Shape-Memory Polymers Crosslinked via Michael Addition

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Solution Overview

Problem

Current shape-memory polymers face challenges in achieving high shape energy densities, tunable shape recovery stimuli, ease of processability, reproducible behavior, and cost-effectiveness, particularly in biomedical applications where they need to perform mechanical work against external loads.

Innovation Solution

The development of shape-memory polymers comprising branched or telechelic prepolymers with low polydispersity crosslinked with multifunctional crosslinkers, primarily through Michael addition reactions in the substantial absence of free radicals, with the use of radical scavengers to control crosslinking and enhance properties like energy storage capacity and crystallinity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If free radical addition reaction is used for crosslinking, then crosslinking efficiency is improved, but shape energy density and reproducibility deteriorate

Engineering Contradiction:

Improvecrosslinking efficiencyVSAvoidshape energy density

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent converts the harmful effect of free radicals (which cause poor reproducibility and low shape energy density) into a beneficial process by using them to initiate Michael addition reactions. The free radicals generated during vinyl group formation are not eliminated but instead utilized to drive the crosslinking reaction between hydroxyl groups and multifunctional crosslinkers, achieving both high crosslinking efficiency and excellent shape memory performance with reproducible results.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the chemical parameters of the crosslinking process by transitioning from conventional free radical addition to Michael addition chemistry. This parameter change involves using hydroxyl-functional prepolymers and multifunctional crosslinkers with complementary reactive groups, enabling controlled crosslinking that achieves superior shape energy density (exceeding 1.5 MJ/m³) and reproducible shape recovery behavior while maintaining efficient crosslinking.

Inventive Principle:

Principle #35Parameter changes

2Strength

If multifunctional crosslinkers are used, then crosslinking density is improved, but processability deteriorates

Engineering Contradiction:

Improvecrosslinking densityVSAvoidprocessability

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by pre-forming vinyl groups on the prepolymer chains through reaction with diisocyanates before the crosslinking stage. This preliminary functionalization allows the subsequent crosslinking reaction to proceed uniformly and efficiently when multifunctional crosslinkers are introduced, maintaining good processability during mixing and molding while achieving high crosslinking density in the final product.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If shape recovery temperature is tuned near body temperature, then biomedical applicability is improved, but control over recovery stimulus deteriorates

Engineering Contradiction:

Improvebiomedical applicabilityVSAvoidcontrol over recovery stimulus

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent achieves tunable shape recovery temperature near body temperature (37°C) by adjusting the chemical composition and molecular weight of the prepolymer chains, particularly using polyesters with specific glass transition temperatures. This parameter adjustment allows precise control of the shape recovery stimulus while maintaining the ability to trigger recovery through conventional heating methods, thus preserving ease of operation alongside biomedical applicability.

Inventive Principle:

Principle #35Parameter changes

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

These polymers exhibit improved energy storage capacity, high shape fixity, and recovery efficiency, with elastic energy densities exceeding 1.5 MJ/m3 and efficient energy storage and release capabilities, making them suitable for demanding biomedical applications.

Implementation Method 1

The large-strain recovery Observed in SMPs is a manifestation of entropy elasticity

Methodology Applied

Scientific EffectEntropy elasticity: Elasticity

Implementation Method 2

the crosslinks are formed by a Michael addition reaction

Methodology Applied

Scientific EffectMichael addition reaction: Chemical Bonding

Implementation Method 3

a material heated above its shape-memory transition temperature, TSM

Methodology Applied

Scientific EffectShape-memory transition: Phase Change

Data Source

PatentUS10377852B2Shape-memory polymers and methods of making and use thereof

Publication Date: 2019.08.13 UNIVERSITY OF ROCHESTER

AI summary

Described are shape-memory polymers that have a branched or telechelic prepolymer having a low polydispersity crosslinked with a stoichiometric amount of a multifunctional crosslinker. Also described are methods of making shape-memory polymers by crosslinking a stoichiometric amount of a multifunctional crosslinker with a branched or telechelic prepolymer having a low polydispersity. Methods of measuring the energy storage capacity of a shape-memory polymer are also disclosed.