Addition-Fragmentation Agents with Pendent Amine Groups
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Solution Overview
Problem
Free-radical polymerization in polymerizable compositions often results in volumetric shrinkage, leading to stress and microcracks, which can cause adhesion failure and affect durability, especially when transferred to a substrate interface.
Innovation Solution
Incorporating addition-fragmentation agents with labile linkages that can cleave and reform during polymerization, delaying the gel point and allowing for network reorganization to relieve stress, and incorporating tertiary amine groups to reduce unreacted volatile amines and improve polymerization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If free-radical polymerization is used to convert monomers to polymer, then polymerization efficiency is improved, but volumetric shrinkage produces stress and microcracks leading to adhesion failure
Solution Approach 1:
The patent changes the chemical parameters of the polymerization system by incorporating addition-fragmentation agents with labile linkages that can cleave and reform during polymerization. This allows the system to maintain high conversion efficiency while dynamically adjusting the network structure to relieve stress, thereby preventing adhesion failure despite the inherent shrinkage of free-radical polymerization.
Solution Approach 2:
The addition-fragmentation agents introduce dynamic labile crosslinks that can continuously break and reform during the polymerization process. This dynamic behavior allows the polymer network to reorganize and relieve stress in real-time, maintaining adhesion durability while preserving the high productivity of free-radical polymerization.
2Reliability
If addition-fragmentation agents with labile linkages are incorporated to relieve stress, then adhesion durability is improved, but the complexity of the polymerizable composition increases
Solution Approach 1:
The addition-fragmentation agents serve multiple functions simultaneously: they act as chain transfer agents to control molecular weight, provide labile crosslinks for stress relief, and delay the gel point to extend the viscous flow period. By consolidating these multiple functions into a single agent type, the patent improves adhesion durability while minimizing the increase in composition complexity.
3Productivity
If tertiary amine groups are incorporated to accelerate photopolymerization, then polymerization efficiency is improved, but unreacted volatile amines adversely affect physical properties of the cured composition
Solution Approach 1:
The patent merges the tertiary amine co-initiator function with the addition-fragmentation agent structure itself. The amine groups are covalently bonded to the addition-fragmentation agent backbone, ensuring they remain part of the polymer matrix after curing. This eliminates the problem of unreacted volatile amines separating or migrating, while maintaining the accelerated photopolymerization rate.
Solution Approach 2:
The patent extracts the harmful volatile amine component from the system by incorporating it into the non-volatile addition-fragmentation agent structure. The amine groups are no longer free-standing volatile molecules but are chemically bound within the polymer network, removing their harmful effects while preserving their beneficial catalytic function.
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 addition-fragmentation agents effectively reduce polymerization-induced stress and shrinkage, enhancing the mechanical properties and adhesion of the cured compositions by integrating labile crosslinks and reducing volatile amine residues.
Implementation Method 1
a labile addition-fragmentation group that can cleave and reform to relieve strain
Implementation Method 2
Type II photoinitiators may be used to photoinitiate polymerization... Tertiary amines are often used as co-initiators to accelerate the rate of photopolymerization
Implementation Method 3
The pendent tertiary amine groups serve as a reducing agent that works with the peroxy catalyst oxidant to produce a redox polymerizable composition
Data Source
AI summary
Provided is an addition-fragmentation agent of the formula (I) where Ramine comprises a tertiary amine group; R2 linking group of valence a+2; Z is an ethylenically unsaturated polymerizable group; and subscript a is 0 or 1.