EVALUATION OF TERTIARY AMINE CO-INTIATORS USING DIFFERENTIAL SCANNING PHOTOCALORIMETRY

Abstract

The purpose of this investigation was to compare the degree of photo- and thermal-polymerization obtained using various tertiary amine co-initiators of differing reactivities and molar concentrations, utilizing differential scanning photocalorimetry (DPC) and DSC. Amines tested were 2-(dimethylamino)ethyl methacrylate (A), triethanolamine (B), N,N,3,5-tetramethyl-aniline (C), ethyl 4-dimethylaminobenzoate (D), 0.95 (A) and 0.05 (D) in combined mixture (E), 4-N,N-(dimethylamino)phe-nylacetic acid (F) and a newly-synthesized tertiary aromatic amine methacryloxyethyl substituted 4-N,N-(dimethyla-mino)phenylacetamide (G). The monomer system consisted of Bis-GMA and triethylene glycol dimethacrylate neat resins, and 0.5% camphoroquinone for all groups tested. Samples of the blended monomers with 0.5–4.0 mol/eq (co-initiator to initiator) were irradiated with visible light under N₂. The heat of reaction (ΔH) was calculated for each run in order to determine the degree of polymerization (DP). D resulted in a significantly higher degree of photopolymerization than A or B (p<0.05). No significant differences were noted between C, E, F and G (α= 0.05). ΔH values for DSC correlated well with those of DPC. DPC appears to be an efficient tool in the evaluation of photo-initiated free radical polymerized systems.

Keywords:

• Co-initiators
• Tertiary Aromatic Amines
• Differential Photocalorimetry
• Methacrylates

Acknowledgments