Facile Access to Polymeric Vesicular Nanostructures: Remarkable ω-End group Effects in Cholesterol and Pyrene Functional (Co)Polymers
Hydrophilic homopolymers of N,N-dimethylacrylamide (DMA) and N-(2-hydroxypropyl) methacrylamide (HPMA), as well as select examples of statistical copolymers with N-acryloxysuccinimide (NAS) were prepared with well-defined molecular characteristics employing a series of new RAFT chain transfer agents...
| Main Authors: | , , , , |
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| Format: | Journal Article |
| Published: |
2011
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| Online Access: | http://hdl.handle.net/20.500.11937/42743 |
| _version_ | 1848756503109959680 |
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| author | Xu, J. Tao, L. Boyer, C. Lowe, Andrew Davis, T. |
| author_facet | Xu, J. Tao, L. Boyer, C. Lowe, Andrew Davis, T. |
| author_sort | Xu, J. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | Hydrophilic homopolymers of N,N-dimethylacrylamide (DMA) and N-(2-hydroxypropyl) methacrylamide (HPMA), as well as select examples of statistical copolymers with N-acryloxysuccinimide (NAS) were prepared with well-defined molecular characteristics employing a series of new RAFT chain transfer agents containing 1−4 hydrophobic functional groups in the R fragment based on pyrene, cholesterol, or octadecane, resulting in hydrophilic homopolymers containing between only 6−23 wt % hydrophobic end groups. PolyDMA (PDMA) and polyHPMA (PHPMA) homopolymers, of varying molar masses, with either bis pyrenyl or cholesteryl end groups self-assembled in aqueous media forming spherical vesicles with sizes in the range of several hundred nm up to ca. one micrometer. Lower molar mass PDMA−NAS copolymers with two cholesteryl end-groups at the ω-termini assemble to give clear tubular vesicles, whereas such copolymers of a higher molar mass preferentially form spherical polymersomes. The presence of two spatially close rigid rings at the ω-terminus is shown to be crucial in vesicle formation since a PDMA homopolymer with two octadecyl ω-end-groups self-assembles to yield polymeric micelles with an average hydrodynamic diameter of ~20 nm as determined by dynamic light scattering.The presence of a C16 alkyl spacer in the R fragment in a novel dithioester CTA with two pyrenyl functional groups and its use in the polymerization of a PDMA homopolymer yields spherical polymersomes in water, in a similar manner to those formed using a CTA without a spacer, except there is no direct FE-SEM evidence of open-mouth species perhaps indicating that the added flexibility associated with the spacer groups helps facilitate full vesicle closure. The synthesis of a biodegradable bis-pyrenyl dithioester, containing disulfide bridges, facilitates the preparation of PDMA-based polymersomes capable of dithiothreitol-induced pyrene release as evidenced by fluorescence emission spectroscopy. The same biodegradable polymersomes are also shown to be able to sequester the hydrophilic model drug Rhodamine B whose controlled release is demonstrated to be dependent on the presence, or absence, of dithiothreitol as determined by UV−vis spectroscopy. |
| first_indexed | 2025-11-14T09:13:14Z |
| format | Journal Article |
| id | curtin-20.500.11937-42743 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:13:14Z |
| publishDate | 2011 |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-427432017-09-13T15:04:46Z Facile Access to Polymeric Vesicular Nanostructures: Remarkable ω-End group Effects in Cholesterol and Pyrene Functional (Co)Polymers Xu, J. Tao, L. Boyer, C. Lowe, Andrew Davis, T. Hydrophilic homopolymers of N,N-dimethylacrylamide (DMA) and N-(2-hydroxypropyl) methacrylamide (HPMA), as well as select examples of statistical copolymers with N-acryloxysuccinimide (NAS) were prepared with well-defined molecular characteristics employing a series of new RAFT chain transfer agents containing 1−4 hydrophobic functional groups in the R fragment based on pyrene, cholesterol, or octadecane, resulting in hydrophilic homopolymers containing between only 6−23 wt % hydrophobic end groups. PolyDMA (PDMA) and polyHPMA (PHPMA) homopolymers, of varying molar masses, with either bis pyrenyl or cholesteryl end groups self-assembled in aqueous media forming spherical vesicles with sizes in the range of several hundred nm up to ca. one micrometer. Lower molar mass PDMA−NAS copolymers with two cholesteryl end-groups at the ω-termini assemble to give clear tubular vesicles, whereas such copolymers of a higher molar mass preferentially form spherical polymersomes. The presence of two spatially close rigid rings at the ω-terminus is shown to be crucial in vesicle formation since a PDMA homopolymer with two octadecyl ω-end-groups self-assembles to yield polymeric micelles with an average hydrodynamic diameter of ~20 nm as determined by dynamic light scattering.The presence of a C16 alkyl spacer in the R fragment in a novel dithioester CTA with two pyrenyl functional groups and its use in the polymerization of a PDMA homopolymer yields spherical polymersomes in water, in a similar manner to those formed using a CTA without a spacer, except there is no direct FE-SEM evidence of open-mouth species perhaps indicating that the added flexibility associated with the spacer groups helps facilitate full vesicle closure. The synthesis of a biodegradable bis-pyrenyl dithioester, containing disulfide bridges, facilitates the preparation of PDMA-based polymersomes capable of dithiothreitol-induced pyrene release as evidenced by fluorescence emission spectroscopy. The same biodegradable polymersomes are also shown to be able to sequester the hydrophilic model drug Rhodamine B whose controlled release is demonstrated to be dependent on the presence, or absence, of dithiothreitol as determined by UV−vis spectroscopy. 2011 Journal Article http://hdl.handle.net/20.500.11937/42743 10.1021/ma102386j restricted |
| spellingShingle | Xu, J. Tao, L. Boyer, C. Lowe, Andrew Davis, T. Facile Access to Polymeric Vesicular Nanostructures: Remarkable ω-End group Effects in Cholesterol and Pyrene Functional (Co)Polymers |
| title | Facile Access to Polymeric Vesicular Nanostructures: Remarkable ω-End group Effects in Cholesterol and Pyrene Functional (Co)Polymers |
| title_full | Facile Access to Polymeric Vesicular Nanostructures: Remarkable ω-End group Effects in Cholesterol and Pyrene Functional (Co)Polymers |
| title_fullStr | Facile Access to Polymeric Vesicular Nanostructures: Remarkable ω-End group Effects in Cholesterol and Pyrene Functional (Co)Polymers |
| title_full_unstemmed | Facile Access to Polymeric Vesicular Nanostructures: Remarkable ω-End group Effects in Cholesterol and Pyrene Functional (Co)Polymers |
| title_short | Facile Access to Polymeric Vesicular Nanostructures: Remarkable ω-End group Effects in Cholesterol and Pyrene Functional (Co)Polymers |
| title_sort | facile access to polymeric vesicular nanostructures: remarkable ω-end group effects in cholesterol and pyrene functional (co)polymers |
| url | http://hdl.handle.net/20.500.11937/42743 |