Hyperbranched polyester with mixed methacryloyl and aliphatic ester terminal groups: Synthesis, characterization, and application in dental restorative formulations

摘要

Boltron H30 is a polyester polyol with a dendritic structure, developed by Perstop Corp. Complete methacrylated H30 oligomers were obtained by using three different reaction routes, i.e., treatment of H30 with methacrylic anhydride, methacryloyl chloride and 2-isocyanatoethyl methacrylate (IEM). The viscosities of the three H30 hyperbranched materials at 45degreesC were 22.4, 23.5, and 42.8 Poise, respectively, compared to commonly used BisGMA having a viscosity of 33.5 Poise at 45degreesC. All three completely methacrylated H30 materials were combined with TEGDMA (50/50, wt/wt) to formulate visible light-curable (VLC) neat resins. The experimental VLC resins exhibited significant reduction of polymerization shrinkage and higher C=C double bond conversion, compared to the VLC BisGMA/TEGDMA (50150, wt/wt) control. The three new resins, with the exception of the H30-IEM based formulation, have mechanical properties comparable to a BisGMA/TEGDMA control. But, the VLC H30-IEM based resin exhibited higher compressive and flexural strengths than the BisGMA/TEGDMA control, possibly due to hydrogen bonding. H30 was also esterified by using different acid chlorides to investigate the effect of other ester terminal groups on H30, in relation to the viscosities of the oligomers, The results show that the viscosities of the esterified H30 are strongly depended on the ester groups, where benzoate > acetate > propionate > isobutyrate ester > butyrate ester. However, the T-g of the cured resins depends more on the level of hydrogen bonding, rather than the terminal ester groups. A H30 oligomer, with half of the terminal hydroxyl groups replaced by methacrylate residues and half by different carboxylates. such as acetate, propionate, butyrate and isobutyrate ester, were prepared and used to formulate VLC resins. All these formulated resins, with partly methacrylated H30, have Much higher double bond conversion and less linear polymerization shrinkage. But, they exhibited lower T-g values and less attractive mechanical properties. The latter was especially true in comparing acetate to butyrate ester terminal groups. A third series of partly methacrylated H30 were prepared, where methacrylation was achieved by combining acetyl chloride/methacryloyl chloride in the 70/30, 50/50, and 30/70 (wt/wt) ratios, respectively. were prepared and used to formulate VLC resins. The results showed that higher methacrylation of the terminal hydroxyls on H30 failed to bring about better mechanical properties for the cured resins, when the replacement portion was >50%. [References: 17]