5 Transforming a Helix–Coil into a Helix–Helix Transition
and Eliminating Intramolecular Electrocyclization
As demonstrated in the lecture given during the IUPAC of Macromolecules in
Tashkent in 1978 [94], in its contributing publications, and in more recent publications [94–103], the cis-transoidal and cis-cisoidal polyphenylacetylenes exhibit
helical conformations that undergo an intramolecular electrocyclization during
their transition to the coil conformation. A limited extent of cis–trans isomerization
takes place during this process (Fig. 10).
Fig. 8 Dependence of the shape of the macromolecule dendronized with quasi-equivalent
dendrons on the degree of polymerization (DP). Reprinted with permission from [62]. Copyright
1998 Macmillan Publishers Ltd. (Nature)
186
V. Percec
and Eliminating Intramolecular Electrocyclization
As demonstrated in the lecture given during the IUPAC of Macromolecules in
Tashkent in 1978 [94], in its contributing publications, and in more recent publications [94–103], the cis-transoidal and cis-cisoidal polyphenylacetylenes exhibit
helical conformations that undergo an intramolecular electrocyclization during
their transition to the coil conformation. A limited extent of cis–trans isomerization
takes place during this process (Fig. 10).
Fig. 8 Dependence of the shape of the macromolecule dendronized with quasi-equivalent
dendrons on the degree of polymerization (DP). Reprinted with permission from [62]. Copyright
1998 Macmillan Publishers Ltd. (Nature)
186
V. Percec