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 poly(<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