Quad-polymer precursor for producing carbon fiber, method for producing same and method for using same

Abstract

A quad-polymer composition includes monomers of (a) acrylonitrile, (a) vinylimidazole, (c) methyl acrylate and (d) either acrylic acid or itaconic acid. Such quad-polymer compositions may be used to form fibers (such as by melt spinning) that may then be annealed, stabilized, and/or carbonized to produce carbon fibers. The quad-polymer composition may be used for supercapacitors, lithium battery electrodes once carbonized, and as synthesized, it may be used for wound healing fibers, fabrics, coatings, and films, and anti-bacterial/anti-microbial fibers, fabrics, coatings and films. The carbon fibers formed from the quad-polymer composition may be used for the fiber composites for automobile, aerospace structures, marine structures, military equipment/parts, sporting goods, robotics, furniture, and electronic parts.

Claims

1. A quad-polymer composition comprising a chemical structure selected from the group consisting of: ##STR00015## wherein (i) X, Y, Z, and M are wt % of the quad-polymer composition, (ii) X+Y+Z+M=100%, and (iii) n is an integer number of repeating units of the chemical structure.

2. The quad-polymer composition of claim 1, wherein the quad-polymer composition has the chemical structure of: ##STR00016##

3. The quad-polymer composition of claim 2, wherein (a) X is in a range from 0.1 to 40.0 wt %; (b) Y is in a range from 50.0 to 99.0 wt %; (c) Z is in a range from 0.1 to 50.0 wt %; and (d) M is in a range from 0.1 to 40.0 wt %.

4. The quad-polymer composition of claim 2, wherein (a) X is in a range from 0.1 to 10.0 wt %; (b) Y is in a range from 60.0 to 95.0 wt %; (c) Z is in a range from 2.5 to 30.0 wt %; and (d) M is in a range from 0.1 to 10.0 wt %.

5. The quad-polymer composition of claim 2, wherein (a) X is in a range from 0.1 to 5.0 wt %; (b) Y is in a range from 70.0 to 92.5 wt %; (c) Z is in a range from 2.5 to 25.0 wt %; and (d) M is in a range from 0.1 to 5.0 wt %.

6. The quad-polymer composition of claim 1, wherein the quad-polymer composition has the chemical structure of: ##STR00017##

7. The quad-polymer composition of claim 6, wherein (a) X is in a range from 0.1 to 40.0 wt %; (b) Y is in a range from 50.0 to 99.0 wt %; (c) Z is in a range from 0.1 to 50.0 wt %; and (d) M is in a range from 0.1 to 40.0 wt %.

8. The quad-polymer composition of claim 6, wherein (a) X is in a range from 0.1 to 10.0 wt %; (b) Y is in a range from 60.0 to 95.0 wt %; (c) Z is in a range from 2.5 to 30.0 wt %; and (d) M is in a range from 0.1 to 10.0 wt %.

9. The quad-polymer composition of claim 6, wherein (a) X is in a range from 0.1 to 5.0 wt %; (b) Y is in a range from 70.0 to 92.5 wt %; (c) Z is in a range from 2.5 to 25.0 wt %; and (d) M is in a range from 0.1 to 5.0 wt %.

10. The quad-polymer composition of claim 1, wherein (a) the quad-polymer composition has a molecular weight ranging from 18 KDa to 200 KDa, and (b) the quad-polymer composition has a polydispersity index (PDI) ranging from 1.2 to 3.0.

11. A method of preparing a quad-polymer composition comprising synthesizing the quad-polymer composition from (a) acrylonitrile, (b) vinylimidazole, (c) methyl acrylate, and (d) an acid selected from the group consisting of acrylic acid and itaconic acid, wherein, (i) the quad-polymer has a chemical structure in which: (A) when the acid is the acrylic acid, the chemical structure is: ##STR00018## (B) when the acid is the itaconic acid, the chemical structure is: ##STR00019## (ii) X, Y, Z, and M are wt % of the quad-polymer composition, and (iii) X+Y+Z+M=100%, and (iv) n is an integer number of repeating units of the chemical structure.

