Cleavable Crosslinking Monomer for Dynamic Polymer Networks
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Solution Overview
Problem
Current polymer compositions lack the ability to effectively change physical properties, such as storage modulus and peel adhesion, upon cleavage of crosslinking monomers, which limits their adaptability and functionality in applications like pressure-sensitive adhesives.
Innovation Solution
A composition comprising polymerized units derived from a cleavable crosslinking monomer with at least two free-radically polymerizable groups and a group having the formula -O-C(R2)(R3)-O-, which can undergo cleavage upon exposure to energy sources like UV radiation, resulting in changes to physical properties like storage modulus and peel adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional crosslinking monomers are used to form polymer networks, then structural strength and stability are improved, but the ability to change physical properties upon cleavage is lost
Solution Approach 1:
The crosslinking monomer is segmented into distinct functional regions: polymerizable groups for network formation and a cleavable acetal/ketal group for controlled degradation. This segmentation allows the molecule to simultaneously provide structural strength through crosslinking and adaptability through selective cleavage of the acetal/ketal linkage upon exposure to acid or enzymatic conditions
Solution Approach 2:
The patent introduces dynamic reversibility to the polymer network by incorporating cleavable acetal or ketal groups that can be broken under specific conditions (acidic environment or enzymatic treatment). This transforms the static crosslinked network into a dynamic system that can transition from a strong, stable state to a degraded, adaptable state, enabling changes in physical properties like storage modulus and peel adhesion
2Stress or pressure
If highly crosslinked polymer networks are formed, then storage modulus and structural integrity are improved, but peel adhesion and flexibility deteriorate
Solution Approach 1:
The patent enables parameter changes in the polymer network by incorporating cleavable crosslinkers that respond to environmental triggers. Upon exposure to acid or enzymes, the acetal/ketal groups cleave, fundamentally changing the network parameters from highly crosslinked (high storage modulus) to partially degraded (reduced storage modulus, increased flexibility), thereby improving peel adhesion while maintaining structural integrity when needed
3Reliability
If stable polymer compositions are used, then reliability and durability are improved, but adaptability to different conditions and applications is reduced
Solution Approach 1:
The patent extracts the cleavable acetal or ketal group as a separate, removable functional element within the crosslinking monomer structure. This extracted component can be selectively removed through acid treatment or enzymatic degradation, allowing the polymer composition to transition from a stable, reliable state to an adaptable state where physical properties can be modified for different applications such as pressure-sensitive adhesives
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 composition exhibits significant changes in physical properties, including decreased storage modulus and increased peel adhesion, making it suitable for applications requiring adaptability and improved adhesive performance.
Implementation Method 1
a coatable syrup that can be cured to a viscoelastic material when radiation-sensitive alpha-cleaving groups in either the polymer or one of the monomers are exposed to UV radiation
Implementation Method 2
radiation-sensitive alpha-cleaving groups in either the polymer or one of the monomers are exposed to UV radiation
Data Source
AI summary
A composition is described comprising a polymer. The polymer comprises polymerized units derived from a cleavable crosslinking monomer. The cleavable crosslinking monomer comprises at least two free-radically polymerizable groups and at least one group having the formula -O-C(R2)(R3)-O-, wherein R2 and R3 are independently hydrogen, alkyl, or aryl. The composition has a Tg no greater than 50°C. In some embodiments, the composition has a storage modulus greater than 3 X 105 Pa at 25°C and 1 Hz and may be characterized as a non-tacky polymer. In other embodiments, the composition is a pressure sensitive adhesive. Upon cleavage of at least a portion of the polymerized monomeric units derived from the cleavable crosslinking monomer, the composition exhibits a change in at least one physical property. In another embodiment, the composition comprises a polymer and fragments. The fragments comprise the reaction product of a free-radically polymerizable group bonded to a polymer chain and a pendent hydroxyl group. The composition has a Tg no greater than 50°C. Also described are articles, comprising the composition described herein (i.e. before and/or after cleavage); as well as methods of making the composition and methods of making articles.