On the influence of thermal annealing on molecular relaxations and structure in thermotropic liquid crystalline polymer

Romo-Uribe, Ángel; Reyes‐Mayer, Adriana; Rodríguez, Manuela Calixto; Sarmiento-Bustos, E.

doi:10.1016/j.polymer.2021.124506

Cited by 8 publications

(3 citation statements)

References 31 publications

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“…After the degradation, additional peaks appeared at 2θ = 23.9°. A similar change in the XRD profiles was characterized to a polymorphic transformation from pseudohexagonal to orthorhombic lattices. − However, these changes were induced by annealing at 200 °C and above. The pseudohexagonal lattice has a less chain-packed structure than the orthorhombic lattice .…”

Section: Resultsmentioning

confidence: 99%

Degradation of a Wholly Aromatic Main-Chain Thermotropic Liquid-Crystalline Polymer Mediated by Superbases

Watanabe,

Fukushima,

Kato

2024

JACS Au

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Plastic circular economy needs to be established to solve environmental issues related to plastic waste. Superengineering plastics such as liquid-crystalline (LC) polymers exhibit excellent thermal and mechanical properties, resulting in poor degradability in natural environment. Herein, we report the degradation of a wholly aromatic thermotropic LC polyester, poly(4-hydroxybenzoic acid-co-6-hydroxy-2-naphthoic acid) (Vectra) mediated by superbases. Methanolysis and hydrolysis of Vectra yield its monomeric compounds, 4-hydroxybenzoic acid, 6hydroxy-2-naphthoic acid, and their methyl esters. Among several transesterification catalysts explored, 1,5,7-triazabicylco[4.4.0]dec-5-ene (TBD) is the most suitable for the methanolysis of Vectra. The complete degradation of Vectra is achieved under reflux. The degradation proceeds heterogeneously via a surface erosion mechanism, preferentially starting from less chain-packed regions. Model reactions using aryl arylates reveal that monomeric compound−superbase complexes could mediate the cleavage of the ester bonds in both homogeneous and heterogeneous systems. The ester bonds of Vectra have inherent poor reactivity and are protected by oriented robust structures of the polymer. Nevertheless, the superbases enable the degradation of Vectra via the cleavage of the ester bonds by methanol. These outcomes open the way for recycling high-performance plastics as well as demonstrate the feasibility of recovering precious aromatic compounds from plastic waste as aromatic feedstock.

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Section: Resultsmentioning

confidence: 99%

Degradation of a Wholly Aromatic Main-Chain Thermotropic Liquid-Crystalline Polymer Mediated by Superbases

Watanabe,

Fukushima,

Kato

2024

JACS Au

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“…However, its poor notched impact toughness (especially at low temperatures) restricts its overall performance, which limits its applications in modern plastic industries and newly emerging fields [ 5 , 6 , 7 , 8 , 9 ], e.g., wearable fabrics [ 4 ], self-supporting water purification films [ 9 ], and nanofiltration membrane [ 7 ], etc. To solve this issue, PA6 matrix has been modified by reinforcing materials, such as hydrogenated acrylonitrile-butadiene-styrene (ABS) [ 10 ], styrene-co-acrylonitrile (SAN) [ 11 ], hydrogenated styrene-butadiene-styrene (SEBS) [ 12 ], polyamide 66 [ 13 ], poly(tetrafluoroethylene) (PTFE) [ 14 ], and thermotropic liquid crystalline polymer (TLCP) [ 15 ], etc. For those reinforcing monomers or polymers, they have similar functional groups to that of PA6, which is advantageous to obtain compatible polymer composites to overcome the phase separation problem at the interface of PA6 and reinforcing additives through chemical and physical interactions or adhesions between them.…”

Section: Introductionmentioning

confidence: 99%

“…As we know, among those polymer modifiers [ 10 , 11 , 12 , 13 , 14 , 15 ], TLCP is one promising choice. Because of the peculiar rigid-rod chemical structures, TLCP in the solid form possesses many unique properties, e. g., low melt viscosity and high mechanical modulus in the oriented direction.…”