12. The method of claim 11, wherein (a) wt % of the acrylonitrile, wt % of the vinylimidazole, wt % of the methyl acrylate, and wt % of the total acid with respect to a total wt % equals 100%; (b) the wt % of the acrylonitrile is in a range from 50.0 to 99.0 wt %; (c) the wt % of the vinylimidazole is in a range from 0.1 to 40.0 wt %; (d) the wt % of the methyl acrylate is in a range from 0.1 to 50.0 wt %; and (e) the wt % of the acid is in a range from 0.1 to 40.0 wt %.

13. The method of claim 12, wherein (a) the wt % of the acrylonitrile is in a range from 60.0 to 95.0 wt %; (b) the wt % of the vinylimidazole is in a range from 0.1 to 10.0 wt %; (c) the wt % of the methyl acrylate is in a range from 2.5 to 30.0 wt %; and (d) the wt % of the acid is in a range from 0.1 to 10.0 wt %.

14. The method of claim 12, wherein (a) the wt % of the acrylonitrile is in a range from 70.0 to 92.5 wt %; (b) the wt % of the vinylimidazole is in a range from 0.1 to 5.0 wt %; (c) the wt % of the methyl acrylate is in a range from 2.5 to 25.0 wt %; and (d) the wt % of the acid is in a range from 0.1 to 10.0 wt %.

15. A quad-polymer composition comprising a first monomer, a second monomer, a third monomer, and a fourth monomer, wherein (a) the first monomer is acrylonitrile at a wt % of Y in the quad-polymer composition; (b) the second monomer is selected from the group consisting of 1-vinylimidazole, 4-vinylimidazole, 2-vinylimidazole and 1-methyl-2-vinylimidazole, wherein the second monomer is at a wt % of X in the quad-polymer composition; (c) the third monomer is an acrylate at a wt % of Z in the quad-polymer composition, wherein the acrylate is selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, and tert-butyl acrylate; (d) the fourth monomer is an acid at a wt % of M in the quad-polymer composition, wherein the acid is selected from the group consisting of acrylic acid, itaconic acid, and methacrylic acid; and (e) the total of the Y wt % of the first monomer, the X wt % of the second monomer, the Z wt % of the third monomer, and the M wt % of the fourth monomer equals 100%.

16. The quad-polymer composition of claim 15, wherein (a) the second monomer is 1-vinylimidazole; (b) the third monomer is methyl acrylate; and (c) the fourth monomer is acrylic acid or itaconic acid.

17. A device or product comprising the quad-polymer composition of claim 1.

18. The quad-polymer composition of claim 1, wherein the quad-polymer composition is capable of being melt spun into a carbon fiber comprising the quad-polymer composition.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a synthesis scheme of an AN-VIM-MA-AA quad-polymer precursor by free radical polymerization.

(2) FIG. 2 shows an AN-VIM-MA-AA quad-polymer synthesis scheme, including a first range of ratios of monomers (by wt %) in the feed and resulting polymers.

(3) FIG. 3 shows the AN-VIM-MA-AA quad-polymer synthesis scheme, including a second range of ratios of monomers (by wt %) in the feed and resulting polymers.

(4) FIG. 4 shows the AN-VIM-MA-AA quad-polymer synthesis scheme, including a third range of ratios of monomers (by wt %) in the feed and resulting polymers.

(5) FIG. 5 is a graph showing the ATR-FTIR spectra of two AN-VIM-MA-AA quad-polymers synthesized using embodiments of the present invention.

(6) FIG. 6 is a graph showing the .sup.1H-NMR spectra of the two AN-VIM-MA-AA quad-polymers whose ATR-FTIR spectrum is shown in FIG. 5.

(7) FIG. 7 is a graph showing the GPC chromatogram of the two AN-VIM-MA-AA quad-polymers whose ATR-FTIR spectrum is shown in FIG. 5.

(8) FIG. 8 is a graph showing the DSC thermogram of the two AN-VIM-MA-AA quad-polymers whose ATR-FTIR spectrum is shown in FIG. 5.

