Biodegradable Block Copolymer with Controlled Crystallization
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Solution Overview
Problem
Existing biodegradable polymers used for medical coatings lack both conformability and degradability, leading to unsatisfactory performance when implanted in the body.
Innovation Solution
A biodegradable block copolymer comprising a polyalkylene glycol block and a polyhydroxyalkanoic acid block, with specific mass ratios and crystallization rates, ensuring high conformability and degradability by controlling the crystallization rates and molecular mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a triblock polymer structure with polyhydroxyalkanoic acid blocks at both ends of a polyalkylene glycol block is used, then degradability is improved, but conformability deteriorates
Solution Approach 1:
The patent changes the structural parameters of the block copolymer by placing the polyalkylene glycol block at both ends instead of the polyhydroxyalkanoic acid blocks, and by controlling the mass ratio of polyalkylene glycol block to total mass within 10-60%. This parameter change resolves the contradiction by achieving both high conformability (through flexible polyalkylene glycol blocks) and excellent degradability (through biodegradable polyhydroxyalkanoic acid blocks in the middle section).
Solution Approach 2:
The patent creates a composite block copolymer structure combining polyalkylene glycol blocks and polyhydroxyalkanoic acid blocks with specific architecture (Formula I). The composite structure leverages the flexibility and non-toxicity of polyalkylene glycol at the ends for conformability, while the biodegradable polyhydroxyalkanoic acid blocks in the middle provide degradability, thus resolving the technical contradiction between these two properties.
2Stability of the object's composition
If a low molecular weight compound is used as a linker molecule in the polyhydroxyalkanoic acid block, then crystallinity is decreased, but tensile strength deteriorates
Solution Approach 1:
The patent extracts and eliminates the low molecular weight linker molecule (General Formula C) from the polymer structure by directly bonding the polyhydroxyalkanoic acid blocks together without intervening linker molecules. This extraction removes the source of decreased crystallinity and tensile strength while maintaining the desired low crystallinity for conformability through the polyalkylene glycol block architecture.
Solution Approach 2:
The patent segments the block copolymer into distinct polyalkylene glycol blocks at the ends and polyhydroxyalkanoic acid blocks in the middle, connected directly without linker molecules. This segmentation creates a clean block structure (Formula I) that achieves optimal balance between crystallinity and tensile strength by allowing each block to fulfill its specific function without interference from linker molecules.
3Adaptability or versatility
If the mass ratio of polyalkylene glycol block is increased to improve conformability, then flexibility is improved, but degradability deteriorates
Solution Approach 1:
The patent optimizes the mass ratio parameter of polyalkylene glycol block to total mass within the specific range of 10-60%. This parameter optimization ensures that there is sufficient polyalkylene glycol content to provide flexibility and conformability, while maintaining adequate polyhydroxyalkanoic acid block content (40-90%) to ensure biodegradability, thus resolving the contradiction between conformability and degradability.
Data Source
AI summary
A biodegradable block copolymer has high conformability and excellent degradability. The block copolymer including a polyalkylene glycol block and a polyhydroxyalkanoic acid block, wherein the mass ratio of the polyalkylene glycol block with respect to the total mass is 10 to 60%; the carbonyl carbon has a carbon nuclear relaxation time T1ρ of not more than 20 ms; and the block copolymer satisfies Equation (1): χ=χ1×χ2>20 (1) χ1: crystallization rate of the polyalkylene glycol block; χ2: crystallization rate of a poly-A block, wherein A represents, among the repeat units contained in the polyhydroxyalkanoic acid block, a repeat unit whose homopolymer composed of the same repeat units has a highest crystallization rate.