Visible-Light Initiated Radical Polymerization Dark Curing

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Solution Overview

Problem

Conventional visible-light initiated radical polymerization systems cease polymerization when the light source is extinguished due to short-lived radical active centers, limiting dark curing capabilities with commonly used monomers.

Innovation Solution

A three-component initiator system comprising a photo-oxidizable photosensitizing agent, an electron donor, and an electron acceptor is dissolved in monomers like 2-hydroxyethyl methacrylate, enabling continued polymerization after light removal by maintaining active radical centers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional visible-light initiated radical polymerization systems are used, then rapid and readily controllable reaction kinetics are achieved, but polymerization ceases when the light source is extinguished due to short-lived radical active centers

Engineering Contradiction:

Improvereaction kineticsVSAvoiddark curing capability

Core Design Contradiction:

SpeedVSDuration of action of stationary object

Solution Approach 1:

The polymerization process is segmented into two distinct phases: a light-initiated phase that provides rapid kinetics and a dark phase that enables extended curing. The three-component initiator system is designed so that the photo-initiated radicals generate long-lived species capable of sustaining polymerization in the dark phase, effectively dividing the overall process into complementary stages that each excel at different functions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the chemical parameters of the initiator system by introducing a three-component composition (photosensitizer, electron donor, and electron acceptor) that fundamentally alters the lifetime characteristics of the active centers. This parameter change transforms the radical active centers from short-lived (conventional) to long-lived (invention), enabling dark curing while maintaining rapid reaction kinetics during illumination.

Inventive Principle:

Principle #35Parameter changes

2Speed

If continuous initiation is required to maintain polymerization, then rapid reaction kinetics are maintained, but processing time increases and initiator concentration must be higher

Engineering Contradiction:

Improvereaction kineticsVSAvoidprocessing time

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The light source performs preliminary action by initiating the formation of long-lived radical active centers during the illumination phase. These pre-formed long-lived radicals then sustain polymerization during the dark phase without requiring continuous light initiation, thereby reducing total processing time and allowing lower initiator concentrations while maintaining rapid kinetics.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention ensures continuity of useful action by designing a system where polymerization seamlessly transitions from light-initiated rapid kinetics to dark-phase extended curing. The long-lived radical active centers bridge the two phases, maintaining continuous polymerization activity without interruption when the light source is extinguished, thus reducing overall processing time.

Inventive Principle:

Principle #20Continuity of useful action

3Strength

If radical-based photopolymerization is used, then rapid reaction kinetics and excellent mechanical properties are achieved, but dark curing is limited due to short active center lifetimes

Engineering Contradiction:

Improvemechanical propertiesVSAvoiddark curing capability

Core Design Contradiction:

StrengthVSDuration of action of stationary object

Solution Approach 1:

The initiator system functions as a composite material combining three distinct components (photosensitizer, electron donor, and electron acceptor) that work synergistically. This composite initiator system produces radical active centers with unusual long-lived characteristics while maintaining the rapid reaction kinetics and excellent mechanical properties associated with conventional radical polymerization, thereby enabling dark curing without sacrificing other critical performance attributes.

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

This approach allows for extensive dark curing of polymerizable compositions, reducing processing times and enhancing curing depths in shadow regions, even with conventional monomers.

Implementation Method 1

a photo-oxidizable photosensitizing agent

Methodology Applied

Scientific EffectPhoto-oxidation: Photo-oxidation

Implementation Method 2

visible-light initiated controlled radical polymerization

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Implementation Method 3

an electron donor, and an electron acceptor

Methodology Applied

Scientific EffectElectron transfer: Redox Reactions

Data Source

PatentUS8883948B2Methods for extensive dark curing based on visible-light initiated, controlled radical polymerization

Publication Date: 2014.11.11 THE REGENTS OF THE UNIVERSITY OF COLORADO

AI summary

Optimized methods to achieve extensive dark curing from a three-component visible light-initiated system though controlled radical polymerization and compositions useful in these optimized methods are provided. These compositions and methods are particularly suited for use in certain dental applications.