(9) FIG. 9 is an image of a melt-extruded continuous fiber from an AN-VIM-MA-AA quad-polymer.

(10) FIG. 10 is an image of an as-spun fiber from an AN-VIM-MA-AA quad-polymer having a diameter of ˜68 mm.

(11) FIG. 11 is an image of an as-spun fiber from an AN-VIM-MA-AA quad-polymer having a diameter of ˜25 mm.

(12) FIG. 12 is an image of an as-spun fiber from an AN-VIM-MA-AA quad-polymer made by a stretching method, with the fiber having a diameter of 20 mm.

(13) FIGS. 13A-13F are diagrams of heating programs of stabilization for embodiments of the present invention.

(14) FIG. 14 is an image of a stabilized fiber made from an AN-VIM-MA-AA quad-polymer, with the fiber having a diameter of ˜132 mm.

(15) FIG. 15 is an image of stabilized multi fibers made from AN-VIM-MA-AA quad-polymer fibers where a tow of five fibers is stabilized together and none of the fibers fused together.

(16) FIGS. 16A-16E are diagrams of heating programs of carbonization for embodiments of the present invention.

(17) FIG. 17 is an image of a thermally stabilized fiber having a diameter of 147 μm.

(18) FIG. 18 is an optical image of a carbon fiber made from the AN-VIM-MA-AAquad-polymer.

(19) FIG. 19 is a graph showing the stress-strain curve of the carbon fiber shown in FIG. 18.

(20) FIG. 20 shows a synthesis scheme of an AN-VIM-MA-IA quad-polymer precursor by free radical polymerization.

(21) FIG. 21 shows the AN-VIM-MA-IA quad-polymer synthesis scheme, including a first range of ratios of monomers (by wt %) in the feed and resulting polymers.

BEST MODE

(22) The present invention provides a method for preparing a carbon fiber via the use of a four-component system of monomers. Each monomer has a specific purpose and use for the development of melt processable carbon fiber. The acrylonitrile (AN) is the main component that is required for the development of carbon fiber. It is a nitrile group that is cyclized to form the network of carbon fibers. The N-vinylimidazole (VIM) is the component that allows for the melt processability while keeping the carbon-to-nitrogen (C/N) ratios at the proper level for development of high strength fibers. While the third component methyl acrylate (MA) is also a melt processable monomer unit, the main purpose is for the lowering of costs which offsets the higher costs of N-vinylimidazole. Then the fourth components, acrylic acid (AA) or itaconic acid (IA), are used for the advancement of the initiation of stabilization in a thermal environment. The main purpose of the development of a quad-polymer system is for (1) the lowering of the developmental costs associated with the high price of the original copolymer, while also (2) enhancing the stabilization of the polymer fibers.

(23) AN-VIM-MA-AA Quad-Polymer Synthesis

(24) Yang '050 PCT Patent Application discloses and teaches various synthesis of AN-based copolymers, including the synthesis of acrylonitrile (AN) and N-vinylimidazole (VIM) to form a copolymer (See, e.g., FIG. 1 of Yang '050 PCT Patent Application). Although the polymerization of the present invention may be performed in a similar fashion, the monomers that are used are altered, as in the scheme shown in FIG. 1, which illustrates a scheme of the solution polymerization of AN, VIM, MA, and AA. Yang '050 PCT Patent Application is attached hereto at Appendix 1 and is hereby incorporated by reference in its entirety of all purposes.

(25) In an embodiment of the present invention, the free radical solution polymerization of AN, VIM, MA, and AA monomers was carried out in 250-2,000 mL flasks fitted with a thermocouple probe, a condenser, an addition funnel and a nitrogen inlet. The flask was charged with DMF and purged with nitrogen for 30 minutes. Then the monomers, AIBN, and chain transfer agent, 1-dodecanethiol were added drop wise into the flask over a period of 2-8 hours. The polymerization reactions were carried out at 70° C. with continuous stirring over-night. The polymer was precipitated in de-ionized water, filtered and washed with methanol and hexane to remove residual monomers and then dried in a vacuum oven for two days till constant weight was obtained.

