Modified Thioxanthone Photoinitiators for Dual-Mode Polymerization
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Solution Overview
Problem
There is a need for new photoinitiators with higher efficiencies for free-radical polymerization that surpass the performance of existing photoinitiators like thioxanthone and 2-chlorothioxanthen-9-one, particularly when used in combination with onium salt compounds for photoinitiating and photocatalyzing cationic polymerization.
Innovation Solution
The development of polymerizable compositions incorporating specific compounds represented by certain formulas, such as diaryliodonium salts and compounds with alkyl and alkoxy groups, which serve as photoinitiators for free-radical and cationic polymerization, enhancing the polymerization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing photoinitiators like thioxanthone and chlorothioxanthone are used, then polymerization can be initiated, but the polymerization efficiency is insufficient and conversion rates are limited
Solution Approach 1:
The patent modifies the molecular structure of thioxanthone by introducing specific substituents (R1 = alkyl group with 1-6 carbon atoms, R2 = H, alkyl group with 1-4 carbon atoms, alkoxy group with 1-4 carbon atoms, F, Cl, or Br) to create compounds with enhanced photoinitiation efficiency. This structural parameter change results in higher polymerization efficiency and improved conversion rates compared to conventional photoinitiators
Solution Approach 2:
The patent combines the modified thioxanthone compound with onium salt compounds to create a composite photoinitiator system that can simultaneously initiate both free-radical and cationic polymerization. This composite approach synergistically enhances the overall polymerization efficiency and enables dual-mode polymerization capability
2Adaptability or versatility
If a single photoinitiator system is used, then the system is simple, but it cannot effectively initiate both free-radical and cationic polymerization
Solution Approach 1:
The patent designs a photoinitiator system where the modified thioxanthone compound works in conjunction with onium salts to provide multi-functional capability. The same compound structure can initiate both free-radical polymerization (with appropriate monomers) and cationic polymerization (with onium salts), eliminating the need for separate photoinitiator systems for different polymerization types
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
These compositions demonstrate improved polymerization efficiencies and properties, achieving high conversion rates and desirable characteristics in polymerized reaction products, suitable for applications like protective coatings and sealants.
Implementation Method 1
Photopolymerization of monomers is widely practiced in the manufacture of polymers, and especially thin polymer coatings
Implementation Method 2
Various types of photoinitiator systems are known including, for example, Type I photoinitiators that function by unimolecular decomposition, Type II photoinitiator systems typically based on intermolecular H-atom abstraction
Implementation Method 3
They are useful for photoinitiating and/or photocatalyzing cationic polymerization when combined with certain onium salt compounds
Data Source
AI summary
Polymerizable compositions comprise at least one free-radically or cationically polymerizable compound; and a photoinitiator system, wherein the photoinitiator system comprises a compound represented by the formula: (I) wherein: each R1 independently represents an alkyl group having from 1 to 6 carbon atoms, and each R2 independently represents H, an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, F, Cl, or Br. Polymerized reaction products are also disclosed.