Crosslinked Polyisobutylene Polyurethanes for Durable Implants
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Solution Overview
Problem
Existing medical implant materials, such as polycarbonate-urethane (PCU), are prone to embrittlement and degradation over time, making them unsuitable for long-lasting orthopedic devices like artificial meniscus and anterior cruciate ligament (ACL) due to oxidation and hydrolysis of carbonate groups.
Innovation Solution
The development of polyisobutylene-based polyurethane or polyurea polymers with crosslinks between polymer chains, formed by reacting hydroxyl-terminated polyisobutylene with a diisocyanate and a trifunctional chain extender, or using a thermal-activated crosslinker, to enhance mechanical, thermal, and chemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polycarbonate-urethane (PCU) is used for medical implant devices, then the device can be initially strong and durable, but it embrittles and degrades over time due to oxidation and hydrolysis
Solution Approach 1:
The patent changes the chemical composition parameters by replacing polycarbonate diol with polyisobutylene diol, eliminating the carbonate group that undergoes hydrolysis. This parameter change transforms the material from degradable PCU to biostable polyisobutylene-based polyurethane, resolving the contradiction between initial strength and long-term stability
Solution Approach 2:
The patent creates a composite polymer structure combining polyisobutylene soft segments with diisocyanate hard segments, forming a new material system that integrates the biostability of polyisobutylene with the mechanical strength of urethane linkages, achieving both durability and long-term reliability
2Strength
If crosslinks are added between polymer chains, then mechanical strength and stability are enhanced, but device complexity increases
Solution Approach 1:
The patent modifies the polymerization parameters by incorporating trifunctional chain extenders alongside difunctional extenders, which naturally creates crosslinks between polymer chains. This parameter change in the synthesis process achieves enhanced mechanical strength and stability without requiring separate crosslinking steps or complex post-processing
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 crosslinked polyisobutylene-based polymers provide improved mechanical strength, stability, and resistance to oxidation, resulting in tougher and longer-lasting medical implant devices.
Implementation Method 1
reacting hydroxyl-terminated polyisobutylene with a diisocyanate to form a prepolymer
Implementation Method 2
crosslinks between polymer chains in the polymer include crosslinks between hard segments in the polymer chains that are derived by reaction of the trifunctional chain extender and isocyanate groups of the diisocyanate
Implementation Method 3
The hydroxyl-terminated polyisobutylene can include a thermal-activated crosslinker. Heat can be applied to the prepolymer, or to a reaction product derived therefrom, to form the polyurethane or polyurea polymer
Data Source
AI summary
Methods are disclosed for preparing polyurethane or polyurea polymers with crosslinks between polymer chains as well as orthopedic devices and other medical implant devices formed by the polyurethane or polyurea polymers and related methods of fabricating and/or assembling such devices. The crosslinks can enhance their mechanical, thermal, chemical, electrical, and dimensional properties, providing improved performance and expanding their range of applications compared to non-crosslinked polymers.