Poly isotactic, epitaxial crystallization

Epitaxial Crystallization of Isotactic Poly(l-Butene), Form I. 26... 

Epitaxial crystallization of helical polymers may involve three different features of the polymer chain or lattice. These are (a) the interchain distance (as for stretched out polymers), (b) the chain axis repeat distance, and (c) the interstrand distance - the distance between the exterior paths of two successive turns of the helix. The two former periodicities are normal and parallel to the chain axis direction, and are therefore not usually sensitive to the chirality of the helix (unless the substrate topography is asymmetric and favors a given helical hand). However, the interstrand distance is oblique to the helix axis (it is normal to the orientation of the outer chain path) and therefore has different, symmetric orientations relative to the helix axis for left-handed and right-handed helices (Fig. 2). In other words, epitaxies that involve the interstrand distances are discriminative with respect to helix chirality. This discrimination becomes visible if the crystal structure is based on whole layers of isochiral helices. Such a situation does indeed exist for isotactic poly(l-butene), Form I, that will be considered soon. 

Stocker, W. et al. (1998). Epitaxial Crystallization and AFM Investigation of a Frustrated Polymer Structure Isotactic Poly(propylene), p Phase. Macromolecules, Vol.31, Issue 3, pp. 807-814. 

Stocker, W Schumacher, M. Graff, S. Thierry, A. Wittmann, J.-C. Lotz, B. Epitaxial crystallization and AFM investigation of a frustrated polymer structure Isotactic poly(propylene), y phase. Macromolecules 1998, 31, 807-814. 

Brinkhuis RHR, Schouten AJ. Thin-fikn behavior of poly (methyl methacrylates). 3. Epitaxial crystallization in thin films of isotactic poly(methyl methacrylate) using crystalline Langmuir-Blodgett layers. Macromolecules 1992 25 2717-2724. 

Liu J, Wang J, Li H, Shen D, Zhang J, Ozaki Y, Yan S. Epitaxial crystallization of isotactic poly (methyl methacrylate) on highly oriented polyethylene. J Phys Chem B 2006 110 738-742. 

Sun Y, Li H, Huang Y, Chen E, Gan Z, Yan S. Epitaxial crystallization of poly (butylene adipate) on highly oriented isotactic polypropylene thin film. Polymer 2006 47 2455-2459. 

Epitaxy of Isotactic Poly (1-butene) Isotactic poly(1-butene) (iPBul) is an archetypical polymorphic polymer with three different structures that differ by the chain conformation, and thus by the unit-cell geometry and symmetry (cf Chapter 2).The three crystal phases could be obtained by epitaxial crystallization on appropriate substrates [48-50]. Most interesting among them are the epitaxy of Form I (trigonal unit cell, threefold helical conformation, racemic phase) and that of Form III (orthorhombic unit cell, fourfold helical geometry, chiral crystal phase). 

It should be pointed out here that the epitaxy caused by special crystallographic interaction provides another efficient way to control the crystal modification of semicrystalline polymers together with molecular chain orientation [83,88,139-142]. As examples, while the crystal structure of isotactic poly(l-butene) (iPB-1) is successfully controlled through using substrates with different crystal structures... 

Recent experiments (211) have shown that the lamellar thickness of poly(ethylene), PE, on oriented isotactic poly(propylene), changes from 16 to 39 nm upon annealing. This thickening is attributed to dimensional matching and secondary nucleation with the requirement (212) that the PE crystal(s) are thiimer than the PP dimension along the chain-row matching direction. However, no detailed kinetic measurements were reported on the rate of epitaxial growth here, or elsewhere in the literature. 

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