Polydimethylsiloxane-Polyoxyalkylene Block Copolymers for Solventless Silicone Hydrogel Lenses

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Solution Overview

Problem

The development of silicone hydrogel contact lenses faces challenges in achieving high oxygen permeability and compatibility with hydrophilic components, particularly due to the hydrophobic nature of polydimethylsiloxane vinylic crosslinkers, which can result in non-homogeneous formulations and require the use of organic solvents, making it difficult to produce solventless lens formulations with desirable mechanical properties.

Innovation Solution

The use of polymerizable polydimethylsiloxane-polyoxyalkylene block copolymers with hydrophilic segments and amide-rich linkers, which are compatible with hydrophilic monomers, allowing for the creation of clear, solventless lens formulations with high oxygen permeability and suitable mechanical properties, such as elastic modulus, without the need for organic solvents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polydimethylsiloxane vinylic crosslinkers are used to achieve high oxygen permeability, then oxygen permeability is improved, but compatibility with hydrophilic components deteriorates

Engineering Contradiction:

Improveoxygen permeabilityVSAvoidcompatibility with hydrophilic components

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent uses block copolymers comprising hydrophobic polydimethylsiloxane segments and hydrophilic polyoxyalkylene segments. This composite structure allows the material to simultaneously provide high oxygen permeability (from the siloxane segments) and compatibility with hydrophilic monomers (from the polyoxyalkylene segments), resolving the contradiction between these two properties.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The block copolymer structure creates local hydrophobic regions (siloxane segments) for oxygen transport and local hydrophilic regions (polyoxyalkylene segments) for compatibility with hydrophilic components. This local differentiation of properties allows the single material to satisfy both contradictory requirements.

Inventive Principle:

Principle #3Local quality

2Reliability

If polydimethylsiloxane vinylic crosslinkers are used to achieve high oxygen permeability, then oxygen permeability is improved, but formulation homogeneity deteriorates

Engineering Contradiction:

Improveoxygen permeabilityVSAvoidformulation homogeneity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The block copolymer combines hydrophobic and hydrophilic segments in a single molecular structure, creating an amphiphilic material that can uniformly mix with both hydrophobic and hydrophilic components in the lens formulation, thereby achieving homogeneous formulations while maintaining high oxygen permeability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies the molecular structure of the crosslinker by incorporating polyoxyalkylene segments, which changes the hydrophobicity parameter of the crosslinker. This parameter change enables better compatibility and uniform distribution in the hydrophilic lens matrix, improving formulation homogeneity.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If conventional polydimethylsiloxane crosslinkers are used, then oxygen permeability is improved, but ease of manufacture deteriorates due to requirement of organic solvents

Engineering Contradiction:

Improveoxygen permeabilityVSAvoidease of manufacture

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The block copolymer structure changes the solubility parameters of the crosslinker, enabling it to be soluble in water and hydrophilic monomers without requiring organic solvents. This parameter change simplifies the manufacturing process while maintaining the high oxygen permeability provided by the siloxane segments.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The polyoxyalkylene segments act as intermediaries that bridge the hydrophobic siloxane segments and the hydrophilic lens matrix, enabling direct mixing without organic solvents. This intermediary structure facilitates ease of manufacture by eliminating the need for solvent removal steps.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP3526277B1Polymerizable polydimethylsiloxane-polyoxyalkylene block copolymers

Publication Date: 2020.08.12 ALCON INC

AI summary

The invention provides a polymerizable polydimethylsiloxane-polyoxyalkylene block copolymer which comprises (1) a linear polymer chain comprising at least two polydimethylsiloxane segments, one hydrophilic polyoxyalkylene segment between each pair of polydimethylsiloxane segements, and one amide-rich linker between each pair of one polydimethylsiloxane segment and one hydrophilic polyoxyalkylene segment, and (2) two terminal (meth)acryloyl groups. The hydrophilized polydiorganosiloxane vinylic crosslinker has a weight average molecular weight of at least 3000 Daltons. The invention is also related to a silicone hydrogel contact lens produced from a polymerizable polydimethylsiloxane-polyoxyalkylene block copolymer of the invention.