different surface patterns to change their surface properties

Low-pressure plasmas of carbon tetrafluoride (CF4), oxygen (O2), and air were used to treat the surfaces of polycarbonate (PC) and polymethyl methacrylate (PMMA) to achieve a variety of surface attributes, such as hydrophilicity, hydrophobicity, and surface free energy. Patterns of straight line, triangular and square shapes with different sizes e.g., 0.5 mm, 0.75 mm, and 1 mm dimensions as templates were constructed from stainless -steel sheets with a thickness of 1 mm, via laser cutter, were used to induce the corresponding shape of the functionality on PC and PMMA surfaces during plasma gas treatment were also investigated. The untreated PC and PMMA surfaces have a contact angle (theta) value of 70 degrees +/- 0.47 degrees and 77 degrees +/- 0.80 degrees, respectively. As expected upon CF4 plasma treatment, their contact angle values were increased to 109.04 degrees +/- 0.35 degrees and 105.76 degrees +/- 0.61 degrees, respectively; whereas the air plasma treated surfaces became more hydrophilic with the contact angle values of 29.34 degrees +/- 0.14 degrees and 43.99 degrees +/- 0.22 degrees, correspondingly. Moreover, O2 plasma treated surfaces became more hydro-philic with the contact angle values of 25.32 degrees +/- 0.77 degrees for PC and 39.94 degrees +/- 2.05 degrees for PMMA. Also, surface free energy (SFE) values were decreased to 11 +/- 0.87 mN/m from 41.16 +/- 0.42 mN/m for PC and to 12.11 +/- 1.53 mN/m from 35.93 +/- 1.12 mN/m for PMMA upon CF4 treated surfaces. Furthermore, SFE values were increased to 57.59 +/- 1.12 and 62.13 +/- 1.15 mN/m for PC and PMMA after air plasma treatment. PC surface's, advancing and receding contact angles were determined as 101.48 degrees +/- 0.33 degrees and 65.60 degrees +/- 0.11 degrees respectively for 34.77 degrees +/- 0.50 degrees slide-off angles. Moreover, the advancing and receding contact angles for PMMA were found as 93 degrees +/- 0.64 degrees and 61.60 degrees +/- 1.19 degrees, respectively with a sliding angle of 24.49 degrees +/- 1.14 degrees. X-ray Photoelectron Spectroscopy (XPS) analysis results confirmed the fluorination and oxidation of both PC and PMMA after CF4 and O2 plasma treatments, individually. PC and PMMA surfaces were treated multiple times with CF4 and Air, Air and CF4, O2 and CF4, and CF4 and O2 plasmas in succession. After multiple treatment, PC and PMMA surfaces contact angle values were decreased as low as 10.62 degrees +/- 0.88 degrees and 14.96 degrees +/- 0.2 degrees, respectively.