Self-assembling phenylpropyl ether dendronized helical polyphenylacetylenes.
The first example of a self-assembling phenylpropyl ether based dendronized polymer has been reported and its preferred helical handedness has been determined. Dendronized polymer poly(10) and its nondendritic analogue poly(8) are high-cis-content polyphenylacetylenes (PPAs) prepared by using [Rh(nbd)Cl]2/NEt3 (nbd: 2,5-norbornadiene). Both polymers possess a stereocenter in their side chain, which selects a preferred helical handedness. Based on negative exciton chirality observed in the CD spectra of poly(10), we have designated this molecule as a right-handed helical polymer, which persists over a wide temperature range. Poly(10) self-organizes into both Phiioh and Phih lattices in bulk. The Phiioh-to-Phih transition is associated with thermoreversible cis-cisoidal to cis-transoidal isomerization of the helical PPA, accompanied by a dramatic decrease in the column diameter and a decrease in the pi-stacking correlation length along the column. A model for the right-handed helical dendronized PPA has been proposed wherein dendrons from adjacent column strata interdigitate to effectively fill space.
Percec
Virgil
V
Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA. percec@sas.upenn.edu
Peterca
Mihai
M
Rudick
Jonathan G
JG
Aqad
Emad
E
Imam
Mohammad R
MR
Heiney
Paul A
PA
D000114:Acetylene / Q000031:analogs & derivatives* / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D010647:Phenyl Ethers / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D012996:Solutions; D013053:Spectrophotometry; D013696:Temperature; D014961:X-Ray Diffraction
D010647:Phenyl Ethers; D011108:Polymers; D012996:Solutions; C519145:poly(phenylacetylene); D000114:Acetylene