Silane-Based Chain Transfer Agents for Polymer Networks
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Solution Overview
Problem
Existing chain transfer agents used in radical polymerization, such as sulfur compounds, can leak out of cured materials and be washed away by saliva, posing toxicological concerns and affecting the stability and properties of polymers.
Innovation Solution
Development of silanes with specific structures that form polysiloxane condensates or are bound to fillers, which act as chain transfer agents, ensuring they remain within the polymer network and are insoluble in water, thereby preventing leakage and enhancing polymer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low-molecular-weight chain transfer agents are used, then chain transfer activity is effective, but the agents leak out of cured materials and are washed out by saliva
Solution Approach 1:
The patent combines chain transfer agents with silane groups to create hybrid molecules that can participate in both radical polymerization and siloxane network formation. This composite structure allows the chain transfer agent to be incorporated into the crosslinked polymer network, preventing leakage while maintaining chain transfer activity
Solution Approach 2:
The patent changes the molecular weight and structural parameters of the chain transfer agents by using silane-based compounds that can form polysiloxane condensates. This parameter change transforms the agents from low-molecular-weight leak-prone compounds to higher-molecular-weight network-integrated structures that resist washout
2Manufacturing precision
If conventional chain transfer agents are used, then polymerization control is achieved, but toxicological concerns arise due to saliva washout
Solution Approach 1:
The silane group acts as an intermediary that connects the chain transfer agent to the polymer network. This intermediary structure enables the chain transfer agent to be anchored within the material, eliminating toxicological concerns while preserving polymerization control
Solution Approach 2:
By creating composite chain transfer agents with silane functionality, the patent integrates the active chain transfer component into the structural polymer network, ensuring both controlled polymerization and elimination of toxicological risks
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 silanes effectively control polymerization, reduce polymerization shrinkage stress, and produce more homogeneous networks with improved mechanical properties, particularly in dental applications, by being bound into the polymer matrix and resistant to saliva washout.
Implementation Method 1
polysiloxane condensates, which can be obtained by hydrolytic condensation of these silanes
Implementation Method 2
radically polymerizable silanes... suitable per se... as chain transfer agents for the monitoring and control of the network structure in radical polymerization
Implementation Method 3
Double bond-containing reagents which react according to a radical addition-fragmentation chain transfer (AFCT) mechanism have proved particularly useful as chain transfer agents
Data Source
AI summary
Radically polymerizable silane according to the general formula Iin which R1 is a linear or branched aliphatic C1-C9-alkyl radical, phenyl or alkylated phenyl radical, R2, R3 independently of each other in each case are absent or are a linear or branched aliphatic C1-C20-alkylene radical, which can be interrupted by S or O atoms, R4, R5, R6 independently of each other in each case are —Cl, —O—CH3, —O—C2H5, —CH3 or —C2H5, X is CH2 or O, Y is absent, or is O or NR′, wherein R′ is H or a C1-5-alkyl radical, and Z is absent, or is O, NR″, —CO—O—, —CO—NR″—, —O—CO—O—, —O—CO—NR″—, or —NR″—CO—NR″—, wherein R″ is H or a C1-5-alkyl radical and wherein the radicals R2 and R3 cannot be absent at the same time and Z is absent if R2 or R3 is absent, polycondensates based thereon and fillers surface-modified therewith.