Without knowing more about what is involved with such a problem, it is hard to give a concrete answer. What is trying to be solved, is it a set of non linear partial differential equations? What is the length scale of the solution? What is the length scale of the internal forces?

@ Dr. Matt

I am not referring to any particular problem. In the literature we cannot find such (complete) simulations  

Perhaps a deeper knowledge about nanoparticles, plasmonics and its basis, can help you to assess how you can simulate that kind of systems.

some references (and related bibliography) could help you:

-Substrate effects on the optical properties of spheroidal nanoparticles Phys. Rev. B 61, 10427

-http://pubs.acs.org/doi/abs/10.1021/jp405773p (https://www.researchgate.net/publication/256707220_UV_Plasmonic_Behavior_of_Various_Metal_Nanoparticles_in_the_Near-_and_Far-Field_Regimes_Geometry_and_Substrate_Effects)

-https://www.researchgate.net/publication/273445198_Using_linear_polarization_to_monitor_nanoparticle_purity

Best regards

Article UV Plasmonic Behavior of Various Metal Nanoparticles in the ...

Article Using linear polarization to monitor nanoparticle purity

What physics of the system you are looking for, resonance frequencies; localized field enhancement; field propagation; transmittion or reflection coefficients and so on. Then, the big problem is how can you model your system as a mathematical model. What are the assumsions have to be imposed to simplify your model to make it posible for numerical method. How can you model the polymer layers? Can it be modelled as the continuum media with known dielectric function? Your question is difficult to answer unless you specify what you need to calculate and what is your system detail.

Many more analytical and numerical approaches have been done to study the plasmonic effects in polymers like PEOPT, P3HT, P3HT:PCBM and PEDOT.

This link may help you

http://link.springer.com/article/10.1007/s00339-013-8061-0/fulltext.html