Combinatorial Initiated CVD for Polymeric Thin Films

Abstract

A new combinatorial initiated (i)CVD system is fabricated and used to efficiently determine the deposition kinetics for two new polymeric thin films, poly(diethylaminoethylacrylate) (PDEAEA) and poly(dimethylaminomethylstyrene) (PDMAMS). The results of combinatorial depositions are compared to blanket iCVD under identical conditions using the appropriate vinyl monomer with tert-amylperoxide as the initiator. Fourier transform infrared spectroscopy (FTIR) reveals similar chemical structure in blanket and combinatorial films. FTIR also shows that functional groups are retained in iCVD of PDMAMS, whereas essentially all fine chemical structure of the material is destroyed in plasma-enhanced (PE)CVD. The maximum observed growth rates of PDEAEA and PDMAMS were 43 and 11 nm min -1 , respectively. The activation energy of growth with respect to filament temperature (E a,filament ) was 88.4±1.6 kJ mol -1 for PDEAEA and 42.0±1.7 kJ mol -1 for PDMAMS. Activation energies for growth with respect to substrate temperature (E a,substrate ) are -59.5±2.7 kJ mol -1 for PDEADA and -82.7±2.6 kJ mol -1 for PDMAMS, with the negative values consistent with adsorption-limited kinetics. The molecular weight of PDEAEA films ranges from 1 to 182 kDa as a function of substrate temperature. It is found that in all cases the combinatorial system agreed (within experimental uncertainty) with results of blanket iCVD, thus validating the use of the combinatorial system for future iCVD studies.

Chemical Vapor Deposition of Conformal, Functional, and Responsive Polymer Films

“…The ability to vary properties down the length of a film also allows for combinatorial discovery. For example, multiple filament temperature zones were used to rapidly quantify the kinetics of iCVD poly(diethylaminoethyl acrylate) and poly(dimethylamino methyl styrene) thin film growth 273…”

“…Most iCVD takes advantage of the thermal decomposition of the initiator, achieved upon contact with a resistively heated filament array in the vacuum chamber 78, 107, 177, 273, 285, 288. Thermal initiators for iCVD include perfluorooctane sulfonyl fluoride,78 triethylamine, 288 tert ‐butyl peroxide,107 and tert ‐amyl peroxide 285.…”

“…Alternatively, a Type II photoinitiator that creates free‐radical sites on the substrate surface, such as benzophenone, can be used to graft the polymer to the substrate 233, 290. Successful free‐radical polymerization and copolymeriza‐ tion by iCVD has been reported for a wide range of monomers,1 including acrylates,6, 86, 180, 198, 233, 273, 285, 287, 291–294 methacrylates,5, 6, 59, 81, 85, 107, 109, 177, 180, 181, 198, 199, 247, 263, 287–300 styrenics,108, 233, 273, 286, 301, 302 1‐vinyl‐2‐pyrrolidone,188 maleic anhydride,108, 286 and 1,3,5‐trivinyltrimethylcyclotrisiloxane 180, 303–305…”

“…For iCVD, where radicals form from the thermal decomposition of initiator molecules, the filament temperature strongly influences deposition rate. At low filament temperatures, deposition rate increases with filament temperature according to the Arrhenius relation 78, 107, 273, 339. The gas temperature between the filaments and the surface can be modeled using a logarithmic temperature profile from which an apparent activation energy can be derived 340, 341.…”

Micro- and nano-surface structures based on vapor-deposited polymers

“…In an extended work, another version of the gradient copolymer containing aldehydes and amine gradients was generated, and a subsequent cell-culture study showed that cell-signaling adenovirus was correlated along the copolymer gradients [ 74 ]. A similar combinatorial approach has also been demonstrated to generate poly(diethylaminoethylacrylate) and poly(dimethylaminomethylstyrene) gradients using an initiated CVD system [ 75 ]. The route-controlled click reactions, including a thiol-yne reaction and a copper-free alkyne/azide click reaction, were enabled to create continuous and reverse gradients on a CVD deposited poly[(4-methylpropiolate- p -xylylene)- co -( p -xylylene)] surface.…”