Design and architecture of macromolecular structures

The embryonic state of the ionic methyl methacrylate (MMA) and of trihaloacetaldehyde polymerization was studied. The composition of the oligomer mixtures, the end groups and the stereochemistry of individual compounds of the oligomers was investigated. Depending upon the initiating systems the oligomerization of methyl methacrylate can give either isotactic or syndiotactic oli omers. Trihaloacetaldehye oligomerization IS highly depenjent on the ceiling temperature of polymerization. The oligomerization of fluoral and chloral is compared with a more detailed study of the bromal polymerization and even more interestingly with the cooligomerization of chloral and bromal.

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Ferrochirality: a simple theoretical model of interacting, dynamically invertible, helical polymers, 2. Molecular field approach: supports and the details

Baumgarten

1995

Macro Theory & Simulations

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SUMMARYUsing a molecular field approach, the effect of interaction between reversibly invertible, helical polymers is investigated theoretically. The helices are modelled by nearest-neighbour statistical thermodynamics. If the interaction energy between two helices of common handedness is lower than that of oppositely handed ones, a critical temperature T, exists, below which the system spontaneously must leave the racemic state, though there is no contact to any chiral centre or force. This is analogous to the second-order phase transition of ferromagnets. The critical point increases with molecular weight and optical persistence of the helices. At the critical point the system is highly sensitive to any chiral influence. Doping with 1 ppb of a chiral additive leads to a relative optical rotation of order at the critical point. This corresponds to an intrinsic energy difference of left-to right-handed monomeric units of only lo-* J/mol. The cooperative effects in chirally doped nematic poly(hexy1 isocyanate) (PHIC) can be easily described without using the improbable assumption that the supramolecular cholesteric arrangement with an axisto-axis rotation of only 0,001 ' must be the reason for the collective helix sense preference in this system. On the other hand, if the chain-to-chain interaction is transmitted through this supermolecular twist, the structure of the equations is altered slightly only and critical behaviour must be expected as well.

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Design and architecture of macromolecular structures

Cited by 6 publications

References 20 publications

Ferrochirality: A simple theoretical model of interacting dynamically invertible helical polymers, 1. The basic effects

Ferrochirality: A simple theoretical model of interacting dynamically invertible helical polymers, 1. The basic effects

Oligomers of stereoregular polymers

Ferrochirality: a simple theoretical model of interacting, dynamically invertible, helical polymers, 2. Molecular field approach: supports and the details

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