(26) The co-monomers in the AN-VIM-MA-AA quad-polymer may be present in any suitable ratio in the quad-polymer. For example, if four monomers AN, VIM, MA, and AA are used, the resulting quad-polymer may have a range of weight ratios of AN:VIM:MA:AA, such that the total of the monomers adds up to 100% in wt %.

(27) In certain embodiments of the present invention, the amount of each monomer in the feed and product of a quad-polymer varies as shown in FIG. 2. Specifically, these are as follows.

(28) Feed ratios (wt %): AN+VIM+MA+AA=100%, where

(29) AN=50.0-99.0 wt %

(30) VIM=0.1-40.0 wt %

(31) MA=0.1-50.0 wt %

(32) AA=0.1-40.0 wt %

(33) and the product (AN-VIM-MA-AA polymer) has the following chemical formula

(34) ##STR00008##

(35) with polymer composition (wt %): X+Y+Z+M=100%, where

(36) X=0.1-40.0 wt %

(37) Y=50.0-99.0 wt %

(38) Z=0.1-50.0 wt %

(39) M=100−X−Y−Z %.

(40) In certain embodiments, more preferably, the amount of each monomer in the feed and product of a quad-polymer varies as shown in FIG. 3. Specifically, these are as follows:

(41) Feed ratios (wt %): AN+VIM+MA+AA=100%, where

(42) AN=60.0-95.0 wt %

(43) VIM=0.1-10.0 wt %

(44) MA=2.5-30.0 wt %

(45) AA=0.1-10.0 wt %

(46) and the product (AN-VIM-MA-AA polymer) has the following chemical formula

(47) ##STR00009##

(48) with polymer composition (wt %): X+Y+Z+M=100%, where

(49) X=0.1-10.0 wt %

(50) Y=60.0-95.0 wt %

(51) Z=2.5-30.0 wt %

(52) M=100−X−Y−Z %.

(53) In certain embodiments, most preferably, the amount of each monomer in the feed and product of a quad-polymer varies as shown in FIG. 4. Specifically, these are as follows.

(54) Feed ratios (wt %): AN+VIM+MA+AA=100%, where

(55) AN=70.0-92.5 wt %

(56) VIM=0.1-5.0 wt %

(57) MA=2.5-25.0 wt %

(58) AA=0.1-5.0 wt %

(59) and the product (AN-VIM-MA-AA polymer) has the following chemical formula

(60) ##STR00010##

(61) with polymer composition (wt %): X+Y+Z+M=100%, where

(62) X=0.1-5.0 wt %

(63) Y=70.0-92.5 wt %

(64) Z=2.5-25.0 wt %

(65) M=100−X−Y−Z %.

(66) For example, in an embodiment of the present invention (“Example A”), the free radical polymerization of 28.80 gm of a mixture of AN, VIM, MA and AA monomers (AN: 79.0 parts, VIM: 2.5 parts, MA: 16.0 parts and AA: 2.5 parts by weight) was carried out in a 500 mL flask fitted with a thermocouple probe, a condenser, an addition funnel, and a nitrogen inlet. The flask was charged with 33 gm of DMF and purged with nitrogen for 30 minutes. Then the monomers, DMF (33.6 gm), AIBN (0.123 gm), and chain transfer agent, 1-dodecanethiol (0.016 gm) were added drop wise into the flask over a period of 2 hours. The polymerization reactions were carried out at 70° C. with continuous stirring over-night. The polymers were precipitated in de-ionized water, filtered and washed with methanol and hexane to remove residual monomers and then dried in a vacuum oven for two days till constant weight was obtained. Polymer yield was in between 95 and 85%. This resulting product is referred to as “Example A” herein and in FIGS. 5 to 8.

