Radiopolymerization of β(-)pinene: A case of chiral amplification

γ-Radiation Induced Polymerization of a Chiral Monomer: A New Way to Produce Chiral Amplification

“…As described in the experimental section, the resin was easily separated from the residual monomer and it was washed and dried before determining the yield gravimetrically. A linear response between radiation dose and resin yield was observed (Cataldo and Keheyan 2006); the maximum yield of 6.5% of solid resin over the initial mass of the monomer was achieved after 600 kGy. Due to radiolysis, the formation of the insoluble resin of poly(β(−)pinene) was accompanied also by the formation of a pinene dimer which was soluble in the β(−)pinene monomer but was easily separated from the irradiated monomer when it was dissolved in acetonitrile.…”

“…Instead, the spectra of the poly(β(−)pinene) resins obtained by radiopolymerization are richer in absorption bands displaying a series of additional bands which are not present at all in the spectrum of the resin obtained by cationic polymerization. This fact may suggest an higher structural regularity for the pinene radiopolymers in comparison to the resin obtained by cationic polymerization or the presence of structural fragments and units different from those commonly known in the β(−)pinene resin prepared by Friedel-Crafts catalysts (Cataldo and Keheyan 2006).…”

“…Due to radiolysis, the formation of the insoluble resin of poly(β(−)pinene) was accompanied also by the formation of a pinene dimer which was soluble in the β(−)pinene monomer but was easily separated from the irradiated monomer when it was dissolved in acetonitrile. Elsewhere (Cataldo and Keheyan 2006) it is shown that the yield of the pinene dimer always exceeded the amount of solid resin produced, being almost double in amount with respect to the solid resin.…”

“…FT-IR spectroscopy on the radiopolymer poly(β(−)pinene) and pinene dimer A complete discussion of the infrared spectra of the monomer before and after the radiation treatment and in comparison with the spectra of the β(−)pinene dimer and the poly(β(−) pinene) resin is reported elsewhere (Cataldo and Keheyan 2006). The infrared spectra show that β(−)pinene polymerizes under the action of + radiation with the mechanism of ring− opening polymerization, with the shift of the double bond from the exocyclic position (in the monomer) to the endocyclic position as commonly accepted in literature also for the cationic polymerization of this monomer.…”

“…The details of the cationic polymerization of β(−)pinene as reference resin have been reported previously (Cataldo and Keheyan 2006). The specific optical rotation of this resin in toluene (c = 2) was found [!]…”