Silicone Elastomer Curing via Bis-dithiocarbamate Photoiniferters
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Solution Overview
Problem
Silicone-based elastomeric materials cured with conventional photoinitiators often exhibit poor mechanical properties.
Innovation Solution
The use of bis-dithiocarbamate or bis-dithiocarbonate compounds as controlled radical initiators, which can act as iniferters, to polymerize silicone compounds with at least two ethylenically unsaturated groups under actinic radiation, improving mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional photoinitiators (Norrish type-1) are used for free radical polymerization, then the curing method can occur in the absence of organic solvents and in the presence of heat-sensitive materials, but the resulting silicone-based elastomeric material has poor mechanical properties
Solution Approach 1:
The invention changes the chemical parameters of the polymerization system by replacing conventional photoinitiators with controlled radical initiators (photoiniferters) having specific molecular structures (Formula I). This parameter change transforms the polymerization mechanism from uncontrolled free radical to controlled radical polymerization, thereby improving mechanical properties while maintaining the solvent-free curing advantage
Solution Approach 2:
The invention uses composite initiator systems comprising specific photoiniferters (bis-dithiocarbamate or bis-dithiocarbonate compounds) that combine multiple functions: initiation, transfer, and termination capabilities within a single molecular structure. This composite approach enables controlled polymerization with improved mechanical properties
2Strength
If controlled radical initiators (photoiniferters) are used to improve mechanical properties, then the polymerization process requires specific molecular structures with particular functional groups, increasing the complexity of initiator selection
Solution Approach 1:
The invention specifies precise molecular structure parameters for photoiniferters (Formula I), defining the relationship between structural features (dithiocarbamate or dithiocarbonate groups, central carbon atom, substituent patterns) and polymerization control. By establishing these structural parameters, the invention simplifies initiator selection despite the requirement for controlled polymerization
Solution Approach 2:
The photoiniferters described in the invention perform multiple functions simultaneously: they act as initiators, transfer agents, and terminators in a single molecular entity. This multi-functionality reduces the need for separate additives and simplifies the overall polymerization system while achieving controlled radical polymerization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting silicone-based elastomeric materials demonstrate enhanced mechanical properties compared to those formed by free radical polymerization with conventional photoinitiators, showing increased toughness and elasticity.
Implementation Method 1
polymerizing silicone compounds having at least two ethylenically unsaturated groups in the presence of actinic radiation and a controlled radical initiator
Implementation Method 2
exposing the reaction mixture to actinic radiation to form a silicone-based elastomeric material
Data Source
AI summary
Silicone-based elastomeric materials, articles containing the silicone-based elastomeric materials, reaction mixtures used to form the silicone-based elastomeric materials, and methods of making the silicone-based elastomeric materials are described. The silicone-based elastomeric materials are prepared by polymerizing silicone compounds having at least two ethylenically unsaturated groups in the presence of actinic radiation and a controlled radical initiator. The controlled radical initiators are bis-dithiocarbamate or bis-dithiocarbonate compounds having a single carbon between the two dithiocarbamate or dithiocarbonate groups. The silicone-based elastomeric materials typically have improved mechanical properties compared to silicone-based elastomeric materials formed by free radical polymerization reactions in the presence of conventional photoinitiators.