EPOXY RESIN OLIGOMER WITH SECOND ORDER NONLINEAR OPTICAL PROPERTIES, CHROMOPHORES, AND METHOD OF MANUFACTURING THE OLIGOMER-CONTAINING CROSSLINK LAYERED EPOXY/MMT COMPOSITE MATERIAL WITH SECOND ORDER NONLINEAR OPTICAL PROPERTIES

Abstract

Epoxy/MMT composite material and a crosslinking method for epoxy/MMT composite material with second order nonlinear optical properties are introduced. Chromophore-containing intercalating agents are applied to modify montmorillonites (MMTs) to form organoclays by an ion-exchange process, wherein the chrmophores are neatly packed on exfoliated epoxy/organoclay nanocomposites. As a result, optical nonlinearity, i.e. the Pockels effect is observed for the nanocomposites without resorting to the poling process due to self-assembly process. Furthermore, a series of epoxy/MMT nanocomposites comprising thermally reversible furan-norbornene Diels-Alder adducts are prepared to establish a crosslinking feature. Self-alignment behavior, electro-optical (EO) coefficient and temporal stability of the epoxy/MMT nanocomposites are improved by the Diels-Alders crosslinking.

Claims

1. An epoxy resin oligomer with second order nonlinear optical properties, having one of structural formulas as follows: ##STR00008## where n is 3˜10.

2. A method of manufacturing a crosslink layered epoxy/MMT composite material with second order nonlinear optical properties, comprising the steps of: (a) dissolving p-nitrosonitrobenzene and 4,4′,4″-triamino-phenylamine in acetic acid to form p-nitrosonitrobenzene solution and 4,4′,4″-triamino-phenylamine solution, respectively; (b) instilling p-nitrosonitrobenzene solution into 4,4′,4″-triamino-phenylamine solution, blending the solutions to allow a reaction to occur thereto, so as to obtain diamine chromophores bis(4-aminophenyl(4-(4-nitrophenyl)-diazenyl)phenyl)amine (DAC compound) as expressed by a structural formulas as follows: ##STR00009## (c) mixing diglycidyl ether of bisphenol A (DGEBA) expressed by structural formula ##STR00010## and DAC uniformly to allow a polymerization reaction to take place in presence of nitrogen gas, at a constant temperature range and for a specific period of time to obtain DGEBA-DAC oligomer; and (d) allowing ion exchange to occur between DGEBA-DAC oligomer and montmorillonite (MMT) such that the crosslink layered epoxy/MMT composite material exhibits second order nonlinear optical properties.

3. The method of claim 2, wherein the constant temperature range is 100˜150° C.

4. The method of claim 2, wherein the polymerization reaction lasts for 24˜48 hours.

5. A method of manufacturing a crosslink layered epoxy/MMT composite material with second order nonlinear optical properties, comprising the steps of: (a) mixing DO3, NaNO.sub.2 and water, followed by adding concentrated hydrochloric acid to the aqueous mixture; (b) adding ice water to the solution formed in step (a) to allow a reaction to occur in an ice bath, thereby forming a diazonium salt mixture solution; (c) adding the diazonium salt mixture solution formed in step (b) to 1,3-phenylenediamine solution, followed by blending them to allow a reaction to occur thereto; (d) mixing sodium hydroxide aqueous solution and the solution formed in step (c) to obtain diamine chromophores 2,4-diamino-4′-(4-nitrophenyl-diazenyl)-azobenzene (DNDA compound) as expressed by a structural formulas as follows: ##STR00011## (e) mixing diglycidyl ether of bisphenol A (DGEBA) expressed by structural formula ##STR00012## and DNDA uniformly to allow a polymerization reaction to take place in presence of nitrogen gas, at a constant temperature range and for a specific period of time to obtain DGEBA-DNDA oligomer; and (f) allowing ion exchange to occur between DGEBA-DNDA oligomer and montmorillonite (MMT) such that the crosslink layered epoxy/MMT composite material exhibits second order nonlinear optical properties.

