| Polystyrene (PS), which is made of free radicals polymerization reaction of styrene monomer, is one of the important polymers in the numerous applications for fabrication of everyday life objects and has been widely used in biomedical material as tissue culture dishes for its ageing resistance, high transparence, low toxicity, good rigidity, low cost and easy processing etc. However, the utilization as disposal culture dishes is inhibited by its hydrophobic property and consequent weak combination with cells. It is the surface that contact with the tissue directly and plays a critical role in practice. In this regard, much effort has gone into the surface modification, including acid treatment, surface biological coating, ion implantation, plasma processing and surface grafted polymerization and so on. Low-temperature plasma technology, as a versatile and environmental benign technique, has the propensity for highly efficient surface chemistry modification for both organic and inorganic material. However, different plasma discharge mode and plasma formed by different gas have a different activation effect and consequent different modification effect on material surface.In this paper, Low-temperature plasma technology and/or UV light induced surface grafted polymerization were used for immobilization bioactive molecules polyacrylamide (PAAm) onto PS surface. In order to obtain excellent hydrophilicity and cellular compatibility of PS surface, the effect of PAAm grafting yield and cellular compatibility of modified surface by different methods were investigated. The main work is shown as follows:(1) Study on RF plasma-induced UV graft-polymerization of AAm on the PS surfaceAfter Ar plasma pretreatment, peroxide group, free radical and the oxygen-containing polar groups might be formed on the substrate PS surface, followed acrylamide (AAm) graft-polymerized on the activated surface in the UV irradiation. Contact angle (CA) test identified the most effective plasma parameters were 3 min,40 Pa,50 W and the optimal concentration of AAm and irradiation were 30 wt% and 40 min, respectively. ATR-FTIR and XPS results showed that AAm can effectively grafted polymerized on PS surface without initiator by RF Ar plasma-induced UV graft-polymerization and the element content of N was 4.56%. SEM and CA showed that surface hydrophilic increased and it is mainly resulted from the chang of surface composition instead of surface microstructure.(2) Study on PS surface modification by HF plasma induced graft-polymerizationIn this research, HF Ar plasma was used to activate PS surface and followed by graft-polymerization of AAm on PS surface in Ar plasma atmosphere and UV irradiation, respectively. CA test identified the most effective HF Ar plasma parameters were 2 kV,50 Pa,50 kHz and 2 min and the CA was down to 5.5°. ATR-FTIR and XPS results showed that both of the two methods can realize the graft-polymerization of AAm on PS surface and the UV irradiation was more effective for the 4.78% N element content. DCA analysis showed that the hysteresis phenomena of the contact angle on the modified PS surface was significant, which suggested an improved wettability. Cellular compatibility test showed the cytotoxicity scale (CTS) of the modified surface was 1, which suggested that the modified sample was almost non toxic to L929 cells, up to snuff of the materials cytotoxicity in GB/T 16886.5-2003.(3) Study on different HF plasma induced UV graft-polymerization on PS surfaceThe PS surface might form different chemical constituents and micro-morphology for the different mechanism of the different plasma initiation. Three kinds of HF Ar, O2 and Ar/O2 (1:1) induced UV graft-polymerization were used on PS surface to modify the surface wettability and cellular compatibility of PS surface. CA and SEM analysis showed an improved wettability and few of micromorphology change on the modified surface. In addition, the most decrease occurred on the HF O2 plasma induced graft-polymerization surface for the most polar groups on it. ATR-FTIR and XPS results showed that all of three kinds of gases can realize the graft-polymerization of AAm on PS surface and the HF O2 plasma induced graft-polymerization was most effective for the 9.06% N element content. Cellular compatibility test showed that the PAAm modified PS surfaces of the different plasma-induced were beneficial to cell growth with a good cellular compatibility and the more grafting yield, the better cellular compatibility. |
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