(67) Further, for example, in another embodiment of the present invention (“Example B”), the free radical polymerization of 281.0 gm of a mixture of AN, VIM, MA and AA monomers (AN: 85.0 parts, VIM: 2.5 parts, MA: 10.0 parts and AA: 2.5 parts by weight) was carried out in a 2000 mL flask fitted with a thermocouple probe, a condenser, an addition funnel and a nitrogen inlet. The flask was charged with 330.0 gm of DMF and purged with nitrogen for 30 minutes. Then the monomers, DMF (336 gm), AIBN (1.232 gm) and chain transfer agent, 1-dodecanethiol (0.16 gm) were added drop wise into the flask over a period of 8 hours. The polymerization reactions were carried out at 70° C. with continuous stirring over-night. The polymers were precipitated in de-ionized water, filtered and washed with methanol and hexane to remove residual monomers and then dried in a vacuum oven for two days till constant weight was obtained. Polymer yield was in between 93 and 88%. This resulting product is referred to as “Example B” herein and in FIGS. 5 to 8.

(68) The success of polymerization was evaluated by ATR-FTIR spectroscopy and .sup.1H-NMR spectroscopy as shown in FIG. 5 and FIG. 6, respectively.

(69) FIG. 5 shows the ATR-FTIR spectrum 501 of Example A and the ATR-FTIR spectrum 502 of Example B. These spectra 501 and 502 show the polymerizations of Examples A and B were successful. The major peaks were identified and marked in FIG. 5, which are OH stretching 503 (3606 cm.sup.−1), CH.sub.2 stretching 504 (2930 cm.sup.−1), C≡N stretching 505 (2241 cm.sup.−1), C═O stretch 506 (1724 cm.sup.−1), CH.sub.2 band of backbone 507 (1442 cm.sup.−1), C—N ring stretching 508 (1226 cm.sup.−1), C—H ring in-phase bending 509 (1080 cm.sup.−1), and imidazole ring bending 510 (665 cm.sup.−1).

(70) FIG. 6 shows the .sup.1H-NMR spectrum 601 of Example A and the .sup.1H-NMR spectrum 602 of Example B. These spectra 601 and 602 show the polymerizations of Examples A and B were successful. Insert 603 is a magnified view of the spectra in dashed box 604. In the chemical formula, the major peaks were identified and marked in FIG. 6 (corresponding the following polymer), which is also shown in the insert 603.

(71) ##STR00011##

(72) The monomer ratios in the feed and the polymer were in accordance with the ratios set forth in FIG. 4 (for the most preferred compositions).

(73) Generally, higher molecular weight polymers will produce higher strength fibers. However, extremely high molecular weight polymers adversely may affect the ability of melt-processing because a high molecular weight polymer yields higher melt viscosity. When the viscosity is too high, the resulting compositions may be difficult to extrude.

(74) In embodiments of the present invention, the molecular weight of the quad-polymers ranged from 18 KDa-300 KDa with a polydispersity index (PDI) of 1.2-4.0. In certain embodiments of the present invention, the molecular weight of the quad-polymers ranged from 40 KDa-120 KDa with a PDI of 1.2-2.0.

(75) FIG. 7 shows the GPC chromatogram 701 of Example A and the GPC chromatogram 702 of Example B. The result of this GPC analysis is shown below in Table 1.

(76) TABLE-US-00001 TABLE 1 GPC analysis of polymer samples from Example A and Example B Example Mn, KDa Mw, KDa PDI A 71.4 95.5 1.3 B 67.0 95.1 1.4

(77) FIG. 8 shows the DSC thermogram 801 of Example A and the DSC thermogram 802 of Example B, with the DSC analysis of Example A and Example B having a glass transition temperature at −98° C. and −103° C., respectively, as shown in this figure.

(78) The polymer samples from both Example A and Example B showed excellent thermal stability, as evident from their high degradation temperature (−250° C.) evident from thermo-gravimetric analysis (TGA). High char yield (˜52%) for both Examples A and Example B were also observed from char yield analysis. The summary of the DSC, TGA, and char yield analysis are shown below in Table 2.

