Polyrotaxane Elastomer Crosslinking Density Control
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Solution Overview
Problem
Existing crosslinked polyrotaxane compositions do not exhibit an initial elastic modulus within an appropriate range for applications in actuators or sensors, despite efforts to optimize their mechanical properties.
Innovation Solution
The use of a crosslinking agent with a higher molecular weight than conventional ones, combined with a double-reactive component and a single-reactive component, to reduce crosslinking density and achieve an initial elastic modulus of 0.6 to 2 MPa in the elastomer composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional crosslinking agents with lower molecular weight are used to crosslink polyrotaxane, then the crosslinking density is high and the material structure is stable, but the initial elastic modulus becomes too high (above 2 MPa) for actuator and sensor applications
Solution Approach 1:
The patent changes the molecular weight parameter of the crosslinking agent from conventional low values (e.g., polyethylene glycol with Mn=1,000) to high values (Mn=1,200 to 7,000). This parameter change reduces the crosslinking density while maintaining network stability, achieving an initial elastic modulus of 0.6 to 2 MPa suitable for actuators and sensors.
Solution Approach 2:
The patent creates a composite crosslinking system by combining high molecular weight crosslinking agents with double-reactive components and single-reactive components. This composite approach allows control over crosslinking density and network architecture, achieving the desired balance between stability and low elastic modulus.
2Strength
If crosslinking density is increased to improve material stability, then the elastomer becomes too rigid with initial elastic modulus above 2 MPa, but if crosslinking density is reduced, the material becomes too soft and loses structural integrity
Solution Approach 1:
The patent utilizes parameter changes in the crosslinking agent molecular weight (Mn=1,200 to 7,000) to achieve optimal crosslinking density. This specific parameter range provides the right balance: enough crosslinking for structural stability but not so much that the elastic modulus exceeds 2 MPa.
Solution Approach 2:
The patent introduces local quality variations through the use of double-reactive components and single-reactive components in combination with the high molecular weight crosslinking agent. This creates a non-uniform crosslinking distribution that maintains local stability while reducing overall crosslinking density, achieving the target elastic modulus range.
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 elastomer composition exhibits a reduced crosslinking density, leading to an appropriately low initial elastic modulus in the low deformation region, which is suitable for applications in actuators and sensors, with a hysteresis loss of 5% or less.
Implementation Method 1
a crosslinked polyrotaxane prepared by crosslinking of two polyrotaxane cyclic molecules with a crosslinking moiety present therebetween
Implementation Method 2
A polyrotaxane is expected to be used in various applications, since it exhibits viscoelasticity resulting from sliding of the cyclic molecule on the straight chain molecule
Data Source
AI summary
Provided is an elastomer which is suitable for application in actuators or sensors, and which exhibits an appropriately low initial elastic modulus in a low deformation region.An elastomer composition containing the following components (A) to (D):component (A): a polyrotaxane;component (B): a crosslinking agent containing a second linear molecule having a molecular weight of 1,200 to 7,000, and a functional group disposed at both ends of the second linear molecule;component (C): a double-reactive component having a reactive group at both ends; andcomponent (D): a single-reactive component having a reactive group at only one end, wherein at least a portion of the functional group in the component (B) is directly or indirectly bonded to the cyclic molecule in the component (A), and the elastomer composition exhibits an initial elastic modulus of 0.6 to 2 MPa.