Initial studies
Higashimura, has extensively studied the HI/I2 and HI/Lewis acid initiated cationic polymerisations of acyclic vinyl ethers.
We have conducted similar polymerisations using isobutyl vinyl ether, 2,3-dihyrofuran and 3,4-dihydropyran, which provide suitable models for our glycal substrates.
Isobutyl vinyl ether
For comparison with our polymerisation studies of dihydrofuran these reactions were run over a longer period of time than reported by Higashimura.1 This is reflected in the slightly larger polydispersities than those achieved previously, representing the onset of chain transfer processes.
2,3-Dihydrofuran
Polymerisations in hexane give low conversion of monomer which may be a consequence of poor polymer solubility.
The number average molecular mass increases in direct proportion to monomer conversion in dichloromethane at -78 °C, however, polydispersity does not indicate a living polymerisation. This may be an effect of the long reaction times necessary to achieve full conversion allowing competing chain transfer processes.
In dichloromethane at -15 °C polymerisation is complete within 30 min and not indicative of living polymerisation.
High molecular mass polymers are obtained when ZnI2 is used as co-catalyst, indicating cross-linked material.
The polymerisation of dihydrofuran using acetyl perchlorate as initiator has been extensively studied and sets a precident for future investigations.2
3,4-Dihydropyran
The cationic polymerisation of dihydropyran has long been known.3 However, materials with low Mpk values4 and wide polydispersities have been obtained when HI/I2 is used as initiator.
