Grafted Polymer Networks Balancing Oxygen Permeability and Hydrophilicity
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Solution Overview
Problem
Existing polymer materials, such as silicone hydrogels, face challenges in combining oxygen permeability and hydrophilicity due to incompatibility between silicone and hydrophilic components, making it difficult to produce materials with desired properties for medical devices like contact lenses.
Innovation Solution
A process involving a first reactive composition containing a polymerization initiator that forms multiple free radical groups, a crosslinker, and ethylenically unsaturated compounds, followed by activation steps to create a crosslinked substrate network with a covalently bound activatable free radical initiator, which is combined with a second reactive composition to form a grafted polymeric network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone-containing monomers and hydrophilic monomers are polymerized together to form silicone hydrogels, then oxygen permeability is improved, but compatibility between components deteriorates making production difficult
Solution Approach 1:
The patent divides the polymerization process into two separate stages: first forming a crosslinked substrate network from silicone-containing monomers, then separately grafting hydrophilic polymers onto this network. This segmentation allows each component to be optimized independently while avoiding compatibility issues during polymerization.
Solution Approach 2:
The crosslinked substrate network is prepared in advance before combining with hydrophilic components. By pre-forming the silicone network with pendant reactive groups, the patent eliminates the need to simultaneously polymerize incompatible silicone and hydrophilic monomers, thereby resolving production difficulties while maintaining high oxygen permeability.
2Adaptability or versatility
If silicone components and hydrophilic components are combined in polymer mixtures, then desired material properties are improved, but component compatibility deteriorates
Solution Approach 1:
The patent creates a composite structure where hydrophilic polymer chains are grafted onto a crosslinked silicone substrate network. This composite architecture allows the silicone component to provide oxygen permeability while the grafted hydrophilic component provides hydrophilicity, achieving desired material properties without direct mixing of incompatible components.
Solution Approach 2:
The crosslinked substrate network with pendant reactive groups serves as an intermediary structure that connects the silicone component and hydrophilic component through covalent bonding. This intermediary approach allows incompatible components to be combined in a stable configuration without direct interaction in the polymerization mixture.
3Productivity
If a polymerization initiator forms multiple free radical groups upon activation, then polymerization efficiency is improved, but control over the polymerization process deteriorates
Solution Approach 1:
The patent uses a polymerization initiator that forms multiple free radical groups at specific pendant positions on the crosslinked substrate network, rather than uniform distribution. This localized initiation provides high polymerization efficiency at the graft sites while maintaining overall process control through the structured network architecture.
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 process enables the formation of polymer compositions that overcome incompatibility issues, resulting in materials with enhanced oxygen permeability and hydrophilicity suitable for medical devices, particularly contact lenses.
Implementation Method 1
a polymerization initiator that is capable, upon a first activation, of forming two or more free radical groups
Implementation Method 2
activating the covalently bound activatable free radical initiator of the crosslinked substrate network such that the second reactive composition polymerizes therein
Data Source
AI summary
Provided are polymer compositions made by a process comprising: (a) providing a first reactive composition containing: (i) a polymerization initiator that is capable, upon a first activation, of forming two or more free radical groups, at least one of which is further activatable by subsequent activation; (ii) one or more ethylenically unsaturated compounds; and (iii) a crosslinker; (b) subjecting the first reactive composition to a first activation step such that the first reactive composition polymerizes therein to form a crosslinked substrate network containing a covalently bound activatable free radical initiator, (c) combining the crosslinked substrate network with a second reactive composition containing one or more ethylenically unsaturated compounds; and (d) activating the covalently bound activatable free radical initiator of the crosslinked substrate network such that the second reactive composition polymerizes therein with the crosslinked substrate network to form a grafted polymeric network and a byproduct polymer. Also provided are precursors to the polymer compositions, processes for preparation of the polymer compositions, and methods of using the polymer compositions, for instance in medical devices.