In recent years, optical polymers like PMMA and PC have replaced glass products in many optical applications where low weight, chemical inertness, high impact resistance, flexible formability and relatively low cost are of major importance [1]. The performance of polymers can further be enhanced by applying functional coatings such as protective layers, optical coatings, gas permeation barriers and others. However, the desirable bulk properties of polymers are often compromised by their unfavourable surface characteristics, such as low hardness, low resistance to abrasion and scratching, and low surface energy, which generally leads to low wettability and poor adhesion [1, 2].

Low pressure soft plasma treatment has been successfully used as a dry process to alter the surface properties of polymers (for review see [3]). Major contributions to the modification of polymer surface are due to the chemically active species and energetic photons generated by the discharge. These induce the effects of surface cleaning, ablation, crosslinking and surface chemical functionalization [3-5]. The effect of plasma treatment depends on a variety of parameters such as the kind of plasma (DC, radio frequency (RF) or microwave (MW)), the discharge power density, the pressure and flow rate of the gas or gas mixture, as well as the treatment time [6-8]. Different radio frequency glow discharge plasma treatments that influence the polymer surface energy have been described in the literature [9-12]. It has been found that noble gas plasmas (eg He or Ar) are effective in creating free radicals, but do not add new chemical functionalities from the gas phase. Typically, a reactive plasma (H2O or O2) is used to add a polar functional group which can dramatically increase the surface free energy of the polymer [9, 10]. Hook et al.[10] have