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postgraduate thesis: Synthesis of photosensitizing diblock copolymers for functionalizationof carbon nanotubes and their applications

TitleSynthesis of photosensitizing diblock copolymers for functionalizationof carbon nanotubes and their applications
Authors
Issue Date2012
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Citation
Li, C. [李志豪]. (2012). Synthesis of photosensitizing diblock copolymers for functionalization of carbon nanotubes and their applications. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4786937
AbstractBlock copolymers containing pendant pyrene, terpyridine and poly(3- hexylthiophene) moieties with different block ratios and chain lengths were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The block copolymers obtained had narrow molecular weight distribution. The applications of these polymers for non-covalent functionalization of carbon nanotubes and in photovoltaic devices were studied. The molecular weight distribution and block sizes of the block copolymers could be controlled quite well. The polydispersities measured were below 1.25. The block copolymers could be functionalized on the surface of CNTs. The functionalized CNTs had an improved dispersing ability and a maximum dispersing ability of 0.30 mgmL-1 in DMF was achieved. The photosensitizing properties of an individual functionalized CNT were studied by conductive atomic force microscopy. In the presence of the photosensitizing unit, the photocurrent was measured to be 6.4 nAμW-1 at 580 nm. This suggests the role of metal complexes in the photosensitizing process in the block copolymer. Poly(3-hexylthiophene)-block-pendant pyrene copolymers were synthesized by Grignard metathesis and RAFT polymerization. Different loadings of the block copolymers functionalized CNT were employed as the electron accepting materials in bulk heterojunction photovoltaic devices. A maximum power conversion efficiency of 0.77 × 10-3 % was achieved for the poly(3- hexylthiophene): 0.5% polymer functionalized CNT devices. The poor efficiency was attributed to the low CNT loadings that limited the electron transport in the devices. The poly(3-hexylthiophene)-block-pendant pyrene copolymer were employed as compatibilizer for poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction photovoltaic devices. With the addition of 20 % of the block copolymer, a maximum power conversion efficiency of 1.62 % could be achieved. The long term stability of the encapsulated photovoltaic devices was studied. There was more than 30 % reduction in the degradation of performance after 30 days when the block copolymer was added as compatibilizer. These results suggested the role of the block copolymer compatibilizers in improving both the photovoltaic performances and stability of the devices. Differential scanning calorimetry results suggested that the improved photovoltaic performances may be attributed to the enhanced compatibility between poly(3- hexylthiophene) and PCBM.
DegreeDoctor of Philosophy
SubjectCopolymers - Synthesis.
Nanotubes - Carbon content.
Dept/ProgramChemistry
Persistent Identifierhttp://hdl.handle.net/10722/183040

 

DC FieldValueLanguage
dc.contributor.authorLi, Chi-ho-
dc.contributor.author李志豪-
dc.date.accessioned2013-05-05T03:00:13Z-
dc.date.available2013-05-05T03:00:13Z-
dc.date.issued2012-
dc.identifier.citationLi, C. [李志豪]. (2012). Synthesis of photosensitizing diblock copolymers for functionalization of carbon nanotubes and their applications. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4786937-
dc.identifier.urihttp://hdl.handle.net/10722/183040-
dc.description.abstractBlock copolymers containing pendant pyrene, terpyridine and poly(3- hexylthiophene) moieties with different block ratios and chain lengths were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The block copolymers obtained had narrow molecular weight distribution. The applications of these polymers for non-covalent functionalization of carbon nanotubes and in photovoltaic devices were studied. The molecular weight distribution and block sizes of the block copolymers could be controlled quite well. The polydispersities measured were below 1.25. The block copolymers could be functionalized on the surface of CNTs. The functionalized CNTs had an improved dispersing ability and a maximum dispersing ability of 0.30 mgmL-1 in DMF was achieved. The photosensitizing properties of an individual functionalized CNT were studied by conductive atomic force microscopy. In the presence of the photosensitizing unit, the photocurrent was measured to be 6.4 nAμW-1 at 580 nm. This suggests the role of metal complexes in the photosensitizing process in the block copolymer. Poly(3-hexylthiophene)-block-pendant pyrene copolymers were synthesized by Grignard metathesis and RAFT polymerization. Different loadings of the block copolymers functionalized CNT were employed as the electron accepting materials in bulk heterojunction photovoltaic devices. A maximum power conversion efficiency of 0.77 × 10-3 % was achieved for the poly(3- hexylthiophene): 0.5% polymer functionalized CNT devices. The poor efficiency was attributed to the low CNT loadings that limited the electron transport in the devices. The poly(3-hexylthiophene)-block-pendant pyrene copolymer were employed as compatibilizer for poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction photovoltaic devices. With the addition of 20 % of the block copolymer, a maximum power conversion efficiency of 1.62 % could be achieved. The long term stability of the encapsulated photovoltaic devices was studied. There was more than 30 % reduction in the degradation of performance after 30 days when the block copolymer was added as compatibilizer. These results suggested the role of the block copolymer compatibilizers in improving both the photovoltaic performances and stability of the devices. Differential scanning calorimetry results suggested that the improved photovoltaic performances may be attributed to the enhanced compatibility between poly(3- hexylthiophene) and PCBM.-
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.source.urihttp://hub.hku.hk/bib/B47869379-
dc.subject.lcshCopolymers - Synthesis.-
dc.subject.lcshNanotubes - Carbon content.-
dc.titleSynthesis of photosensitizing diblock copolymers for functionalizationof carbon nanotubes and their applications-
dc.typePG_Thesis-
dc.identifier.hkulb4786937-
dc.description.thesisnameDoctor of Philosophy-
dc.description.thesislevelDoctoral-
dc.description.thesisdisciplineChemistry-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.5353/th_b4786937-
dc.date.hkucongregation2012-

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