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Crystal lamella monolayer crystals

A different sort of three-dimensional structure may arise from chain folding, however. Should the folds on one side of a monolayer crystal be bulkier than those on the other side, the resultant strain can cause the lamella to curve to the point where it is best described as a scroll. Nylon 6.6 crystallized under conditions that give amine folds on one basal surface and acid folds on the other surface is shown in Figure 3.14 [22]. The... [Pg.79]

Figure 3.40 Phase contrast optical image of a monolayer crystal of poly(ethylene oxide) grown at 55°C in a 10 pm molten film. Edges of the 22 nm thick lamella are revealed by self-decoration after quenching. The 6-axis is vertical and the a -axis is horizontal this shape may be compared with that in Figure 3.9. Width of the micrograph is 150 pm. From Kovacs and Gonthier [57] with kind permission from Springer Science-tBusiness Media B.V. Figure 3.40 Phase contrast optical image of a monolayer crystal of poly(ethylene oxide) grown at 55°C in a 10 pm molten film. Edges of the 22 nm thick lamella are revealed by self-decoration after quenching. The 6-axis is vertical and the a -axis is horizontal this shape may be compared with that in Figure 3.9. Width of the micrograph is 150 pm. From Kovacs and Gonthier [57] with kind permission from Springer Science-tBusiness Media B.V.
In solutions of water and surfactant, the surfactant monolayers can join, tail side against tail side, to form bilayers, which form lamellar liquid crystals whose bilayers are planar and are arrayed periodically in the direction normal to the bilayer surface. The bilayer thickens upon addition of oil, and the distance between bilayers can be changed by adding salts or other solutes. In the oil-free case, the hydrocarbon tails can be fluidlike (La) lamellar liquid crystal or can be solidlike (Lp) lamellar liquid crystal. There also occurs another phase, Pp, called the modulated or rippled phase, in which the bilayer thickness varies chaotically in place of the lamellae. Assuming lamellar liquid crystalline symmetry, Goldstein and Leibler [19] have constructed a Hamiltonian in which (1) the intrabilayer energy is calculated... [Pg.183]

Crystal morphologies of glycine can be controlled by using surfactant monolayers at the air/water interface as templates. Catalyzed nucleation may, for example, yield 010 pyramids of glycine in supersaturated aqueous phases below surface monolayers or at foam lamellae (Chen et aL, 1998). [Pg.523]

Stearic acid. The effect of coating on crystallization depends on the number of layers deposited on the filler surface. Figure 7.2 shows the effect of excessive coating of filler surface. The nucleation of the PP lamellae is accomplished by the deposition of the first stem of lamellae on a smooth surface of the monolayer coating. The nucleation efficiency is diminished if there is an excess amount of stearic acid (absence of the smooth surface). It should be also noted that agglomeration of particles will diminish the nmnber of nuclei. Agglomeration can be caused by the lack of coating or the excessive amoimt of coated filler in formulation. [Pg.90]

The logarithmic-time dependence of crystal thickness can be deduced easily. By assuming a frictional barrier (AfJ for chain-sliding diffusion proportional to the lamella thickness (/), thus the thickening rate of monolayer lamellar crystal under a certain temperature is... [Pg.137]

Fig. 15 Illustrations of some typical phases exhibited by semillexible polymers and liquid crystals, (a) Nematic, (b) Bilayer smectic A/lamellae. (c) Monolayer smectic A/lamellae. (d) Monolayer smectic C/tilted lamellae. Red sticks represent r-staeked rod rigid sections, blue lines flexible coil sections. Adapted and reproduced with permission liom [157]. Copyright... Fig. 15 Illustrations of some typical phases exhibited by semillexible polymers and liquid crystals, (a) Nematic, (b) Bilayer smectic A/lamellae. (c) Monolayer smectic A/lamellae. (d) Monolayer smectic C/tilted lamellae. Red sticks represent r-staeked rod rigid sections, blue lines flexible coil sections. Adapted and reproduced with permission liom [157]. Copyright...
Well defined lath-shaped lamellar crystals of isotactic polypropylene were grown from solution [163]. The thickness of these lamellae, as determined by small-angle X-ray diffraction of crystal aggregates, is 125 A. The crystals were mainly monolayer with the shorter and larger dimensions, respectively, of about 0.2 and 1 pm. Similar lamellar crystals were observed by Sauer et al. [164], Morrow et al. [165], Kojima [166], and Lotz and Wittmann [167]. Fibrils parallel to the longitudinal direction of the lamella were often observed. According to Kojima [166] these fibrils connect the planes of fracture and cleavage that are parallel to the a axis. This is an indication that the 010 planes are the most probable fold planes. Lotz and... [Pg.191]


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See also in sourсe #XX -- [ Pg.142 , Pg.143 ]




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Crystal lamella

Monolayer crystals

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