From microns to nanometers: Morphology development in semicrystalline polymers by scanning force microscopy

Abstract

In studies of spherulitic crystallization in polymers, many questions pertaining to the mechanism of the crystallization process have remained unanswered. A currently accepted view describes the development of spherulites from a framework of individual dominant lamellae that splay apart and branch (e.g., by a dislocation mechanism). This model, in addition, assumes that the space between the dominant lamellae is filled by subsidiary lamellae. In the center of a spherulitic entity, there is a hedritic core that occupies a relative volume that depends on the level of maturity of the spherulitic development. Typical hedritic views consist of lamellae that have a flat stack, or sheaflike, splaying appearance depending on the angle and depth of observation with respect to the central stack of lamellae. Visualization of the three-dimensional appearance of these hedrites by atomic force microscopy (AFM) and the observation of their growth in situ are the subjects of this article. First, we describe AFM studies of hedrites observed at etched surfaces of p-isotactic polypropylene 492 VANCSO ET AL.porting splaying, branching via dislocations, and development of curved lamellae is presented. In the second part, we describe real-time hot-stage AFM in situ observations of the hedritic growth in poly(ethy1ene oxide) (PEO) and poly-(E-caprolactone) (PCL).

Crystal Growth in Poly(L‐lactide) Thin Film Revealed by in situ Atomic Force Microscopy

“…Vancso et al [26] have determined the effect of a cantilever tip on the nucleation in poly(ethylene oxide) (PEO) thin film by using AFM. They demonstrated that a strong shear force on the PEO surface induced the nucleation parallel to the scanning direction by contact mode AFM tip.…”

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

“…The formation of chain-folded lamellae (i.e., primary nucleation) leads to further growth of the lamellae through the processes of branching and splaying (e.g., see Fig. 4 in Vancso et al 75 ). The degree of branching and splaying is mainly controlled by the degree of undercooling (i.e., the difference between the T m 0 and the T c : ⌬T ϭ T m 0 Ϫ T c ) in an increasing manner.…”

AFM-tip-induced crystallization of poly(ethylene oxide) melt droplets

“…Pearce and Vancso [1,2] reported that the AFM tip could not induce poly(ethylene oxide) (PEO) crystallization. However, for poly(e-caprolactone) (PCL), Beekmans et al [3] observed the AFM-tip-induced nucleation of the PCL chains, which further resulted in the growth of edge-on crystals normal to the scan direction. The above two different results arise from their difference in strength of lateral forces applied in the AFM experiments.…”