Synthesis of liquid crystalline copolyesters with low melting temperature for in situ composite applications

Download
2011
Erdoğan, Selahattin
The objective of this study is to synthesize nematic-thermotropic liquid crystalline polymers (LCP) and determine their possible application areas. In this context, thirty different LCP’s were synthesized and categorized with respect to their fiber formation capacity, melting temperature and mechanical properties. The basic chemical structure of synthesized LCP’s were composed of p-acetoxybenzoic acid (p-ABA), m-acetoxybenzoic acid (m-ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA) and isophthalic acid (IPA) and alkyl-diacids monomers. In addition to mentioned monomers, polymers and oligomers were included in the backbone such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) polymers, and polybutylene naphthalate (PBN), polyhexylene naphthalate (PHN) and poly butylene terephthalate (PBT) oligomers that contain different kinds of alkyl-diols. We adjusted the LCP content to have low melting point (180oC-280oC) that is processable with thermoplastics. This was achieved by balancing the amount of linear (para) and angular (meta) groups on the aromatic backbones together with the use of linear hydrocarbon linkages in the random copolymerization (esterification) reaction. LCP species were characterized by the following techniques; Polarized Light Microscopy, Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Analysis (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), X-ray Scattering (WAXS, Fiber diffraction), surface free energy, end group analysis (CEG), intrinsic viscosity (IV) and tensile test. According to these analysis LCPs were classified into five main categories; (I) fully aromatics, (II) aromatics+ PET/PEN, (III) aromatics + oligomers (IV) aromatics + short aliphatic diacids, (V) aromatics + long aliphatic diacids. The foremost results of the analysis can be given as below. DSC analysis shows that some LCPs are materials that have stable LC mesogens under polarized light microscopy. In TGA analysis LCPs that have film formation capacity passed the thermal stability test up to 390oC. NMR results proved that predicted structures of LCPs from feed charged to the reactor are correct. In FTIR due to the inclusion of new moieties, several peaks were labeled in the finger-print range that belongs to reactants. In X-ray analysis, LCP24 (containing PET) was found to be more crystalline than LCP25 (containing PEN) which is due to the symmetrical configuration. Block segments were more pronounced in wholly aromatic LCP2 than LCP24 that has flexible spacers. Another important finding is that, as the amount of the charge to the reactor increases CEG value increases and molecular weight of the product decreases. Selected group V species were employed as reinforcing agent and mixed with the thermoplastics; acrylonitrile butadiene styrene (ABS), nylon6 (PA6), polyethylene terephthalate (PET), polypropylene (PP) and appropriate compatibilizers in micro compounder and twin screw extruder. The blends of them were tested in dog-bone and/or fiber form. In general LCPs do not improve the mechanical properties except in composite application with polypropylene. A significant increase in tensile properties is observed by LCP24 and LCP25 usage. Capillary rheometer studies show that the viscosity of ABS decreases with the inclusion PA6 and LCP2 together. In addition to the composite applications, some LCPs are promising with new usage areas. Such as nano fibers with 200nm diameter were obtained from LCP27 by electrospinning method. The high dielectric constant of LCP29 has shown that it may have application areas in capacitors.

Suggestions

Synthesis and Stimuli-Responsive Properties of Metallo-Supramolecular Phosphazene Polymers Based on Terpyridine Metal Complexes
Sezer, Selda; KÖYTEPE, SÜLEYMAN; GÜLTEK, AHMET; SEÇKİN, TURGAY (2021-08-01)
In this study, terpyridine functionalized phosphazene based metallo-supramolecular polymers were synthesized by three step reaction method. In the first step, 4 '-(4-aminophenyl)-2,2 ':6 ',2 ''-terpyridine was synthesized with p-nitro benzaldehyde and 2-acetylpyridine. Then, the monomer containing six terpyridine (TPY) units attached to the phosphazene was prepared from 4 '-(4-aminophenyl)-2,2 ':6 ',2 ''-terpyridine and hexachlorocyclotriphosphazene by a condensation reaction. Finally, metallo-supramolecula...
Production and characterization of boron containing flame retardant polyamide-6 and polypropylene composites and fibers
Doğan, Mehmet; Bayramlı, Erdal; Department of Polymer Science and Technology (2011)
The main objective of this study was to produce flame retardant polyamide-6 (PA-6) and polypropylene (PP) composites and fibers containing boron compounds. The synergistic effect on flame retardancy of boron compounds (boron silicon containing oligomer (BSi), zinc borate (ZnB), boron phosphate (BPO4), metal oxide doped BPO4 and lanthanum borate (LaB)) with conventional flame retardants were investigated. The synergistic effect of nano-clay with commercial flame retardants was also investigated in order to r...
Combination of donor characters in donor-acceptor-donor type polymers containing benzothiadiazole and quinoxaline as the acceptor units
Şendur, Merve; Toppare, Levent Kamil; Department of Chemistry (2011)
Donor-acceptor-donor approach is one of the effective ways to synthesize low band gap polymers. The monomers that will be designed with respect to donor-acceptor-donor approach have low band gap achieved by the coupling of a strong donor with high HOMO level to a strong acceptor with low LUMO level. Thus, the new donor-acceptor material will have a reduced bandgap (Eg) relative to either of its parent components. Due to this point of view, in this study, new electroactive benzothiadiazole and 2,3-bis(4-(ter...
Synthesis and characterization of copolymers of diisocyanates and dialcohol
Keskin, Selda; Usanmaz, Ali; Department of Polymer Science and Technology (2008)
This study was aimed to synthesize low molecular weight hydroxyl terminated polyurethane acrylate polymers that can be used in biomedical applications. Acrylate end capping via inter-esterification reaction was successfully achieved with the methacryloyl chloride addition to the hydroxyl ends of the polyurethane at low temperatures. Isocyanate terminated polyurethane acrylates were also synthesized for the sake of comparison. TDI, HDI and MDI were used as diisocyanates for urethane synthesis and they were e...
Synthesis of some novel derivatives of 2,6-diaminoanthraquinone dyes
Yildirir, Yilmaz; Özdemir, Melek; Disli, Ali; Çolak, Naki (2008-11-01)
In present study, some derivatives of 2,6-diaminoanthraquinone dyes are synthesized and their UV-visible spectra are investigated in various conditions. Ten compounds (la-e) and (2a-e), two of which (1a, 1b) were previously obtained in low yields, have been synthesized by using diazonium salts of 2,6-diaminoanthraquinone and characterized by spectroscopic methods.
Citation Formats
S. Erdoğan, “Synthesis of liquid crystalline copolyesters with low melting temperature for in situ composite applications,” Ph.D. - Doctoral Program, Middle East Technical University, 2011.