Photochromic Coating Microcapsule Segmentation
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Solution Overview
Problem
Photochromic compounds face degradation and loss of optical and interconversion properties when directly deposited on solid surfaces due to exposure to external factors and steric impediments, leading to reduced reversibility and rapid degradation.
Innovation Solution
Encapsulating photochromic compounds in hollow micro- or nanocapsules with a solid, impermeable cortex within a liquid solvent, allowing the capsules to be dispersed in a polymeric matrix, which maintains the photochromic properties and provides protection from external factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photochromic compounds are directly deposited on solid surfaces, then the coating provides photochromic functionality, but the photochromic compounds suffer degradation and loss of optical properties due to exposure to external factors and steric impediments
Solution Approach 1:
The photochromic coating is segmented into discrete microcapsules (5-50 μm diameter) containing photochromic compounds in liquid solvent. Each microcapsule acts as an isolated environment that protects the photochrome from external factors while maintaining solution-like properties inside. This segmentation resolves the contradiction by providing physical protection without compromising photochromic functionality.
Solution Approach 2:
The photochromic compounds are nested within microcapsules that have a liquid solvent core and a protective cortex wall. The microcapsules are then dispersed and embedded within a solid polymeric matrix coating. This nested structure provides multiple levels of protection while maintaining the photochromic compounds in a protective yet functional environment.
2Strength
If photochromic compounds are dispersed in a polymeric matrix, then the coating provides mechanical stability, but the interconversion velocity is significantly reduced due to steric impediments from polymeric chains
Solution Approach 1:
By segmenting the photochromic compounds into microcapsules, the system eliminates direct contact between photochrome molecules and polymeric chains. The microcapsule structure provides a liquid internal environment that maintains fast interconversion kinetics while the external polymeric matrix provides mechanical stability, thus resolving the speed-strength contradiction.
Solution Approach 2:
The microcapsule cortex wall acts as an intermediary barrier between the photochromic compounds and the polymeric matrix. This intermediary structure allows the photochrome to remain in a liquid solvent environment for fast interconversion while the polymeric matrix provides mechanical support without directly interfering with the photochromic molecules.
3Stability of the object's composition
If photochromic compounds are used in crystalline form or dispersed in polymer, then the coating provides structural integrity, but the optical properties and absorption spectra are significantly altered
Solution Approach 1:
The microcapsule structure segments the photochromic compounds into isolated liquid droplets, preventing crystallization and maintaining the compounds in solution form. This preserves the original optical properties and absorption spectra while the microcapsules themselves provide the structural integrity within the polymeric matrix.
Solution Approach 2:
The invention changes the physical state parameter of the photochromic compounds from crystalline or polymer-dispersed to liquid solution within microcapsules. This parameter change preserves the optical properties characteristic of solution-state photochromes while the microcapsule-matrix composite provides the necessary structural integrity.
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 encapsulation method preserves the optical and interconversion properties of photochromic compounds, enhancing their durability and stability, and allows for their use in various applications without additional protective layers, maintaining rapid interconversion kinetics similar to those in solution.
Implementation Method 1
Photochromic compounds are systems which, by stimulation with electromagnetic radiation, interconvert between two states (A and B) which have different colors. Once the irradiation by light is interrupted, the photoinduced state B may be thermally cooled down and return at the initial state A (B → A). Furthermore, the interconversion B → A may be induced by photochemical means, irradiating at a wavelength different from that used for the interconversion A → B.
Data Source
Figure 1a~1d
Figure 2a~2f
Figure 3a~3f
AI summary
Coating with photochromic properties, method for producing said coating and use thereof applicable to optical articles and glazed surfaces. The coating is formed by the combination of the following three elements: (1) a polymeric matrix, which is typically rigid and deposited on the surface of interest; (2) hollow, sealed micro- and/or nanocapsules dispersed within said matrix; and (3) solutions of photochromic compounds (chosen from a group comprising spirooxazine, azobenzenes or chromenes) in a liquid solvent that does not react (with the photochromic compound and with the capsule wall), which are encapsulated inside said micro- or nanocapsules.