Initiated chemical vapor deposition of perfectly alternating poly(styrene-alt-maleic anhydride)

The ability of initiated chemical vapor deposition (iCVD) to precisely control compositions of polymer thin films has been extended to the deposition of perfectly alternating copolymers of styrene (S) and maleic anhydride (Ma). The driving force for alternation is the electropositive nature of the maleic anhydride monomer complemented by the electronegative character of the styrene monomer. These interactions permit the incorporation of monomers that do not react (or only to a limited extent) via traditional free-radical homopolymerizations. This is seen in iCVD deposition rates of 0 and 5.5 nm/min for poly(styrene) and poly(maleic anhydride) thin films, respectively, when tert-butyl peroxide (TBPO) is used as initiator. Combining styrene and maleic anhydride yields a maximum deposition rate of 75.4 nm/min. At different gas feed ratios of Ma to S, films of identical composition are obtained. XPS survey scans reveal that the carbon to oxygen ratio is 4, in agreement with the predicted alternating structure. Additionally, alternating structures of the copolymers were confirmed using 13C NMR, which reveals triad distributions. activity of the anhydride functionality has been exploited in solventless derivatizations of films with 2-aminoethanethiol. The extent of derivatization is monitored with Fourier transform infrared spectroscopy (FTIR).