Thermal Conductivity of Semicrystalline Polymer Networks: Crystallinity or Cross-Linking?

Maurya, Manoj Kumar; Wu, James; Singh, Manjesh Kumar; Mukherji, Debashish

doi:10.1021/acsmacrolett.2c00341

Cited by 8 publications

(5 citation statements)

References 29 publications

(63 reference statements)

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“…Therefore, the design of polymers with low thermal conductivity cannot be solely based on reducing the cross-linking density. It is imperative to also consider factors such as crystallinity, bond types, and microstructure together for engineering the thermal conductivity of polymers. − …”

Section: Resultsmentioning

confidence: 99%

Thermal Conductivity of Polyurethane Thin Films

Zhou,

Li,

Chen

et al. 2024

Macromolecules

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Heat transport by solid conduction of polyurethane (PU) is a significant fraction of the total thermal conductivity of rigid PU foam. Despite its significance, the intrinsic thermal conductivity of solid PU materials is not well characterized, a circumstance largely attributable to the challenges of preparing fully dense materials that are free of voids due to CO 2 gas formation and entrapment caused by the fast reaction between a trace amount of water in a polyol and isocyanate during curing. We developed a protocol to prepare dense homogeneous PU thin films with thicknesses on the order of 100 nm, prepared eight formulations of PU films from a series of polyols and isocyanates with different functionalities, and measured their thermal conductivity, heat capacity, longitudinal speed of sound, and density by timedomain thermoreflectance, picosecond acoustics, and Rutherford backscattering spectrometry, respectively. The thermal conductivity of these PU materials spans a narrow range of 0.19 ± 0.03 W/(m K). The glass transition temperature of polymer thin films as thin as 100 nm was measured based on a photothermal displacement method. We used data for the longitudinal speed of sound and atomic density to predict the thermal conductivity using the minimum thermal conductivity model (MTCM). While the MTCM agrees with the measured thermal conductivity to within 30%, the variations in the thermal conductivity that we observe experimentally cannot be explained by the small variations in sound velocity and density. Our findings provide new insights into thermal conduction properties of PU solids in rigid PU foam and provide a fundamental basis for the construction of models of the thermal performance and the development of better insulation materials.

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Section: Resultsmentioning

confidence: 99%

Thermal Conductivity of Polyurethane Thin Films

Zhou,

Li,

Chen

et al. 2024

Macromolecules

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“…Traditionally, most studies on thermal transport have attempted to unveil the structureproperty relationship in nanomaterials [157][158][159][160][161][162]. Recent interest has been devoted to studying κ behavior in macromolecular systems [151][152][153]155,[163][164][165][166][167][168][169] because of the inherent advantage of polymers in designing advanced functional materials. Therefore, in the following, we will highlight two related, yet distinct, topics that are relevant in the context of the heat flow in organic materials: (1) thermal switching controlled via coil-to-globule transition and (2) the heat flow in organic solids.…”

Section: Heat Flow In Smart Polymersmentioning

confidence: 99%

“…Recently, tuning the κ values of organic solids has attracted great attention. This has been achieved via macromolecular engineering, which has included the following: (1) tuning the microscopic (nonbonded) interactions in linear polymers and polymer blends [150][151][152][153][154]182] and (2) by using covalent bonds [163,[167][168][169]175,180,183,184].…”

Section: Smart Polymers For Organic Solidsmentioning

confidence: 99%

“…Taking motivation from the observed significantly higher energy transfer rates between bonded monomers in comparison to nonbonded monomers, systems have been synthesized where the properties were dominated by bonded interactions. The systems where properties are dominated by the covalent bonds are chain-oriented systems (such as polymer fibers and molecular forests) [163,175,180] and crosslinked networks (such as epoxies and vitrimers) [167][168][169]183,184]. While the chain-oriented systems showed the κ → 100 W/Km [163], the maximum attainable κ 0.3 W/Km was observed for the epoxies [167,184].…”

Section: Tuning κ Via Bonded Interactionsmentioning

confidence: 99%

“…Epoxies with a certain degree of crystalline order can show a bit of a higher κ value. For example, semicrystalline epoxies have shown the κ → 0.5 W/Km [168,169], and, for the liquid crystalline epoxies, they have shown the κ → 1.0 W/km [187].…”

Section: Tuning κ Via Bonded Interactionsmentioning

confidence: 99%

See 2 more Smart Citations

Smart Polymers for Soft Materials: From Solution Processing to Organic Solids

Mukherji,

Kremer

2023

Polymers

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Polymeric materials are ubiquitous in our everyday life, where they find a broad range of uses—spanning across common household items to advanced materials for modern technologies. In the context of the latter, so called “smart polymers” have received a lot of attention. These systems are soluble in water below their lower critical solution temperature Tℓ and often exhibit counterintuitive solvation behavior in mixed solvents. A polymer is known as smart-responsive when a slight change in external stimuli can significantly change its structure, functionm and stability. The interplay of different interactions, especially hydrogen bonds, can also be used for the design of lightweight high-performance organic solids with tunable properties. Here, a general scheme for establishing a structure–property relationship is a challenge using the conventional simulation techniques and also in standard experiments. From the theoretical side, a broad range of all-atom, multiscale, generic, and analytical techniques have been developed linking monomer level interaction details with macroscopic material properties. In this review, we briefly summarize the recent developments in the field of smart polymers, together with complementary experiments. For this purpose, we will specifically discuss the following: (1) the solution processing of responsive polymers and (2) their use in organic solids, with a goal to provide a microscopic understanding that may be used as a guiding tool for future experiments and/or simulations regarding designing advanced functional materials.

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Reprocessable and Chemically Recyclable Hard Vitrimers Based on Liquid‐Crystalline Epoxides

Trinh

Yeo

2023

Advanced Materials

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The rapid increase in demand for recyclable and reusable thermosets has necessitated the development of materials with chemical structures that exhibit these features. Thus, functional mesogenic epoxide monomers bearing both ester and imine groups that can be vitrimerized and recycled are reported herein. The compounds show mesophase characteristics at 100–200 °C and can be converted into hard epoxides by a common curing reaction. The obtained hard epoxides have high isotropic thermal conductivity (≈0.64 W m−1 K−1), which is derived from their highly ordered microstructures. The cured products can be easily reprocessed through imine metathesis and transesterification, and decomposed products can be obtained through imine hydrolysis under acidic or basic conditions and subsequently be re‐cured. Surprisingly, recycled materials can be repeatedly reprocessed or chemically decomposed. The reprocessed materials retain the properties of their pristine counterparts, and the recycled products preserve the advantages of the hard thermosets without alteration to any of their unique properties. A dehydration reaction occurs between the residual hydroxyl groups during the re‐hardening, which dramatically increases the glass transition temperature by ≈60 °C. These reprocessable and recyclable vitrimers demonstrate the effectiveness and environmental friendliness of the molecular design strategy reported herein.

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Thermal Conductivity of Semicrystalline Polymer Networks: Crystallinity or Cross-Linking?

Cited by 8 publications

References 29 publications

Thermal Conductivity of Polyurethane Thin Films

Thermal Conductivity of Polyurethane Thin Films

Smart Polymers for Soft Materials: From Solution Processing to Organic Solids

Reprocessable and Chemically Recyclable Hard Vitrimers Based on Liquid‐Crystalline Epoxides

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