Red-NIR Photoinduced Thermal Polymerization of Thick Samples

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Solution Overview

Problem

Current free radical polymerization methods face challenges such as the need for external thermal energy, poor temperature control, and limitations in polymerizing thick samples due to UV-induced photopolymerization, which is hazardous and inefficient.

Innovation Solution

A red to near-infrared (red-NIR) photoinduced thermal-initiating composition comprising a heat-generating dye and a thermal initiator, where the dye generates heat upon irradiation, triggering the thermal initiator to initiate polymerization without electron transfer, allowing for controlled polymerization of thick samples.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If UV-induced photopolymerization is used, then polymerization speed is improved, but safety deteriorates due to noxious effects on eyes and skin

Engineering Contradiction:

Improvepolymerization speedVSAvoidsafety

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the wavelength parameter from UV range to visible light range (400-700 nm), specifically using blue light around 450 nm. This parameter change maintains polymerization efficiency while eliminating the harmful UV radiation effects on eyes and skin, as visible light is less noxious but still sufficient to activate the photoinitiator system.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If UV-induced photopolymerization is used, then polymerization efficiency is improved, but sample thickness capability deteriorates

Engineering Contradiction:

Improvepolymerization efficiencyVSAvoidsample thickness

Core Design Contradiction:

ProductivityVSLength of stationary object

Solution Approach 1:

The patent transitions from UV wavelength dimension to visible light wavelength dimension, specifically using blue light with longer wavelength (400-700 nm). This dimensional change in the electromagnetic spectrum allows deeper light penetration into the sample, enabling polymerization of thicker samples while maintaining polymerization efficiency through appropriate photoinitiator selection.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Length of stationary object

If thermal free radical polymerization is used, then sample thickness capability is improved, but temperature control deteriorates due to thermal runaway

Engineering Contradiction:

Improvesample thicknessVSAvoidtemperature control

Core Design Contradiction:

Length of stationary objectVSTemperature

Solution Approach 1:

The patent introduces a photoinitiator system as an intermediary that absorbs visible light and converts it to chemical energy to initiate polymerization. This intermediary mechanism allows for controlled polymerization in thick samples because the light can penetrate deeply and initiate reaction throughout the volume, avoiding the thermal runaway problem of conventional thermal polymerization while achieving thick sample polymerization.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Object-affected harmful factors

If visible light photopolymerization is used, then safety is improved compared to UV, but polymerization efficiency deteriorates due to less energetic photons

Engineering Contradiction:

ImprovesafetyVSAvoidpolymerization efficiency

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The patent optimizes the photoinitiator system parameters to match the visible light wavelength range (400-700 nm), specifically using photoinitiators with absorption maxima around 450 nm (blue light). This parameter optimization ensures that the less energetic visible light photons are still effectively absorbed and converted to initiate polymerization, maintaining efficiency while improving safety.

Inventive Principle:

Principle #35Parameter changes

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

This method enables efficient thermal free radical polymerization with improved temperature control and safety, allowing for deeper penetration of light and polymerization of thicker samples, overcoming the limitations of traditional thermal and photo-initiated methods.

Implementation Method 1

a heat-generating dye that generates heat, when exposed to a 625-2500 nm light source

Methodology Applied

Scientific EffectPhotothermal conversion: Photoacoustic Effect

Implementation Method 2

at least one thermal initiator which undergoes homolytic cleavage to generate two free radicals upon exposure to the heat generated in the composition

Methodology Applied

Scientific EffectThermal decomposition: Thermolysis

Implementation Method 3

The invention also relates to the use of a heat-generating dye in association with a thermal initiator for controlling the onset of thermal free radical polymerization

Methodology Applied

Scientific EffectFree radical polymerization: Photopolymerisation

Data Source

PatentUS11384167B2Thermal amplification of free radical polymerization induced by red to near-infrared irradiation

Publication Date: 2022.07.12 UNIVERSITE DE HAUTE ALSACE

AI summary

The present invention relates to compositions thermally curable on demand by red to near infrared irradiation, method of using same for thermal amplification of free radical polymerizations, and articles obtained by such method. The invention also relates to the use of a heat-generating dye in association with a thermal initiator for controlling the onset of thermal free radical polymerization.