Design And Synthesis Of Macromolecular Surface Modifiers And Their Application In The Modification Of Surface Polarity Of Polystyrene

Polystyrene has been widely applied in many fields, for example, electronic appliance, instruments, food packing, toys, commodities etc. However, just because of its low surface energy, many applications such as wettability, paintability, adhesion susceptibility, biocompatibility and so on, were heavily limited by its poor surface hydrophilicity and superficial cohesiveness. Therefore, many methods of surface modification have been developed as an important technique to improve the combined properties of the materials and satisfy the special requirement for the surface application. Conventional polymer surface functionalization always depended on the chemical or physical techniques including corona, plasma or flame treatment, chemical reaction, surface grafting, surface coating or etching and so on. However, the complicated processes and the specialized equipment are always required by using these techniques. Especially, for the intricate articles, the completed and uniform functional surface can not be easily achieved. In addition, the expensive post treatment has also greatly limited the application of these methods. Therefore, much attention has been focused on the exploitation of the new low-cost, reliable methods for the large-scale polymer surface functionalization.Recognizing the drawbacks of these methods, another approach of selective migration of functionalized additives in host polymer to achieve the designed surface is being aspiring researched as a potential solution. It is not only a practical, convenient and low-cost way to obtain the functional surface, but also an effective method to achieve the uniform and integrate functionalized surface layers with plentiful gradient structure. Because the effective duration of the surface modification by these small molecular additives was always heavily shortened for their easy efflux by washing with water, rain or other solvent in outer environment, the technique of adding macromolecular surface modifier can overcome this limitation effectively. But, the efficiency of its preferential surface migration is always low due to its chain tangling with polymer matrix. Thus, the key problem in this study is to balance the contradiction between the longevity of their surface modification and the applied efficiency of the surface modifying macromolecules.In this paper, the polyether silicone oil was selected as the responding macromolecular surface modifier. The attenuated total reflectance Fourier transform infrared spectroscopy(ATR-FTIR) and contact angle measurement were used to detect the surface structure and surface properties. It was indicated the influence of contact medium on the selective migration of polyether silicone oil was much important. The glass induced more polyether chain segments on the polystyrene surface and the air induced more silicone oil chain segments on its surface.The selective aggregation of the polyether silicone oil(PSO) on the surface of the polystyrene films was investigated by using the contact angle measurement and the attenuated total reflectance Fourier transform infrared spectroscopy. By utilizing the"surface target"effect of the chain segments of the silicone oil, the applied efficiency of the macromolecular surface modifier(PSO) was enhanced greatly. Due to the good hydrophilicity of polyether chain segment, the surface free energy(γ) of the blends was enhanced 180% and the polar portion of itsγincreased nine times. Because the chain segments of silicone oil could preferential aggregate on the surface of the PSO/PS blends, it led the polyether chain segments migrated on the surface of the films which took the climacteric role in improving the hydrophilicity of the films. It also found that the preferential surface migration of PSO was heavily depended on the surface properties of the contact medium. Compared with the different mechanisms of the surface migration, the inducement of polar groups on substrates (glass or polyimide) made more chain segments of polyether aggregated on the blends surface and the polar portion of the surface energy of the films was increased greatly. Whatever the samples were annealed by polyimide or polytetrafluoroethylene, the concentration of silicon chain segments in the surface was much higher than that in bulk. It certified that the"surface target"effect of the silicon oil chain segments was much intensive in the blends. In the process of the surface migration, the abundant surface structure was reconstructed. Because the inducement of the polar substrates was attenuated quickly as the operating distance increased, the surface concentration gradient of PSO declined acutely when the samples were annealed on glass or polyimide. But the surface concentration gradient of PSO altered gently when the samples were annealed on polytetrafluoroethylene.To further study the effect of the surface macromolecules of the duration of the surface modification, poly(ethylene glycol)-g-polystyrene grafted polymers was used to blend into polystyrene matrix. The comb-like amphiphilic copolymers (PEG-g-PS) based on styrene–maleic anhydride copolymer (SMA) backbone was synthesized by esterification of SMA with poly(ethylene glycol) (PEG). When PEG-g-PS was melt blended with polystyrene, the preferential surface enrichment of PEG-g-PS was much evident resulting in the surface polarity increasing over 100%. The effective duration of the surface functionalizatoin was also hugely extended as SMMs were added into the blends because this SMM was not run off by ethanol. Furthermore, more polyether chain segments on PEG-g-PS could selectively migrate to the surface by the inducement of polar solvent. The surface functionalization for polystyrene even became all life for the material. During the washing by ethanol, more chain segments of the PS-g-PEG1000 could aggregate on the surface of the films of the polymer blends. The surface polarity of the blends was enhanced 36% after 180 minutes washing in ethanol.The drawback of the short duration of the surface modification by using the small molecular additives was effectively overcome as some SMMs were added into the blends, but their efficiency of surface modification was low for their good compatibility with host polymer resulting in plentiful SMMs being necessary to achieve the suitable functional surface. Then many properties of matrix polymer would be influenced. When the PS-g-PEG1000 was used as the compatibilizer between the poly(ethyl glycol) and polystyrene, the duration of the surface modification was obviously extended and the selective enrichment of the surface additives on the film surface was also increased as the films were washed in ethanol solution. Just because of the increase of the compatibility between the surface additives and host polymer, more polyether became steady enough not to be run off by ethanol when it was aggregated on the surface. It was a preferable solution to extend the effective duration of surface functionalization based on its high efficiency of surface modification.The PESO/PS-g-PEG/PS blends were also investigated to discover the efficiency and duration of surface modification. When apropos amount of PS-g-PEG was added into the PS/PESO blends as the compatibilizer between PEG and PS, the"selective target"effect of the polyether silicone oil is the essential factor to ensure its high applied efficiency and the good miscibility between polystyrene and the surface modifiers greatly increased the duration of the surface modification. It was an effective solution to balance the conflict between the duration and efficiency of the surface modifying additives.