[Basic studies on radiopaque monomer. (3) Synthesis of monomers having Di-, tri-bromophenoxy groups, their properties, radiopacity and physical properties of their bulk polymers].

Radiopaque monomers were synthesized to examine their properties and the physical properties of their bulk polymers, to obtain basic data for new radiopaque filling composite resin. Octachlorocyclotetraphosphazene (P4N4Cl8) was used as material to be synthesized, and 2,4,6-tribromophenol, (Br3C6H2OH) and 2,4-dibromophenol (Br2C6H3OH) were selected as organic compounds having radiopacity. As a polymerizing functional group, 2-hydroxyethylmethacrylate (HEMA) was used. Radipaque monomers were synthesized as follows: 1 Cl of P4N4Cl8 was replaced by 1 mol of 2,4,6-tribromophenol, or 2 Cls by 2 mols of 2,4-dibromophenol, and the remaining 7 or Cls were replaced by HEMA, polymerizing functional group, to obtain 2 kinds of radiopaque monomers; 4 PN-(Br3Ph)1-(EMA)7 and 4 PN-(Br2Ph)2-(EMA)6. The specific gravity of these monomers was 1.4629 and 1.4978, refractive index 1.5315 and 1.5423 and viscosity, 70 and 80 poise respectively. Radiopacity was measured by an X-ray apparatus. Al equivalent, of specimen, 10 phi x 3 mm, 4 PN-(Br3Ph)1-(EMA)7 was 5.8 mm and 4 PN-(Br2Ph)2-(EMA)6 7.0 mm. 4 PN-(Br3Ph)1-(EMA)7 and 4 PN-(Br2Ph)2-(EMA)6, both wet specimens, had compressive strength of 83.7 and 81.3 MPa, in transverse strength of 45.5 and 53.0 MPa and knop hardness of 25.8 and 22.6 respectively. After 7 days, 4 PN-(Br3Ph)1-(EMA)7 had water sorption of 1.46 wt%, and 4 PN-(Br2Ph)2-(EMA)6, 0.84 wt%, and solubility of 0.15 and 0.14 wt%, respectively.