•Ultrathin gold and copper coatings are thermally evaporated on polydimethylsiloxane.•Gold is growing in the form of isolated particles (Volmer-Weber growth mode).•Copper is growing in the form of a ...continuous film (Stranski–Krastanov growth mode).•Substrate elastic modulus has a negligible role in the microstructure of the coating.
This article presents a morphological study of ultrathin gold and copper coatings (between 1 nm and 20 nm equivalent metal thickness) thermally evaporated on polydimethylsiloxane (PDMS). Results are discussed on the basis of transmission electron microscopy and atomic force microscopy. Gold is demonstrated to grow in the form of isolated particles following a Volmer-Weber growth mode, whereas copper more likely grows in the form of a continuous film, following a Stranski–Krastanov growth mode. Our results demonstrate a negligible role of the PDMS elastic modulus (between 0.5 and 2.5 MPa) in the gold and copper coatings morphology respectively. However, significant morphological changes are observed when the metals are thermally evaporated on a PDMS substrate of extremely higher surface elastic modulus obtained after O2 plasma exposure.
Stimuli‐responsive materials have properties that depend on the environment in which they are used. In most cases, the material itself is formulated to react to the corresponding stimulus. However, ...many phenomena occur at the surface of the material. In this context, the design and the investigation of the reactivity of stimuli‐responsive surfaces are particularly interesting. More precisely, this review focuses on functional coatings that react via Diels–Alder (DA) chemistry, a thermoreversible reaction between a diene and a dienophile. According to the nature of the substrate, these coatings are mainly based on self‐assembled monolayers or silane assemblies, on polydopamine derivatives, or on polymer thin films deposited by vapor‐phase processes including plasma polymerization. The different works discussed here show that interfacial thermoreversible reactions occur between a DA‐functionalized surface and a DA reactant in solution but also between two solid substrates are possible. The direct cycloaddition is always described in the cited papers but the reversibility of the reaction is less discussed. The latter however remains very challenging for smart applications in material science.
This review reports on the fabrication of functional surfaces with thermoreversible properties and the understanding of their reactivity via the Diels–Alder reaction. Based on various functionalization processes, the designed surfaces have various physico‐chemical properties, leading to different Diels–Alder reactivity. The direct cycloaddition is always described in the cited papers but the reversibility of the reaction is less discussed.
The chemical properties of plasma polymers strongly depend on the operating conditions of plasma polymerization and impact their final application. Low‐pressure pulsed plasma polymerization of maleic ...anhydride was investigated at different positions from the glow discharge in a unique 1‐m‐long reactor. Based on a macroscopic approach, the growth kinetics of maleic anhydride plasma polymerization was investigated, leading to the identification of three growth regimes. The calculation of apparent activation energies associated with each regime and each position and the chemical characterization of polymer films by X‐ray photoelectron spectroscopy and attenuated total reflection–Fourier‐transform infrared as well as optical emission spectroscopy analyses of plasma species formed during deposition strongly indicate a combined spatial and temporal influence on the plasma polymerization kinetics.
A laboratory experiment for the determination of the cross-linking density of silicone elastomers is described on the basis of swelling experiments and mechanical tests. In the experiment, the ...macroscopic swelling and mechanical behaviors of the elastomers were discussed as a function of the cross-linking density, which can be easily controlled by varying the base-to-curing-agent ratio during elastomer synthesis. The cross-linking density and the average molecular weight between cross-links were calculated from the swelling degree at equilibrium through the Flory–Rehner theory and from a simple mechanical model. The results have shown a good convergence of the average molecular weight between cross-links calculated from the two methods, respectively. On a more general note, the suggested experiments and the associated results offered numerous opportunities for discussions on macromolecular architectures, interactions between polymers and solvents, and mechanical properties of elastomeric materials.
Pressurized Metered Dose Inhalers (PMDIs) are mostly used for the treatment of respiratory diseases. The long-term durability of Pressurized Metered Dose Inhalers heavily depends on the functionality ...of the elastomeric gaskets they contain. The mechanical, chemical, and morphological stability of those elastomeric gaskets is of a great concern to the overall performance of PMDIs. Elastomers used as sealing materials ethylene-propylene-diene monomer (EPDM), have been investigated in this work, during an accelerated ageing study. The evolution of two formulation of EPDM has been reported via standard characterization techniques. Optical microscopy was used to determine any topographic changes on the surface impacted by chemical or mechanical stress. Attenuated total reflection Fourier transform infrared (ATR-FTIR), swelling tests, and thermogravimetric analysis (TGA) were performed to assess the chemical and structural modification of the materials before and after ageing. Surface NMR measurement were conducted to study the degradation as a function of the thickness of the elastomeric gaskets. In the presence of chemical constraints, degradations were observed compared to mechanical constraints which did not lead to significant changes.
•Control of two formulation of EPDM used in Pressurized Metered Dose Inhalers.•EPDM gaskets aged within metering valves under chemical and mechanical stress degraded faster than under regular stress.•Surface NMR was used as a unique tool to follow and understand the chemical modifications induced by accelerated ageing.
