The thermal conductivity of PMMA films with thicknesses from 5 to 50 nanometers and
layered over a treated silicon substrate is explored numerically by the application of the
reverse non-equilibrium molecular dynamics (NEMD) technique and the development of
a coarse-grained model for PMMA, which allows for the simulation time of hundreds of
nanoseconds required for the study of large polymer systems.
The results showed a constant average thermal conductivity of 0.135 W/m_K for
films thickness ranging from 15 to 50 nm, while films under 15 nm in thickness showed
a reduction of 30% in their conductivity. It was also observed that polymer samples with
a degree of polymerization equal to 25% of the entanglement length had 50% less
thermal conductivity than films made of longer chains. The temperature profiles through
the films thickness were as predicted by the Fourier equation of heat transfer.
The relative agreement between the thermal conductivity from experiments
(0.212 W/m_K for bulk PMMA) and the results from this investigation shows that with
the proper interpretation of results, the coarse-grained NEMD is a useful technique to
study transport coefficients in systems at larger nano scales.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-05-7676 |
| Date | 2010 May 1900 |
| Creators | Silva Hernandez, Carlos Ardenis A. |
| Contributors | Marotta, Egidio, Cagin, Tahir |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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