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    Macromolecular Engineering: New Routes Towards the Synthesis of Well-??Defined Polyethers/Polyesters Co/Terpolymers with Different Architectures

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    Name:
    Haleema Alamri - Dissertation - Final Draft.pdf
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    21.11Mb
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    Type
    Dissertation
    Authors
    Alamri, Haleema cc
    Advisors
    Hadjichristidis, Nikos cc
    Committee members
    Nunes, Suzana Pereira cc
    Takanabe, Kazuhiro cc
    Apostolos, Avgeropoulos
    Program
    Chemical Science
    KAUST Department
    Physical Science and Engineering (PSE) Division
    Date
    2016-05-18
    Embargo End Date
    2017-08-14
    Permanent link to this record
    http://hdl.handle.net/10754/618398
    
    Metadata
    Show full item record
    Access Restrictions
    At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2017-08-14.
    Abstract
    The primary objective of this research was to develop a new and efficient pathway for well-defined multicomponent homo/co/terpolymers of cyclic esters/ethers using an organocatalytic approach with an emphasis on the macromolecular engineering aspects of the overall synthesis. Macromolecular engineering (as discussed in the first chapter) of homo/copolymers refers to the specific tailoring of these materials for achieving an easy and reproducible synthesis that results in precise molecular characteristics, i.e. molecular weight and polydispersity, as well as specific structure and end?group choices. Precise control of these molecular characteristics will provide access to new materials that can be used for pre-targeted purposes such as biomedical applications. Among the most commonly used engineering materials are polyesters (biocompatible and biodegradable) and polyethers (biocompatible), either as homopolymers or when or copolymers with linear structures. The ability to create non-linear structures, for example stars, will open new horizons in the applications of these important polymeric materials. The second part of this thesis describes the synthesis of aliphatic polyesters, particularly polycaprolactone and polylactide, using a metal-free initiator/catalyst system. A phosphazene base (t?BuP2) was used as the catalyst for the ring-opening copolymerization of ?-aprolactone (??CL) and L,Lactide (LLA) at room temperature with a variety of protic initiators in different solvents. These studies provided important information for the design of a metal-free route toward the synthesis of polyester?based (bio) materials. The third part of the thesis describes a novel route for the one?pot synthesis of polyether-b polyester block copolymers with either a linear or a specific macromolecular architecture. Poly (styrene oxide)?b?poly(caprolactone)?b?poly(L,lactide) was prepared using this method with the goal of synthesizing poly(styrene oxide)-based materials since this styrene oxide (SO) monomer has been less investigated than other well-known epoxide monomers. The new one?pot synthesis of polyether?b?polyester block copolymers allowed a high degree of control with respect to the molecular weight and molecular weight distribution. It also eliminates the need for a multi-step process in which the first block must be isolated and purified prior to its subsequent use as a macroinitiator for the second block. It is also worth noting that this approach is based primarily on the use of organocatalyst because this class of block copolymers has greater potential in biomedical and pharmaceutical applications and because organocatalysts are believed to be less toxic than their metallic counterparts. The fourth part of the thesis describes the extension of the scope of the newly developed catalyst?switching approach in the synthesis of different macromolecular architectures, with a special focus on styrene oxide as a monomer, which had not previously been explored either as a linear copolymer with other monomers (except with EO) or with a macromolecular architecture such as block star or mikto arm star. The results detailed in Chapter 4 demonstrate the validity of extending the newly developed strategy to the synthesis of a variety of polymers with different macromolecular architectures. Since organic catalysts (phoshazene bases) have been utilized in this work for the synthesis of polyethers and polyesters with the aim of alleviating the toxic properties associated with metal-based catalysts, it was necessary to investigate the toxicity of this class of organocatalyst since, until now, no evidence has appeared of any attempt to address this issue. The objective of the work presented in the fifth part of this thesis was therefore to assess whether this class of organocatalysts are safe with respect to human health and whether their structure and concentration are dependent on an evaluation of the level of cytotoxicity or on other parameters. Both the pure catalyst and the polymers synthesized using this class of catalysts were tested using a CKK?8 assay, which is a very well?known protocol for measuring cytotoxicity.
    Citation
    Alamri, H. (2016). Macromolecular Engineering: New Routes Towards the Synthesis of Well-??Defined Polyethers/Polyesters Co/Terpolymers with Different Architectures. KAUST Research Repository. https://doi.org/10.25781/KAUST-271CH
    DOI
    10.25781/KAUST-271CH
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-271CH
    Scopus Count
    Collections
    PhD Dissertations; Physical Science and Engineering (PSE) Division; Chemical Science Program

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