6. The method of claim 5, wherein the constant temperature range is 100˜150° C.

7. The method of claim 5, wherein the polymerization reaction lasts for 24˜48 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a schematic view of synthesis of second order nonlinear epoxy resin oligomer according to the present invention;

[0017] FIG. 2 is a graph of IR variations of DACP polymerization group according to the present invention;

[0018] FIG. 3 is a graph of molecular weight of second order nonlinear optical oligomer according to the present invention;

[0019] FIG. 4 is a UV-Vis spectrogram of second order nonlinear optical material oligomer according to the present invention;

[0020] FIG. 5 is MMT exfoliation XRD spectrogram according to the present invention;

[0021] FIG. 6 is a graph of Diels-Alder crosslinking reaction temperature changes observed by DSC according to the present invention; and

[0022] FIG. 7 is a graph of pyrolysis temperature changes observed by TGA before and after Diels-Alder crosslinking according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The manufacturing process of the present invention is illustrated with preferred embodiments. Manufacturing criteria and results of the present invention are illustrated with comparisons.

Embodiment 1

[0024] Step (a): synthesis of epoxy resin oligomer with second order nonlinear optical properties dissolving 1.22 g (8 mmole) of p-nitrosonitrobenzene and 4.07 g (14 mmole) of 4,4′,4″-triamino-phenylamine in an appropriate amount of acetic acid, instilling p-nitrosonitrobenzene solution slowly into 4,4′,4″-triaminophenylamine solution, blending them so that they react for 12 hours, neutralizing it with acetic acid sodium saturated solution to pH 6 such that purple solid precipitate is produced, performing solid-liquid separation by suction filtration, and rinsing the filter disk with a large amount of deionized water in several instances to obtain a purple solid mixture, wherein the collected solid mixture is purified by column chromatography to extract a product therefrom, wherein an eluent of n-hexane:ethyl acetate is of a ratio 1:3, so as to produce DAC, which is a bright green solid, and the aforesaid chemical reaction is expressed by the structural formulas as follows:

##STR00003##

mixing 2 g (6 mmol) of DGEBA and 2 g (6 mmol) of DAC uniformly to allow polymerization to take place at 150° C. for 40 hours, and then instilling the mixture, drop by drop, into 50 mL of CH.sub.3OH and blending it to produce DGEBA-DAC oligomer (DACP). The aforesaid chemical reaction is monitored with FTIR. The completion of the aforesaid chemical reaction is confirmed by the disappearance of the absorption peak of the characteristics of the epoxy group with a wave number of 913 cm.sup.−1. The aforesaid chemical reaction is expressed by the structural formulas as follows:

##STR00004##

where n is 3˜10.

[0025] Step (b): modifying montmorillonite (MMT) with DGEBA-DAC oligomer allowing DGEBA (1.6 g, 4.7 mmol) and DAC(2g, 4.7 mmol) to undergo polymerization at 150° C., wherein the polymerization temperature is determined by DSC. Polymer crosslinking begins to take place as soon as the temperature increases to above 150° C., thereby precluding dissolution. Hence, when the temperature is below 150° C., DGEBA and primary amine react for 24 hours. The aforesaid chemical reaction is monitored with FTIR. The completion of the aforesaid chemical reaction is confirmed by the disappearance of the absorption peak of the characteristics of the epoxy group with a wave number of 913 cm.sup.−1. The resultant oligomer (abbreviated as DCAP, Mn=5000˜14000 g/mol) can be directly dissolved in a solvent (DMAc) to undergo ion exchange with MMT (1.20 mequiv/g for Na.sup.+ MMT) by amine titration and acidification of oligomers. The second order nonlinear optical characteristics of the exfoliated oligomer MMT composite material are measurable. For details, see Macromol. Rapid Commun., 2008, 29,587-592.; Polym. Adv. Technol., 2009, 20, 493-500.; ACS Applied Materials & Interfaces, 2009, 1, 2371-2381, Polym. Chem., 2013, 4, 2747-2759.

