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  • 1.
    Ndizeye, Natacha
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    New Strategies for Preparing Polymers with Hierarchical Architectures2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The objective of this thesis was to explore novel approaches for controlling morphologies and molecular recognition behaviour of polymers and to use these strategies in conjunction with the molecular imprinting technique in order to either enhance polymer performance in quartz crystal microbalance (QCM) sensor applications, or as an alternative to conventional solvents of polymerization. In Papers I and II, the use of liquid crystalline media in the synthesis of molecularly imprinted polymers was demonstrated. When used in conjunction with the molecular imprinting technique the LC media induced hierarchical material architectures, which provided an enhancement of QCM-sensor sensitivity. The use of a class of novel solvents, so-called “non-ionic deep eutectic solvents (ni-DESs)”, was explored in polymer synthesis, Paper III, and for molecularly imprinted polymer synthesis, Paper IV. The use of these solvents produced polymers with morphological features comparable to those prepared in conventional solvents, and sensitivities towards bupivacaine template were observed. Collectively these results present a new strategy for generating new hierarchical polymer architectures and a new class of solvent for polymer synthesis, which can also be used for molecular imprinting, that can be used as an alternative to conventional and sometimes flammable or toxic polymerization solvents.

  • 2.
    Ndizeye, Natacha
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Suriyanarayanan, Subramanian
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Nicholls, Ian A.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Hierarchical polymeric architectures through molecular imprinting in liquid crystalline environments2018In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 106, p. 223-231Article in journal (Refereed)
    Abstract [en]

    The use of liquid crystalline (LC) media as sacrificial templates during the polymer synthesis has been explored. The LC-media introduce morphological features into resultant polymers which when used together with molecular imprinting can produce materials with hierarchical architectures. Bupivacaine (1) imprinted co-polymers of 2-hydroxyethylmethacrylate (HEMA) (2a) and 1,4-divinylbenzene (DVB) (3a) were synthesized using photochemical initiation in lyotrophic liquid crystalline phases of AOT (5) in water/p-xylene and Triton X-100 (6) /water systems. SEM studies revealed the impact of the LC-media on polymer morphology, with polymer brush-like structures, with bristles of ≈30 nm diameter. The polymer morphology reflects that of the hexagonal phase of the LC medium. The rebinding characteristics of polymer films were evaluated quartz crystal microbalance (QCM, under FIA conditions). The influence of the presence of imprinting-derived recognition sites in AOT (5) in water/p-xylene polymer film induced brush-like features which provided a 25-fold enhancement of sensor sensitivity. This chemosensor was shown to be selective for the local anesthetic template, bupivacaine, through studies using the structural analogues ropivacaine and mepivacaine.

  • 3.
    Ndizeye, Natacha
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Suriyanarayanan, Subramanian
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Nicholls, Ian A.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Polymer synthesis in non-ionic deep eutectic solvents2019In: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 10, no 39, p. 5289-5295Article in journal (Refereed)
    Abstract [en]

    Herein, we report the use of the use of non-ionic deep eutectic solvents (ni-DESs) as porogens in polymer synthesis. Three ni-DES systems, acetamide-N-methylacetamide (AA-NMA), N-methylacetamide-N-methylurea (NMA-NMU) and N-methylacetamide-N,N'-dimethylurea (NMA-NN'DMU), were deployed in the synthesis of a series of cross-linked copolymer monoliths comprised of a functional monomer, methacrylic acid (MAA) or hydroxyethylmethacrylate (HEMA), and a cross-linking monomer, ethylene glycol dimethylacrylate (EGDMA) or divinylbenzene (DVB) or 1,4-bis(acryloyl)piperazine (BAP). Polymers were synthesized under thermally initiated conditions with 2,2'-azobis(2-methylpropionitrile) (AIBN) or 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAH) as an initiator. The resulting polymer monoliths were ground and sieved to yield particles of 63-125 mu m. Corresponding polymers prepared in conventional porogens, acetonitrile, toluene and water were synthesized to serve as controls. The influence of the respective niDESs on polymer morphologies was examined by Brunauer-Emmett-Teller (BET) N2-adsorption, Fourier transform infrared spectroscopy (FT-IR), elemental analysis, scanning electron microscopy (SEM) and zeta potential measurements. The materials displayed surface areas, pore volumes and pore diameters of 115-532 m(2) g(-1), 0.1-1.4 cm(3) g(-1) and 5.2-12.5 nm, generally comparable with those of polymers obtained using conventional solvents, thus presenting these ni-DESs as viable alternatives to conventional organic solvents. The post-polymerization recovery of the ni-DESs (>80%) was demonstrated, highlighting the potential for using these novel liquids as alternatives to conventional, and often more expensive, toxic, flammable or volatile solvents in polymer synthesis.

  • 4.
    Suriyanarayanan, Subramanian
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Nawaz, Hazrat
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Ndizeye, Natacha
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Nicholls, Ian A.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences. Uppsala University.
    Hierarchical Thin Film Architectures for Enhanced Sensor Performance: Liquid Crystal-Mediated Electrochemical Synthesis of Nanostructured Imprinted Polymer Films for the Selective Recognition of Bupivacaine2014In: Biosensors, ISSN 2079-6374, Vol. 4, no 2, p. 90-110Article in journal (Refereed)
    Abstract [en]

    Nanostructured bupivacaine-selective molecularly imprinted 3-aminophenylboronic acid-p-phenylenediamine co-polymer (MIP) films have been prepared on gold-coated quartz (Au/quartz) resonators by electrochemical synthesis under cyclic voltammetric conditions in a liquid crystalline (LC) medium (triton X-100/water). Films prepared in water and in the absence of template were used for control studies. Infrared spectroscopic studies demonstrated comparable chemical compositions for LC and control polymer films. SEM studies revealed that the topologies of the molecularly imprinted polymer films prepared in the LC medium (LC-MIP) exhibit discernible 40 nm thick nano-fiber structures, quite unlike the polymers prepared in the absence of the LC-phase. The sensitivity of the LC-MIP in a quartz crystal microbalance (QCM) sensor platform was 67.6 ± 4.9 Hz/mM under flow injection analysis (FIA) conditions, which was ≈250% higher than for the sensor prepared using the aqueous medium. Detection was possible at 100 nM (30 ng/mL), and discrimination of bupivacaine from closely related structural analogs was readily achieved as reflected in the corresponding stability constants of the MIP-analyte complexes. The facile fabrication and significant enhancement in sensor sensitivity together highlight the potential of this LC-based imprinting strategy for fabrication of polymeric materials with hierarchical architectures, in particular for use in surface-dependent application areas, e.g., biomaterials or sensing.

  • 5.
    Suriyanarayanan, Subramanian
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Olsson, Gustaf D.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Kathiravan, Suppan
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Ndizeye, Natacha
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Nicholls, Ian A.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Non-Ionic Deep Eutectic Liquids: Acetamide-Urea Derived Room Temperature Solvents2019In: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 20, no 12, article id 2857Article in journal (Refereed)
    Abstract [en]

    A family of non-ionic deep eutectic liquids has been developed based upon mixtures of solid N-alkyl derivatives of urea and acetamide that in some cases have melting points below room temperature. The eutectic behaviour and physical characteristics of a series of eleven eutectic mixtures are presented, along with a molecular dynamics study-supported hypothesis for the origin of the non-ideal mixing of these substances. Their use as solvents in applications ranging from natural product extraction to organic and polymer synthesis are demonstrated.

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