Crystallization in Polymer Thin Films: Morphology and Growth

Abstract

Confinement of semi-crystalline polymers into thin films can affect both the morphology and the growth of the resultant crystals. Several morphologies, including polycrystalline and single crystalline, can be obtained in thin films under certain conditions. In addition, the molecular orientation and kinetics can be affected by the temperature, film thickness, and interfacial energy. This chapter is a review of various reports in thin film crystallization.

Solution Crystallization Behavior of Crystalline−Crystalline Diblock Copolymers of Poly(ethylene oxide)-block-poly(ε-caprolactone)

“…The tethering density of the PCL on the PEO single crystal surface is calculated to be 1.19 nm -2 , which is quite high for tethered polymer chains. Although the PCL chains are small, with an estimated R g of 2.6 nm, 39 the σ ~value is 25.4. This value greatly exceeds the onset of entering the highly stretched region of 14.3.…”

“…The lack of crystallization may be due to either the low tethering density or a small layer thickness, d AM , of the tethers ( d AM = 3.2 nm for both systems, which is also on the order of R g ). Nucleation may be significantly hindered at room temperature by a lack of material (tethering density) and/or the constraints of a single layer thickness, especially when one end is tethered to the surface. − It has been shown that at small thicknesses (on the order of R g ) homopolymer crystallization can be hindered because the size (thickness or volume) does not support a stable nucleus; however, some reports show a stable crystal with a d -value larger than the film thickness. In our case, the tethering of one end hinders the mobility of the chains to form these crystals even if a stable nucleus could be formed.…”

Poly(alkylene 2,5-furanoate)s thin films: Morphology, crystallinity and nanomechanical properties

“…Moreover, polymer thin films have been a subject of academic debates for over the past 20 years [28][29][30][31]. In the particular case of semicrystalline polymers, the confinement imposed by the thin film geometry, and the polymer-substrate adsorption effects, resulted in differences in the crystallization rate [32,33], crystalline morphology [34][35][36], thermal transitions and polymers' molecular dynamics [32,37]. In turn, preparing poly(alkylene 2,5-furanoate)s can be also a way to tune their physical properties, at nanoscale levels.…”

Manipulation of Crystallization Sequence in PEO-b-PCL Films Using Solvent Interactions

“…The acetone film (green line) appeared to have a little more amorphous fraction (band absorbance at 1734 cm –1 ), and the toluene film (red line) appeared to have a little less, though neither of these samples was drastically different than the others. If these results are taken to be significant, it would imply that the crystallization from acetone may be less perfect due to fast evaporation and that the flat-on orientation in the toluene film provided the space to increase crystallinity since growth was two-dimensional, parallel to the substrate, instead of the typical three-dimensional spherulitic growth …”

“…If these results are taken to be significant, it would imply that the crystallization from acetone may be less perfect due to fast evaporation and that the flat-on orientation in the toluene film provided the space to increase crystallinity since growth was two-dimensional, parallel to the substrate, instead of the typical threedimensional spherulitic growth. 66 With the morphological evidence from the POM image in Figure 5c and the FTIR spectra of Figure 6b, it was concluded that the toluene film has flat-on crystals with some aggregates. Perpendicular vibrational bands associated with crystallization were present in the toluene spectra; therefore, crystallization was confirmed, though not obvious from the POM image.…”