Mesogen length

When different classes of polymers are compared, however, the correlation with length is not so straightforward. The polymers with OTO and THT ester triads of Table 2 which have mesogenic lengths of approximately 19A, melt and clear at lower... 

Figure 10. Weight and number distributions of mesogens. Mesogen length is defined as the number of aromatic units per mesogen.

The MI is first calculated for the empirical monomer structure, on a molar basis, for all [A] + [B] units. It is then multiplied by the mesogenic length factor corresponding to the minimum number of rings needed in a mesogen of that chemical type (e.g. 2 for ester, 3 for amide, 2.5 for a 1 1 esteramide, etc.). 

The values for polyimide groups and the corresponding mesogenic length were derived from work carried out by the author [43] on the synthesis and characterisation of liquid crystalline polyimides. Imide groups contribute +2 and have a mesogenic length of 2. 

Figure 11.7 Chemical structures of liquid crystalline epoxy resins with deferent mesogenic length. Reproduced from reference 27.

Figure 11.22 illustrates the correlation among the mesogenic length, glass transition temperature and modulus of liquid crystalline thermosets obtained for the LCERs in Figure 11.7 cured with DDS. 

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