Synthesis of pH-responsive and thiol-degradable hollow microspheres

Gu, W; Ting, SRS; Stenzel, MH

Synthesis of pH-responsive and thiol-degradable hollow microspheres

Gu, W Ting, SRS

Stenzel, MH

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Publication Type:: Journal Article
Citation:: Polymer, 2013, 54 (3), pp. 1010 - 1017
Issue Date:: 2013-02-05

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Field	Value	Language
dc.contributor.author	Gu, W	en_US
dc.contributor.author	Ting, SRS https://orcid.org/0000-0002-7787-7906	en_US
dc.contributor.author	Stenzel, MH	en_US
dc.date.issued	2013-02-05	en_US
dc.identifier.citation	Polymer, 2013, 54 (3), pp. 1010 - 1017	en_US
dc.identifier.issn	0032-3861	en_US
dc.identifier.uri	http://hdl.handle.net/10453/29277
dc.description.abstract	Hollow microspheres were synthesized using an oil in water suspension system. The oil droplets were comprised of ethylene glycol dimethacrylate (EGDMA) and n-butyl acetate. Upon radical polymerization and gel formation, the polymer phase-separated from the solution and precipitated on the interface between water and organic solvent. The solvent n-butyl acetate was found to be crucial in the process as other solvent did not lead to hollow particles. The ratio between EGDMA and n-butyl acetate determined the structure of the microspheres with low EGDMA amounts leading to solid particles while increasing amounts of EGDMA results in bigger particles with larger shells. The crosslinking density of the microspheres could be adjusted by copolymerization of EGDMA with methyl methacrylate (MMA) or tert-butyl methacrylate (tBuMA). The latter allowed easy hydrolysis under acidic conditions to create pH-responsive hollow microspheres with methacrylic acid repeating units (MAA). Depending on the crosslinking density, the microsphere increased in size from around 75 μm in acidic conditions to more than 150 μm at high pH value creating hollow spheres that expand and collapse depending on the pH value. Replacing the stable EGDMA crosslinker with the cleavable crosslinker bis(2-methacryloyloxyethyl) disulfide (DSDMA) leads to the formation of hollow spheres held together by disulfide bridges. Degradation of hydrophobic (with MMA as comonomer) and hydrophilic (with MAA as comonomers) microspheres were tested in a reductive environment, which was simulated by the addition of thiols. While the hydrophilic hollow microspheres had a weight loss of more than 50-70% after 3 days, only 20 wt% of the hydrophobic microspheres were lost after one week. © 2013 Elsevier Ltd. All rights reserved.	en_US
dc.relation.ispartof	Polymer	en_US
dc.relation.isbasedon	10.1016/j.polymer.2012.12.052	en_US
dc.subject.classification	Polymers	en_US
dc.title	Synthesis of pH-responsive and thiol-degradable hollow microspheres	en_US
dc.type	Journal Article
utslib.citation.volume	3	en_US
utslib.citation.volume	54	en_US
utslib.for	0912 Materials Engineering	en_US
utslib.for	0303 Macromolecular and Materials Chemistry	en_US
utslib.for	03 Chemical Sciences	en_US
utslib.for	09 Engineering	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology
pubs.organisational-group	/University of Technology Sydney/Strength - CHT - Health Technologies
utslib.copyright.status	closed_access
pubs.issue	3	en_US
pubs.publication-status	Published	en_US
pubs.volume	54	en_US

Abstract:

Hollow microspheres were synthesized using an oil in water suspension system. The oil droplets were comprised of ethylene glycol dimethacrylate (EGDMA) and n-butyl acetate. Upon radical polymerization and gel formation, the polymer phase-separated from the solution and precipitated on the interface between water and organic solvent. The solvent n-butyl acetate was found to be crucial in the process as other solvent did not lead to hollow particles. The ratio between EGDMA and n-butyl acetate determined the structure of the microspheres with low EGDMA amounts leading to solid particles while increasing amounts of EGDMA results in bigger particles with larger shells. The crosslinking density of the microspheres could be adjusted by copolymerization of EGDMA with methyl methacrylate (MMA) or tert-butyl methacrylate (tBuMA). The latter allowed easy hydrolysis under acidic conditions to create pH-responsive hollow microspheres with methacrylic acid repeating units (MAA). Depending on the crosslinking density, the microsphere increased in size from around 75 μm in acidic conditions to more than 150 μm at high pH value creating hollow spheres that expand and collapse depending on the pH value. Replacing the stable EGDMA crosslinker with the cleavable crosslinker bis(2-methacryloyloxyethyl) disulfide (DSDMA) leads to the formation of hollow spheres held together by disulfide bridges. Degradation of hydrophobic (with MMA as comonomer) and hydrophilic (with MAA as comonomers) microspheres were tested in a reductive environment, which was simulated by the addition of thiols. While the hydrophilic hollow microspheres had a weight loss of more than 50-70% after 3 days, only 20 wt% of the hydrophobic microspheres were lost after one week. © 2013 Elsevier Ltd. All rights reserved.

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http://hdl.handle.net/10453/29277