Phase-Segregated Block Copolymers for Biomedical Shape Memory
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a need for phase segregated polymeric systems with tunable properties that can be tailored for specific applications, as existing shape memory polymers lack the necessary flexibility and biocompatibility for biomedical applications, particularly in materials that come into contact with human body tissues.
Innovation Solution
The development of phase segregated block copolymers comprising α-hydroxy acid blocks (PHA) and polydimethylsiloxane blocks (PDAS) linked through urethane linkages, with controlled molecular weights and compositions to achieve desired glass transition temperatures and biodegradability, allowing for shape memory properties and tailored properties for biomedical applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic materials are used for shape memory applications, then shape memory properties are achieved, but biocompatibility and tissue compatibility deteriorate
Solution Approach 1:
The invention changes the material parameter from metallic to polymeric composition, specifically using phase-separated block copolymers with hard and soft segments. The hard segments (e.g., poly(L-lactide)) provide shape memory functionality through crystalline phase transformations, while the soft segments (e.g., polydimethylsiloxane) provide biocompatibility and flexibility. This parameter change resolves the contradiction by achieving shape memory properties through polymer phase transitions rather than metallic transformations.
Solution Approach 2:
The invention creates a composite block copolymer system where distinct hard and soft segments are chemically linked. The hard segments contain crystalline moieties that enable shape memory effect, while the soft segments provide biocompatibility and elastomeric properties. This composite structure allows simultaneous achievement of shape memory functionality and biocompatibility for biomedical applications.
2Object-affected harmful factors
If existing shape memory polymers are used, then biocompatibility is improved, but mechanical strength and tunability deteriorate
Solution Approach 1:
The invention segments the polymer into distinct hard and soft blocks within a block copolymer architecture. The hard segments (e.g., poly(α-hydroxy acid) blocks) provide mechanical strength through crystalline domains, while the soft segments (e.g., polydimethylsiloxane blocks) provide biocompatibility and flexibility. This segmentation allows each block to contribute its optimal properties, resolving the contradiction between strength and biocompatibility.
Solution Approach 2:
The invention applies local quality by giving different regions of the block copolymer different properties: hard segments with high crystallinity and melting points for strength and shape memory, and soft segments with low glass transition temperatures for biocompatibility and flexibility. This local differentiation of properties within the single material enables simultaneous achievement of mechanical strength and biocompatibility.
3Reliability
If block copolymers with hard and soft segments are synthesized, then shape memory properties are achieved, but manufacturing complexity increases
Solution Approach 1:
The invention uses preliminary action by employing ring-opening polymerization of cyclic monomers (e.g., L-lactide and glycolide) to form well-defined block structures with controlled molecular weights and compositions. This preliminary polymerization step creates precursors that can then be coupled through urethane linkages, simplifying the overall synthesis compared to attempting to create block copolymers through more complex step-growth polymerization routes.
Solution Approach 2:
The invention uses an intermediary approach by introducing urethane linkages as connecting groups between hard and soft segments. These urethane linkages serve as mediators that chemically join the poly(α-hydroxy acid) hard blocks with polydimethylsiloxane soft blocks, creating a stable block copolymer structure. This intermediary linkage simplifies the synthesis by providing a well-established polyaddition reaction pathway.
4Object-affected harmful factors
If phase segregated block copolymers are designed for biomedical applications, then biodegradability is achieved, but control over degradation rate and properties deteriorates
Solution Approach 1:
The invention enables control over degradation rate through parameter changes in the polymer structure: varying the composition ratio of hard to soft segments, adjusting the molecular weight of each block, and selecting different α-hydroxy acid monomers (e.g., L-lactide, glycolide, caprolactone). These parameter changes allow tuning of both the degradation rate and the mechanical properties, resolving the contradiction between achieving biodegradability and maintaining control over degradation characteristics.
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 resulting polymers exhibit a balance of strength and ductility, enabling temperature-triggered shape recovery suitable for biomedical applications, such as stents, and offer biodegradability and biocompatibility, reducing the need for surgical removal and minimizing thrombosis risks, while allowing for controlled drug delivery during degradation.
Implementation Method 1
Shape memory, in the context of the present invention, is to be understood as the ability of a material to remember and recover its original shape after it has been subjected to a deformation... This phenomenon is generally based on structural phase transformations in the material.
Implementation Method 2
The term transition temperature denotes the melting point in case of a crystalline segment or the glass transition temperature in case of an amorphous segment.
Implementation Method 3
Djonlagic et al., J. Appl. Pol. Sci. Vol. 122, Issue 4, pp 2715-2730 (2011) describe novel polyurethane copolymers derived from a diisocyanate, butane diol and a hydroxy terminated PCL-PDMS-PCL oligomer which are synthesized by a two step polyaddition reaction.
Data Source
AI summary
Phase segregated block-copolymer based on repeating structural elements represented by formula I wherein PHA represents at least one block based on one or more α-hydroxy acids, PDAS represents a central block based on a dialkylsiloxane, the PDAS block has a weight average molecular weight in the range of from 4000 to 10000, the blocks PHA have a weight average molecular weight in the range of from 2000 to 10 000, the phase segregated block copolymer has a weight average molecular weight of from 40 000 to 120 000.