An X-ray and neutron reflectometry study of ‘PEG-like’ plasma polymer films

Abstract

Plasma-enhanced chemical vapour-deposited films of di(ethylene glycol) dimethyl ether were analysed by a combination of X-ray photoelectron spectroscopy, atomic force microscopy, quartz crystal microbalance with dissipation monitoring (QCM-D), X-ray and neutron reflectometry (NR). The combination of these techniques enabled a systematic study of the impact of plasma deposition conditions upon resulting film chemistry (empirical formula), mass densities, structure and water solvation, which has been correlated with the films' efficacy against protein fouling. All films were shown to contain substantially less hydrogen than the original monomer and absorb a vast amount of water, which correlated with their mass density profiles. A proportion of the plasma polymer hydrogen atoms were shown to be exchangeable, while QCM-D measurements were inaccurate in detecting associated water in lower power films that contained loosely bound material. The higher protein resistance of the films deposited at a low load power was attributed to its greater chemical and structural similarity to that of poly(ethylene glycol) graft surfaces. These studies demonstrate the utility of using X-ray and NR analysis techniques in furthering the understanding of the chemistry of these films and their interaction with water and proteins.

Low‐Pressure Plasma Methods for Generating Non‐Reactive Hydrophilic and Hydrogel‐Like Bio‐Interface Coatings – A Review

“…The stability of PEO‐like plasma coatings in liquids has been reported to be satisfactory . Lopez et al soaked tetraglyme plasma polymers for one month in water and did not detect any changes except for some initial dissolution during the first minute of soaking although other types of PEO‐like coatings showed a reduction of their density, which was likely caused by water absorption . There were no changes in the chemical structures detectable by curve‐fitting of XPS C1s spectra within 5 d of incubation in water at 25 °C .…”

Antibiotic-decorated titanium with enhanced antibacterial activity through adhesive polydopamine for dental/bone implant

“…The high-resolution C 1s spectrum of the pristine Ti was deconvoluted into three different curves. The binding energies centred at 284.8, 286.5 and 288.8 eV were assigned to the carbon skeleton (-C-C-/-C-H-), hydroxyl group (-C-OH) and carbonyl group (-C¼O), respectively [32,33]. A broad peak assigned to the -C-Nbond at about 285 eV was recorded on both Ti-pDA and Ti-pDA-CS samples, indicating the presence of pDA and CS.…”

Probing the Interfacial Structure of Bilayer Plasma Polymer Films via Neutron Reflectometry

“…Interestingly, the film density and plasma glow discharge load power correlation seen in the HMDSO PP films is the opposite of what was observed in the DG PP system (lower power ¼ higher mass density), but is consistent with our previous reports on HMDSO and DG PP's. [30,31] The significant difference in the HMDSO bilayer broadening between the high and low power depositions can therefore be attributed to a significantly greater mass density and a higher degree of unsaturation/crosslinking for the high power film, which would result in less ablation/mixing during deposition of the dDG PP topcoat film.…”

“…This data indicates that the DG40 PP film is more unsaturated and is consistent with previous reports by us on these films. [31] For the HMDSO and AA PP films, the XPS high resolution C 1s spectra ( Figure 2) do not provide information on their degree of unsaturation, as the overlay of the spectra are of identical shape. The mass densities for the AA PP's at the two different load powers are the same but their compositions differ somewhat in terms of their hydrogen content (Table 3) indicating the lower power AA PP film is less unsaturated than the higher power AA PP film.…”

“…The SLD obtained for the PP films in this study are similar to those reported in the literature. [28,30,31] For the single layer HMDSO, AA, and DG PP films the structural model consists of a thin transition layer between the silicon substrate and the layer describing the majority of the PP film, except for the HM10 PP which can be described by a single layer. The remainder of the film (for all PP) possesses a uniform SLD and is very smooth at the air-film interface.…”