Oxyethylene -type spacers

Abe, A., Hiejima, T., Kobayashi, Y, Zhou, Z., and Nakafuku, C., Thermodynamic characteristics of chain molecules in the nematic state PVT studies of main chain liquid crystal comprising a long oxyethylene-type spacer. Macromolecules, 40,1746-1753 (2007). 

Hiejima, T., Seki, K., Kobayashi, K., and Abe, A., Orientational and conformational characteristics of oxyethylene-type spacers involved in dimer hquid crystals, 7. Macromol. Sci., B42, 431 39 (2003). 

FIGURE 7.9 Variation of the transition entropy AS ilR with the number of constituent atoms (n) of the spacer BCBOn (CBA-n) [Emsley et al., 1984] and MBBE- [Kobayashi, 2004 Abe et al., 2007]. While the former comprises PM-type spacers, the latter includes a POE-type spacer. Note that the oxyethylene spacers of MBBE-x are expressed by the number of constituent atoms. The oxygen atoms of the ether linkage located at both chain terminals are not counted in n. 

The distinct odd-even alternation in ASjsn is a character peculiar to the polymethylene (PM)-type spacers. A comparison between the two different types of spacer, BCBOn (designated as CBA-n in this paper) [25] and MBBE-x with the oxyethylene (OE)-type spacer [26, 27] is shown in Fig. 5, where the latent entropy ASjsfi/R is plotted against the number of crmstituent atoms ( ) of the spacer. For MBBE-x with the OE spacer, irrespective of the parity of n, the A5ni versus n plot tends to decrease monotonicaUy with some tiny bumps. The odd-even trend characteristic of the tetrahedrally bonded chain system is rapidly smeared out by the... 

Polymers of this type have been prepared with various mesogenic units connected by oligomers of poly(ethylene oxide), PEO, and it is possible in some cases to use spacers having a broad distribution of molecular weights instead of a monodisperse molecular species. It shoxxld be noted that each oxyethylene unit adds three bond lengths to the spacer, so the comparison of polymers with different types of spacers should be between spacers having the same numbers of atoms in the spacer chain. 

This type of polymer support seems to be an interesting alternative to conventional polystyrene because the simple procedures for the experimental work-up of the Merrifield synthesis can be applied and simultaneously quasi-homogeneous reaction conditions are attained by reason of the hydrophilic poly(oxyethylene) spacer group. 

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