title: Influence of chain extender length of aromatic dimethacrylates on polymer network development.
abstract: OBJECTIVE
  To investigate the role of chain extender size from Bis-EMA monomers on the polymerization profiles and properties of the crosslinked polymers. Additionally, the influence of Bis-GMA was also evaluated.
  
  
  METHODS
  The polymer network from homopolymers Bis-EMA4, Bis-EMA10 and Bis-EMA30 was characterized, as well as copolymers formed among these monomers and Bis-GMA. The degree of conversion from neat and blended monomers as a function of photo-activation time was evaluated by FTIR. Rate of polymerization, network parameter and cross-link density from materials were demonstrated. Water sorption and solubility were determined according to ISO 4049 specification and the data obtained were analyzed by two-way ANOVA/Tukey's test (alpha=0.05). Flexural strength and Young's modulus from polymerized monomers/co-monomers were measured after 24h water storage at 37 degrees C and the results were analyzed by one-way ANOVA/Tukey's test (alpha=0.05).
  
  
  RESULTS
  Monomers with larger ethylene oxide units presented the highest values regarding the degree of conversion and cross-link density. The effect of the chain extender length was also observed in water sorption and solubility polymer characteristics, with Bis-EMA4 being the most hydrophobic polymer. Bis-EMA10 and Bis-EMA30 homopolymers were not able to be tested with the three point bending test due to their great flexibility. The addition of Bis-GMA produced stronger and more rigid Bis-EMA polymers (p<0.05).
  
  
  CONCLUSIONS
  Aromatic dimethacrylates with different chain extender lengths can be a useful alternative in controlling the properties of a dental material, adjusting those to specific applications.
authors.affiliation: Department of Operative Dentistry, School of Dentistry, Federal University of Pelotas, Rua Gonçalves Chaves, 457, CEP 96015-560, Pelotas, RS, Brazil.
authors.forename: Fabrício A
authors.initials: FA
authors.lastname: Ogliari
authors.forename: Caroline
authors.initials: C
authors.lastname: Ely
authors.forename: Cesar H
authors.initials: CH
authors.lastname: Zanchi
authors.forename: Carmen B B
authors.initials: CB
authors.lastname: Fortes
authors.forename: Susana M W
authors.initials: SM
authors.lastname: Samuel
authors.forename: Flávio Fernando
authors.initials: FF
authors.lastname: Demarco
authors.forename: Cesar L
authors.initials: CL
authors.lastname: Petzhold
authors.forename: Evandro
authors.initials: E
authors.lastname: Piva
mesh_terms: D000042:Absorption; D000327:Adsorption; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry / Q000528:radiation effects; D004548:Elasticity; D005027:Ethylene Oxide / Q000737:chemistry; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008027:Light; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry* / Q000528:radiation effects; D018583:Pliability; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D003764:Dental Materials; D008689:Methacrylates; D011108:Polymers; D014867:Water; C041979:2,2-bis-(4-(2-methacryloxyethoxy)phenyl)propane; D017438:Bisphenol A-Glycidyl Methacrylate; D005027:Ethylene Oxide