Section: Introductionmentioning

confidence: 99%

The Preparation of Monomer Casting Polyamide 6/Thermotropic Liquid Crystalline Polymer Composite Materials with Satisfactory Miscibility

Qiu

Yue

et al. 2022

Polymers

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It is highly expected to develop a simple and effective method to reinforce polyamide 6 (PA6) to enlarge its application potential. This is challenging because of frequently encountered multi-component phase separations. In this paper, we propose a novel method to solve this issue, essentially comprising two steps. Firstly, a kind of poly (amide-block-aramid) block copolymers, i.e., thermotropic liquid crystalline polymer (TLCP)-polyamide 6 (TLCP-PA6), that contains both rigid aromatic liquid crystal blocks, and flexible alkyl blocks were synthesized. It is unique in that TLCP is chemically linked with PA6, which is advantageous in excellent chemical and physical miscibility with the precursors of monomer casting polyamide 6 (MCPA6), i.e., ε-caprolactam. Secondly, such newly synthesized block copolymer TLCP-PA6 was dissolved in the melting ε-caprolactam, and followed by in situ polymerization to obtain composite polymer blends, i.e., MCPA6/TLCP-PA6. The thermodynamic, morphological, and crystalline properties of MCPA6/TLCP-PA6 can be easily manipulated by tailoring the loading ratios between TLCP-PA6 and ε-caprolactam. Especially, at the optimized condition, such MCPA6/TLCP-PA6 blends show an excellent miscibility. Systematic characterizations, including nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimeter (DSC), and polarizing optical microscope (POM), were performed to confirm these statements. In view of these results, it is anticipated that the overall mechanical properties of such PA6-based polymer composites will be satisfactory, which should enable applications in the modern plastic industry and other emerging areas, such as wearable fabrics.

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Selective adsorption and separation of salicylic acid and 4‐hydroxyisophthalic acid from industry‐grade 4‐hydroxybenzoic acid on UiO‐66

Yuan,

Sun,

Peng

et al. 2024

Asia-Pacific J Chem Eng

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In this study, UiO‐66 was employed for the first time as an adsorbent to separate phenolic acid analogues, specifically 4‐hydroxyisophthalic acid and salicylic acid, from impurities. Synthesized in‐house, UiO‐66 was shown to exhibit high selectivity towards 4‐HIPA/4‐HBA and SA/4‐HBA when a molar equivalent of acetic acid modulator to terephthalic acid was set at 44. The adsorption capacities for 4‐HBA, 4‐HIPA, and SA were determined to be 56.34, 55.02, and 60.34 mg/g, respectively. Furthermore, it was observed that after six regeneration cycles, the adsorption capacity for 4‐HBA remained nearly unchanged, whereas those for 4‐HIPA and SA decreased by 5.6% and 2.6%, respectively. FTIR and XPS analyses revealed that all three compounds were adsorbed at the same dominant Zr cluster site on UiO‐66, primarily through hydrogen bonding and electrostatic interaction. Dynamic adsorption experiments revealed that 4‐HBA was the first to elute, maintaining the residual contents of 4‐HIPA and SA below 0.1 wt%. Compared to traditional separation techniques, this paper provided a simple and effective method to purify industrial grade 4‐hydroxybenzoic acid.

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On the influence of thermal annealing on molecular relaxations and structure in thermotropic liquid crystalline polymer

Cited by 8 publications

References 31 publications

Degradation of a Wholly Aromatic Main-Chain Thermotropic Liquid-Crystalline Polymer Mediated by Superbases

Degradation of a Wholly Aromatic Main-Chain Thermotropic Liquid-Crystalline Polymer Mediated by Superbases

The Preparation of Monomer Casting Polyamide 6/Thermotropic Liquid Crystalline Polymer Composite Materials with Satisfactory Miscibility

Selective adsorption and separation of salicylic acid and 4‐hydroxyisophthalic acid from industry‐grade 4‐hydroxybenzoic acid on UiO‐66

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