(79) TABLE-US-00002 TABLE 2 Summary of thermal analysis Example Te, ° C. Td, ° C. Char, % A 98 250 50 B 103 260 52

(80) Further, for example, in another embodiment of the present invention (Example C″), a quad-polymer precursor was prepared that demonstrated excellent extrude ability, thermal stabilization, and carbonization capability. Example C is an AN-VIM-MA-AA quad-polymer with a feed composition of AN:VIM:MA:AA=79:2.5:16:2.5 wt %. This new precursor polymer has low T.sub.g of 97° C. and may be extruded into thin fiber. One major advantage is its capability of thermal stabilization. Similar to the AN-VIM copolymer precursor (disclosed and taught in Yang 050 PCT Patent Application), this new quad-polymer precursor is thermally stabilizable so it does not require any UV treatment. The raw material cost for this quad-polymer precursor will be ˜1.45 $/lb which is ˜22% lower than the threshold value of 1.85 $/lb for the AN-VIM copolymer precursor. Mechanical testing results also showed excellent properties for these precursors. The carbonized fiber with 77 μm diameter showed a tensile strength (TS) of 894 MPa and Young's modulus (YM) of 220 GPa while the stabilized fiber showed a TS of 294 MPa and a modulus of 7004 MPa. The TSs of neat and annealed fibers were 109 MPa and 163 MPa, respectively. Also upon optimized extrusion condition, very thin fiber may be made. Such a fiber with 25 μm diameter showed high mechanical strength as TS of 369 MPa and YM of 7.4 GPa.

(81) Melt Spun Fibers

(82) As noted above, the thermal properties render the quad-polymers suitable to be melt-processable. For example, an AN-VIM-MA-AA quad-polymer precursor as described above was ground into coarse granules in a grinder. A Rosaland RH-7 capillary rheometer was used to extrude the fibers. In a typical trial, 11 g of copolymer was loaded in preheated rheometer in between 100 and 200° C. in atmospheric condition and left there to heat up for 10 minutes. Melted polymers passed through a die having a diameter within a range of 0.01-1.0 mm. A continuous fiber 901 was made by this method, where the fiber 901 is shown in FIG. 9 (with ruler 902 in FIG. 9 to provide scale). FIGS. 10 and 11 show as-spun fibers from and AN-VIM-MA-AA quad-polymer, which fibers have diameters of ˜68 mm and ˜25 mm, respectively. Also, for another method, the melted polymers were stretched under tension to get thinner fibers. FIG. 12 shows an as-spun fiber from AN-VIM-MA-AA quad-polymer made by a stretching method, which fiber has a diameter of diameters of 20 mm.

(83) Annealing and Stabilization

(84) Annealing or drawing is the step to align the polymer chains parallel to the fiber axis. This process is important to increase the fiber strength. Annealing and stabilization steps are done either together or separately.

(85) In heating program, HP1 (as shown in FIG. 13A), annealing and stabilization steps are done together and in HP2 (as shown in FIG. 13B), these are done separately. The fiber diameter is reduced up to 10-150% by the annealing stabilization process under applied tension.

(86) Stabilization is the step of cyclization of the acrylonitrile groups. Heating programs of the stabilization step are shown in FIGS. 13A to 13F.

(87) As shown in FIG. 13A, the first heating program, HP1, was set directly to 190° C. at a rate of 3° C. per minute and kept at that temperature for 180 minutes, then the temperature was raised to 240° C. at a rate of 1° C. per minute and kept at that temperature for another 180 minutes before cooled down to room temperature.

(88) As shown in FIG. 13B, in HP2, the fibers were heated to 130° C. for 48 hours before repeating the same steps performed in HP1. It has been found from the experimentation and from the results, that the heating program HP2 worked best for forming stabilized fibers. Other heating programs HP3-HP6 are shown in FIGS. 13C to 13F. In all heating programs HP1-HP6, the fibers stabilized were performed with added tension of a weight at the end of the fiber during heating.

(89) FIG. 14 shows an optical microscope photograph of a stabilized fiber made from an AN-VIM-MA-AA quad-polymer. The fiber had a diameter of ˜132 mm.

(90) Multi-Fiber Annealing and Stabilization

(91) In another embodiment of the present invention, the stabilization of multi-filament in a tow of fiber is carried out without any melting or fusing of the fiber. FIG. 15 showed the result of this multi-fiber stabilization process, namely stabilized multi fibers made from AN-VIM-MA-AA quad-polymer fibers, where a tow of five fibers stabilized together and none of the fibers were fused together.

