Modified Biodegradable Polymer End-Group Substitution
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Solution Overview
Problem
Biodegradable polymers used in stent manufacturing suffer from low mechanical strength due to thermal degradation during processing, leading to reduced molecular weight and limited applicability, with existing methods complicating the polymerization process and potentially using toxic catalysts.
Innovation Solution
A method involving pre-coating biodegradable polymers with a solution containing additives to substitute hydroxyl end groups with carboxylic or hydroxyl groups, followed by solid-phase mixing extrusion molding, which inhibits chain breakdown and molecular weight loss, and enhances mechanical properties without additional processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If melt processing method (extrusion, injection, compression molding) is used during polymer molding, then manufacturing efficiency is improved, but molecular weight decreases due to thermal degradation, reducing mechanical strength
Solution Approach 1:
The patent applies preliminary action by conducting end-group modification before the main extrusion molding process. The hydroxyl end groups are converted to carboxylic acid groups in advance, which prevents molecular chain breakdown during subsequent thermal processing. This preliminary chemical modification ensures that when the polymer undergoes melt processing, the molecular weight is preserved and mechanical strength is maintained while still achieving efficient manufacturing.
2Strength
If hydroxyl end group is substituted by adding acid anhydride as polymerization component, then degradation rate is reduced and mechanical strength is improved, but polymerization process becomes complicated
Solution Approach 1:
The patent applies segmentation by dividing the modification process into two independent stages: first, polymerization to produce the base polymer; second, end-group modification by reacting the polymer with acid anhydride. This segmentation allows each stage to be optimized separately and simplifies the overall process compared to attempting to incorporate modification during the polymerization itself.
Solution Approach 2:
The patent uses acid anhydride as an intermediary substance that reacts with hydroxyl end groups to form carboxylic acid groups. This intermediary approach allows modification of the polymer without requiring complex catalysts or changing the fundamental polymerization process, thus maintaining process simplicity while achieving the desired end-group functionality.
3Duration of action of stationary object
If functional group is substituted by using catalyst during solution polymerization, then degradation properties are modified, but polymerization process becomes complicated and toxic catalysts may be used
Solution Approach 1:
The patent employs acid anhydride as a safe intermediary that reacts with hydroxyl end groups under mild conditions without requiring toxic catalysts. This intermediary approach modifies the degradation properties of the polymer by converting end groups to carboxylic acid functionality, thereby controlling degradation rate while avoiding the complications and safety issues associated with catalyst-based modification methods.
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
This method effectively improves the mechanical strength and biodegradability of biodegradable polymers, allowing for the production of stents with controlled degradation periods and simplified processing, while avoiding the use of toxic catalysts.
Implementation Method 1
pre-coating the biodegradable polymer with a solution prepared by dissolving an additive for substituting a hydroxyl end group of the biodegradable polymer with a carboxylic group or another hydroxyl group
Data Source
AI summary
Disclosed are a method for preparing a modified biodegradable polymer by using various additives and plasticizers in a biodegradable polymer which is non-toxic to human bodies, a biodegradable polymer prepared therefrom, and a biodegradable stent prepared by using the biodegradable polymer. Specifically, it is possible to reduce a decrease in molecular weight resulting from a thermal degradation occurring during the solid-phase molding processing of a biodegradable polymer by coating a solution in which various additives are dissolved during the modification of the biodegradable polymer to convert the hydroxyl end group into a functional group of a carboxylic group or a different kind of hydroxyl group.