Silica Microcapsule Encapsulation via Polyalkoxysiloxane Emulsifier
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Solution Overview
Problem
Current methods for encapsulating substances in silica-based micro- and nanocapsules face challenges in achieving mechanical stability and high payload capacity without the use of additional surfactants or preformed particles, particularly in forming small-sized capsules with controlled internal morphology and high encapsulation efficiency.
Innovation Solution
A method using polyalkoxysiloxane (PAOS) as both a silica precursor and emulsifier, combined with shearing forces and solidification of the organic phase, to form silica-based micro- and nanocapsules with up to 99% payload capacity, without additional surfactants or preformed particles, allowing for the encapsulation of hydrophobic and hydrophilic substances in oil-in-water and water-in-oil-in-water emulsions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sol-gel technology with surfactant-stabilized emulsions is used to encapsulate substances in silica microcapsules, then encapsulation efficiency can be achieved, but the capsules lack mechanical stability and require additional surfactants that are difficult to remove completely
Solution Approach 1:
The patent applies polyalkoxysiloxane (PAOS) as a multi-functional material that simultaneously serves as the silica precursor for capsule shell formation and as the emulsifier for stabilizing the emulsion droplets. This eliminates the need for separate surfactant additives and preformed particle stabilizers, resolving the contradiction between mechanical stability and process complexity
Solution Approach 2:
The invention merges the functions of silica source and emulsifier into a single compound (PAOS). The polyalkoxysiloxane provides both the silicon atoms needed for silica shell formation and the amphiphilic properties needed for emulsion stabilization, thereby simplifying the system while improving mechanical stability
2Quantity of substance
If high payload capacity is achieved by increasing the concentration of encapsulated substance, then encapsulation efficiency improves, but the mechanical stability and structural integrity of the capsules deteriorate
Solution Approach 1:
The patent utilizes changes in physical parameters during the process - specifically temperature-induced solidification of the organic phase and pH-triggered sol-gel conversion of PAOS to silica. These parameter changes allow the formation of a rigid silica shell that can support high payload concentrations without compromising structural integrity
Solution Approach 2:
The invention exploits phase transitions in two key steps: (1) solidification of the organic phase containing the payload substance to lock it in place within the droplet, and (2) sol-gel transition of PAOS to form the rigid silica shell. These phase transitions enable high payload capacity while maintaining capsule strength
3Volume of moving object
If small-sized capsules (0.01-10 μm) are formed to increase surface area and control release, then encapsulation surface-to-volume ratio improves, but manufacturing precision and control of internal morphology become more difficult
Solution Approach 1:
The PAOS molecule serves itself by forming micellar structures in the emulsion that self-organize into uniform droplets of controlled size. The amphiphilic nature of PAOS drives spontaneous self-assembly into spherical micelles with well-defined dimensions, eliminating the need for complex external templating or preformed particles to control morphology
Solution Approach 2:
The patent performs preliminary formation of uniform PAOS micelles before the sol-gel conversion to silica. This preliminary structuring establishes a monodisperse size distribution and controlled internal morphology that is preserved during the subsequent shell formation process, enabling precise control even at small capsule dimensions
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 mechanically stable silica-based microcapsules with sizes ranging from 0.01 to 100 μm, achieving high encapsulation efficiency and payload, and allows for the formation of core-shell structures with controlled particle size and morphology, suitable for various industrial applications.
Implementation Method 1
oil-in-water emulsions are formed. The formation of water-in-oil-in-water double emulsions is required to encapsulate hydrophilic compounds
Implementation Method 2
a silica precursor polymer, polyalkoxysiloxane (PAOS), preferentially polyalkylalkoxoxysiloxane (R-PAOS), which acts not only as a silica source but also an emulsifier
Implementation Method 3
emulsifying a hydrophobic, water insoluble liquid comprising (i) PAOS or amphiphilic PAOS that are partially substituted with hydrophilic groups and (ii) a hydrophobic organic liquid in an aqueous solution, without additional surfactants and without any preformed (nano)particles like silica nanoparticles, under shearing forces
Implementation Method 4
Sol-gel technology which combines the control of composition and microstructure at the molecular level with the ability to shape the material to particles, fibers, and thin films under mild and low-energy conditions
Implementation Method 5
In order to obtain mechanically more stable capsules, the conversion of PAOS or R-PAOS is accompanied with the solidification of the organic phase
Data Source
AI summary
The present invention relates to a method for enclosing either hydrophobic or hydrophilic substances in silica-based micro- and nanocapsules via emulsion techniques. More specifically, it relates to a method for the preparation of 0.01-100 μm, particularly 0.01-10 μm, silica-based microcapsules containing up to 99% (w/w) payload using a silica precursor polymer, polyalkoxysiloxane (PAOS), preferentially polyalkylalkoxysiloxane (R-PAOS), which acts not only as a silica source but also an emulsifier. In order to obtain mechanically stable capsules, the conversion of PAOS or R-PAOS is accompanied with the solidification of the organic phase. For the encapsulation of hydrophobic substances, oil-in-water emulsions are formed. The formation of water-in-oil-in-water double emulsions is required to encapsulate hydrophilic compounds.