Silicone Hydrogel Contact Lenses via RAFT Polymerization
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Solution Overview
Problem
Existing silicone hydrogel contact lenses face challenges in achieving a balance between high oxygen permeability, comfort, and ease of manufacture, with issues related to hydrophobic surface formation and complex, time-consuming production processes.
Innovation Solution
The development of silicone hydrogel contact lenses using siloxane-containing homopolymers with a thio carbonyl thio fragment of a reversible addition fragmentation chain transfer (RAFT) agent, which allows for the formation of a polymer network with lower cross-link density and improved comfort, while being easier to manufacture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicone-containing monomers are used to form silicone hydrogels, then oxygen permeability is improved, but hydrophobic surface formation occurs which worsens wettability and comfort
Solution Approach 1:
The patent applies local quality by creating amphiphilic block copolymers with distinct hydrophobic (siloxane) and hydrophilic (methacrylate) blocks. The hydrophobic blocks provide oxygen permeability while the hydrophilic blocks create wettable surfaces, allowing different regions of the polymer structure to have different properties that collectively solve the contradiction.
Solution Approach 2:
The patent uses composite materials by combining siloxane-containing monomers with hydrophilic monomers to form amphiphilic block copolymers. This composite polymer structure integrates the oxygen-permeable siloxane segments with water-loving methacrylate segments, simultaneously achieving high oxygen permeability and good wettability.
2Manufacturing precision
If complex RAFT polymerization processes are used to prepare amphiphilic copolymers, then polymer structure control is improved, but manufacturing time and complexity increase
Solution Approach 1:
The patent applies preliminary action by using pre-synthesized siloxane-containing monomers with built-in functional groups that can directly participate in polymerization. This eliminates the need for separate crosslinking steps and intermediate processing, reducing manufacturing time while maintaining structure control.
Solution Approach 2:
The patent uses universality by designing monomers that serve multiple functions: the siloxane-containing monomers act as both structural building blocks and crosslinking agents, while the hydrophilic monomers provide both polymer chain formation and surface wetting properties. This multi-functionality reduces the number of separate process steps required.
3Strength
If crosslinking agents are added to increase cross-link density, then material strength is improved, but modulus increases which worsens comfort
Solution Approach 1:
The patent applies parameter changes by carefully controlling the degree of crosslinking and the composition ratios of different monomers. By optimizing these parameters, the patent achieves sufficient material strength while maintaining low enough modulus for comfort, finding the optimal balance point rather than maximizing either property.
Solution Approach 2:
The patent uses composite materials with amphiphilic block copolymers where the hydrophilic blocks act as spacers that reduce cross-link density in the bulk material. This composite structure provides mechanical strength through the crosslinked network while maintaining comfort by reducing the modulus through the flexible hydrophilic segments.
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 solution results in contact lenses with high oxygen permeability and enhanced comfort, achieved through a simpler and cost-effective manufacturing process, addressing the limitations of previous silicone hydrogel production methods.
Implementation Method 1
a contact lens is provided which comprises a polymerization product of a mixture comprising (a) one or more siloxane-containing homopolymers comprising one thio carbonyl thio fragment of a reversible addition fragmentation chain transfer (RAFT) agent
Data Source
AI summary
Biomedical devices such as silicone hydrogels formed from a polymerization product of a mixture comprising (a) one or more siloxane-containing homopolymers comprising one or more thio carbonyl thio fragments of a reversible addition fragmentation chain transfer (RAFT) agent; and (b) one or more biomedical device-forming monomers are disclosed.