Chain extender mesogenic

Wan et al. used TEMPO-mediated polymerizations to prepare liquid crystalline (LC) polymers [147,148]. pSt-TEMPO was chain extended with a mesogen-jacketed LC monomer, 2,5-bis [(4-methoxyphenyl)oxycarbonyl] styrene (MPCS, Fig. 9) to form a rod-coil diblock copolymer. The resulting copolymer had an Mn=19,500 with an Mw/Mn=1.48. There was tailing to lower molecular weights, indicating the presence of some unreacted macroinitiator, but after extraction with cyclohexane, the remaining macroinitiator was removed, leaving pure block copolymer. H and 13C HMR analysis indicated the presence of both blocks, as did DSC analysis, which showed two Tgs,one at 117.2 °C (pMPCS) and... 

Extended mesogenic core / in polymer side chain... 

The above shown structure has amesogenic core, (hard central segment) correlated with dynamic packing of anisometric shapes. The flexible tales, often hydrocarbon chains, extend from the mesogenic core and facihtate the transformatirHi from the sohd state to the liquid crystaUine phase. 2. A calamitic liquid crystal... 

While rods and disks represent extremes of shape anisotropy that give rise to mesophases, one class of compoimds appears to bridge the gap between these extremes. These materials are termed polycatenar liquid crystals (30), where polycatenar simply means many tails. The mesogens are characterized by their rod-like shape, with a rather extended core, and by possession of three to six terminal chains. There are several isomeric possibihties for such systems, two of which sae considered in this review. 

The dendritic core adopts an extended conformation which is possible due to the great flexibility (conformational freedom) of the PAMAM and PPI skeletons. In this way, the molecular model of thick disks proposed for the LC dendrimers with two-terminal chain mesogenic units is transformed into a model consisting of a long cylinder, which is the result of the axial elonga-... 

In the polymers of Roviello and Sirigu discussed above, the chain direction was perpendicular to the layers, yet the fully extended repeat unit of the polymer with mesogenic structure 2 had a length of approximately 29 A while a spacing of only 20.6 A was observed These examples indicate that the spacer may not always be completely extended in the liquid crystalline state, but the spacer is certainly much more extended than if it were in a random coil configuration. 

Linear LC siloxanes have been well known since the end of the seventies [4] and an enormous variety of compounds, including networks, have been synthesized in the meantime [5]. These side-chain polymers are usually synthesized by a well-established standard procedure, that is, the coupling of co-alkenyl substituted mesogenic groups to H-siloxanes with the aid of a Pt catalyst. This concept has been extended to various geometric and chemical classes of backbone siloxanes, linear [6], cyclic [7, 8] and cage-like siloxanes [9], or siloxanes with a great variety of substituents [10]. 

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