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Title: Synthesis of functional water-soluble polymers
Author: Li, Muxiu
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2013
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The objective of this work was to synthesise water-soluble polymers bearing desirable functionality, particularly to improve water-solubility of phthalocyanines by incorporation of hydrophilic polymers for personal oral care applications. Prior to preparation of water-soluble polymers containing phthalocyanine, the second chapter described the synthesis of ferrocenyl initiator for polymerisation of tert-butyl acrylate by SET-LRP, followed by acidolysis of tert-butyl group yielding poly(acrylic acid) containing ferrocenyl end group. The resulting polymer could be used as the scale inhibitor for a potential oil drilling application, and further detected by cyclic voltammetry due to the presence of the ferrocene end group. The majority of the thesis is focussed on an investigation of novel approaches for covalently attachment of water-soluble polymers to (copper or zinc) phthalocyanines. The initial PEGylated CuPc complexes were obtained via DCC/EDC coupling reactions, and the resulting blue powder showed excellent solubility in water; however, it revealed a broad molecular weight distribution due to the presence of mono-, di-, and tri- substitutions of PEG chains as confirmed by GPC analysis. PEGylation of phthalocyanines were further improved via a combination of Mitsunobu reaction and CuAAC “click” reaction. In this approach, the substituted macrocycles were prepared from 4,5-bis-(4-hydroxyphenoxy)phthalonitrile as a precursor. The final PEGylated CuPcs or metal-free Pcs with different PEG chain lengths were prepared by two different routes. The incorporation of the (Cu)Pc core with the polymer chain was confirmed and distinguished by THF-GPC equipped with a PDA detector, and also showed an increase in hydrodynamic volume with increasing the PEG chain length with a narrow dispersity remained. PDMAEMA, as a dual responsive polymer was also introduced to ZnPc using a core-first approach by a combination of ATRP and CuAAC reaction with sharing the same CuBr/PMDETA catalyst, yielding the star-shaped water-soluble polymer. The polymer solution represented tuneable LCSTs in range between 83 and 33 oC with increasing the pH of the buffer solution from 7 to 10. The polymer was further transformed into highly polyelectrolyte stars with ZnPc core by quaternization of the pendant amino groups with either methyl iodide or 1,3-propanesultone. The resulting zwitterionic star after quaternized with propanesultone, ZnPc-PMEDSAH, exhibited a UCST value 17 oC, compared with the quaternized salt, ZnPc-PMETAI with no obvious phase transition observed. In addition, their optical properties and aggregation behaviour in water were investigated by UV-Vis spectroscopy. The final study involved the synthesis of water-soluble zinc phthalocyanines conjugated to poly(galactose) by an arm-first approach. The well-defined protected galactose oligomer arm was synthesised by SET-LRP with a desirable ω-chain end as confirmed by MALDI-ToF MS analysis which were ready for postfunctionalisation. Following a click reaction and deprotection of the acetal groups, the isolated green powder achieved good water-solubility and emitted a sharp fluorescent band at approximate 695 nm via excitation at 610 nm in DMF. The GPC analysis also showed that a narrow molecular weight distribution remained after deprotection and confirmed the presence of ZnPc core by the PDA detector.
Supervisor: Not available Sponsor: Unilever (Firm)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry