Synthesis and Characterization of Novel Amphiphilic Diblock Copolymers Poly (2-Ethyl-2-Oxazoline)-b-Poly (Vinylidene Fluoride)

  • Norah Aljeban

Student thesis: Master's Thesis

Abstract

Poly (2-ethyl-2-oxazoline)-based amphiphilic diblock copolymer has the potential to form promising membrane materials for water purification due to the thermal stability and good solubility in aqueous solution and also for gas separation because of the presence of polar amide group along the polymer backbone. Moreover, their self-assembly into micelles renders them candidate materials as nanocarriers for drug delivery applications. In this study, a novel well-defined linear PEtOx-based amphiphilic diblock copolymer with a hydrophobic fluoropolymer, i.e., PVDF, have been successfully synthesized by implementing a synthesis methodology that involves the following four steps. In the first step, poly (2-ethyl-2-oxazoline) (PEtOx) was synthesized via living cationic ring-opening polymerization (LCROP) of 2-ethyl-2-oxazoline (EtOx) monomer. The “living” nature of LCROP allows the desirable termination to occur by using the proper termination agent, namely, water, to achieve the polymer with a terminal hydroxyl group, i.e., PEtOx-OH. The hydroxyl end group in PEtOx-OH was converted to PEtOx-Br using 2-bromopropionyl bromide via an esterification reaction. In the third step, the PEtOx-Br macro-CTA was subsequently reacted with potassium ethyl xanthate to insert the necessary RAFT agent via nucleophilic substitution reaction to obtain PEtOx-Xanthate. It s worth mentioning that this step is vital for the sequential addition of the second block via the RAFT polymerization reaction of fluorinated monomer, i.e., VDF, to finally obtain the well-defined amphiphilic diblock copolymer with variable controlled chain lengths. Proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR) and Fourier Transform Infrared Spectroscopy (FT-IR) confirmed the structure of the macroinitiator and final copolymer, respectively. Size Exclusion Chromatography (SEC) determined the number-average molecular weight (Mn) and the polydispersity index (PDI) of the obtained copolymer. Furthermore, the polymorphism of the diblock copolymer characterized by X-Ray Diffraction (XRD) indicated that the copolymer displays the electroactive α-phase. The resultant amphiphilic diblock copolymer exhibits spherical micelles morphology, as confirmed by Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM). Moreover, Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) investigated the thermal decomposition behavior of the copolymer and determined the glass transition temperature (Tg ≈ 70 °C), melting temperature (Tm ≈ 160-170 °C), and crystallization temperature (Tc ≈ 135-143 °C) of the diblock copolymer, respectively.
Date of AwardJun 2021
Original languageEnglish (US)
Awarding Institution
  • Physical Science and Engineering
SupervisorNikos Hadjichristidis (Supervisor)

Keywords

  • Poly (2-oxazoline)
  • Poly (vinylidene fluoride)
  • Cationic ring opening polymerization
  • Living radical ploymerization
  • Amphiphilic diblock copolymer

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