title: Synthesis, characterization and evaluation of urethane derivatives of Bis-GMA.
abstract: OBJECTIVE
  The aims of the study were to synthesize derivatives of Bis-GMA having pendant n-alkyl urethane substituents and to characterize and evaluate their physicochemical properties.
  
  
  METHODS
  Stoichiometric amounts of Bis-GMA and n-alkyl isocyanates were reacted in dichloromethane with dibutyltin dilaurate as a catalyst. Volumetric shrinkage, water uptake, degree of vinyl conversion, refractive index and viscosity of resulting urethane monomers and those of Bis-GMA were measured. The flexural strengths of their corresponding homopolymers and that of Bis-GMA were also measured.
  
  
  RESULTS
  These types of urethane derivatives of Bis-GMA exhibited lower viscosities and were more hydrophobic than Bis-GMA. Generally, the viscosity of these experimental monomers decreased with increasing chain length of the alkyl urethane substituent. Photopolymerization of the new monomers gave high degrees of vinyl conversion compared to Bis-GMA. The experimental monomers also yielded polymers with lower polymerization shrinkages at equivalent degrees of vinyl conversion, than Bis-GMA. The refractive indices of these urethane derivatives were similar to Bis-GMA, but the flexural strengths of their polymers were lower than that of the Bis-GMA homopolymer, decreasing with increasing chain length of the alkyl urethane substituent.
  
  
  CONCLUSIONS
  Because of their excellent overall properties, these new derivatives of Bis-GMA have potential as dental monomers that can improve many properties of resin based dental materials that utilize methacrylate monomer systems.
authors.affiliation: NIST, Polymers Division, 100 Bureau Drive, Mail Stop 8545, Gaithersburg, MD 20899-8545, USA. chetan.khatri@nist.gov
authors.forename: Chetan A
authors.initials: CA
authors.lastname: Khatri
authors.forename: Jeffery W
authors.initials: JW
authors.lastname: Stansbury
authors.forename: Carl R
authors.initials: CR
authors.lastname: Schultheisz
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Antonucci
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D003485:Cyanates / Q000737:chemistry; D018772:Dental Marginal Adaptation; D003799:Dental Stress Analysis; D004548:Elasticity; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D008689:Methacrylates / Q000138:chemical synthesis / Q000737:chemistry; D011140:Polyurethanes / Q000138:chemical synthesis / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014520:Urethane / Q000138:chemical synthesis / Q000737:chemistry*; D014783:Viscosity; D017155:Wettability
chemical_list: D003485:Cyanates; D008689:Methacrylates; D011140:Polyurethanes; C029824:urethane dimethacrylate luting resin; D014520:Urethane; D017438:Bisphenol A-Glycidyl Methacrylate