Structural modification of poly (methyl methacrylate) due to electron irradiation

We have studied the changes in various properties of Poly (methyl methacrylate) (PMMA) after irradiation with electron beam using several techniques and tried to understand the correlation of modification with electron beam energy and current. This work was carried out with an aim to fabricate 3D structures in freestanding PMMA thin films by lithography. Chemical, structural and electrical alterations in PMMA thin film after irradiation with different doses were monitored using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and frequency dependent dielectric measurements, respectively. All the measurements invariably showed that the irradiation induced degradation of PMMA resulted in breaking of parental chain and associated changes. FTIR indicated increase in un-saturation (CC bonds) and formation of carbon dioxide in irradiated samples with increase in electron beam energy and dose. The radial distribution function (RDF) analysis showed a change in the short range order with increase in dose, ascribed to the increase in the breaking of polymer chain. Frequency dependent dielectric measurements revealed that the conductivity was more for un-irradiated PMMA. All the measurements invariably showed that the amount of damage increased with increase in electron energy and dose.