Polysiloxane Prepolymer End-Capping via Two-Stage Reactivity
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Solution Overview
Problem
The existing methods for end-capping polysiloxane prepolymers in biomedical devices, such as contact lenses, often use methacryloyl chloride, which is hazardous and forms dimers, necessitating a safer and more cost-effective alternative.
Innovation Solution
A method involving the reaction of polysiloxane prepolymers with a non-free radical polymerizable reactive end-capping agent followed by a free radical polymerizable reactive end-capping agent, controlling crosslink density and modulus of the resulting polysiloxane prepolymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If methacryloyl chloride is used as an endcapping agent, then the end-capping reaction proceeds effectively, but the process becomes hazardous and requires additional steps to remove dimers
Solution Approach 1:
The patent introduces an intermediary substance (alternative endcapping agent) that mediates the end-capping reaction without producing harmful byproducts. The intermediary reacts with the polysiloxane prepolymer to achieve effective end-capping while avoiding the formation of harmful dimers and eliminating the hazards associated with methacryloyl chloride handling
Solution Approach 2:
The patent extracts or removes the harmful component (methacryloyl chloride) from the end-capping process and replaces it with a safer alternative. This extraction eliminates the source of hazards while maintaining the essential function of end-capping the polysiloxane prepolymer
2Strength
If polysiloxane prepolymer crosslink density is increased, then structural strength is improved, but the modulus increases and water content decreases
Solution Approach 1:
The patent changes the chemical parameters of the endcapping agent to control the crosslinking reaction. By selecting specific endcapping agents with different reactivities and molecular structures, the patent optimizes the crosslink density to achieve the desired balance between structural strength and material properties such as modulus and water content
Solution Approach 2:
The patent creates a composite structure by combining the polysiloxane prepolymer with carefully selected endcapping agents. This composite approach allows tuning of the material properties to achieve both adequate structural strength and appropriate modulus/water content for biomedical applications
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
This approach allows for the production of polysiloxane prepolymers with reduced modulus and increased water content, enhancing the properties of biomedical devices like contact lenses while avoiding the hazards of methacryloyl chloride.
Implementation Method 1
reacting a polysiloxane prepolymer having reactive functional end groups with a non-free radical polymerizable reactive end-capping agent
Implementation Method 2
reacting the reaction product of step (a) with a free radical polymerizable reactive end-capping agent
Data Source
AI summary
A method is disclosed which involves the steps of (a) reacting a polysiloxane prepolymer having reactive functional end groups with a non-free radical polymerizable reactive end-capping agent; and (b) reacting the reaction product of step (a) with a free radical polymerizable reactive end-capping agent.