POS1-0763
Polymerization of alkyl-substituted [3]dendralenes
When and Where
Nov 30, -0001
12:00am - 12:00am
Presenter(s)
Haruto Tanaka (Institute of Science Tokyo)
Co-Author(s)
Abstract
Dendralenes are a class of hydrocarbons containing multiple conjugated double bonds. The simplest dendralene is [3]dendralene, which contains three carbon-carbon double bonds. [3]Dendralene possesses a cross-conjugated structure in which two conjugated 1,3-dienyl units share a central carbon-carbon double bond. Since [3]dendralene is highly reactive and immediately dimerizes via Diels-Alder reaction, the polymerization of [3]dendralene has not been attempted. In contrast, 2- and 1-substituted [3]dendralenes are quite stable compared with the non-substituted [3]dendralene. After isolation, even the polymerization of 2- and 1-substituted [3]dendralenes has been reported under the suitable conditions.
Anionic polymerization of 2-n-hexyl[3]dendralene (2nH) has been examined with potassium naphthalenide in THF at –78 °C. The polymerization of 2nH quantitatively proceeded to afford a polymer possessing a controlled molecular weight and a narrow molecular weight distribution (Mw/Mn < 1.2). Other anionic initiators such as lithium naphthalenide and diphenylmethylpotassium also gave the well-defined poly(2nH)s. The polymerization proceeded via the conjugate addition from the C4 carbon of 2nH, affording a mixed repeating unit including 4,1- and 4,6-addition modes. This indicates that 2nH certainly acts as a conjugated diene monomer under the anionic condition. We also attempted to polymerize 2-alkyl[3]dendralenes possessing cyclohexyl and n-dodecyl groups to investigate the effects of steric hindrance and alkyl chain length. Furthermore, the corresponding 1-alkyl[3]dendralenes carrying n-hexyl, cyclohexyl-, and n-dodecyl groups were also synthesized and polymerized to clarify the effect of substituent position. The polymerization behaviors of monomers and the microstructures and thermal properties of the resulting polymers were systematically evaluated.
Anionic polymerization of 2-n-hexyl[3]dendralene (2nH) has been examined with potassium naphthalenide in THF at –78 °C. The polymerization of 2nH quantitatively proceeded to afford a polymer possessing a controlled molecular weight and a narrow molecular weight distribution (Mw/Mn < 1.2). Other anionic initiators such as lithium naphthalenide and diphenylmethylpotassium also gave the well-defined poly(2nH)s. The polymerization proceeded via the conjugate addition from the C4 carbon of 2nH, affording a mixed repeating unit including 4,1- and 4,6-addition modes. This indicates that 2nH certainly acts as a conjugated diene monomer under the anionic condition. We also attempted to polymerize 2-alkyl[3]dendralenes possessing cyclohexyl and n-dodecyl groups to investigate the effects of steric hindrance and alkyl chain length. Furthermore, the corresponding 1-alkyl[3]dendralenes carrying n-hexyl, cyclohexyl-, and n-dodecyl groups were also synthesized and polymerized to clarify the effect of substituent position. The polymerization behaviors of monomers and the microstructures and thermal properties of the resulting polymers were systematically evaluated.
