pH-Responsive Fluorescent Compounds for Hair Washfastness
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Solution Overview
Problem
Current methods for treating hair with fluorescent compounds face challenges such as washfastness, acid perspiration resistance, and penetration depth, with cationic fluorophores being prone to fading and not effectively resisting acid perspiration due to ion exchange with human sweat.
Innovation Solution
The use of fluorescent compounds with one to two permanent cations and one to four incipient cations, where the incipient cations change from neutral to positively charged at acidic pH, allowing for enhanced binding to hair shafts and improved washfastness and acid perspiration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cationic fluorophores are used to treat hair, then washfastness is improved compared to anionic fluorophores, but they still fade with repetitive shampoo use and lack acid perspiration resistance
Solution Approach 1:
The patent applies dynamics by incorporating pH-responsive incipient cations that dynamically change their charge state based on environmental pH. During application at high pH, the incipient cations are neutral, allowing deep penetration into the hair shaft. Upon rinsing with acidic water, they become positively charged to provide washfastness and resist acid perspiration. This dynamic charge transformation resolves the contradiction between penetration efficiency and durability.
Solution Approach 2:
The patent utilizes parameter changes by designing fluorophores whose charge state changes in response to pH variations. The incipient cations remain neutral at application pH (10-12) for optimal penetration, then transform to positively charged states at acidic pH (4-6) during rinsing and use, enhancing binding strength and resistance to fading and acid perspiration over time.
2Reliability
If polycationic fluorescent compounds are used to increase binding strength, then bleeding and washfastness are minimized, but penetration depth into the hair shaft is reduced
Solution Approach 1:
The patent resolves this contradiction through dynamic charge modulation. The fluorophores are applied with multiple incipient cations in their neutral form at high pH, enabling deep diffusion into the hair shaft without strong electrostatic repulsion. After penetration, acidic rinsing protonates these incipient cations, creating strong positive charges that form intense binding sites within the cortex, achieving both deep penetration and strong binding.
Solution Approach 2:
The patent applies preliminary action by first delivering the fluorophores in a neutral charge state to enable unrestricted penetration to the desired depth, then subsequently activating the binding function through pH-induced protonation of incipient cations after the fluorophores are already positioned within the hair shaft.
3Illumination intensity
If conventional cationic fluorophores are deposited on hair, then they provide optical effects, but they undergo ion exchange with acid perspiration and fade
Solution Approach 1:
The patent addresses acid perspiration resistance through parameter changes in the charge state of the fluorophores. The incipient cations remain neutral during application and initial rinsing, preserving optical effects. During acid perspiration events, the low pH environment protonates the incipient cations, creating strong positive charges that resist ion exchange with sweat cations, thereby maintaining optical effects and preventing fade.
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 described method provides improved washfastness and resistance to acid perspiration, ensuring the optical effects of the fluorophores are maintained with minimal loss over time and enhanced penetration into the hair shaft.
Implementation Method 1
the pH of the hair after rinsing is from about 3.5 to about 6; and wherein the rinsing of the hair causes one or more of the one to four incipient cations to change from neutral to positively charged inside of the hair shaft
Implementation Method 2
one or two permanent positive charges, one to four incipient cations... change from neutral to positively charged inside of the hair shaft, making them more resistant to water, shampoo and acid perspiration
Implementation Method 3
Fluorophores that absorb UV but emit visible light
Implementation Method 4
one or more C5-C9 hydrophobic moieties
Data Source
AI summary
Described herein is a hair treatment composition including one or more fluorescent compounds. The one or more fluorescent compounds each include a fluorophore, one or two permanent cations, one to four incipient cations, and one or more hydrophobic moieties. The incipient cations are pendant to the core structure and are neutral. The one or more fluorescent compounds enter the hair shaft after the hair treatment composition is applied to the hair. The hair treatment composition has a pH of from about 7 to about 11.