Enhancing intrinsic thermal conductivities of epoxy resins by introducing biphenyl mesogen-containing liquid crystalline co-curing agents

Dang, Jinjin; Zhang, Junliang; Li, Mukun; Lin, Dong; Gu, Junwei

doi:10.1039/d2py01157c

Cited by 23 publications

(9 citation statements)

References 46 publications

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“…This is ascribed to the increase of the heat flow each unit time at a higher heating rate, which leads to a stronger thermal effect, causing the exothermic peak shift to a higher temperature. [ 37 ] The plot of the exothermic peak temperature as a function of heating rate is shown in Figure S2 (Supporting Information). It reveals a linear relationship between the peak temperature and the heating rate, where the peak temperature of 147.4±4.8 °C at a heating rate of 0 °C/min can be obtained through linear fitting.…”

Section: Resultsmentioning

confidence: 99%

Fast Degradable and Thermally Conductive Silicone Rubber Vitrimer with Low Dielectric and UV‐Shielding Properties

Zhang,

Dang,

Zhang

2023

Macro Chemistry & Physics

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Silicone rubbers have been widely employed in various fields such as electronics, electrical engineering, mobile communications, aerospace, and automotive industries. However, silicone rubbers are typically challenging to reprocess and degrade. Moreover, with the advancement of technology, higher demands have been placed on its thermal conductivity and dielectric properties. In this study, diglycidyl ether terminated polydimethylsiloxane was cured by 4,4′‐dithiodibutyric acid which contains dual dynamic covalent disulfide and ester bonds with triazobicyclodecene as the ester exchange catalyst to prepare silicone rubber vitrimers (SRVs) through a casting method. The SRVs demonstrated a relatively higher intrinsic thermal conductivity of 0.26 W/(m·K) compared to ∼0.20 W/(m·K) of conventional silicone rubber. Besides, the SRVs exhibited very low and stable dielectric constant and dielectric loss at both low and high frequencies (X‐band). The lowest dielectric constant and dielectric loss tangent at 10 GHz were 2.75 and 0.0639, respectively. Besides, the dual dynamic covalent bonds enabled the SRVs to have excellent reprocessability and fast degradability. Moreover, the SRVs revealed UV‐shielding capability, as the transmittance of the SRVs was 0% from 200 to 400 nm of UV light.This article is protected by copyright. All rights reserved

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Section: Resultsmentioning

confidence: 99%

Fast Degradable and Thermally Conductive Silicone Rubber Vitrimer with Low Dielectric and UV‐Shielding Properties

Zhang,

Dang,

Zhang

2023

Macro Chemistry & Physics

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“…The thermal conductivities of polymers enhance with increasing the phonon mean free path, which is inversely correlated to the phonon scattering. , Therefore, enhancing the degree of crystallinity or the molecular chain orientation of polymers is considered an effective means of increasing the phonon mean free path . Previous researchers mainly introduced liquid crystal units such as biphenyl, fused benzene rings, or aryl esters , into epoxy monomers or curing agents to improve the regularity of the microstructure within the cross-linking network of epoxy resins. The phonon scattering is then suppressed through the formation of π–π stacking, thus enhancing the intrinsic thermal conductivity .…”

Section: Introductionmentioning

confidence: 99%

Effect of the Structure of Epoxy Monomers and Curing Agents: Toward Making Intrinsically Highly Thermally Conductive and Low-Dielectric Epoxy Resins

Zhang,

Dang,

Zhang

et al. 2023

JACS Au

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The low intrinsic thermal conduction and high dielectric properties of epoxy resins have significantly limited their applications in electrical and electronic devices with high integration, high frequency, high power, and miniaturization. Herein, a liquid crystalline epoxy (LCE) monomer with a biphenyl mesogenic unit was first synthesized through an efficient one-step reaction. Subsequently, bisphenol AF (BPAF) containing low-polarizable −CF 3 groups and 4,4′-diaminodiphenylmethane (DDM) were applied to cure the LCE and commercial diglycidyl ether of bisphenol A-type epoxy (E-51), respectively, to afford four kinds of epoxy resins with various intrinsic thermal conductivity and dielectricity values. Owing to the dual effect of microscopically stacking of mesogens and the contribution of fluorine to the formation of liquid crystallinity, ordered microstructures of the nematic liquid crystal phase were formed within the cross-linking network of LCE as confirmed by polarized optical microscopy and X-ray diffraction. Consequently, phonon scattering was suppressed, and the intrinsic thermal conductivity was improved considerably to 0.38 W/(m·K), nearly twice as high as that of E-51 cured with DDM (0.20 W/(m·K)). Additionally, the ordered microstructure and ultralow polar −CF 3 groups within LCE cured with BPAF enabled the epoxy resin to exhibit a remarkably lower and stable dielectric constant (ε) and dielectric loss tangent (tan δ) over both low and high frequencies compared to E-51 cured with DDM. The ε decreased from 3.40 to 2.72 while the tan δ decreased from 0.044 to 0.038 at 10 GHz. This work presents a scalable and facile strategy for breaking the bottleneck of making epoxy resins simultaneously with high inherent thermal conduction and low dielectric performance.