(92) Such multi-fiber stabilization was a significant achievement. Previously, with the AN-VIM precursor (disclosed and taught in Yang 050 PCT Patent Application), this was not possible. However, with the quad-polymer precursors of the present invention, multi-fiber thermal stabilization has been successfully performed.

(93) Carbonization

(94) Thermally stabilized fibers may be used to make high strength carbon fiber by carbonization process under inert conditions. Both single precursor fiber and tow of the precursor fibers may be thermally stabilized and carbonized to yield carbon fibers.

(95) For example, a heating program of the carbonization step is shown in FIG. 16A (CP1). Carbonization is the last step in the formation of carbon fiber (which is carried out under inert condition), where the stabilized fiber is subjected to further heating. A typical heating program involves multiple steps (such as in CP1, which is shown in FIG. 16A). For instance, in the first step of CP1, the fiber is heated up to 150° C. at 1.5° C. per minute and held at that temperature for 10 minute, then the temperature is raised to 440° C. at a rate of 0.75° C. per minute, and held at that temperature for 60 minutes. The temperature is then raised to 600° C. at a rate of 2° C. per minute and kept at that temperature for 10 minutes before raised again to 900° C. at a rate of 2.5° C. per minute and held for 10 minutes. The carbonized fiber is then cooled down to room temperature.

(96) Alternative heating programs of the carbonization step are shown in FIGS. 16B to 16E (CP2-CP5, respectively).

(97) An AN-VIM-MA-AA quad-polymer was synthesized (using processes discussed and described above) and was extruded by using a single fiber extruder (rheometer), and the extruded fiber was then stabilized at 190° C. for 180 min followed by heating 240° C. at a step of 3° C. per minute, applying tension followed by a carbonization to produce a carbon fiber. The carbonization condition used was to heat the stabilized fiber in an oven under nitrogen atmosphere to reach the temperature at 900° C. in multiple steps (as shown in FIG. 16A (CP1)).

(98) A carbon fiber of approximately 6 cm or 2.25 inch long was successfully prepared by carbonization of the stabilized fiber made from an AN-VIM-MA-AA copolymer.

(99) Annealing, Stabilization, and Carbonization

(100) In an embodiment of the present invention, for example, for a melt-extruded fiber with diameter within 338 mm when annealed and stabilized by following heating program HP2 (FIG. 13B), a stabilized fiber with a diameter of 86 mm may be made (“Example D”). Table 3 shows the properties of as-spun fiber vs. stabilized fiber.

(101) TABLE-US-00003 TABLE 3 Melt spun fiber vs. stabilized fiber by following HP 2 Fiber TS YM Diameter Melt spun 109 MPa 3890 MPa 338 mm Annealed 163 MPa 6645 MPa 270 mm Thermally 235 MPa  183 GPa 147 mm Stabilized

(102) FIG. 17 shows the thermally stabilized fiber having a diameter of 147 μm for Example D.

(103) In an embodiment of the present invention, for example, for a melt-extruded fiber with a diameter within 168 mm when annealed and stabilized by following heating program HP1 (FIG. 13A) and carbonized by following carbonization heating program CP1 (FIG. 16A) (Example E″), a carbon fiber with a diameter of 77 mm was made. Table 4 shows the properties of as-spun fiber vs. stabilized and carbonized fiber.

(104) TABLE-US-00004 TABLE 4 Melt spun fiber vs. stabilized and carbonized fiber: stabilization by HP 1 and carbonization shown in FIG. 16A Fiber TS YM Diameter Melt spun 192 MPa 3092 MPa 168 mm Thermally 294 MPa 7004 MPa 136 mm Stabilized Carbonized 894 MPa  220 GPa  77 mm

(105) FIG. 18 shows the carbon fiber of Example E having a diameter of 77 μm. FIG. 19 shows the results of an Instron measurement test done with the carbon fiber of Example E. The fiber yielded a tensile strength (TS) of approximately 894 MPa and a Young's Modulus (YM) of 220 GPa.

