Thermal Conductivity, Heat Capacity, and Elastic Constants of Water-Soluble Polymers and Polymer Blends

Abstract

We use time-domain thermoreflectance (TDTR), and the generation and detection of longitudinal and surface acoustic waves, to study the thermal conductivity, heat capacity, and elastic properties of thin films of poly­(vinyl alcohol) (PVA), poly­(acrylic acid) (PAA), polyacrylamide (PAM), poly­(vinyl­pyrrolidone) (PVP), methyl cellulose (MC), poly­(4-styrene­sulfonic acid) (PSS), poly­(N-acryloyl­piperidine) (PAP), poly­(methyl methacrylate) (PMMA), and a polymer blend of PVA/PAA. The thermal conductivity of six water-soluble polymers in the dry state varies by a factor of ≈2, from 0.21 to 0.38 W m–1 K–1, where the largest values appear among polymers with a high concentration of hydrogen bonding (PAA, PAM, PSS). The longitudinal elastic constants range from 7.4 to 24.5 GPa and scale linearly with the shear elastic constants, suggesting a narrow distribution of Possion’s ratio 0.35 < ν < 0.40. The thermal conductivity increases with the average sound velocity, as expected based on the model of the minimum thermal conductivity. The thermal conductivity of polymer blends of PVA (0.31 W m–1 K–1) and PAA (0.37 W m–1 K–1) is in agreement with a simple rule of mixtures.

High and low thermal conductivity of amorphous macromolecules

“…We found that the height of the step edges matched To extract Λ and C from the TDTR data, we used a heat diffusion model to fit the three V in /V out curves simultaneously. 5 The model consists of three layers: the Al transducer, the thin film for investigation and the Si substrate. All the geometric parameters and thermal properties of the Al transducer and Si substrate are measured separately or adopted from literature values; the only fitting variables are Λ and C of the thin film.…”

“…For example, MTCM accurately predicts the pressure dependence of the thermal conductivity of poly(methyl methacrylate) (PMMA), 4 and the scaling of thermal conductivity with sound velocity for several water-soluble polymers. 5 Although the disagreement between the predicted and measured values is often 20% to 40%, MTCM has the advantages of using only two easily measured variables (i.e., the atomic density and average sound velocity) to describe the complex reality of heat conduction in macromolecules.…”

“…7 In contrast, the highest value reported for an amorphous macromolecular material is about an order of magnitude smaller (≈ 0.4 W m -1 K -1 for poly(acrylic acid) and polyacrylamide). 5,8 Regarding the lower limit, we attribute Λ min of cesium iodide (CsI, 0.14 W m -1 K -1 ) as the benchmark, due to the small (if not the smallest) combined values of n (2.09 x 10 22 cm -3 ) and V (V l = 2000 m s -1 and V t = 713 m s -1 ). 9 Recently, fullerene derivatives such as [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) and [6,6]-phenyl-C61-butyric acid n-butyl ester (PCBNB) were discovered to have thermal conductivities (≈ 0.06 W m -1 K -1 ) well below this benchmark.…”

Generation of planar blast waves using carbon nanotubes-poly-dimethylsiloxane optoacoustic transducer

“…[10][11][12][13][14][15] Values previously reported in literatures are adopted, however, the kinematic viscosity of solids over MHz frequency has not been characterized experimentally to our knowledge. To find the kinematic viscosity of the solids used in CPOT, the value is assumed to be homogeneous over the CPOT structure and is fitted to match the calculated frequency spectrum of the pressure wave with the measured one as shown in Fig.…”

Further resolution enhancement of high-sensitivity laser scanning photothermal microscopy applied to mouse endogenous

“…The laser diode power of pump and probe is 4.8 mW and 6.3 mW, respectively. In the GNP measurement case, the temperature rise of 16.5 K is calculated for sample thickness ¼ 50 lm, pump power ¼ 2.3 MW/cm 2 , heat capacity C ¼ 1.62 Â 10 6 J/K m 3 , 27 and absorbance at pump energy ¼ 0.6%. The temperature increase distribution is considered to be Gaussian from the diffusion process.…”