Structures et propriétés diélectriques des poly(α-acétoxystyréne)s parasubstitués

The relations between structure and isothermal, dielectric properties of poly(α-acetoxystyrene)s substituted in para position by ? OCOCH₃ ( 1a ), ? OCOCH₂CH₃ ( 1b ), ? OCOCH₂CH₂CH₃ ( 1c ), ? OCOC₆H₅ ( 1d ), ? OCOCH₂CH₂Cl ( 1f ) and ? OCOOCH₃ ( 1g ) were studied. The dielectric constants, at 10⁵ Hz and 20 ± 2°C, were found to be: 3,79 ( 1a ), 3,36 ( 1b ), 3,18 ( 1c ), 3,51 ( 1d ), 3,36 ( 1e ), 3,65 ( 1f ) and 3,07 ( 1g ). The polymers 1a – 1g do not show any α- or β-transition. Increasing bulkiness of the para substituent gives rise to a decreasing dielectric constant due to an increase of the degree of syndiotacticity, as determined from ¹H and ¹³C NMR spectra.