(106) General Synthesis of AN-VIM-MA-IA Quad-Polymer

(107) As noted above, in embodiments of the present invention, the fourth components may be itaconic acid (IA) instead of acrylic acid (AA). The free radical solution polymerization of AN, VIM, MA and IA monomers was carried out in 250-2000 mL flasks fitted with a thermocouple probe, a condenser, an addition funnel and a nitrogen inlet. The flask was charged with DMF and purged with nitrogen for 30 minutes. Then, the monomers, AIBN and chain transfer agent, 1-dodecanethiol were added drop wise into the flask over a period of 2-8 hours. The polymerization reactions were carried out at 70° C. with continuous stirring over-night. The polymers were precipitated in de-ionized water, filtered and washed with methanol and hexane to remove residual monomers and then dried in a vacuum oven for two days till constant weight was obtained. FIG. 20 illustrates a scheme of the solution polymerization of AN, VIM, MA and IA.

(108) The monomers in the AN-VIM-MA-IA quad-polymer may be present in any suitable ratio in the quad-polymer. For example, if four monomers AN, VIM, MA and IA are used, the resulting quad-polymer may have a range of weight ratios of AN:VIM:MA:IA, such that the total amount of the monomers adds up to 100% in wt %. In certain embodiments of the present invention, the amount of each monomer in the feed and product of a quad-polymer varies from as shown in FIG. 21. Specifically, these are as follows:

(109) Feed ratios (wt %): AN+VIM+MA+IA=100%, where

(110) AN=50.0-99.0 wt %

(111) VIM=0.1-40.0 wt %

(112) MA=0.1-50.0 wt %

(113) IA=0.1-40.0 wt %

(114) and the product (AN-VIM-MA-IA polymer) has the following chemical formula

(115) ##STR00012##

(116) with polymer composition (wt %): X+Y+Z+M=100%, where

(117) X=0.1-40.0 wt %

(118) Y=50.0-99.0 wt %

(119) Z=0.1-50.0 wt %

(120) M=100−X−Y−Z %.

(121) In certain embodiments, more preferably, the amount of each monomer in the feed and product of a quad-polymer varies as follows:

(122) Feed ratios (wt %): AN+VIM+MA+IA=100%, where

(123) AN=60.0-95.0 wt %

(124) VIM=0.1-10.0 wt %

(125) MA=2.5-30.0 wt %

(126) IA=0.1-10.0 wt %,

(127) and the product (AN-VIM-MA-IA polymer) has the following chemical formula

(128) ##STR00013##

(129) with polymer composition (wt %): X+Y+Z+M=100%, where

(130) X=0.1-10.0 wt %

(131) Y=60.0-95.0 wt %

(132) Z=2.5-30.0 wt %

(133) M=100−X−Y−Z %.

(134) In certain embodiments, most preferably, the amount of each monomer in the feed and product of a quad-polymer varies as follows:

(135) Feed ratios (wt %): AN+VIM+MA+IA=100%, where

(136) AN=70.0-92.5 wt %

(137) VIM=0.1-5.0 wt %

(138) MA=2.5-25.0 wt %

(139) IA=0.1-5.0 wt %,

(140) and the product (AN-VIM-MA-IA polymer) has the following chemical formula

(141) ##STR00014##

(142) with polymer composition (wt %): X+Y+Z+M=100%, where

(143) X=0.1-5.0 wt %

(144) Y=70.0-92.5 wt %

(145) Z=2.5-25.0 wt %

(146) M=100−X−Y−Z %.

Additional/Alternative Embodiments

(147) In additional embodiments: the second monomer (N-vinylimidazole) may be, alternatively, 4-vinylimidazole, 2-vinylimidazole or 1-methyl-2-vinylimidazole; the third monomer (methyl acrylate) may be, alternatively, ethyl acrylate, butyl acrylate, methyl methacrylate, or tert-butyl acrylate; and the fourth monomer (acrylic acid or itaconic acid) may be, alternatively, methacrylic acid.