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Locate full-text(opens in a new window)|Full Text(opens in a new window)|View at Publisher| Export | Download | Add to List | More... Macromolecules Volume 40, Issue 4, 20 February 2007, Pages 1089-1100 Optical properties of composites of PMMA and surface-modified zincite nanoparticles (Article) Demir, M.M.a, Koynov, K.a, Akbey, Ü.a, Bubeck, C.a, Park, I.ab, Lieberwirth, I.a, Wegner, G.a a Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany b Seoul National University, School of Chemistry, Korea, South Korea View references (65) Abstract Composites that show visible light transmittance, UV absorption, and moderately high refractive index, based on poly(methyl methacrylate) (PMMA) and zinc oxide (zincite, ZnO) nanoparticles, were prepared in two steps. First, surface-modified ZnO nanoparticles with 22 nm average diameter were nucleated by controlled precipitation via acid-catalyzed esterification of zinc acetate dihydrate with pentan-1-ol. The surface of growing crystalline particles was modified with tert-butylphosphonic acid (tBuPO3H2) in situ by monolayer coverage. Particle size and graft density of -PO3H 2 on the particle surface were controlled by the amount of surfactant applied to the reaction solution. Second, the surface-modified particles were incorporated into PMMA by in-situ bulk polymerization. Free radical polymerization was carried out in the presence of these particles using AIBN as initiator. Volume fraction (0) of the particles was varied from 0.10 to 7.76% (0.5 to 30 wt %). Although the particles are homogeneously dispersed in monomer, segregation of the individual particles upon polymerization was observed. Optical constants of the films ca. 2.0 μm including absorption and scattering efficiencies, indices of refraction, and dispersion constants were determined. The absorption coefficient at 350 nm increases linearly with ZnO, obeying Beer's law at low particle contents. However, it levels off toward a value of about 5000 cm-1 and shows a negative deviation at high concentrations because of aggregation of the individual particles. Waveguide propagation loss coefficients of the composite films were examined by prism coupling. A steep increase of the loss coefficient was found with a slope of 52 dB cm-1 vol %-1 as the volume fraction of the particle increases. The refractive index of the composites depends linearly on volume fraction of ZnO and varies from 1.487 to 1.507 (φ = 7.76%) at 633 nm. The dispersion of refractive index was found to be consistent with Cauchy's formula.

Dispersing surface-modified zinc oxide nano-particles (ZnO) in methyl methacrylate (MMA) improves the free radical bulk polymerization process as well as the thermal stability of the formed polymer. Hydroxy groups available on the ZnO surface may induce a degenerative transfer. This suppresses the gel effect, which leads to a better control of the heat evolution during the late stages of polymerization. The formation of chains having vinylidene end groups and head-to-head links is suppressed, which shifts the onset of thermal decomposition to the regime where decomposition occurs by random chain scission.

Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

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