Polymer Morphology Single Crystals

FIGURE 11.5 Schematics of possible chain morphology in a single polymer crystal (a) regular folding with adjacent reentry of chains, (b) switchboard model with random reentry of chains. 

In what follows, we use simple mean-field theories to predict polymer phase diagrams and then use numerical simulations to study the kinetics of polymer crystallization behaviors and the morphologies of the resulting polymer crystals. More specifically, in the molecular driving forces for the crystallization of statistical copolymers, the distinction of comonomer sequences from monomer sequences can be represented by the absence (presence) of parallel attractions. We also devote considerable attention to the study of the free-energy landscape of single-chain homopolymer crystallites. For readers interested in the computational techniques that we used, we provide a detailed description in the Appendix. ... 

The volume inside the semicrystalline polymers can be divided between the crystallized and amorphous parts of the polymer. The crystalline part usually forms a complicated network in the matrix of the amorphous polymer. A visualization of a single-polymer crystallite done [111] by the Atomic Force Microscopy (AFM) is shown in Fig. 9. The most common morphology observable in the semicrystalline polymer is that of a spherulitic microstructure [112], where the crystalline lamellae grows more or less radially from the central nucleus in all directions. The different crystal lamellae can nucleate separately... 

M. J. Folkes and A. Keller, The birefringence and mechanical properties of a single crystal from a tri-block copolymer, Polymer, 12,222 (1971) M. J. Folkes and A. Keller, Optical and swelling properties of macroscopic single crystals of an S-B-S copolymer. I. Samples possessing a lamellar morphology, J. Polym. Sci., Polym. Phys. Ed., 14, 833 (1976). 

Several authors have analyzed the miscibility of iPP and PB-1, by means of different analytical approaches. Piloz et al. (16) found a single, composition-dependent, glass transition behavior for these blends, and concluded that they are compatible in the amorphous state. Sjegmann (17,18) reported that the composition dependence of tensile properties evidences a high degree of compatibility of iPP and PB-1 and observed a marked effect of the composition on the morphology of melt-crystallized samples. Conversely, the analysis of the crystallized blends indicates the presence of separated crystal phases of the two polymers, even if a mutual influence during the crystallization cannot be excluded. 

Morphology of Polymer Single Crystals Grown from Solution... 

The interplay of phase separation and polymer crystallization in the multi-component systems influences not only the thermodynamics of phase transitions, but also their kinetics. This provides an opportunity to tune the complex morphology of multi-phase structures via the interplay. In the following, we further introduce three aspects of theoretical and simulation progresses enhanced phase separation in the blends containing crystallizable polymers accelerated crystal nucleation separately in the bulk phase of concentrated solutions, at interfaces of immiscible blends and of solutions, and in single-chain systems and interplay in diblock copolymers. In the end, we introduce the implication of interplay in understanding biological systems. 

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