| Silicone rubber(SIR) samples are modified by CF4 radio frequency(RF) capacitively coupled plasma(CCP) and inductively coupled plasma(ICP), respectively.Surface morphology,functional groups,and hydrophobic and oleophobic properties of the CF4 plasma modified SIR samples are characterized by using atomic force microscopy(AFM),attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopy,X-ray photoelectron spectroscopy(XPS) and static contact angle(SCA) measurement.Surface root-mean-square(RMS) roughness(Rq) of the SIR samples, which were modified by CF4 RE CCP and ICP at power of 200 W and gas flux of 20 sccm for treatment of 5 min,respectively,increases from 42.460 nm for original surface to 134.425 and 46.613 nm.It is concluded that the amendment in surface morphology by CF4 CCP process is better than that by CF4 ICP process because the positive ions of CF4 CCP have more kinetic energy than CF4 ICP to ablate or etch the SIR samples' surfaces owing to the higher self-bias existing in the sample holder.The peak ratios of Si-O-Si/Si-(CH3)2,-CH3/Si-(CH3)2,and C-H/Si-(CH3)2 in ATR-FTIR spectra of SIR samples modified by CF4 CCP at RE power of 200 W for 20 min treatment decrease from 0.914,0.414,and 0.081 for original surface to 0.796,0.131,and 0.029,respectively;And if the samples are treated by Ar CCP at RE power of 100 W for 5 min treatment before the same treatment of CF4 CCP,those peak ratios decrease to 0.795,0.226,and 0.060. XPS were analyzed by deconvolution method and some conclusions are listed as follows:there are fluorocarbon groups such as C-F2,C-CFn,and CF-CFn, and fluosilicic structures such as -[-SiFCH3-O-SiFCH3-]n-,-[-SiF2-O-SiF2-]n-, and -[-SiFCH3-O- SiF2-]n- on the surfaces of SIR samples modified by CF4 ICP,and the percentage concentration of F-Si increases and gradually preponderates over that of F-C with the increase of treatment time,moreover, the maximum of F content reaches 20.05%at the treatment time of 10 min. Compared CF4 CCP process with CF4 ICP process,although there are similar fluosilicic structures on the surfaces of SIR sample modified by the two types of processes,there is only one type of fluorocarbon groups----C-CFn discovered on the modified surfaces.In addition,the percentage concentration of F-Si is always exceeding in that of F-C,and the maximum of F content is only 14.01%at 20 min treatment.According to the data above,it is concluded that the treatment process of CF4 CCP overruns that of CF4 ICP in the ablation of fluorocarbon groups and formation of fluosilicic structures.CF4 CCP treatment process predominates over CF4 ICP treatment process in improving the hydrophobic and oleophobic properties of SIR surfaces.The static contact angle for H2O and CH2I2 were improved from 100.7°and 61.6°for original sample to 150.2°and 123.6°under the condition of optimal technological parameter which is CF4 CCP at RF power of 200 W for 5 min treatment.In conclusion,although there are differences in treatment process between the two types of CF4 coupled plasmas,the decrease of surface energy and increase of the static contact angle for H2O and CH2I2 are both decided by increasing the fluoric groups and surface roughness according to the two types of processes.The main reason,for which the modified effects of hydrophobic and oleophobic properties of CF4 RF CCP are better than that of CF4 RF ICP, lies in self-bias existing in the sample holder so that the positive ions of CF4 plasma can be accelerated and acquire higher kinetic energy to bombard,to ablate,and to etch the samples' surfaces,meanwhile,meet the need to increase the fluoric groups and surface roughness which influence the hydrophobic and oleophobic properties of SIR samples.Moreover,it is proved that the degree of hydrophobic and oleophobic properties improved through the increase of surface roughness is better than that through the introduction of fluoric groups.
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