Mesophase oligomer

Table III. Characteristics of Mesophase Oligomers (p=5) with General Formula ...

The phase behavior of several polybibenzoates with oxyalkylene spacers has been reported [11,14,15,20-27]. These spacers include the dimer of trimethylene glycol and different ethylene oxide oligomers. The most noticeable characteristic of these polybibenzoates with ether groups in the spacer is the considerable decrease of the rate of the mesophase-crystal transformation. Thus, Fig. 8 shows the DSC curves corresponding to a sample of poly[oxybis(trimethylene)p,p -bibenzoate], PDTMB, with a structure similar to that of P7MB but with the... 

Meier et al. have also contributed to the field of cyclic PAV oligomers with the synthesis of cyclic dl -trans (all- ) trimers (e.g. 113) containing alkoxy-substituted 1,7-naphthylene and 1,9-phenanthrylene building blocks, via a Siegrist-type trimerizing olefination [134,135]. Suitable substitution at the periphery of the cyclic trimers allows for the formation of stable, thermotropic discotic mesophases [134]. 

Highly branched oligomer or polymer of dendritic structure containing mesogenic groups that can display mesophase behaviour. 

It is reported that ammonium sulfate can produce the negatively charged oligomers through sulfate bridges, which induced the electrostatic interaction with the surfactant and therefore facilitate the formation of zirconia/CTAB mesophase [9]. Since Ti(S04)2 was used as Ti precursor in the present study, a various amounts of (NH4)2S04 was added into the CTAB solution in order to investigate the sulfate effect... 

Three oligomer hydroxy-terminated CTAs (HCTA) were first prepared. Their molecular weight and A and B pdnts in TFA-CH2Q2 (6 4 v/v) are in Table Xin. That is, these oligomers formed mesophases in TFA-CH2CI2 and the critical... 

Figure 8.10 shows a mechanism proposed for the transformation of a surfactant-silicate system from the lamellar to the hexagonal mesophase. On the left, small silica oligomers act as mutildentate ligands, which have sufficiently high charge density to... 

The structures and corresponding calculated MI values are given in Table 7 (nos. 1-5). Mesophases were observed for scores of MI=12 and 13 but not for the odd structures (MI range 9.5-11). In addition, a series of imide-amide oligomers were synthesised with molecular weights above 1000, in which the terminal groups were nadic anhydride. Mis ranged from 8.3 to 10.7 but no positive identification of mesophases were made in any of these (Table 7, nos. 6-9)... 

The first soluble oligomer with significant field-effect mobility was 5,5" -dihexyl-quaterthiophene, described by the Gamier group in 1998 [25]. The chemical stracture is shown in Figure 5.3.1. The compound exhibits a mesophase transistion below 100°C. The hexyl chains improve the ordering of the compound relative to unsubstituted quaterthiophene, which in turn is believed to lead to improved mobility as... 

While most molecular solid semiconductors are end-to-end symmetric, a recent publication focuses on thiophene oligomers with two different hydrocarbon end groups (Figure 5.3.3). This work also emphasizes the desirability of mesophase transitions in the processing to make films. Terthiophene with a hexynyl and a propyl end group and quaterthiophene with a propyl and hexynyl end group both exist in smectic phases at room temperature. Time-of-flight mobilities for these phases approach 0.1 cmWs [34]. 

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