Conformation of spacers in smectic poly(ester imide)s

Wutz, Christoph; Schleyer, Dana

doi:10.1002/(sici)1099-0488(19980915)36:12<2033::aid-polb3>3.3.co;2-c

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“…However, since the thickness of the mesogen layer is uniform due to the regular mesogen packing, a larger variation in the thickness of the spacer layer has to be concluded. This conclusion is confirmed by the results of the conformational analysis of the spacer segments by 13 C NMR CP/MAS on PEI 2 n = 12, 16 . As mentioned above, the spacers adopt a rather uniform alternate trans conformation in the LC phase.…”

Section: Discussionsupporting

confidence: 74%

“…This conclusion is confirmed by the results of the conformational analysis of the spacer segments by 13 C NMR CP/MAS on PEI 2 n ) 12, 16. 2 As mentioned above, the spacers adopt a rather uniform alternate trans conformation in the LC phase. In contrast, the amounts of both ordered trans-trans sequences and completely disordered segments are increased in the smectic-crystalline phase, resulting in a nonuniform conformation.…”

Section: Discussionmentioning

confidence: 92%

“…For the LC melt as well as for the frozen LC phase, a very uniform spacer conformation is found, which corresponds to the alternate-trans-model. It consists of a regular sequence of stable trans bonds alternating with disordered bonds which undergo rapid trans−gauche interconversions. ,, …”

Section: Discussionmentioning

confidence: 99%

“…It consists of a regular sequence of stable trans bonds alternating with disordered bonds which undergo rapid trans-gauche interconversions. 2,21,22 From the meridional component of the reflections scattering angle, a spacing of the smectic layers in fiber direction d f , corresponding to the length of the repeating unit, can be calculated via the Bragg equation. The resulting d f values for all samples are listed in Table 1.…”

Section: Discussionmentioning

confidence: 99%

“…Since the crystal-like packing of the mesogens results in additional reflections in the wide-angle X-ray scattering (WAXS, 2θ = 5−40°), these phases are named “smectic crystalline” in this article. Nevertheless, the spacer segments exhibit a substantial conformational disorder, in contrast to true three-dimensional crystal phases.

1 Chemical structure of PEI 1 , 2 , and 3 .

2 Schematic representation of the molecular order in different smectic phases. …”

Section: Introductionmentioning

confidence: 98%

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Molecular Order of the Mesogens in Smectic Poly(ester imide) Fibers

et al. 1999

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The molecular order of the mesogens in the smectic liquid-crystalline (LC) and smectic-crystalline phases of different poly(ester imide)s (PEI) with similar chemical structure is investigated by means of X-ray fiber patterns. During the fiber spinning from the melt, the smectic LC phase is frozen. Above the glass transition temperature, a transition into a higher-ordered smectic-crystalline phase occurs. The PEI which are based on aminobenzoic acid trimellitimide and long aliphatic spacers form exclusively orthogonal smectic phases (SA, SB, SE). In contrast, the PEI based on aminocinnamic acid trimellitimide and those derived from 4-hydroxyphthalic acid, aminophenol, and aliphatic dicarbon acids form tilted SC phases. The layer line broadening of the X-ray reflections indicates a poor lateral order of the smectic layers in the LC phase due to a frequent inversion of the staggering direction between adjacent mesogens. As a result of the equatorial smearing of the four-point-pattern, the splitting angle of the reflections is not identical with the tilt angle between the mesogens and the normal of the smectic layer plane. The order of the mesogens in the direction perpendicular to the fiber axis is evaluated on the basis of the paracrystallinity model. The resulting local tilt angle corresponds to an average staggering amount of the mesogens. Furthermore, the parameter ε, introduced by Porod, is interpreted as a probability for the inversion of the staggering direction.

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Section: Discussionsupporting

confidence: 74%

Section: Discussionmentioning

confidence: 92%