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Synthesis, spectral, and thermal characterization of photosensitive poly(ether–ester)s containing α,β‐unsaturated ketone moieties in the main chain derived from 2,6‐bis[4‐(3‐hydroxypropyloxy)‐3‐methoxybenzylidene]cyclohexanone

“…To obtain polymers with considerably low T m 's and increased solubility, several chemical modifications can be made: (1) the introduction of bulky or nonsymmetrical substituents; (2) the introduction of long, flexible spacers into the mesogen backbones; (3) the use of nonlinear or bent monomers; and (4) the copolymerization of different monomers. 6 Most studies have paid attention to semiflexible polymers, in which the hard mesogenic groups are connected by flexible spacer groups. To this point, an enormous number of semiflexible-type thermotropic polymers have been synthesized.…”

The Preparation of Helical Cyclophanes Containing Five-membered Rings

“…The starting point of our considerations is [2.2](1,4)phenanthrenoparacyclophane (5), [4,5] the parent hydrocarbon of all angularly annelated [2.2]cyclophanes. A five-membered ring may be annelated to its phenanthrene deck in several ways; two such possibilities are shown as 6 and 7 in Scheme 2.…”

“…In fact, we have recently described the first synthesis of the parent molecule of 9 Ϫ i.e., the hydrocarbon without the condensed five-membered rings Ϫ and various of its geometrical isomers. [4] Ligands such as 9 are related to the helicenes 10 investigated thoroughly by Katz and co-workers, who also have been successful in converting these into chiral metallocenes. [7,8] The main difference between the structures discussed here and those described by the American authors is that our helicenes contain an additional ''step'' provided by the [2.2]paracyclophane nucleus, through which the helical annelation is continued at a ''higher level''.…”

“…Since a complete separation of 20 and 21 by column chromatography could not be accomplished, the crude product mixture was dehydrogenated with DDQ. Although the quinone 21, formed in 90% yield, and for which NOEs were again of invaluable help in providing unambiguous structural proof (see below), full aromatization to the corresponding [4]helicenophane quinone could not be achieved. One reason for this failure might be excessively severe steric interactions between one methylene group of an ethano bridge of the phane and a quinone oxygen atom, in the event of complete aromatization being attained.…”

Investigation on dual properties of photosensitive thermotropic liquid‐crystalline poly(benzylidene‐ether)s containing alkanones and methylene spacers in the main chain

“…The peak observed around 376-391 nm for all of the polymers corresponded to the p!p* transition of the benzylidene chromophores. Further, the absorption bands around 307-315 nm and 265-275 nm may be assigned as n!p* transition of keto group and p!p* transition within the benzenoid system,68,69 respectively. During initial periods of Representative HOPM photographs of IIIb, IIIc, IIId, and 4,4 0 -diformyl-2,2 0 -dimethoxy-a,x-diphenoxybutane (iii).…”