The impact of surface chemistry on the morphogenesis of maleic anhydride plasma polymer is investigated on silicon wafers with very well‐controlled surface chemistries (i.e., native oxide, ...hydroxyl‐rich, and alkyl‐rich). A particular attention is paid to characterize the early stages of growth. Two different morphologies of polymer films are obtained, depending on the hydrophilic or hydrophobic nature of the substrate surface, even though the chemical composition is very similar. Homogeneous and dense polymer films are formed on hydrophilic substrates due to the strong affinity of plasma species toward the surface. Elongated nanostructures resulting in a less dense polymer film grow on the hydrophobic surface, which are assumed to be the result of the low affinity of plasma species.
The morphogenesis of maleic anhydride plasma polymer is investigated on hydrophilic and hydrophobic surfaces. Whereas homogeneous, smooth, and dense polymer films are formed on hydrophilic substrates, elongated nanostructures resulting in a less dense polymer film grow on the hydrophobic surface. These results are supported by a thorough characterization of the polymer thin films from the early stages of plasma exposure, including atomic force microscopy and X‐ray reflectivity.
We report a new class of functionalized polylutidine polymers that are prepared by chemical vapor deposition polymerization of substituted 2(1,4)benzeno2(2,5)pyridinophanes. To prepare sufficient ...amounts of monomer for CVD polymerization, a new synthesis route for ethynylpyridinophane has been developed in three steps with an overall yield of 59 %. Subsequent CVD polymerization yielded well‐defined films of poly(2,5‐lutidinylene‐co‐p‐xylylene) and poly(4‐ethynyl‐2,5‐lutidinylene‐co‐p‐xylylene). All polymers were characterized by infrared reflection–absorption spectroscopy, ellipsometry, contact angle studies, and X‐ray photoelectron spectroscopy. Moreover, ζ‐potential measurements revealed that polylutidine films have higher isoelectric points than the corresponding poly‐xylylene surfaces owing to the nitrogen atoms in the polymer backbone. The availability of reactive alkyne groups on the surface of poly(4‐ethynyl‐2,5‐lutidinylene‐co‐p‐xylylene) coatings was confirmed by spatially controlled surface modification by means of Huisgen 1,3‐dipolar cycloaddition. Compared to the more hydrophobic poly‐p‐xylylyenes, the presence of the heteroatom in the polymer backbone of polylutidine polymers resulted in surfaces that supported an increased adhesion of primary human umbilical vein endothelial cells (HUVECs). Vapor‐based polylutidine coatings are a new class of polymers that feature increased hydrophilicity and increased cell adhesion without limiting the flexibility in selecting appropriate functional side groups.
Coat of many nitrogens! Chemical vapor deposition based polymers have been widely used as biomedical interfaces, but all of these coatings are restricted to simple all‐carbon backbones. For the first time, a class of functionalized lutidine polymers has been prepared by chemical vapor deposition (see figure). This reactive coating opens new perspectives for the design of new cell biomedical applications.
The properties of the final product resulting from plasma polymerization strongly depend on the operating conditions and they impact the final application of the plasma polymer coating. Low‐pressure ...pulsed plasma polymerization of maleic anhydride was investigated at two different positions in relation to the glow discharge in a 1‐m‐long tubular reactor. Interestingly, competition was observed in the deposition of maleic anhydride plasma polymer in the form of a smooth thin film versus that in the form of nanoparticles. The possibility of a spatiotemporal control of plasma polymerization enabled the deposition of a plasma coating with tunable morphological properties depending on the sample position from the glow discharge and on the plasma pulse parameters (on‐time and off‐time).
Low‐pressure pulsed plasma polymerization of maleic anhydride was investigated at two different positions in relation to the glow discharge in a tubular reactor. Interestingly, competition was observed in the deposition of maleic anhydride plasma polymer in the form of a smooth thin film versus that in the form of nanoparticles. The morphology of the plasma polymer coating could be tailored by selecting the appropriate sample position from the glow discharge and plasma pulse parameters (on‐time and off‐time).
Functional ultrafiltration membranes can be used for water decontamination. Here, we investigate the use of plasma polymerization to modify polymeric membranes with poly(allylamine) in order to ...filtrate aqueous solutions contaminated with Ni(II) ions. A preliminary study is performed to control growth kinetics of polymer thin films with respect to the energy provided to the precursor during deposition. Filtration experiments then enable to quantify the efficiency of the different functional coatings as for their retention of Ni(II) ions and to identify the optimal characteristics of the polymer thin films. Retention rate as high as 96% can be achieved by this single‐step functionalization process, which is very competitive compared to conventional multi‐step wet chemical functionalization techniques.
Ultrafiltration membranes are functionalized with poly(allylamine) by plasma polymerization for water decontamination. By controlling growth kinetics and physico‐chemical properties of plasma coatings, retention rate of Ni(II) ions as high as 96% can be achieved by this single‐step functionalization process, which is very competitive compared to conventional multi‐step wet chemical techniques.
In this work, the use of Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) was explored as a technique for monitoring the interfacial retro Diels–Alder (retro DA) reaction occurring on ...well-controlled self-assembled monolayers (SAMs). A molecule containing a Diels–Alder (DA) adduct was grafted on to the monolayers, then the surface was heated at different temperatures to follow the reaction conversion. A TOF-SIMS analysis of the surface allowed the detection of a fragment from the molecule, which is released from the surface when retro DA reaction occurs. Hence, by monitoring the decay of this fragment’s peak integral, the reaction conversion could be determined in function of the time and for different temperatures. The viability of this method was then discussed in comparison with the results obtained by 1H NMR spectroscopy.
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