Chemical vapor deposition of antimicrobial polymer coatings

Abstract

There is large and growing interest in making a wide variety of materials and surfaces antimicrobial. Initiated chemical vapor deposition (iCVD), a solventless low-temperature process, is used to form thin films of polymers on fragile substrates. To improve research efficiency, a new combinatorial iCVD system was fabricated and used to efficiently determine the deposition kinetics for two new polymeric thin films, poly(diethylaminoethylacrylate) (PDEAEA) and poly(dimethylaminomethylstyrene) (PDMAMS), both candidates for antimicrobial coatings. Fourier transform infrared (FTIR) spectroscopy shows that functional groups are retained in iCVD of PDMAMS and PDEAEA, whereas essentially all fine chemical structure of the material is destroyed in plasma-enhanced CVD. It was found that the combinatorial system in all cases provided agreement, within experimental certainty, with results of blanket iCVD depositions, thus validating the use of the combinatorial system for future iCVD studies. Finished nylon fabric was subsequently coated with PDMAMS by iCVD with no affect on the color or feel of the fabric. Coatings PDMAMS of up to 540 gg/cm2 were deposited on fabric.

(cont.) A coating of 40 gpg/cm2 of fabric was found to be very effective against gram-negative E. coli, with over a 99.9999%, or 6 log, reduction in viable bacteria in one hour. A coating of 120 gg/cm2 was most effective against the gram-positive B. subtilis. Further tests confirmed that the iCVD polymer did not leach off the fabric. Type-II photoinitiation was utilized to perform vapor phase deposition of covalently-bound polymer coatings of the polymer PDMAMS. The durability was improved so that 80 wt% of the fabric coating was retained after extended antimicrobial testing and three rounds of ultrasonication. The coating was effective, killing 99.9% of E. coli in one hour. The gCVD process was then further explored using the less-UV-sensitive monomer DEAEA for deposition onto spun cast PMMA thin films. Durable films up to 54 nm thick retained 94% of their thickness after 10 rounds of ultrasonication. Gel Permeation Chromatography (GPC) and Variable Angle Spectroscopic Ellipsometry (VASE) swelling cell measurements gave estimated ranges of 72-156 kDa for the molecular weight and 0.1-0.24 chains/nm2 for the graft density.