Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles
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- 作者：Mustafa M. Demir ; Kaloian Koynov ; Ü ; mit Akbey ; Christoph Bubeck ; Insun Park ; Ingo Lieberwirth ; Gerhard Wegner
- 刊名：Macromolecules
- 出版年：2007
- 出版时间：February 20, 2007
- 年：2007
- 卷：40
- 期：4
- 页码：1089 - 1100
- 全文大小：745K
- 年卷期：v.40,no.4(February 20, 2007)
- ISSN：1520-5835
文摘
Composites that show visible light transmittance, UV absorption, and moderately high refractiveindex, based on poly(methyl methacrylate) (PMMA) and zinc oxide (zincite, ZnO) nanoparticles, were preparedin two steps. First, surface-modified ZnO nanoparticles with 22 nm average diameter were nucleated by controlledprecipitation via acid-catalyzed esterification of zinc acetate dihydrate with pentan-1-ol. The surface of growingcrystalline particles was modified with tert-butylphosphonic acid (tBuPO3H2) in situ by monolayer coverage.Particle size and graft density of -PO3H2 on the particle surface were controlled by the amount of surfactantapplied to the reaction solution. Second, the surface-modified particles were incorporated into PMMA by in-situbulk polymerization. Free radical polymerization was carried out in the presence of these particles using AIBNas initiator. Volume fraction (
) of the particles was varied from 0.10 to 7.76% (0.5 to 30 wt %). Although theparticles are homogeneously dispersed in monomer, segregation of the individual particles upon polymerizationwas observed. Optical constants of the films ca. 2.0 
m including absorption and scattering efficiencies, indicesof refraction, and dispersion constants were determined. The absorption coefficient at 350 nm increases linearlywith ZnO, obeying Beer's law at low particle contents. However, it levels off toward a value of about 5000 cm-1and shows a negative deviation at high concentrations because of aggregation of the individual particles. Waveguidepropagation loss coefficients of the composite films were examined by prism coupling. A steep increase of theloss 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 to1.507 ( = 7.76%) at 633 nm. The dispersion of refractive index was found to be consistent with Cauchy'sformula.
) of the particles was varied from 0.10 to 7.76% (0.5 to 30 wt %). Although theparticles are homogeneously dispersed in monomer, segregation of the individual particles upon polymerizationwas observed. Optical constants of the films ca. 2.0 m including absorption and scattering efficiencies, indicesof refraction, and dispersion constants were determined. The absorption coefficient at 350 nm increases linearlywith ZnO, obeying Beer's law at low particle contents. However, it levels off toward a value of about 5000 cm-1and shows a negative deviation at high concentrations because of aggregation of the individual particles. Waveguidepropagation loss coefficients of the composite films were examined by prism coupling. A steep increase of theloss 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 to1.507 ( = 7.76%) at 633 nm. The dispersion of refractive index was found to be consistent with Cauchy'sformula.