BRIEF DESCRIPTION OF THE DRAWINGS
FIG.—1 is a schematic diagram illustrating polymer modification with tethered polyhedral oligomeric silsesquioxane (POSS).
FIG. 2 is a schematic diagram illustrating copolymer with tethered polyhedral oligomeric silsesquioxane in accordance with one embodiment of the present invention.
FIG. 3 is a schematic table illustrating the reaction of copolymer in accordance with the present invention.
FIG. 4 is a schematic diagram illustrating comparison of characteristics for inorganic material with steric hindrance in combination of polymer in accordance with the present invention.
FIG. 5 is a schematic diagram illustrating comparison of characteristics for MEHPPV and POSS-PPV10-co-MEHPP.
FIG. 6 is a schematic diagram illustrating the luminescence of various polymers in accordance with the present invention.
FIG. 7 is a schematic diagram illustrating the relationships of voltage and luminescence for different copolymer applied to any luminescence devices in accordance with the present invention.
FIG. 8 is a schematic diagram illustrating the luminescence for different devices in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 is a schematic diagram illustrating copolymer with tethered polyhedral oligomeric silsesquioxane in accordance with one embodiment of the present invention. In one embodiment, each copolymer is provided with a main chain 10 and one or more side chains 12. The main chain 10 includes luminescent polymer, such as conjugated polymer. The side chain 12 includes inorganic material with steric hindrance, such as caged polyhedral oligomeric silsesquioxane (POSS). POSS dangling on a side chain may present much freedom degree and attract each another when compared with a conventional POSS on one end of main chain. However, any two neighboring copolymers may main a distance due to the existence of the POSS in steric hindrance configuration, which is called self-assembly structure.
Accordingly, special volume enlarges upon increasing free volume between copolymers, which may reduce the dielectric constant of a copolymer with POSS. Moreover, compared with one prior art having POSS at two ends of a main chain, the POSS according to the present invention is introduced into the side chain of one main chain to enhance mechanical property, thermal stability, heat resistance and luminescence efficiency. Such a side-chain-tethered POSS polymer may be applied to various polymer photoelectric devices, such as electroluminescence LED plate display, plate luminescence source, solar cell, plastic IC or sensor, and so on.
FIG. 3 is a schematic diagram illustrating the reaction of copolymer in accordance with the present invention. 2,5-Dimethylphenol (238 mg, 1.95 mmol) is stirred with K2CO3(4.58 mg, 33.18 mmol), KI (1.57 g, 9.48 mmol) in DMF (30 ml) and THF (15 ml) at room temperature for 1 hour. A small amount of Chlorobenzylcyclopentyl-POSS is added, and then the whole mixture is heated at 70 for 3 hours. The reaction mixture is then extracted, dried and purified to collect POSS-CH3. Next, a mixture of POSS-CH3 (600 mg, 0.510 mmol), NBS (198.6 mg, 1.02 mmol) and AlBN (8.0 mg) is heated under reflux, filtered and purified to collect POSS-CH2Br. Next, a conjugated copolymer, POSS-PPV(p-phenylenevinylene)-co-MEHPPV(poly(2-methoxy-5-[2-ethylhexyloxy]-1,4-phenylenevinylene) is synthesized by Gilch polymerization method.
FIG. 4 is a schematic table illustrating comparison of characteristics for inorganic material with steric hindrance in combination of polymer in accordance with the present invention. In the figure, raw MEHPPV is compared with copolymer with different amounts of POSS-PPV, absorbed or emitting wavelength is measured in THF. The data in parenthesis are the wavelengths of the shoulders and subpeaks. The quantum yield of photoluminescence (PL) are estimated relative to Rhodamine 6G (.FL=0.95). Shown in the figure, the quantum efficiency of POSS-PPV10-co-MEHPPV may reach to 0.87. Moreover, the full width at half maximum is very advantageously narrow (smaller than 100 nm) for the color purity.
FIG. 5 is a schematic diagram illustrating comparison of characteristics for MEHPPV and POSS-PPV10-co-MEHPPV in accordance with the present invention. For exemplary luminescence device with double structure of ITO/PEDOT (Poly-3,4-Ethylenedioxythiophene): PSS/polymer/Calcium/aluminum, after an applied device is annealed at 150 for 2 hours, the PPV with the side-chain-tethered POSS presents enhanced thermal characteristics. FIG. 6 is a schematic diagram illustrating the luminescence of various polymers in accordance with the present invention. Shown in the figure, the electroluminescence (EL) of a conjugated polymer MEHPPV emits reddish orange light (the wavelength 590 nm). After the incorporation of POSS, the full width at half maximum of a conjugated polymer reduced sharply about from 110 nm to 75 nm. The original color purity is improved due to the restrained excimer by the existence of POSS. FIG. 7 is a schematic diagram illustrating the relationships of voltage and luminescence for different copolymer applied to any luminescence devices in accordance with the present invention. It is observed that the luminescence efficiencies of the devices may be improved upon increasing incorporated side-chain-tethered POSS. For a conjugated polymer MEHPPV, the luminance thereof is only 473 cd/m2. On the other hand, one device with incorporation of 10% POSS-PPV presents the luminance of a device is about 2196 cd/m2 which is more than 4 times compared to general one. Furthermore, shown in FIG. 8, when incorporated with increasing side-chain-tethered POSS, the device may load more currents. For example, one device with 10% POSS-PPV copolymer, the loaded current presents two times values when compared with original MEHPPV.
Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that other modifications and variation can be made without departing the spirit and scope of the invention as hereafter claimed.
Patent Application
20080051512
