Core-Shell Microparticle Production via Alkoxyamine Graft Polymerization
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Solution Overview
Problem
Existing methods for producing core-shell microparticles struggle to achieve submicron sizes without swelling the core microparticle, leading to inadequate functional distinction between the core and shell layers, and often require complex steps like re-dispersion and removal of unreacted reagents, resulting in insufficient performance as functional composite microparticles.
Innovation Solution
A method involving the preparation of a monodisperse crosslinked microparticle with an alkoxyamine group, followed by graft polymerization using a monomer mixture containing a crosslinkable monomer and an alkoxyamine group-containing monomer, which allows for the formation of a core-shell microparticle with a high crosslink density and controlled particle size, preventing core swelling and enabling clear functional distinction between the core and shell layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If graft polymerization is performed on a core microparticle with low crosslink density, then shell layer formation is enabled, but the core microparticle swells and polymerization proceeds in the interior portion, causing particle size increase beyond desired size
Solution Approach 1:
The core microparticle is pre-crosslinked before graft polymerization to establish a stable crosslinked structure in advance. This preliminary crosslinking prevents swelling during subsequent shell layer formation, allowing precise control of particle size and preventing polymerization in the interior portion.
2Reliability
If nitroxide compound is reacted with microparticle surface to introduce alkoxyamine group, then living radical polymerization initiating group is introduced, but additional steps of re-dispersing microparticle and removing unreacted reagent are required
Solution Approach 1:
The alkoxyamine group introduction step is merged with the crosslinking step. The crosslinkable monomer serves dual functions: it forms crosslinks in the core microparticle and simultaneously provides alkoxyamine groups on the surface for subsequent graft polymerization. This eliminates the need for separate alkoxyamine introduction and re-dispersion steps.
Solution Approach 2:
The crosslinkable monomer performs multiple functions: it acts as a crosslinking agent to form the core structure, serves as a source of alkoxyamine groups for graft polymerization initiation, and eliminates the need for separate surface modification steps. This multi-functionality simplifies the overall process.
3Manufacturing precision
If core microparticle is produced with low crosslink density, then shell layer can be formed, but the shell layer invades into the interior portion of core microparticle, preventing clear functional distinction
Solution Approach 1:
The core microparticle is crosslinked before shell layer formation to create a stable, non-swelling core structure. This preliminary crosslinking establishes clear boundaries that prevent shell layer invasion into the core, ensuring well-defined core-shell structure with distinct functional regions.
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 enables the production of core-shell microparticles in submicron sizes with high crosslink density, maintaining the core size and ensuring the shell layer forms around the core without invasion, thus enhancing the functional performance and industrial feasibility by simplifying the process.
Implementation Method 1
producing an alkoxyamine group-containing monodisperse crosslinked microparticle by an alkoxyamine group serving as a living radical polymerization initiating group and forming a graft chain on the microparticle
Implementation Method 2
a monomer mixture containing a crosslinkable monomer (15 to 99% by mass) having a plurality of vinyl groups and an alkoxyamine group-containing monomer (1 to 85% by mass) is prepared
Data Source
AI summary
Disclosed is a core-shell microparticle (10) which is produced by heating a mixture of a crosslinked microparticle (11) having an alkoxyamine group (12) and a monomer to 100 to 180° C. to cause graft polymerization. The crosslinked microparticle (11) is produced by allowing a seed particle to absorb a monomer mixture comprising 15 to 99% by mass of a crosslinkable monomer and 1 to 85% by weight of a monomer having an alkoxyamine group, and then adding a polymerization initiator to the resulting product to cause the polymerization of the monomer mixture.