Short communication Study on hydrophilicity of polymer surfaces improved by plasma treatment Jiangnan Lai a , Bob Sunderland b , Jianming Xue a , Sha Yan a , Weijiang Zhao a , Melvyn Folkard b , Barry D. Michael b , Yugang Wang a, * a Key Laboratory of Heavy Ion Physics, Peking University, MOE, Beijing, PR China b Gray Cancer Institute, Mount Vernon Hospital, Northwood, Middlesex, UK Received 12 January 2005; accepted 16 May 2005 Available online 24 June 2005 Abstract Surface properties of polycarbonate (PC), polypropylene (PP), polyethylene terephthalate (PET) samples treated by microwave-induced argon plasma have been studied with contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scanned electron microscopy (SEM). It is found that plasma treatment modified the surfaces both in composition and roughness. Modification of composition makes polymer surfaces tend to be highly hydrophilic, which mainly depended on the increase of ratio of oxygen-containing group as same as other papers reported. And this experiment further revealed that C O bond is the key factor to the improvement of the hydrophilicity of polymer surfaces. Our SEM observation on PET shown that the roughness of the surface has also been improved in micron scale and it has influence on the surface hydrophilicity. # 2005 Elsevier B.V. All rights reserved. Keywords: Plasma; Polymer; SEM; XPS; Contact angle 1. Introduction Polymers are applied widely in modern industry and act as very important roles for many obvious advantages. However, bonding and finishing of many polymers present a problem due to the low hydro- philicity of their surfaces. Because it affects the wettability, paintability, colorability, biocompatabil- ity, anti-electrostatic properties, anti-fogging, adhe- sion, etc., a lot of methods have been devised and commercially used to modify the polymer surfaces. Among them, plasma treatment is now common in industry for it is a very effective way to give the hydrophilicity to a polymer surface [1–4]. Many researchers explained that the improving of surface hydrophilicity was induced by forming of new oxygen-containing groups on the surface, such as – OH, –OOH, etc., for these groups are hydrophilic [3– 7]. However, there are few papers that went deep into www.elsevier.com/locate/apsusc Applied Surface Science 252 (2006) 3375–3379 * Corresponding author. E-mail address: ygwang@pku.edu.cn (Y. Wang). 0169-4332/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2005.05.038