1、Introduction Optical plastics are widely used to produce lenses, viewfinders, windows, data storage media, light-diffusing elements etc. The field is dominated by commodity polymers such as poly (methyl methacrylate) (PMMA), polycarbonate (PC), and polystyrene (PS). However, no one material is ideal
2、 for all applications, leading to numerous efforts of produce optical polymers with customized properties. Cyclic Olefin Copolymers Advanced Materails & Producesses /March 2001COCs One important parameter for optical polymers is dispersion, the variance of refractive index with wavelength. Low dispe
3、rsion in the visible region is desirable for optical plastics because of reduced chromatic aberration. Dispersion is often characterized by the Abbe number, which is approximately inversely proportional to optical dispersion. The other factor for optical polymers is refractive index. Comparison of C
4、OCs and the diamond structure led us to consider whether polymers containing small polycyclic units of diamond (diamondoids) might possess valuable optical properties. It has an extraordinarily high refractive index (nd=2.387) One might hope to gain increased refractive index from the relatively hig
5、h carbon-to-hydrogen ratio (and therefore high density) of diamondoids, but avoid high optical dispersion that is associated with UV absorption bands from unsaturated moieties such as aromatic rings. Along the same lines, saturated polycyclic hydrocarbons such as the diamondoids have very low absorp
6、tion in the visible, obviously crucial for many optical applications.3 JANUARY 2003 VOL 299 SCIENCE www.sciencemag.orgExperimentalTable I. Synthesis and Properties of Adamantane-Containing Acrylic PolymersSynthesis and properties of Poly(1-Vinyladamantane) (pVa)Result and Discussion Thin films of th
7、e title polymers were prepared by spin-coating on silicon wafers. Refractive indexes as a function of wavelength for the polymer films were determined by variable angle spectroscopic ellipsometry (VASE).Abbe numbers阿贝数vd=（nd-1）/（nF-nC） Conclusions Soluble, colorless polymers containing diamondoid mo
8、ieties were successfully synthesized and characterized. Thin films of these polymers could be prepared easily by spin-coating; molding processes should be equally facile (except for pDm, where the Tg is above the polymers decomposition point). These materials exhibited significantly larger refractiv
9、e indexes than PMMA, but similarly low dispersion, an unusual combination among optical plastics. Poly(1-vinyl adamantane) possessed the highest refractive index among the polymers studied, but its molar mass was very low (essentially oligomers). Future experiments should be aimed at improving the c
10、ationic polymerization, or developing alternative polymerization methods for this monomer, with the goal of providing high molar mass. There are many polymers with high refractive index or high Abbe numbers, but very few with at least moderately high values of both simultaneously. Polymers containin
11、g diamondoids seem to fulfill these specifications. This combination of optical properties along with high transparency in the visible may make the title polymers valuable as specialty optical plastics despite their undoubtedly high cost. In particular, polymers based on diamantane seem promising because there may be a natural source of this polycyclic hydrocarbon; at the very least, its synthesis can be accomplished in three catalytic steps from an inexpensive starting material.Thats allThank you