[0026] Step (c): crosslinking and solidifying DGEBA-DAC The nano-composite material (DACPMMT for short), which is produced by modifying MMT with oligomers and exhibits second order central asymmetry, is uniformly dispersed in the solvent DMAc. Then, 0.25 g of 2-Furoyl chloride is introduced into 1.96 g of DACPMMT to react at room temperature for 24 hours so that the product DACPMMT-F is obtained by extraction. The aforesaid steps are repeated. Afterward, 0.31 g of 5-Norbornene-2-carbonyl chloride is added to 1.96 g of DACPMMT to react at room temperature for 24 hours so that the product DACPMMT-N is obtained by extraction. Finally, DACPMMT-F and DACPMMT-N which are equal in equivalent weight react at an appropriate temperature determined by DSC. Eventually, the reaction temperature of the Diels-Alder reaction is set to 237° C. The Diels-Alder reaction enables the modified DACPMMT to form a reticular crosslinking structure characterized by crosslinking solidification and second order central asymmetry.

##STR00005##

Embodiment 2

[0027] Step (a): synthesis of epoxy resin oligomer with second order nonlinear optical properties mixing C.sub.12H.sub.10N.sub.4O.sub.2 (Disperse Orange 3, DO3) (1.33 g, 5.5 mmole), NaNO.sub.2 (0.38g, 5.5 mmole) and 10 ml of water, placing the mixture in a 50 ml flask immersed in an ice bath, introducing 1.5 ml of concentrated hydrochloric acid (37%) and 20 ml of ice water into the mixture solution to react for 30 minutes in the ice bath so as to produce a diazonium salt mixture solution, dissolving 1,3-phenylenediamine (0.60 g, 5.5 mmole) in 20 ml of distilled water and 3 ml of concentrated hydrochloric acid (37%) and placing the solution in another 50 ml flask, adding the diazonium salt solution into the flask slowly and blending the solution therein for 1 hour approximately to finalize the chemical reaction. A sodium hydroxide aqueous solution is prepared and used to neutralize the aforesaid solution such that a dark brown solid precipitate is formed. Afterward, solid-liquid separation is performed by filter funnel-based filtration, and then the filter disk is rinsed with a large amount of distilled water until the filtrate attain neutrality (pH 6˜7), wherein an eluent of n-hexane:ethyl acetate is of a ratio 1:3, so as to produce chromophore DNDA. The chemical reaction is expressed by the structural formulas as follows:

##STR00006##

wherein C.sub.12H.sub.10N.sub.4O.sub.2 (Disperse Orange 3, DO3) has a molecular weight of 242.23 g/mol. mixing 2 g (6 mmol) of DGEBA and 2 g (6 mmol) of DNDA uniformly, allowing the mixture to undergo polymerization at 150° C. for 40 hours, instilling 50 mL of CH.sub.3OH into the mixture, and blending the mixture to obtain DGEBA-DNDA oligomer (DNDAP):

##STR00007##

where n is 3˜10. The aforesaid chemical reaction is monitored with FTIR. The completion of the aforesaid chemical reaction is confirmed by the disappearance of the absorption peak of the characteristics of the epoxy group with a wave number of 913 cm.sup.−1.

[0028] Step (b): modifying MMT with DGEBA-DNDA oligomer DGEBA (1.6 g, 4.7 mmol) and DNDA (2 g, 4.7 mmol) undergo polymerization at 150° C., wherein the polymerization temperature is determined by DSC. Polymer crosslinking begins to take place as soon as the temperature increases to above 150° C., thereby precluding dissolution. Hence, when the temperature is below 150° C., DGEBA and primary amine react for 24 hours. The aforesaid chemical reaction is monitored with FTIR. The completion of the aforesaid chemical reaction is confirmed by the disappearance of the absorption peak of the characteristics of the epoxy group with a wave number of 913 cm.sup.−1. The resultant oligomer (abbreviated as DNDAP, Mn=5000˜14000 g/mol) can be directly dissolved in a solvent (DMAc) to undergo ion exchange with MMT (1.20 mequiv/g for Na.sup.+ MMT) by amine titration and acidification of oligomers. The second order nonlinear optical characteristics of the exfoliated oligomer MMT composite material are measurable. For details, see Macromol. Rapid Commun., 2008, 29,587-592.; Polym. Adv. Technol., 2009, 20, 493-500.; ACS Applied Materials & Interfaces, 2009, 1, 2371-2381, Polym. Chem., 2013, 4, 2747-2759.

