Nucleation and Growth of Poly(ε-caprolactone) on Poly(tetrafluoroethylene) by in-Situ AFM

Abstract

The nucleation behavior of poly( -caprolactone) (PCL) on friction-deposited poly(tetrafluoroethylene) (PTFE) was investigated by means of atomic force microscopy (AFM). This technique allows for imaging of the nucleation and crystallization processes in real time. An estimation of the PCL crystal orientation on the PTFE substrate is made by evaluating the growth rates and the growth geometry of the lamellar crystals formed on PTFE. On the basis of the data collected, it is proposed that PCL crystallizes on PTFE predominantly via a (100) PCL contact plane (∼80%). The crystals adopt an orientation that minimizes the lattice mismatch at the interface between the nucleating PTFE and PCL. A (010) PCL|(100)PTFE contact plane was simultaneously observed at a lower occurrence of approximately 20%. Visualization of the PTFE fibrillar morphology at higher resolution during isothermal crystallization revealed the appearance of a third PCL crystal orientation which developed later in time. The corresponding crystals were observed to develop from grooves on the PTFE substrate, indicating a graphoepitaxial nucleation mechanism.

Influence of Boehmite Nanoparticle Loading on the Mechanical, Thermal, and Rheological Properties of Biodegradable Polylactide/Poly(ϵ‐caprolactone) Blends

“…In each group, the intensity of the BAI peaks was distinctly increased for BAI loadings of 4 wt% or more. The shift in the value of 2 θ toward lower values indicates that there was a change in the crystal type of the base polymer …”

Nucleation versus melting point depression of the polycaprolactone phase in polypropylene/polycaprolactone blends

“…Graphoepitaxy, which implies a pseudoepitaxy process induced by ridges or surface defects of the substrate, has also been proposed [7,35,36]. In the case of polymers, it is generally assumed that true epitaxy is the prevalent mode of nucleation, although it is well proven that surface topography can also determine the orientation of the growing polymer crystals [8].…”

“…Recently, Vancso et al [8] studied PCL crystal growth on highly oriented PTFE fibrils. They demonstrated, by using AFM, that PTFE is an effective nucleating agent for PCL and that either true epitaxy or graphoepitaxy are possible.…”

“…Several phenomena that influence the crystallization behaviour of the system have been reported. Among these phenomena, the following can be mentioned: nucleation and epitaxial crystallization [4][5][6][7][8], migration of heterogeneities from one phase towards the other [9,10], fractionated crystallization [11,12], rejection, engulfing or deformation of the dispersed phase by the growing superstructures of the matrix [13][14][15], and induction of crystal modifications [16]. Although crystallizability of the components induces immiscibility in the solid state in most cases, if a good residence time in the barrel was about 5 min.…”

Crystallization Kinetics

“…New experimental techniques are, however, starting to become available that might lead to a resolution of some of these issues. Scanning probe microscopy offers the opportunity to follow crystal growth at a surface in real-time, with nanometer resolution, and hence to quantify the kinetics by direct observation at length scales that are close to those of the fundamental crystallizing unit, and to the size scale of the polymer chain (92,(145)(146)(147)(148)(149)(150)(151)(152). Several groups (145)(146)(147)149) have reported that lamella crystallization from the melt, at least where several lamellae are growing adjacently, does not occur at a constant temperature-controlled rate.…”