Polymers 2012, 4(2), 1025-1036; doi:10.3390/polym4021025
Article

Radical-Scavenging Activity of Thiols, Thiobarbituric Acid Derivatives and Phenolic Antioxidants Determined Using the Induction Period Method for Radical Polymerization of Methyl Methacrylate

Received: 27 February 2012; in revised form: 2 April 2012 / Accepted: 5 April 2012 / Published: 16 April 2012
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: The radical-scavenging activities of two thiols, eight (thio)barbituric acid derivatives and six chain-breaking phenolic antioxidants were investigated using the induction period method for polymerization of methyl methacrylate (MMA) initiated by thermal decomposition of 2,2’-azobisisobutyronitrile (AIBN) and monitored by differential scanning calorimetry (DSC). The induction period (IP) for the thiols 2-mercaptoethanol (ME) and 2-mercapto-1-methylimidazole (MMI) was about half that for phenolic antioxidants. Except for the potent inhibitor 5,5-dimethyl-2-thiobarbituric acid (3), the IP for thiobarbituric acid derivatives was about one tenth of that for phenolic antioxidants. The IP for 1,3,5-trimethyl-2-thiobarbituric acid (1) and 5-allyl-1, 3-dimethyl-2-thiobarbituric acid (7) was less than that of the control, possibly due to inhibition by a small amount of atmospheric oxygen in the DSC container. The ratio of the chain inhibition to that of chain propagation (CI/CP) for the thiols and thiobarbituric acid compounds except for 1, 3 and 7 was about 10 times greater or greater than that for phenolic compounds. A kinetic chain length (KCL) about 10% greater than that of the control was observed for 1, suggesting that 1 had chain transfer reactivity in the polymerization of MMA. The average molecular weight of polymers formed from thiobarbituric acid derivatives is discussed.
Keywords: organic sulfur compounds; phenolic compounds; radical polymerization; AIBN; MMA; induction period; initial rate of polymerization; chain inhibition; chain propagation
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MDPI and ACS Style

Kadoma, Y.; Fujisawa, S. Radical-Scavenging Activity of Thiols, Thiobarbituric Acid Derivatives and Phenolic Antioxidants Determined Using the Induction Period Method for Radical Polymerization of Methyl Methacrylate. Polymers 2012, 4, 1025-1036.

AMA Style

Kadoma Y, Fujisawa S. Radical-Scavenging Activity of Thiols, Thiobarbituric Acid Derivatives and Phenolic Antioxidants Determined Using the Induction Period Method for Radical Polymerization of Methyl Methacrylate. Polymers. 2012; 4(2):1025-1036.

Chicago/Turabian Style

Kadoma, Yoshinori; Fujisawa, Seiichiro. 2012. "Radical-Scavenging Activity of Thiols, Thiobarbituric Acid Derivatives and Phenolic Antioxidants Determined Using the Induction Period Method for Radical Polymerization of Methyl Methacrylate." Polymers 4, no. 2: 1025-1036.

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