Poly(methyl methacrylate)/single‐walled carbon nanotube (PMMA/SWNT) composites were prepared via in situ polymerization induced either by heat, ultraviolet (UV) light, or ionizing (gamma) radiation. The composites dissolved in methylene chloride and then cast into films exhibited enhanced transparency as compared with the melt‐blended composite material. UV/visible spectroscopy was used to quantitatively analyze the transparency of the composites. The dielectric constant (ε′) was measured via dielectric analysis (DEA) and correlated to the refractive‐index values using Maxwell's relationship. The dielectric constant increased in the composite samples as compared with the neat PMMA samples prepared by the same methods. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) provided images of the polymer–nanotube composites and single‐walled CNTs, respectively.

Single-wall carbon nanotube (SWNT)/poly(methyl methacrylate) (PMMA) composites were fabricated and exposed to ionizing radiation for a total dose of 5.9 Mrads. Neat nanotube paper and pure PMMA were also exposed for comparison, and nonirradiated samples served as controls. A concentration of 0.26 wt% SWNT increased the glass transition temperature (Tg), the Vickers hardness number, and modulus of the matrix. Irradiation of the composite did not significantly change the Tg, the Vickers hardness number, or the modulus; however, the real and imaginary parts of the complex permittivity increased after irradiation. The dielectric properties were found to be more labile to radiation effects than mechanical properties.

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Using Raman spectroscopy, we demonstrate that the anisotropic interaction between single‐walled carbon nanotubes (SWNTs) and poly(methyl methacrylate) (PMMA) causes significant changes in the electronic properties of their composites. Two different procedures were used to prepare the composites: melt blending and in‐situ UV polymerization. Resonant Raman studies relate the electronic density of states (DOS) of the SWNTs to the corresponding vibration symmetry changes of both the PMMA and the SWNTs. Our results show that, in the melt‐blended sample, the SWNTs—originally semiconducting—became predominantly metallic. The changes in the electronic properties were also confirmed by dielectric constant measurements. We propose that the anisotropic interaction between PMMA and SWNTs in the melt‐blended composite is the dominant reason for the observed electronic character change.

Poly(4-methyl-1-pentene), PMP, a high melting polymer composed of hydrogen and carbon, has the potential to become an alternative to polyethylene (PE) as shielding material against Galactic Cosmic Radiation (GCR). PMP exhibits higher thermal stability than PE and is transparent in the UV/visible region of the electromagnetic spectrum. Single walled carbon nanotubes (SWNTs) were pretreated with a polar solvent, N, N-Dimethylformimide (DMF), and then dispersed in a halogenated hydrocarbon, cyclohexyl chloride, which also dissolved the non polar polymer, PMP. The composites were characterized via differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), microhardness measurements, and optical microscopy. DMA data revealed that the carbon nanotubes contributed to the enhancement of the high temperature alpha(c) relaxation which is thought to arise from motion around crystalline regions in the matrix. The storage modulus (60 Hz) increased from 2409 MPa in the neat PMP to 3716 MPa at -50 degrees C. The magnitude of the increase diminished near and above the glass transition region; the glassy matrix restricted motion of the crystalline regions. DSC data showed an increase in the percent crystallinity of the composite (75%) as compared to the neat polymer (68%). Low concentrations of nanotubes, when well dispersed, produced nanocomposites with varying degrees of transparency.