UV-INDUCED GRAFTING AND MODIFICATION OF POLYMERS BY HIGH LET RADIATION

7.1 UV-induced grafting of SuMA onto PET fiber and its applications of protein immobilization

UV light, a kind of electromagnetical radiation can also be used to induce the grafting reaction. In some cases it is more effective. In this work, the succinimidylmethacrylate(SuMA) was grafted on the surface of polyethyleneterephthalate, PET, by UV-irradiation and then the protein was immobilized with SuMA on PET.

7.1.1. UV-induced grafting

7.1.1.1. Effect of HEMA on grafting yields of SuMA onto PS

The monomer SuMA or SuMA together with HEMA was grafted on the surface of PET fiber successfully under UV irradiation by use of NaIO4. Existence of HEMA in SuMA grafting systems enhanced grafting yields of SuMA (see Fig. 28)

The proteins of trypsin and hepatities surface antibody were immobilized onto SuMA grafted PET fibers in the neutral aqueous solutions (Fig. 29, Fig.30)

15 20 25 30 35 40

Fig.26 The change of equilibrium degree of swelling of the prepared gel with temperature B: PVA-g-polyNIPAAm gel C: PVA gel

Fig.27 The release of MB at 15^oC as a function of time B: PVA-g-polyNIPAAm gel C: PVA gel

C B

normalized release MB (%)

Time (min)

0.00 0.01 0.02 0.03 0.04 0.05

FIG. 28. The effect of SuMA conc. on grafting.

0 20 40 60 80 100

FIG. 29. The activity of the trypsin immobilized on SuMA grafted PET.

FIG. 30. The radioactivity of the samples with the immobilized protein.

7.1.1.2. Immobilization of trypsin and hepatities surface antibody

From the figures, it can be seen that although the HEMA could enhance the grafting yields of SuMA, the immobilization of proteins in the same system was inhibited remarkably by existence of HEMA.

7.2. Study on oxidation of polymers treated by high LET radiation

Both high linear energy transfer (LET) radiation e.g. ion beam and low LET radiation e.g. electron beam or J-rays can be used in modification of polymeric materials. High LET radiation has wide energy range and narrow distribution of energy deposition. So it is more useful in surface modification of materials to some extent. Many properties such as optical, electrical and biocompatible properties of materials could be modified by ion implantation. In recent years some applied research has been carried out in this area but the mechanism has not been discussed clearly. In this work the oxidation behaviour of two kinds of polymeric membranes, i.e. silicone rubber (SR) and segmented polyether urethane (SPEU) which are bio -compatible materials was studied by treating with high LET radiation.

2u1.7 MV Tandem Accelerator, 5SDH-2 NEC (Peking university) was used as the ion source equipment. Si⁺ beam with 1MeV energy, 30nA current and ion fluence of 5×10¹⁴ Si⁺/cm². For F⁺ beam energy was 1.2 MeV. XPS (LAB-5, VG, USA), ESR (ER200D SRC Germany) and UV-Vis spectrophotometer (756 MC China) were used to measure the treated samples.

7.2.1. Oxygen content on the treated surface of membranes

The oxygen and carbon contents on the surfaces of SR and SPEU implanted by Si⁺ and F⁺ respectively as a function of time stored in air showed that the oxygen content grew up, while the carbon content lowered down accordingly. The treated samples were washed by ethyl alcohol several times and measured again. The results showed that there was no difference between the two XPS data before and after washing. Therefore, the physical absorption of oxygen from air could be eliminated (see Fig. 31)

7.2.2. Free radicals in implanted samples

The ESR spectra of SPEU and SR membranes implanted by Si⁺ ions showed that the free radicals formed by ion implantation were broad symmetric singlet which were different from that formed by J-rays (see Fig. 32).

0 20 40 60 80

12 14 16 18 20 22 24 26 28 30 32 34 36

a. Variation of O content with time

SPEU-Si SR-Si SR-F

Content (%)

Time (Days)

FIG. 31. Variation of O content on SR and SPEU surface implanted by Si⁺ or F⁺.

FIG. 32. ESR Spectra of Si+-implanted and J-irradiated SPEU and SR.

Those free radicals are the active species to combine with oxygen forming peroxides. It indicated again that the increase of oxygen content was resulted in chemical reaction instead of physical adsorption.

7.2.3. The adsorbability of BSA on SPEU and SR implanted by F⁺ ions

The samples implanted by F⁺ ions adsorbed with BSA to be saturated and then put into water under supersonic measuring the adsorbability of BSA on the surface. It was found that the BSA adsorbed implanted SR was more stable, but for SPEU the opposite results were obtained (see Fig. 33)

FIG. 33. SR and SPEU adsorbed with BSA and implanted by F⁺ions.

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GAMMA RADIATION TECHNOLOGY OF PRODUCING CROSSLINKED