[0029] Step (c): crosslinking solidifying DGEBA-DNDA The nano-composite material (DNDAPMMT for short), which is produced by modifying MMT with oligomers and exhibits second order central asymmetry, is uniformly dispersed in the solvent DMAc. Then, 0.25 g of 2-Furoyl chloride is introduced into 1.96 g of DNDAPMMT to react at room temperature for 24 hours so that the product DNDAPMMT-F is obtained by extraction. The aforesaid steps repeat, and then 0.31 g of 5-Norbornene-2-carbonyl chloride is added to 1.96 g of DNDAPMMTMMT to react at room temperature for 24 hours so that the product DNDAPMMT-N is obtained by extraction. Finally, DNDAPMMT-F and DNDAPMMT-N which are equal in equivalent weight react at an appropriate temperature determined by DSC. Eventually, the reaction temperature of the Diels-Alder reaction is set to 237° C. The Diels-Alder reaction enables the modified DNDAPMMT to form a reticular crosslinking structure characterized by crosslinking solidification and second order central asymmetry.

[0030] Referring to FIG. 1, DGEBA and DAC undergo polymerization at 150° C., wherein the polymerization temperature is determined by DSC. Polymer crosslinking begins to take place as soon as the temperature increases to above 150° C., thereby precluding dissolution. Hence, when the temperature is below 150° C., DGEBA and primary amine react for 24 hours. The aforesaid chemical reaction is monitored with FTIR as shown in FIG. 2. The completion of the aforesaid chemical reaction is confirmed by the disappearance of the absorption peak of the characteristics of the epoxy group with a wave number of 913cm.sup.−1. The resultant oligomer (abbreviated as DCAP) whose average molecular weight is around 8000 as indicated by GPC analysis shown in FIG. 3. DACP is soluble in solvents, such as THF, DMAc, to undergo ion exchange with MMT by amine titration and acidification of oligomers so that MMT attains exfoliation quickly and easily. The exfoliated oligomer MMT composite material undergo XRD, TEM, thermal analysis and optoelectronic property test and thereby the composite material is found to exhibit a second order nonlinear optical properties r.sub.33 coefficient of 8.0.

[0031] With positive charges being carried between the MMT layers, it is necessary to acidify polymers in order for cation exchange to occur, thereby necessitating the second order nonlinear optical oligomer intercalation step shown in FIG. 2 so that polymers which end up between the layers can further exfoliate MMT. The IR spectrogram shows the changes which occur to the epoxy group before and after polymerization, wherein the absorption of intercalated MMT leads to the disappearance of DACP IR characteristic peak. Referring to FIG. 4, the UV-Vis spectrogram shows that 547 cm.sup.−1DAC characteristic absorption peak still features slight red displacement. Hence, the UV-Vis spectrogram of FIG. 4 and the MMT exfoliation XRD spectrogram of FIG. 5 together prove that crosslink layered epoxy/MMT composite material with second order nonlinear optical properties not only separates the layers of MMT but also retains the initial second order nonlinear optical chromophores, as substantiated by the measurement of the second order nonlinear optical characteristics shown in Table 1.

[0032] The exfoliated epoxy/MMT composite material with second order nonlinear optical properties is modified and grafted to the furan functioning as the diene and the norbornene functioning as the dienophile during the Diels-Alder reaction. The DSC of FIG. 6 shows a Diels-Alder reaction exothermic peak which is otherwise initially absent from DACP and thereby confirms the occurrence of the crosslinking reaction. Upon completion of crosslinking, the central asymmetry of the second order nonlinear optical material is fixed so that a second order nonlinear optical properties r33 coefficient of 2.1 of the optical material can be detected even at 120° C. FIG. 7 is a graph of pyrolysis temperature changes in DACP before crosslinking and DAC after crosslinking, showing that 5 wt % thermogravimetric loss temperature increases from 220° C. of DACPMMT to 310° C. of DACPMMT-NF so that an increase in the pyrolytic temperature improves the material operating range.