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“…The mesogenic epoxy showed high TC of 0.29 W/m·K due to the ordered orientation of molecular chains. Based on the molecules' ordered structures, Dang et al 23 synthesized a biphenyl liquid crystal molecule (BLCM) by using 1,6‐dibromohexen and 4,4′‐dihydroxybiphenyl and prepared liquid crystal epoxy resins (LCER) by using E‐51 as matrix and 4,4′‐diaminodiphenylmethane (DDM) and BLCM as curing agent. The TC of the liquid crystal epoxy resins (LCER) was 0.42 W/m·K, which was 2.1 times as much as that of E‐51 cured by DDM only (LCER).…”

Section: Introductionmentioning

confidence: 99%

Flexible and thermally conductive epoxy‐dispersed liquid crystal composites filled with functionalized boron nitride nanosheets

Huang

et al. 2023

Polymer Composites

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In view of the problem of heat accumulation in electronic devices, the development of new composites with high thermal conductivity (TC) is the current research focus. Nowadays, improving TC often lead to inevitable deterioration of the mechanical properties of materials. In this work, the E‐functionalized boron nitride nanosheets (f‐BNNS)/liquid crystal monomer (LCM)/Epoxy‐thiol films with high TC were prepared by using flexible epoxy‐thiol polymer as matrix and LCM and f‐BNNS as thermal fillers via high voltage orientation molding. The epoxy‐thiol polymer possessed high intrinsic TC due to the regular arrangement of molecular chains and the f‐BNNS showed favorable dispersibility because of the modification by isopropyl tri(dioctylpyrophosphate) titanate (ITDPT). The results show that TC of E‐f‐BNNS/LCM/Epoxy‐thiol films with 30 wt% f‐BNNS content achieves 1.65 W/m·K and is 511.11% higher than that of pure epoxy‐thiol polymer (0.27 W/m·K). The tensile strength and elongation at break increase to 24.9 MPa and 47.41%, respectively. The favorable results are attributed to the ordered arrangement of f‐BNNS and molecular chains, resulting from the hydrogen‐bonding interaction between OH group in f‐BNNS, LCM and epoxy‐thiol polymer. This research provides a simple and feasible method for preparing flexible epoxy polymer films with high TC.Highlights The functional BNNS was achieved by isopropyl tri(dioctylpyrophosphate) titanate. Effects of matrix thermal conductivity on films thermal conductivity are probed. High voltage orientation molding are used for preparing epoxy composite films. The films demonstrate excellent thermal conductivity and favorable tensile strength.

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Enhancing intrinsic thermal conductivities of epoxy resins by introducing biphenyl mesogen-containing liquid crystalline co-curing agents

Abstract: In this work, a biphenyl liquid crystalline small molecule (BLCM) containing flexible units was synthesized by one-step condensation reaction of 4,4'-dihydroxybiphenyl (BP) and 1,6'-dibromohexene. Then the commercially available bisphenol A...

Cited by 23 publications

References 46 publications

Fast Degradable and Thermally Conductive Silicone Rubber Vitrimer with Low Dielectric and UV‐Shielding Properties

Fast Degradable and Thermally Conductive Silicone Rubber Vitrimer with Low Dielectric and UV‐Shielding Properties

Effect of the Structure of Epoxy Monomers and Curing Agents: Toward Making Intrinsically Highly Thermally Conductive and Low-Dielectric Epoxy Resins

Flexible and thermally conductive epoxy‐dispersed liquid crystal composites filled with functionalized boron nitride nanosheets

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