Photocrosslinked Polyurethane Block Copolymers for Medical Devices
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Solution Overview
Problem
Current polyisobutylene-based polyurethane block copolymers for medical devices face challenges in achieving the non-linear strain stiffening properties of natural tissues, as thermoplastic versions are prone to creep-induced damage while thermoset versions are stiff but inefficient.
Innovation Solution
Development of cross-linked polyisobutylene-based polyurethane block copolymers with polyfunctional benzophenone cross-linking compounds that form covalent bonds in hard domains, allowing the material to be soft and easily moved under low stress while stiffening under higher stress, mimicking natural tissue behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If thermoplastic polyisobutylene-based polyurethane block copolymers are used, then the material is soft and easily moved under low stress, but the material is prone to creep-induced damage
Solution Approach 1:
The patent applies parameter changes by transitioning the polyisobutylene-based polyurethane block copolymer from a thermoplastic state to a thermoset state through crosslinking. This chemical parameter change transforms the material's structural integrity, enabling it to maintain softness and ease of movement under low stress while simultaneously gaining resistance to creep-induced damage through the formed crosslinked network.
Solution Approach 2:
The patent creates a composite material structure by incorporating crosslinked polyisobutylene-based polyurethane block copolymers into medical device components. This composite approach combines the inherent softness and flexibility of polyisobutylene with the enhanced mechanical stability and creep resistance provided by the crosslinked thermoset structure, achieving both ease of operation and reliability.
2Reliability
If thermoset polyisobutylene-based polyurethane block copolymers are used, then the material resists creep-induced damage, but the material is stiff and inefficient
Solution Approach 1:
The patent applies local quality by creating a segmented block copolymer structure where hard segments (urethane domains) and soft segments (polyisobutylene domains) are distributed throughout the material. The crosslinking occurs primarily in the hard segments, providing localized reinforcement that resists creep-induced damage while leaving the soft segments to maintain flexibility and efficiency of movement. This spatial differentiation of properties resolves the contradiction between stiffness and ease of operation.
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 cross-linked polyisobutylene-based polyurethane block copolymers exhibit efficient and durable performance in medical devices like heart valves by preventing creep-induced damage and maintaining efficient movement, offering a balance between softness and stiffness.
Implementation Method 1
exposing at least a portion of the polymer matrix to radiation to activate the cross-linking compound. The activated cross-linking compound bonds to the polymeric chains in the exposed portion.
Data Source
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AI summary
A block copolymer including a plurality of polymeric chains and a plurality of cross-linking compound residues linking together the plurality of polymeric chains. The plurality of polymeric chains forms a plurality of hard domains and a plurality of soft domains. Each polymeric chain includes a plurality of soft segments and a plurality of hard segments. The plurality of soft segments includes a polyisobutylene diol or diamine residue. The plurality of soft segments forms the plurality of soft domains. The plurality of hard segments including a diisocyanate residue. The plurality of hard segments forms the plurality of hard domains. The cross-linking compound residues link together the hard segments of the plurality of polymeric chains.