Synthesis of Novel N-Phenyl Maleimidyl and Citraconimidyl Esters and Their Applications as Plasticizers for Poly(Vinyl Chloride)

Abstract

Several N-(hydroxy phenyl)maleamic and citraconamic acids were prepared in
high yields (90-94)% from the reaction of maleic and citraconic anhydride
respectively with ortho, meta and p-aminophenols.
Dehydration of the prepared amic acids by fusion technique gave the
corresponding N-(hydroxy phenyl)maleimides and citraconimides in good yields
(75-85)%.
The prepared imides were esterified to the corresponding benzoate,
methacrylate and cinnamate esters in good yields (72-92)%.
Esterification was achieved by reaction of the prepared imides with benzoyl
chloride, methacryloyl chloride and cinnamoyl chloride respectively in the presence
of triethylamine. The prepared new esters were tested as plasticizers for poly(vinyl
chloride) PVC.
Seventy two samples were prepared by mixing and grinding PVC with the
prepared esters in certain ratio and their softening points were recorded.
The results showed that addition of the prepared esters to PVC caused a clear
depression in softening point and this depression was due to the ability of the prepared
esters to form secondary molecular forces with the polymeric chains which inturn
reduced the interchain forces between the polymeric chains themselves and this
reduced softening point.
Comparison the results with dioctyl phthalate (DOP) and dibutyl phthalate
(DBP) the universal plasticizers for PVC indicated that the prepared esters in general
had better plasticizing efficiency than both DOP and DBP.