Quaterphenyl and Higher Oligomers

While in p-quaterphenyl the nematic phase is only metastable, p-quinquephenyl and p-sexiphenyl, and probaHy also p-heptiphenyl, have stable nematic phases Beyond p-quinquephenyl smectic phases are expected and proven for p-sexiphenyl. The magnitudes of the transition entropies corr ond to the general observations on liquid crystals 

The series of p-oligophenyls illustrates thus, as shown in Fig. 5.1, that transition from the rigid crystal to the condis crystal can go with a displacive or with an order-disorder transition. Larger motion can occur with little correlation and thus 

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