| Abstract
| - Initiated chemical vapor deposition (iCVD) of alternating copolymer thin films has been achieved for the first time.Copolymerization is desirable for maleic anhydride (Ma) since this monomer does not homopolymerize to an appreciableextent. At conditions where the observed deposition rates for styrene (S) and Ma homopolymers were only 0 and 5.5nm/min, respectively, combining the two monomers resulted in a much higher deposition rate of 75.4 nm/min. iCVDprocesses utilize low energy (<30 W) to generate peroxy radicals from initiator molecules while avoiding degradationof functional groups in the monomers. Indeed, full retention of the anhydride functionality from the Ma monomerand avoidance of undesirable side reactions was observed in iCVD of poly(styrene-alt-maleic anhydride) (PSMa)copolymer films. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and 13C nuclear magneticresonance (NMR) conclusively demonstrate that all of the copolymer films contain 50% styrene and 50% Ma (withinexperimental error), irrespective of gas feed ratios employed during the deposition. The 13C NMR signal in the136−140 ppm region from the quaternary carbon in styrene and additional distortionless enhancement polarizationtransfer experiments confirmed that the copolymers are strictly alternating. Varying the gas feed ratio of Ma to styreneprovided control over deposition rates and number-average molecular weights. Number-average molecular weightsvaried from 1380 to 4680 g/mol, and deposition rates varied from 6.3 to 75.4 nm/min.
|
