LCST Small-Molecule Smart Windows for Passive Opacity Switching

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Solution Overview

Problem

Existing technologies lack small molecules exhibiting Lower Critical Solution Temperature (LCST) behavior at ambient temperatures, particularly in the range of 25-30°C, which are essential for energy-efficient smart windows that switch opacity/transparency without additional energy input.

Innovation Solution

Development of water-soluble small organic molecules of general formula 1 that exhibit LCST phase transitions in dilute aqueous solutions, allowing temperature-triggered switching between transparent and opaque states near room temperature, with tunable response temperature and switching time via secondary stimuli like light and chemical additives.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If electrochromic or thermochromic materials are used to achieve responsive light transmission control, then the window can switch between transparent and opaque states, but additional energy input in the form of electricity or heat is required

Engineering Contradiction:

Improveautomatic transparency switchingVSAvoidenergy input for switching

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

The patent employs materials that automatically respond to temperature changes without requiring external energy input. The LCST-based polymer system self-regulates its transparency based on ambient temperature, eliminating the need for electrical power or active heating/cooling systems to drive the phase transition.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention utilizes the lower critical solution temperature (LCST) phase transition of polymer solutions. At temperatures below the LCST, the polymer chains are hydrated and the solution remains transparent. Above the LCST, dehydration occurs and the solution becomes opaque, providing automatic temperature-responsive control without additional energy input.

Inventive Principle:

Principle #36Phase transitions

2Use of energy by moving object

If LCST-based polymer systems are used for transparency switching, then the window can operate near ambient temperature without additional energy input, but the response time and switching speed are slower compared to electrochromic materials

Engineering Contradiction:

Improveno additional energy inputVSAvoidresponse time

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The patent optimizes the polymer composition, concentration, and molecular weight to adjust the LCST and improve response kinetics. By carefully selecting polymer parameters and solution concentration, the system achieves faster phase transition speeds while maintaining ambient temperature operation and zero energy input requirements.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If small molecules are used instead of polymers for LCST behavior, then the system can be synthesized with simpler starting materials, but small molecule-based LCST systems are rare and harder to control

Engineering Contradiction:

Improvesynthesis from simple starting materialsVSAvoidLCST behavior control

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent creates a composite system combining small molecule LCST agents with polymer matrices or uses block copolymers that incorporate LCST-active segments. This composite approach leverages the ease of small molecule synthesis while achieving the reliable, controllable LCST behavior characteristic of polymer systems.

Inventive Principle:

Principle #40Composite materials

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

Enables the fabrication of dynamic windows that modulate light and heat transmission for energy efficiency and privacy, with controlled transparency and opacity transitions, reducing indoor energy consumption and providing need-based privacy.

Implementation Method 1

small organic molecules of general formula 1, and their dilute aqueous solutions that change their opacity depending on the applied/environmental temperature, a property known as LCST (lower critical solution temperature)

Methodology Applied

Scientific EffectLower critical solution temperature (LCST) phase transition: Phase Change

Implementation Method 2

dynamic windows that modulate light and heat transmission for energy efficiency and privacy, with controlled transparency and opacity transitions

Methodology Applied

Scientific EffectThermochromism: Thermochromism

Data Source

PatentUS12540278B2Temperature programmable small molecules for thermoresponsive smart windows and applications thereof

Publication Date: 2026.02.03 COUNCIL OF SCI & IND RES

AI summary

Design and applications of a class of water-soluble small molecules represented by formula 1. The molecules, in their dilute aqueous solutions, exhibit lower critical solution temperature (LCST) phase transitions near room temperature, inducing a temperature triggered switching of opacity. Further, disclosed is a scalable smart window, akin to a radiative energy management system, that can be incorporated into the built environment for imparting energy efficiency. The window fabrication is facile wherein the aqueous solution is sandwiched between two transparent glass panes to enable modulation of light and heat transmission. The dynamic window of present invention represents with multifarious applications in developing scalable, smart energy management systems for indoor building environments is envisioned to be a major contribution towards cost effective smart glass technologies.