Biomedical Polyurethanes with Asymmetric Urethane Segments
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Solution Overview
Problem
Biomedical polyurethanes exhibit limited biodegradability, with approximately 20% of the material remaining after prolonged exposure to biodegrading conditions at elevated temperatures, due to their limited solubility and high crystallinity, which affects their mechanical properties and application in medical devices.
Innovation Solution
The development of biomedical polyurethanes with a general formula (A-B-C-B)n, where A is a polyol, B is a diisocyanate moiety, and C is a diol component, with B-C-B segments having a multiform block length and reduced crystallinity, achieved by varying the length of diisocyanate and diol components, resulting in improved solubility and bioresorbability while maintaining mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If biomedical polyurethanes are designed with uniform block-length diol components to achieve high mechanical strength and resistance to tearing, then mechanical properties are improved, but biodegradability deteriorates with approximately 20% mass remaining after prolonged exposure
Solution Approach 1:
The patent applies asymmetry by designing urethane segments where the diisocyanate moiety length differs from the diol component length. This asymmetric structure prevents uniform packing and reduces crystallinity, thereby improving biodegradability while maintaining mechanical strength through the alternating soft-hard segment architecture.
Solution Approach 2:
The patent changes the structural parameters of the polyurethane by varying the length of diisocyanate and diol components in the B-C-B segments. This parameter variation creates multiform block lengths that reduce crystallinity and enhance solubility, leading to improved biodegradability while preserving mechanical properties through controlled composition.
2Strength
If biomedical polyurethanes are designed with high crystallinity to achieve favorable mechanical properties, then mechanical strength is improved, but solubility and biodegradability deteriorate
Solution Approach 1:
The asymmetric design of urethane segments with mismatched diisocyanate and diol lengths disrupts crystalline packing, reducing overall crystallinity. This allows the material to maintain mechanical strength through hydrogen bonding in hard segments while improving solubility and biodegradability through reduced crystalline regions.
Solution Approach 2:
The patent applies local quality by creating distinct soft segments (polyol) and hard segments (urethane) with different properties. The hard segments provide mechanical strength through crystalline ordering, while the asymmetric urethane segments with multiform block lengths create local amorphous regions that enhance solubility and biodegradability.
Data Source
AI summary
The invention is directed to biomedical polyurethanes. The invention is particularly directed to biomedical polyurethanes with improved biodegradability and to an improved preparation of the biomedical polyurethanes. In particular the present invention provides a biomedical polyurethane having the formula (A-B-C-B)n, wherein A denotes a polyol, B denotes a diisocyanate moiety, C denotes a diol component and n denotes the number of recurring units, and wherein the B-C-B segment is bioresorbable.