Development of the Founding Lamella

An explanation based on simple thermodynamics of the preferred orientation of edge-on and flat-on lamellae on thick and thin films, respectively, was given by Wang et al. [80]. As shown in Fig. 10, a primary rectangular nucleus of size a x a x l can assume either edge-on or flat-on orientation on a sub- 

The free energy of formation for a flat-on nucleus attached to a substrate, 

However, in thin films, the growth of the edge-on lamellae is limited by the film thickness (h). The formation of many edge-on lamellae on a thin film cre- 

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Fig. 6 A series of AFM phase images obtained on a BA-C8 film at room temperature, a An embryo b a short lamella (founding lamella) developed from the embryo shown in a c-f. The growth of the founding lamella g-p branching and splaying apart of the subsidiary lamellae [61]...

Theory for the self- and tracer-diffusion of a diblock copolymer in a weakly ordered lamellar phase was developed by Fredrickson and Milner (1990). They modelled the interactions between the matrix chains and a labelled tracer molecule as a static, sinusoidal, chemical potential field and considered the Brownian dynamics of the tracer for small-amplitude fields. For a macroscopically-oriented lamellar phase, they were able to account for the anisotropy of the tracer diffusion observed experimentally. The diffusion parallel and perpendicular to the lamellae was found to be sensitive to the mechanism assumed for the Brownian dynamics of the tracer. If the tracer has sufficiently low molecular weight to be unentangled with the matrix, then its motion can be described by a Rouse model, with an added term representing the periodic potential (Fredrickson and Bates 1996) (see Fig. 2.50). In this case, motion parallel to the lamellae does not change the potential on the chains, and Dy is unaffected by... 

Major research efforts resulted in the development of a modified PTFE, which contains a small amount (0.01 to 0.1 mol%) of a comonomer. The most suitable comonomer was found to be perhuoro propylvinyl ether (PPVE).94 The comonomer reduces the degree of crystallinity and the size of lamellae.95 The polymerization process is similar to that for standard PTFE except additives to control the molecular weight are used.96... 

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