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[Visible-light initiator system using thiobarbituric acid derivatives with methyl substituent]
1Division of Functional Polymer, Institute for Medical and Dental Engineering, Tokyo Medical and Dental University, Tokyo.
Shika Zairyo, Kikai = Journal of the Japanese Society for Dental Materials and Devices
|September 1, 1990
Summary
Methyl substitution on thiobarbituric acid derivatives significantly impacts visible-light curing resins. A single methyl group at position 5 enhances initiation and cure depth, optimizing dental resin performance.
Area of Science:
- Polymer Chemistry
- Dental Materials Science
- Organic Synthesis
Background:
- Visible-light curing resins are crucial in dentistry, relying on photoinitiator systems for polymerization.
- The dl-camphorquinone (CQ)-reducing agent system is widely used, but its efficiency can be modulated by the reducing agent's structure.
- Thiobarbituric acid derivatives have shown potential as reducing agents in such systems.
Purpose of the Study:
- To synthesize and evaluate novel 2-thiobarbituric acid derivatives with methyl substituents.
- To investigate the effect of methyl group substitution on the initiation efficiency of the CQ-thiobarbituric acid system.
- To assess the impact on resin polymerization kinetics and cure depth in experimental visible-light curing resins.
Main Methods:
- Synthesis of seven 2-thiobarbituric acid derivatives with varying methyl substitutions.
- Preparation of experimental visible-light curing resins using these derivatives as reducing agents with dl-camphorquinone (CQ).
- Analysis of polymerization behavior using Differential Scanning Calorimetry (DSC) and measurement of cure depth.
Main Results:
- Methyl substitution significantly altered the solubility of thiobarbituric acid derivatives in triethylene glycol dimethacrylate (3G).
- Substitution at position 1 (3) improved solubility but not initiation ability.
- A single methyl group at position 5 markedly enhanced initiation ability, leading to improved maximum exothermic rate, reduced time to peak polymerization, and increased cure depth.
Conclusions:
- Methyl group substitution at position 5 of thiobarbituric acid is critical for enhancing the initiation ability of the CQ-reducing agent system.
- Optimizing the structure of thiobarbituric acid derivatives can significantly improve the performance of visible-light curing resins.
- Excessive substitution (two methyl groups at position 5) can lead to inhibitory effects, highlighting the importance of controlled structural modification.