POLARISED OPTICAL

Fig. 7 Figure to show the origins of birefringence (left) and a schematic diagram of a polarised optical microscope (right)... 

The liquid crystal properties of the complexes were characterised using polarised optical microscopy and showed a nematic phase for n = 4 and 6 and a SmA phase for n = 6, 8, 10 and 12. The mesophases were monotropic for n = 4 and 6 and enantiotropic for the others the progression from a nematic phase for shorter chain lengths to SmA at longer chain lengths is quite typical for simple, polar mesogens. 

In the ideal situation any supposed LB layer structure would be examined by low angle X-ray diffraction, electron diffraction and by the polarising optical microscope. It is unfortunate that this procedure is rarely carried out. Thus in this chapter only those cases have been discussed where at least some effort has been made to determine the structure and degree of order of the film. 

There are three main techniques used in characterisation of mesophases polarised optical hot-stage microscopy, differential scanning calorimetry (cf. Box 9.1) and small-angle X-ray scattering. 

Two component hydrogen bonded mixtures of dendrimers and T-shaped branched amphiphiles are also a rich source of mesophases. Figure 13.21 shows a polarised optical microscope image of the contact region between the dendrimer 13.18 and the T-shaped amphiphile 13.19. A wide variety of mesophases co-exist as one component diffuses into another. The majority of these have been identified and studied.13... 

Fig. 4.10. General appearance of MOV patterns for a Zeeman doublet. In the example shown here, the polarising optics were not perfect, which results in a Lorentz doublet superimposed on the centre of the rotation pattern (after J.-P.

Figure 2.8 Cross-polarised optical microscope images of PEO blends a) at the beginning of crystallisation b) spherullites with Maltese cross section c) PEO+20 wt% novolac d) PEO+30 wt% novolac...

Such an ordered structure is able to deflect polarised light, so if native starch granules are observed by means of polarised optical microscopy, Maltese crosses will be detected. 

Figure 8.4 Phase contrast microscopy of native (a), gelatinised (c) and destructurised potato starch (e). Polarised optical microscopy of native (b), gelatinised (d) and destructurised (f) potato starch...

Ulrich R and Simon A, Polarisation optics of twisted single-mode fibers , Appl. Optics, 1979,18(13), 2241-51. 

Figure 10.5 Spherulites of poly(vinylidene fluoride) grown at 162.5°C as imaged in the polarising optical microscope. In (a) the light is plane-polarised whereas in (b) it is circularly polarised.

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