Branched Crystalline Patterns of Poly(ε-caprolactone) and Poly(4-hydroxystyrene) Blends Thin Films

Abstract

The chain organization of poly(ε-caprolactone) (PCL) in its blend with poly(4-hydroxystyrene) (PVPh) in thin films (130 ± 10 nm) has been revealed by grazing incident infrared (GIIR) spectroscopy. It can be found that PCL chains orient preferentially in the surface-normal direction and crystallization occurs simultaneously. The morphology of the PCL/PVPh blends films can be identified by optical microscopy (OM). When crystallized at 35 °C, the blends film shows a seaweed-like structure and becomes more open with increasing PVPh content. In contrast, when crystallized at higher temperatures, i.e., 40 and 45 °C, dendrites with apparent crystallographically favored branches can be observed. This characteristic morphology indicates that the diffusion-limited aggregation (DLA) process controls the crystal growth in the blends films. The detailed lamellar structure can be revealed by the height images of atomic force microscopy (AFM), i.e., the crystalline branches are composed of overlayered flat-on lamellae. The branch width has been found to be dependent on the supercooling and PVPh content. This result differs greatly from pure PCL, in which case the crystal patterns controlled by DLA process developed in ultrathin film or monolayers of several nanometers. In the PCL/PVPh blends case, the strong intermolecular interactions and the dilution effect of PVPh should contribute to these results. That is to say, the mobility of PCL chains can be retarded and diffusion of them to the crystal growth front slows down greatly, even though the film thickness is far more than the lamellar thickness of PCL.

Crystallization behavior in miscible blends of poly(ε‐caprolactone) and poly(hexylene adipate) with similar thermal properties studied by time‐resolved Fourier transform infrared spectroscopy

“…The bands at 1295 and 1179 cm −1 are the stretching of COC. Recently, through the use of gazing incidence reflection infrared (GIR‐IR) spectroscopy, the band at 1245 cm −1 has been suggested to be the COC stretching parallel to the CC chain skeleton . The band situated at 841 cm −1 is attributed to the CH 2 rocking mode and was free from other overlapping bands.…”

Effect of thiophene spacers in benzodithiophene‐based polymers for organic electronics

“…Furthermore, the peak at 20.74 (4.28 Å) is due to π–π stacking of the polymer chains, which is again closer to the π–π stacking distance of the analog [poly(bDTBDT)] with no thiophene spacers . Despite the lower molecular weight in poly(Th‐bDTBDT‐Th) the close assembly with comparable conjugation length ensure higher field effect mobility and space charge mobility compared to its previously reported analog [poly(bDTBDT)] …”

Crystallization of Polymer Chains Chemically Attached on a Surface: Lamellar Orientation from Flat-on to Edge-on

“…When the thickness is 72 nm, the chains form a smooth layer with a low RMS roughness (2.08 nm), indicating that PHEMA- g -PCL chains still form a pancake. Obviously, the PCL lamellae favor a flat-on orientation in this case . On the other hand, we can observe many small scattered fragments with lamellar texture in the zoom-in image (indicated by arrows), which are nearly uniform with a RMS roughness of ∼1.25 nm and topologically homogeneous as shown by their phase images (Figure S3a, bright zones).…”