Irradiation grafting

Chitosan is the main structural component of crab and shrimp shells. Chitosan contains both reactive amino and hydroxyl groups, which can be used to chemically alter its properties under mild reaction conditions. Al-acyl chitosans were already reported as blood-compatible materials. UV irradiation grafting technique was utilized to introduce obutyrylchitosan (OBCS) onto the grafted SR film in the presence of the photosensitive heterobifunctional cross-linking agent. The platelet adhesion test revealed that films grafted on OBCS show excellent antiplatelet adhesion. 

Rager, T. 2003. Pre-irradiation grafting of styrene/divinylbenzene onto poly(tetrafluoroethylene-co-hexafluoropropylene) from non-solvents. Helvetica Chimica Acta 86 1966-1981. 

Schmidt-Naake, G., Bohme, M. and Cabrera, A. 2005. Synthesis of proton exchange membranes with pendent phosphonic acid groups by irradiation grafting of VBC. Chemical Engineering and Technology 28 720-724. 

With adequate swelling vinyl monomers can be satisfactorily grafted to cellulose and its derivatives by the three main methods developed for other polymers (98). These are (1) the mutual or direct method where the polymer is irradiated in the presence of the monomer or monomer vapor, (2) the pre-irradiation (sometimes called post-irradiation grafting) method where the polymer is first irradiated and then brought into contact with the monomer, and (3) the peroxide method in which the polymer is irradiated in air and the resulting polymeric peroxide used to initiate graft polymerization. 

Fig. 3. Cumulative and differential molecular weight distribution for polystyrene from pre-irradiation graft...

Resting, R. E., and V. Stannett The pre-irradiation grafting of styrene onto cotton cellulose using gamma rays. Makromol. Chem. 55, 1 (1962). 

The influence of the polymer structure on the irradiation grafting has been examined in the case of styrene to high pressure and low pressure polyethylene films (114). The most important factors which determine the efficiency of grafting are the degree of crystallinity, the thickness of the films and the dose rate. 

M. S. Gluckman and M. J. Kampf The effect of the alkyl group on the irradiation grafting of methyl methacrylate to poly(alkyl methacrylates), J. Polymer Sci. 38, 417 (1959). 

The same authors developed a process of encapsulation of polymers swelled by halogenated solvents in which ozone is greatly soluble but not monomers to be grafted. After ozonization of polymers swelled in solvents, mixtures of mono unsaturated or di unsaturated monomers are added to the activated polymers. Then, grafting is operated by UV irradiation. Grafting is mainly located at the surface of the starting polymer what prevents the modification of its intrinsic properties. This process permits to produce hydrophilic polysiloxanes used in medical applications (contact lenses, tubes, catheters, etc.). 

Photo-grafting can be performed in two different manners simultaneous grafting [105] and post-irradiation grafting [106]. For simultaneous grafting, the substrate, monomer, photosensitiser and solvent under inert conditions are taken in a photoreactor and irradiated with UV. In the latter case, substrate is irradiated in air to generate hydroperoxides on the surface followed by decomposition of these hydroperoxides in the presence of monomer to yield grafted surfaces. 

Fig. 9. Alternate extraction of PMMA homopolymer and unreacted PVA from the reaction product, obtained by the mutual irradiation grafting of MMA onto water-swollen PVA films...

Thus, the surfaces prepared by radiation techniques such as irradiation, grafting, etching, and pore-forming polymerization at low temperatures provide useful materials for cell cultures with better wettability, micro-porous heterogeneous structure and increased positive charges on the polymeric surfaces. 

As mentioned earlier, the first peptide library with a limited number of peptides was generated by using multipin technology in 1984 (1). In this method, acrylic acid is irradiation-grafted onto the tip of polyethylene pins. Each pin is inserted into... 

Concentration profiles obtained with different membranes are shown in Figure 3. Most of these membranes obtained by irradiation grafting have a nonhomogeneous distribution of ionic sites across the thickness. The exchange properties and the ionic conductivity must strongly depend on this asymmetry in the repartition. A new approach to asymmetric membranes may be envisaged from this irradiation grafting technique. 

Figure 3. Concentration profiles for different membranes giving an element concentration (in arbitrary units) across the thickness a and b, Cu concentration after exchange. The membranes have been obtained from a low density polyethylene after irradiation grafting with styrene followed by sulfonation. c, Cu concentration after exchange. The membrane has been obtained from a copolymer of tetra-fluororethylene and fluorinated propylene after irradiation grafting with styrene followed by sulfonation. d, Cl concentration after chlorhydratation of dimethyl annio ethyl methacrylate grafted on polyvinylidene fluoride.

In Table I are summarized the results obtained for different sample Nafion perfluoroethylene membrane (NAF), acrylic acid irradiation grafted polytetrafluoroethylene (PTFE), sulfonated styrene irradiation grafted fluorinated ethylene propylene copolymer (RAI), and sulfonated polysulfone (SPS). 

Polyolefin films have been post-irradiation grafted with materials such as trifluorostyrene or methacrylic acid followed by sulfonation to control ion flow through nickel-cadmium batteries [8, 9], Investigation is underway to use crosslinked films grafted with selected monomers to develop lower cost membranes for fuel cells. A major commercial use of EB grafting has been to modify the surfaces of plastic films and paper with low molecular weight silicones to impart adhesive or release properties. 

B. Gupta, F.N. Biichi, G.G. Scherer, A. Chapiro, Cross-linked ion exchange membranes by radiation grafting of styrene/divinylbenzene into FEP films, J. Membr. Sci., 1996, 118, 231-238 B. Gupta, F.N. Biichi and G.G. Scherer, Cation exchange membranes by pre-irradiation grafting of styrene into FEP films. I. Influence of synthesis conditions,./ Polym. Sci., 1994, 32, 1931-1938. 

S. Tanso, J. Okamoto, I. Ishigaki, T. Sugo, K. Murata, K. Senoo and T. Takayama, A new alkaline battery separator made by pre-irradiation graft polymerization, Yuasa Jiho, 1983, 54, 57. 

Microwave irradiation Grafting onto method Various catalysts are used [4,4 -Azobis (4-cyanovaleric acid)] Telechelic polymers, polyethylene glycol, poly-dimethyl siloxane... 

Gargan, K., Kronfli, E., and Lovell, K.V. 1990. Pre-irradiation grafting of hydrophilic monomers onto polyethylene. I. The influence of homopolymerization inhibitors. Radiat Phys Chem. 36 757-762. 

Rong, M. Z., Zhang, M. Q., Wang, H. B., and H. M. Zeng. 2002. Surface modification of magnetic metal nanoparticles through irradiation graft polymerization. Applied Surface Science 200 76-93. 

Abu Seman, M.N., Khayet, M., Bin Ali, Z.L. and Hilal, N. 2010. Reduction of nanofiltration membrane fouling by UV-irradiated graft polymerization technique. 355 ... 

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