Structures and phase transformations of odd-numbered asymmetric main-chain liquid crystalline polyesters

Jeong, Kwang‐Un; Knapp, Brian S.; Ge, Jason J.; Graham, M. J.; Tu, Yingfeng; Leng, Siwei; Xiong, Huiming; Harris, Frank W.; Cheng, Stephen Z. D.

doi:10.1016/j.polymer.2006.03.025

Cited by 33 publications

(38 citation statements)

References 40 publications

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“…Jeong et al . reported a rather parallel arrangement of liquid crystalline polyester chains within the odd series and a zigzag arrangement within the even series . In this particular paper, a general decreasing trend of the T m values was seen as the aliphatic chain length increased, leading the authors to conclude that even compounds are characterized by higher melting values than odd compounds.…”

Section: Resultsmentioning

confidence: 76%

Single‐step solution polymerization of poly(alkylene terephthalate)s: synthesis parameters and polymer characterization

Giol

Brande

Mele

et al. 2018

Polymer International

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Poly(alkylene terephthalate)s represent one of the most frequently used polymer classes worldwide. Well‐known examples include poly(ethylene terephthalate) (n = 2) and poly(butylene terephthalate) (n = 4). The conventional synthesis method for these polymers is based on melt polycondensation, a two‐stage process performed under harsh conditions that includes the synthesis of an intermediate prepolymer and the presence of a catalyst, which may induce toxicity issues. The present work reports on a straightforward single‐step solution polycondensation method performed under mild conditions and in the absence of a catalyst. A homologous series of poly(alkylene terephthalate)s (n = 5 − 10) of molar masses up to 20 000 g mol−1 and dispersity <2.4 was synthesized and characterized thoroughly. Great attention was given to the thermal properties assessment by using state‐of‐the‐art techniques and a highly sensitive prototype technique called rapid heat − cool DSC. Similar to melt‐synthesized polyesters, a particular odd − even trend of the thermal properties versus the number of methylene groups within the monomer unit was revealed. To the best of our knowledge, this is the first report covering a single‐step solution‐based polycondensation performed in the absence of a catalyst that results in highly reproducible polyesters possessing unaltered thermal properties compared to polyesters synthesized through industrially applied conventional routes. © 2017 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 76%

Single‐step solution polymerization of poly(alkylene terephthalate)s: synthesis parameters and polymer characterization

Giol

Brande

Mele

et al. 2018

Polymer International

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“…Therefore, much effort has been made to improve the processability of thermotropic liquid crystalline polyarylates. The main methods are as follows: (1) introduction of non‐mesogenic flexible spacers in the main chain; (2) introduction of side substituents to reduce the symmetry of the chains; (3) copolymerization of several aromatic monomers to obtain a more random backbone composition . The representative examples are enumerated as follows.…”

Section: Introductionmentioning

confidence: 99%

Novel polyarylates containing aryl ether units: synthesis, characterization and properties

Liu

et al. 2012

Polymer International

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To improve the processability of the poly(p‐hydroxybenzoic acid), copolyarylates containing m‐aryl ether units were synthesized using p‐acetoxybenzoic acid, 1,4‐diacetoxybenzene and 1,3‐bis(4'‐carboxyphenoxy)benzene by melt transesterification reaction. The structure and properties of these polyarylates were characterized using infrared spectra, differential scanning calorimetry, thermogravimetric analyses, wide‐angle X‐ray diffraction and polarized optical microscopy etc. The results showed that all polyarylates were semicrystalline materials and could form a thermotropic liquid crystalline intermediate state. As the content of aryl ether units increased, the crystallization and melting temperatures of the polyarylate decreased; meanwhile, the crystalline ability became lower. The introduction of the aryl ether could restrain the formation of a liquid crystalline structure and reduce the thermal stability to some extent. After solid state polymerization (SSP), the intrinsic viscosity, melting temperature, crystallinity and thermal stability of the polyarylate increased while the melting range narrowed. However, the SSP reaction might be accompanied by degradation and crosslinking.

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“…To reduce the melt temperature of TLCP, different strategies were utilized, such as introducing flexible spacers,35, 36 using isomerous monomers as mesogenic groups,37–39 introducing nonlinear or kinked monomers,40, 41 random copolymerization of monomers as well as introducing bulky substitute onto mesogenic groups,42–46 hyperbranched topologies, and dendritic architectures 47–49. Zhao et al synthesized P‐TLCP‐FS (Scheme ) by introducing flexible spacers onto the mesogenic chains of P‐TLCP which decreased the melt temperature of P‐TLCP from 290 (P‐20) to 205 °C (P‐TLCP‐FS‐60) 50.…”

Section: Introductionmentioning

confidence: 99%

A novel thermotropic liquid crystalline copolyester containing phosphorus and aromatic ether moity toward high flame retardancy and low mesophase temperature

Bian

Chen

Wang

et al. 2010

J. Polym. Sci. A Polym. Chem.

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A series of thermotropic liquid crystalline polyesters containing phosphorus and aromatic ether groups (TLCP‐AEs) were synthesized from p‐acetoxybenzoic acid (p‐ABA), terephthalic acid (TPA), 4,4′‐oxybis(benzoic acid) (OBBA), and acetylated 2‐(6‐oxid‐6H‐dibenz(c,e) (1,2) oxaphosphorin 6‐yl) 1,4‐benzenediol (DOPO‐AHQ). The chemical structure and the properties of TLCP‐AEs were characterized by Fourier‐transform spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electronic microscopy (SEM), polarizing optical microscopy (POM), limiting oxygen index, and UL‐94 tests, respectively. The results showed that TLCP‐AEs had low and broad mesophase temperatures (230–400 °C). TLCP‐AEs also showed excellent thermal stability; their 5%‐weight‐loss temperatures were above 440 °C and the char yields at 700 °C were higher than 45 wt %. All TLCP‐AE polyesters exhibited high flame retardancy with a LOI value of higher than 70 and UL‐94 V‐0 rating. The SEM observation revealed that TLCP‐AEs had good fibrillation ability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1182–1189, 2010

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Structures and phase transformations of odd-numbered asymmetric main-chain liquid crystalline polyesters

Cited by 33 publications

References 40 publications

Single‐step solution polymerization of poly(alkylene terephthalate)s: synthesis parameters and polymer characterization

Single‐step solution polymerization of poly(alkylene terephthalate)s: synthesis parameters and polymer characterization

Novel polyarylates containing aryl ether units: synthesis, characterization and properties

A novel thermotropic liquid crystalline copolyester containing phosphorus and aromatic ether moity toward high flame retardancy and low mesophase temperature

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