Design of long-chain branched copolyesters and manufacture as well as physical properties of their extrusion films

Peng

ACS Appl. Polym. Mater.

et al. 2022

At present, high-performance liquid crystalline polyesters with a good processability, low dielectric constant, and low dielectric loss at a high frequency (GHz) are in high demand ascribed to the rapid development of high-speed communication technology. Here, an imide dicarboxylic acid (IA) with a bulky phenyl side group is designed and synthesized. It is then copolymerized with 4-hydroxybenzoic acid (HBA), isophthalic acid (IPA), 4,4′-dihydroxybipheny (BP), and 4,4′-dihydroxydiphenyl ether (ODP) via solution polycondensation to obtain liquid crystalline poly(ester imide)s (LCPEIs). By controlling the feeding ratio of IA, the solubility, thermal stability, mechanical properties, and dielectric properties of the LCPEIs are tunable. When the molar fraction of IA reaches or exceeds 5%, the obtained LCPEIs are soluble in ordinary organic solvents, such as chloroform, N,N-dimethylformamide, N-methyl-2-pyrrolidinone, and so forth, which allows a simple solution casting to prepare isotropic LC films. The nematic LCPEIs show high glass transition temperatures (T g > 200 °C) but relatively low melting temperatures and isotropization temperatures (T m and T i, <340 °C). The LCPEI prepared with 10 mol % IA shows excellent combined properties, whose ηinh, M n (GPC), T g, T m, T i, T d 5%, tensile strength, tensile modulus, water uptake, dielectric constant, and dielectric loss (at 10 GHz) are 0.92 dL g–1, 20,900 g mol–1, 218 °C, 268 °C, 330 °C, 458 °C, 80.5 MPa, 4.0 GPa, 0.39%, 3.07, and 0.006, respectively. These LCPEIs can be promising candidates for flexible copper-clad laminate substrates.

Section: ■ Results and Discussionmentioning

confidence: 99%

Soluble Liquid Crystalline Poly(ester imide)s with High Glass Transition Temperatures and Improved Dielectric Properties

Peng

ACS Appl. Polym. Mater.

et al. 2022

“…Liquid crystalline polymers are widely used in the automotive and aerospace industries and the medical field due to their excellent heat resistance, mechanical strength, electrical insulation, and chemical resistance. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Among liquid crystalline polymers, head-to-tail type wholly aromatic polyesters exhibit strong second harmonic generation with an increasing degree of polymerization, which has been attracting research on their application to wavelength conversion and optical modulation devices in the electronics and optics fields. [15][16][17] However, even if a single polymer chain has excellent nonlinear-optical properties, the main chain must form an oriented aggregate to exhibit the desired properties when used in a product.…”

Section: Introductionmentioning

confidence: 99%

Preparation of vertically oriented aromatic polyester thin films by thermal chemical vapor deposition

Matsubara,

Aida,

Fukushima

et al. 2024

Jpn. J. Appl. Phys.

Aromatic polyesters exhibit high thermal conductivity and large nonlinear optical effects by controlling the orientation of their main chains. Especially in recent years, with the development of flexible optical and electronic devices utilizing polymer thin films, out-of-plane orientation control in thin films on the order of several hundred nm is required. However, due to the rigidity of aromatic polyesters, it is difficult to control vertical orientation in thin film growth from melt or solution. In this study, we attempted to control the vertical orientation of aromatic polyester thin films from the vapor phase using a thermal chemical vapor deposition. From a single head-to-tail type monomer, aromatic polyester thin films with the most primitive structure, whose melting point exceeds 500°C, were successfully grown. Furthermore, it was found that the vertical orientation of the main chains was enhanced by substrate surface treatment.

“…3 The film named Kuraray's Vecstar CTZ exhibits moderate D k of 3.33 and low D f of 0.0028 at 10 GHz. 4 However, it is difficult for it to be processed into films, because the LCP resin is insoluble in common organic solvents. Moreover, the thin films obtained by melt processing easily produce anisotropy which is not conducive to their application.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, much attention has been paid on polymers with low dielectric constant ( D k ) and low dielectric loss ( D f ) at high frequency (≥10 GHz). , A liquid crystalline all aromatic polyester is regarded as a promising substrate material for the flexible copper clad laminate (FCCL) applied in 5G communication attributed to its prominent properties . The film named Kuraray’s Vecstar CTZ exhibits moderate D k of 3.33 and low D f of 0.0028 at 10 GHz . However, it is difficult for it to be processed into films, because the LCP resin is insoluble in common organic solvents.…”

Section: Introductionmentioning

confidence: 99%

Effect of Fluorinated Substituents on Solubility and Dielectric Properties of the Liquid Crystalline Poly(ester imides)

ACS Appl. Polym. Mater.

Peng

Pan

et al. 2022

With the rapid advancement of 5G communication technology, much attention has been paid on high-performance polymers with a low dielectric constant (D k), a low dielectric loss (D f) and good processability. In order to further research and improve dielectric properties of the liquid crystalline poly(ester imide)s (LCPEIs), four imide dicarboxylic acids (IAs) with fluorinated groups are designed and synthesized. They are then copolymerized with 1,3-phthalic acid (IPA), p-hydroxybenzoic acid (HBA), and bisphenol monomers via solution polycondensation to obtain fluorinated PEIs, whose fluorine content, position of the fluorinated group, and LC behavior are tunable by using different IAs and bisphenol monomers. These PEIs with the highest T g of 238 °C are soluble in general organic solvents, such as m-cresol, N-methyl-2-pyrrolidone (NMP), chloroform, and so on. PEI-6F25AF exhibits the lowest D k of 2.60, while LCPEI-6FD shows the lowest D f of 0.0053 at 10 GHz. It is found that high fluorine content and large pendent group can reduce the D k, while the fluorinated group grafted close to the nitrogen atom and the LC rigid rod-like conformation lead to low D f. We devoutly expect that this research offers some reference for structure design of LCPEIs with both low D k and D f at high frequency.