The present study demonstrates the
successful deposition of poly(ethylhexyl
acrylate) thin films in a large-scale closed-batch initiated chemical
vapor deposition (iCVD) system. A horizontal cylindrical stainless-steel
vacuum tank, which is highly utilized in industrial vacuum applications,
was used as iCVD reactor. The effects of substrate temperature, precursor
ratio, and pressure on the deposition rates were studied, and the
results showed that a deposition rate of 315 nm/min can be achieved
in a single run at a reactor pressure of 600 mTorr. At a lower chamber
pressure of 400 mTorr, deposition rate decreases, whereas film uniformity
increases. By carrying out depositions at successive cycles, thicker
films could be obtained, without the need for extensive monomer consumption.
The yield percentage was found to be 3.5 for the films deposited in
closed-batch system at 400 mTorr, which is 35-fold larger than that
of the classical iCVD flow system.
Further understanding of the interactions between nanoparticles (NPs) and biological molecules offers new possibilities in the applications of nanomedicine and nanodiagnostics. The properties of NPs, including size, shape, and surface functionality, play a decisive role in these interactions. Herein, we evaluated the influences of gold NPs (AuNPs) with different sizes (5-60 nm) and shapes (i.e., spherical, rod, and cage) on the self-assembly of diphenylalanine (Phe-Phe) dipeptides. We found that the size of AuNPs smaller than 10 nm did not affect the self-assembly process of Phe-Phe, while bigger AuNPs (>10 nm) caused the formation of starlike peptide morphologies connected to one center. In the case of shape differences, nanorod and nanocage morphologies acted differently than spherical ones and caused the formation of densely packed, networklike dipeptide morphologies. In addition to these experiments, by combining photothermal properties of AuNPs with a Phe-Phe-based organogel having a thermo-responsive property, we demonstrated that the degelation process of AuNPs embedded organogels may be controlled by laser illumination. Complete degelation was achieved in about 10 min. We believe that such control may open the door to new opportunities for a number of applications, such as controlled release of drugs and tissue engineering.
This paper demonstrates the adhesive and hydrophobic modifications of glass, poly(ethylene terephthalate), and bamboo fabric surfaces using the initiated chemical vapor deposition (iCVD) process. iCVD of functional thin films is an all-dry and low-temperature alternative to the conventional wet coating processes. The as-deposited film is a terpolymer in which ethylhexyl acrylate and acrylic acid units comprised the pressuresensitive adhesive (PSA) part, while perfluorodecyl acrylate (PFDA) acted as the hydrophobic part due to its low surface energy fluorinated side groups. The PFDA composition in the iCVD terpolymer can be systematically varied by adjusting the initial gas feed fractions of monomers, as verified from FTIR and XPS analyses. The usage of the initiator tertbutyl peroxide during the depositions resulted in high deposition rates up to 80 nm/min at a filament temperature of 230 °C. The as-deposited films possessed high optical transparency with high shear and peel strength values. Depending on the chemical composition, the peel strength values were up to 0.5 N/25 mm on flexible PET substrates. After the coating, the highly porous bamboo surface not only became sticky due to the existence of the thin PSA layer on top but also the became near-superhydrophobic. The application of iCVD coating parameters to deposit hydrophobic PSA on moving large-area substrates under roll-to-roll deposition mode resulted in highly uniform coatings, which shows the potential of iCVD to be operated in industrial scales to functionalize the industrially important flexible substrates.
In this study, the successful transfer of chemical vapor deposition (CVD)‐grown graphene on an ordinary printing paper surface is demonstrated. Pristine paper is not a suitable substrate for graphene transfer because of its fragile and hydrophilic nature against the chemicals used during the transfer process. Two different fluoroalkyl polymers, namely poly(hexafluorobutyl acrylate) (PHFBA) and poly(perfluorodecyl acrylate) (PPFDA) are coated on paper surfaces by an initiated CVD (iCVD) technique to make the paper surfaces hydrophobic. Hydrophobicity is found to be an important factor in order for the graphene to be transferred onto the paper substrate. Although surfaces coated with PPFDA possess better hydrophobicity owing to their longer perfluoroalkyl group and higher roughness, the graphene transfer is found to be more successful on a PHFBA‐coated surface. A thin film of PHFBA on the paper surface acts as a prime layer for effective and defect‐free transfer of graphene and makes the paper surface ideal and robust during the graphene transfer process. The as‐transferred graphene layer on the PHFBA‐coated paper surface shows high conductivity values, even after repeated folding and flattening cycles.
This study demonstrates the deposition of poly(ethylhexyl acrylate-co-ethylene glycol dimethacrylate) (P(EHA-co-EGDMA)) copolymer thin films in a batch type initiated chemical vapor deposition (iCVD) reactor. Crosslinked copolymers are desired for many applications because of their high stable properties. iCVD polymers derived by monomers bearing only one vinyl bond are usually linearly structured polymers and hence they are not durable, which is unfavorable for many real-world applications. Robust crosslinked iCVD films can be produced with the help of crosslinkers. In a typical iCVD process, copolymer thin film is produced by constantly feeding monomer vapor and crosslinker into the reactor. The monomer/crosslinker ratio should be precisely controlled for fabrication of reproducible thin films. In order to eliminate problems caused by adjusting the flowrates of precursors, a closed-batch type iCVD reactor was used for the first time in this study to produce copolymer thin films. The variation of precursors' partial pressures allowed control over the copolymer thin film structures. As compared with homopolymer, copolymers showed the better chemical and thermal stable properties. Almost 40% of the copolymer thin film remained on the substrate surface at an annealing temperature of 300 C, whereas the homopolymer film was completely removed at an annealing temperature of 280 C.
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