6 research outputs found
Thickness-Dependent Swelling Behavior of Vapor-Deposited Smart Polymer Thin Films
In this contribution, the temperature-dependent
swelling behavior
of vapor-deposited smart polymer thin films is shown to depend on
cross-linking and deposited film thickness. Smart polymers find application
in sensor and actuator setups and are mostly fabricated on delicate
substrates with complex nanostructures that need to be conformally
coated. As initiated chemical vapor deposition (iCVD) meets these
specific requirements, the present work concentrates on temperature-dependent
swelling behavior of iCVD polyÂ(<i>N</i>-isopropylacrylamide)
thin films. The transition between swollen and shrunken state and
the corresponding lower critical solution temperature (LCST) was investigated
by spectroscopic ellipsometry in water. The films’ density
in the dry state evaluated from X-ray reflectivity could be successfully
correlated to the position of the LCST in water and was found to vary
between 1.1 and 1.3 g/cm<sup>3</sup> in the thickness range 30–330
nm. This work emphasizes the importance of insights in both the deposition
process and mechanisms during swelling of smart polymeric structures
Wrinkling of an Enteric Coating Induced by Vapor-Deposited Stimuli-Responsive Hydrogel Thin Films
Interlink between Tunable Material Properties and Thermoresponsiveness of Cross-Linked Poly(N-vinylcaprolactam) Thin Films Deposited by Initiated Chemical Vapor Deposition
Thickness-Dependent Swelling Behavior of Vapor-Deposited Hydrogel Thin Films
Hydrogel thin films containing temperature sensitive chemical functionalities (such as N-isopropylacrylamide, NIPAAm) are particularly interesting for sensor and actuator setups. Complex 3D structures can be conformally coated by the solvent free technique initiated Chemical Vapor Deposition, with precise control over chemical composition and film thickness. In this study, NIPAAm-based thin films with film thicknesses ranging from tens to several hundreds of nanometers and with different amounts of cross-linking were deposited. Above the lower critical solution temperature (LCST), these films repel out water and hence shrink. The amount of cross-linking and the deposited film thickness were successfully identified to both affect shape and position of the LCST transition of these systems: a promising basis for tuning response properties
Growth Regimes of Poly(perfluorodecyl acrylate) Thin Films by Initiated Chemical Vapor Deposition
Control over thin film growth (e.g.,
crystallographic orientation
and morphology) is of high technological interest as it affects several
physicochemical material properties, such as chemical affinity, mechanical
stability, and surface morphology. The effect of process parameters
on the molecular organization of perfluorinated polymers deposited
via initiated chemical vapor deposition (iCVD) has been previously
reported. We showed that the tendency of polyÂ(1<i>H</i>,1<i>H</i>,2<i>H</i>,2<i>H</i>-perfluorodecyl
acrylate) (pPFDA) to organize in an ordered lamellar structure is
a function of the filament and substrate temperatures adopted during
the iCVD process. In this contribution, a more thorough investigation
of the effect of such parameters is presented, using synchrotron radiation
grazing incidence and specular X-ray diffraction (GIXD and XRD) and
atomic force microscopy (AFM). The parameters influencing the amorphization,
mosaicity, and preferential orientation are addressed. Different growth
regimes were witnessed, characterized by a different surface structuring
and by the presence of particular crystallographic textures. The combination
of morphological and crystallographic analyses allowed the identification
of pPFDA growth possibilities between island or columnar growth