Surface properties of modified polymers

Surface fluorination is in popular use because most ofthe desirable properties offluoropolymers are largely the result of surface phenomena. Surface fluorination enables us to modify the surface properties of a polymer while retaining others often useful bulk properties (e.g., mechanical strength, elasticity, and ease of processability. 

Increasing applications of oxidoreductases for modifying surface properties of synthetic polymers have been reported. A good example is surface modification... 

Surface modification of polymers has so become a vigorous area of polymer research/ Surface functionalization is a means of modifying the surface properties of the polymer without affecting the properties of the bulk phase. For example, surface modification changes the int acial properties of polymers, such as adhesion, biocompatiliby, permeability, wettabilityprintability, weatherability, or friction. ... 

The surface active property of PDMS can be seen even in solid state. PDMS accumulates at the surface when mixed with other polymer. Such a surface accumulation can be used to mocMy the surface property of the polymer blend. Addition of a small amounts of PDMS containing graft copolymer is quite effective in modifying the surface of a bulk polymer without damaging the good mechanical property of a base polymerl 3). 

Zhu, S.-H. McManus, N. T. Tzoganakis, C. Penlidis, A., Effect of a Poly(dimethylsiloxane) Modified Polyolefin Additive on the Processing and Surface Properties of LLDPE. Polym. Eng. Sci. 2007,47,1309-1316. 

RBS has been widely used to study the concentration profiles of metals in polymers, often deposited during implantation processes. Implantation is often carried out to modify the surface properties of a polymer such as wear resistance, but can also be used to modify the ability of a polymer to trap metal ions. This process was demonstrated for polyethylene, which was irradiated with fluorine or arsenic ions at 150 keV. When these materials were exposed to lead acetate solutions, implantation was found to alter dramatically the diffusion of lead into the polymer. The high mass of lead makes it easy to measure as it diffuses into polymers. These experiments showed Fickian diffusion of lead into virgin polyethylene, but for heavily implanted polyethylene somewhat lower diffusion coefSdents were obtained, possibly because of the increased density of highly iuadiated samples. However, at relatively low implantation doses of fluorine or arsenic (< lO cm ), it appeared that lead ions were trapped in a concentration profile defined by the energy deposition profile of the implanted species. 

Sonochemistry is also proving to have important applications with polymeric materials. Substantial work has been accomplished in the sonochemical initiation of polymerisation and in the modification of polymers after synthesis (3,5). The use of sonolysis to create radicals which function as radical initiators has been well explored. Similarly the use of sonochemicaHy prepared radicals and other reactive species to modify the surface properties of polymers is being developed, particularly by G. Price. Other effects of ultrasound on long chain polymers tend to be mechanical cleavage, which produces relatively uniform size distributions of shorter chain lengths. 

It was observed elsewhere that plasma treatment of polymer macromolecules results in their cleavage, ablation, alterations of chemical structure and thus affects surface properties e.g. solubility [75]. The effects of the treatment in Ar plasma on the surface properties of PE were examined in [72]. The parameters of the plasma discharge (240 s, 8.3 W power) were chosen, on the basis of our previous experiments [70-74,78], to guarantee the most pronounced changes of polymer surface. Mean thickness of the ablated PE layer was calculated from the weight difference measured by gravimetry. By Ar plasma (8.3 W, 240 s) 30 8 nm thick surface layer is ablated and thickness of the surface layer removed from plasma-modified PE by 24 hour water etching is 21 5 nm [78]. 

In the process of plasma polymerization, a highly crosslinked polymer is deposited on the surface The deposited plasma polymer changes the surface properties of the substrate dramatically. It modifies the surface of powders in terms of surface energy, functional groups, wettability, interaction with polymers, and dispersion... 

Stagnation flames are also being used to modify the surface properties of various materials. For example, premixed methane-air flames can beneficially alter the properties of polymer films [41,358,381,382,388]. Flames can also modify surface properties of ferrous and nonferrous metals, for example, improving surface hardness [360] by creating... 

Some of the commonly used techniques for measuring contact angle [215, 216, 217] are the sessile drop method, captive bubble method and Wilhelmy plate method. These techniques have been extensively used and well documented for characterisation of modified PE surfaces [218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230] for various applications. Whitesides et al. [231 ] studied the wetting of flame-treated polyethylene film having ionisable organic acids and bases at the polymer-water interface. The effect of the size of substituted alkyl groups in amide and ester moieties on the surface hydrophilicity was also studied [232]. The biocompatibility of the polyethylene film surface modified with various water-soluble polymers was evaluated using the same technique [233]. The surface properties of hy-perbranched polymers have been very recently reported [234]. 

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