RADIATION-INDUCED SURFACE NANOGRAFTING OF POLY(GLYCIDYL METHACRYATE) ONTO HDPE AND BOPP FILMS

FLAVIA QUIROGA; MARIANO GRASSELLI

Jeju Island

Simposio; 11th Meeting of the Ionizing Radiation and Polymers Symposium IRaP; 2014

IRaP IAEA

The incorporation of polymeric grafts induced by ionizing radiation is a very well established technology of polymer modification. The pre-irradiation techniques, in vacuo or in air, are the most industrially demanded as a consequence of the cability to split the process in two independent steps. However the simultaneous grafting technique has particular features which cannot always be replaced. These include the contribution of the solvent radicals and the dispersion of the monomer in the sample during the irradiation process. Glycidyl methacrylate (GMA) monomer is an excellent precursor that allows easy grafting polymerization and further functionalization for different applications. Therefore, it possible to generated materials useful for adsorption with many applications such as metal recovery, proteins purification and cell immobilization. According the application, surface-grafting thickness of the grafts in the micrometer range can be achieved varying proportionally the initial monomer concentration [1], but there are changes in the optical properties of the material as a consequence of the modification. Nanometer-scale grafted layers cannot be achieved by only reducing the monomer concentration. Instead, inhomogeneous surface coating is reached, according AFM images. The aim of this work was to obtain a surface-grafted of pGMA onto films of high density polyethylene (HDPE) and biaxially oriented polypropylene (BOPP) at the nanometer range, keeping the optical properties of the original material. Simultaneous grafting was performed onto HDPE and BOPP films soaked in detergent/GMA aqueous solutions, using a 60Co gamma source. Tween-20 and n-dodecyl sulfate (SDS) in the micromolar concentration (4-40 M - below their critical micellar concentration) were able to dissolve the GMA, which was in concentrations below 1%. After irradiation, with a dose of 10 kGy, only the samples containing SDS shows a homogeneous dispersion. Grafting yields could not be measured by gravimetric determinations because they were in the detection limit. However, the presence of the polyGMA onto the polymer surfaces was confirmed by ATR FT-IR signal at 1720 cm-1, corresponding to the carbonyl of GMA. To quantify the grafting amount it was anchored a fluorescent probe and measured directly onto the surface by a solid-state fluorometer, reaching values between 1 and 9 pmol/cm2 for different conditions. Also this technique was able to demonstrate the uniformity of the surface modification. AFM images show a clearly smoothing of the polymer surfaces and optical properties of materials were not changed. It is also interesting to remark the homopolymer of polyGMA after the irradiation treatment is dispersed in nanoparticles of narrow distribution.