High-refractive-index polymer

[1] Such materials are required for anti-reflective coating and photonic devices such as light emitting diodes (LEDs) and image sensors.

The decomposition temperature changes depending on the substituent that is attached to the monomer used in the polymerization of the high refractive index polymer.

Highly refractive polyesters and polyimides are soluble in common organic solvents such as dichloromethane, methanol, hexanes, acetone and toluene.

This synthesis was first succeeded with polyimidothiethers, resulting in optically transparent polymers with high refractive index.

[2] Polycondensation reactions are also common to make high refractive index polymers, such as polyesters and polyphosphonates.

Sulfur-containing substituents including linear thioether and sulfone, cyclic thiophene, thiadiazole and thianthrene are the most commonly used groups for increasing refractive index of a polymer.

[11][12][13] Polymers with sulfur-rich thianthrene and tetrathiaanthracene moieties exhibit n values above 1.72, depending on the degree of molecular packing.

In 1992, Gaudiana et al. reported a series of polymethylacrylate compounds containing lateral brominated and iodinated carbazole rings.

[14] However, recent applications of halogen elements in microelectronics have been severely limited by the WEEE directive and RoHS legislation adopted by the European Union to reduce potential pollution of the environment.

[15] Phosphorus-containing groups, such as phosphonates and phosphazenes, often exhibit high molar refractivity and optical transmittance in the visible light region.

[3][16][17] Polyphosphonates have high refractive indices due to the phosphorus moiety even if they have chemical structures analogous to polycarbonates.

[10] In addition, polyphosphonates exhibit good thermal stability and optical transparency; they are also suitable for casting into plastic lenses.

[19] Organometallic components result in HRIPs with good film forming ability and relatively low optical dispersion.

Polyferrocenylsilanes[20] and polyferrocenes containing phosphorus spacers and phenyl side chains show unusually high n values (n=1.74 and n=1.72).

[21] They might be good candidates for all-polymer photonic devices because of their intermediate optical dispersion between organic polymers and inorganic glasses.

The factors affecting the refractive index of a high-n nanocomposite include the characteristics of the polymer matrix, nanoparticles and the hybrid technology between inorganic and organic components.

In order to increase optical transparency and reduce Rayleigh scattering of the nanocomposite, the diameter of the nanoparticle should be below 25 nm.

[28] A microlens array is a key component of optoelectronics, optical communications, CMOS image sensors and displays.