Solution-grown lamellae

In general, it is possible to visualize individual solution-grown lamellae by both CM-AFM and TM-AFM. The same is true for many melt-grown lamellae. Due to the contrast based on the difference in energy dissipation between amorphous and crystalline phases in the TM-AFM phase images, the lamellae can be seen with excellent contrast, and hence, high resolution. Two examples of lamellae of poly (ethylene oxide) (PEO) viewed in flat-on and edge-on projection are shown in Fig. 3.19. 

Solution-Grown Lamellae of POM and PE by CM-AFM Sample Preparation Crystallization from Solution... 

In crystalline polymers, the principal relaxation process is associated with melting. In polyethylene, a (1-. and 7-transit ions have been identified and, particularly in higb-tlensity polyethylene, the a-transition has been sub-divided into a and a. In ethylene-based polymers, the y-transitions at —120°C is generally associated with the amorphous phase, in particular, with crankshaft motion of methylene sequences. " However, based upon studies of solution grown lamellae, it has also been suggested that this may llien be associated with... 

Early experiments on solution-grown lamellae revealed not only the earlier melting of the 100 sectors in polyethylene lamellae (25) [which Atomic Force Microscopy (AFM) has confirmed (33) to be thinner than 110 sectors in collapsed, and presumably as-grown, crystals] but also the presence of holes (43) in lamellae that had been heated in contact with a carbon film (Fig. 2). While providing clear evidence of lamellar thickening, the presence of holes is a response to the carbon film, which restrains lateral contraction holes do not appear on thickened upper layers of the same sample that are not so restrained. 

As was noted in the Introduction, the exact nature of the fold surface on dilute solution grown lamellas is still a matter of dispute. " The following models have been proposed i) adjacent reentry using the minimum number of monomer units required, ... 

Taniguchi N, Kawaguchi A. Melt crystallization of constrained polyethylene chains in uniaxially drawn fihn and solution-grown lamellae. Macromolecules... 

Khalifa BA, Bassett DC. Morphological study of chain-extended growth in polyethylene. 3. Annealing of solution-grown lamellae. Polymer 1976 17(4) 291-7. 

The solution-grown crystal (SGC) from dilute solution forms diamond-like crystals of lateral dimension up to several micrometres, but their thickness is about 10 nm in which polymer chains are folded. The chain axes are parallel to the thickness direction of these lamellar crystals. In SGC materials precipitated from dilute solutions (Figure 3A), the lamellae are stacked and oriented parallel to the material surface. 

The next thermal analyses are for solution-grown dendrites, hedrites, and melt-grown lamellae, represented by Eigs. 6.93 and 6.94. The dendrites melt at much lower temperatures than the extended-chain crystals and show multiple melting peaks. 

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