Non-aqueous microgel particles: synthesis, properties and applications

Abstract

Microgels are cross-linked polymer latex particles that can form stable colloidal dispersions. Their typical sizes range from 10 to 1000 nm and they can swell in response to their external environment (pH, temperature and solvency). This swelling behaviour is central to many potential applications for microgels. The existing literature is dominated by studies of the properties of aqueous microgel dispersions. In contrast, this review focusses on the development of microgel particles in non-aqueous systems, looking at the challenges of studying these particles as well as their swelling behaviour. The five main mechanisms of producing microgel particles will be discussed and examples of materials used for microgels that swell in non-aqueous solvents will be given. Finally some examples of applications for non-aqueous microgels are given.

Electrochemically Initiated Synthesis of Polyacrylamide Microgels and Core-shell Particles

“…Presumably, the MA monomer incorporation in the microgel aided in generating globular microgel particles. The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface (Figure d,d′), in accordance with earlier reports. ,, …”

“…The water-soluble NIPAM monomer polymerization mechanism has widely been studied. ,, Similarly, as in the previously described syntheses, in our electrochemically initiated polymerization, the solution for polymerization was initially homogeneous (Scheme ). As the potentiostatic synthesis proceeded, more and more APS was cleaved, and the amount of water-soluble free radicals became sufficient for initiating the polymerization (Scheme ).…”

“…The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface ( Figure 2 d,d′), in accordance with earlier reports. 1 , 53 , 54 …”

“…The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface (Figure 2d,d′), in accordance with earlier reports. 1,53,54 Interestingly, the microgel morphology was different if the solution pH for polymerization was higher than the acid's pK a (Figure S2 in the Supporting Information). At a high pH, where the acid monomer was negatively charged, the microgel particles were partially interconnected, yielding a soft gel-like soluble material.…”

Electrochemically Initiated Synthesis of Polyacrylamide Microgels and Core-shell Particles

“…Presumably, the MA monomer incorporation in the microgel aided in generating globular microgel particles. The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface (Figure d,d′), in accordance with earlier reports. ,, …”

“…The water-soluble NIPAM monomer polymerization mechanism has widely been studied. ,, Similarly, as in the previously described syntheses, in our electrochemically initiated polymerization, the solution for polymerization was initially homogeneous (Scheme ). As the potentiostatic synthesis proceeded, more and more APS was cleaved, and the amount of water-soluble free radicals became sufficient for initiating the polymerization (Scheme ).…”

“…The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface ( Figure 2 d,d′), in accordance with earlier reports. 1 , 53 , 54 …”

“…The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface (Figure 2d,d′), in accordance with earlier reports. 1,53,54 Interestingly, the microgel morphology was different if the solution pH for polymerization was higher than the acid's pK a (Figure S2 in the Supporting Information). At a high pH, where the acid monomer was negatively charged, the microgel particles were partially interconnected, yielding a soft gel-like soluble material.…”

Ultrahigh Throughput On‐Chip Synthesis of Microgels with Tunable Mechanical Properties

“…Swelling behavior is a key parameter that is directly linked to the degree of crosslinking of the microgel particles. [ 29 ] The swelling ratio of microgels as defined as the ratio of the volume of swollen and dry microgels [ 30 ] decreases with increase in the UV dose as shown in Figure C. This trend suggests that microgels with less UV exposure have lower crosslinking density thus are able to swell to a greater extent.…”

Electrochemically Initiated Synthesis of Polyacrylamide Microgels and Core-shell Particles

“…Presumably, the MA monomer incorporation in the microgel aided in generating globular microgel particles. The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface (Figure d,d′), in accordance with earlier reports. ,, …”

“…The water-soluble NIPAM monomer polymerization mechanism has widely been studied. ,, Similarly, as in the previously described syntheses, in our electrochemically initiated polymerization, the solution for polymerization was initially homogeneous (Scheme ). As the potentiostatic synthesis proceeded, more and more APS was cleaved, and the amount of water-soluble free radicals became sufficient for initiating the polymerization (Scheme ).…”

“…The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface ( Figure 2 d,d′), in accordance with earlier reports. 1 , 53 , 54 …”

“…The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface (Figure 2d,d′), in accordance with earlier reports. 1,53,54 Interestingly, the microgel morphology was different if the solution pH for polymerization was higher than the acid's pK a (Figure S2 in the Supporting Information). At a high pH, where the acid monomer was negatively charged, the microgel particles were partially interconnected, yielding a soft gel-like soluble material.…”

Ultrahigh Throughput On‐Chip Synthesis of Microgels with Tunable Mechanical Properties

“…Swelling behavior is a key parameter that is directly linked to the degree of crosslinking of the microgel particles. [ 29 ] The swelling ratio of microgels as defined as the ratio of the volume of swollen and dry microgels [ 30 ] decreases with increase in the UV dose as shown in Figure C. This trend suggests that microgels with less UV exposure have lower crosslinking density thus are able to swell to a greater extent.…”

Electrochemically Initiated Synthesis of Polyacrylamide Microgels and Core-shell Particles

“…Presumably, the MA monomer incorporation in the microgel aided in generating globular microgel particles. The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface (Figure d,d′), in accordance with earlier reports. ,, …”

“…The water-soluble NIPAM monomer polymerization mechanism has widely been studied. ,, Similarly, as in the previously described syntheses, in our electrochemically initiated polymerization, the solution for polymerization was initially homogeneous (Scheme ). As the potentiostatic synthesis proceeded, more and more APS was cleaved, and the amount of water-soluble free radicals became sufficient for initiating the polymerization (Scheme ).…”

“…The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface ( Figure 2 d,d′), in accordance with earlier reports. 1 , 53 , 54 …”

“…The STEM image of the NIPAM-MA-BIS microgel demonstrates the porosity of the particles with a fuzzy surface (Figure 2d,d′), in accordance with earlier reports. 1,53,54 Interestingly, the microgel morphology was different if the solution pH for polymerization was higher than the acid's pK a (Figure S2 in the Supporting Information). At a high pH, where the acid monomer was negatively charged, the microgel particles were partially interconnected, yielding a soft gel-like soluble material.…”

Ultrahigh Throughput On‐Chip Synthesis of Microgels with Tunable Mechanical Properties

“…Swelling behavior is a key parameter that is directly linked to the degree of crosslinking of the microgel particles. [ 29 ] The swelling ratio of microgels as defined as the ratio of the volume of swollen and dry microgels [ 30 ] decreases with increase in the UV dose as shown in Figure C. This trend suggests that microgels with less UV exposure have lower crosslinking density thus are able to swell to a greater extent.…”