Synthesis and dielectric properties of photoreactive polystyrene containing [1-(3-isopropeny -phenyl)-1-methyl-ethyl]-carbamate in the side chain

Novel polystyrene derivatives comprising [1-(3-isopropenyl-phenyl)-1-methyl-ethyl]-carbamate in the side chain were synthesized as photoreactive copolymers. Poly(4-vinylphenol) was made to react with 1-(1-isocyanato-1-methyl-ethyl)-3-isopropenyl-benzene (m-TMI) and the unreacted hydroxyl groups were protected with acetyl chloride. The copolymers are highly sensitive to the radical photoinitiators that can be activated by irradiation of UV light (lambda = 300-365 nm). FTIR spectroscopy was employed to monitor the structural changes in the copolymers exposed to UV irradiation. The dielectric properties of the copolymers were investigated by measuring the capacitance and calculating the permittivity as a function of frequency, along with the I-V characteristics. Their properties were compared with those of thermally crosslinkable poly(4-vinylphenol) blended with poly(melamine-co-formaldehyde), which is frequently used as a dielectric layer in organic field-effect transistors (OFETs). No significant dielectric dispersion was observed in the frequency range of 1 kHz-1 MHz. The dielectric constant was determined to be in the range of 4.2-6.0, which offers a potential for the application of these copolymers to OFET gate insulators. These soluble dielectrics exhibit good film uniformity and can also be patterned using a standard photolithographic technique. (c) 2008 Wiley Periodicals, Inc.