跳至主要内容

Elucidation of Acceleration Mechanisms by a Photosensitive Onium Salt for Nitroxide-Mediated Photocontrolled/Living Radical Polymerization

Read full paper at:
http://www.scirp.org/journal/PaperInformation.aspx?PaperID=48731#.VKNvHMnQrzE

Author(s)  
The acceleration mechanisms by a photosensitive onium salt for the nitroxide-mediated photocontrolled/living radical polymerization (photo-NMP) were determined. The photo-NMP of methyl methacrylate was performed by irradiation at room temperature using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator and (2RS, 2’RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) as the initiator. The polymerization was accelerated in the presence of (4-tertbutylphenyl)diphenylsulfonium triflate (tBuS) to produce a polymer with a molecular weight distribution as narrow as the polymerization in its absence. (±)-Camphor-10-sulfonic acid or 2-fluoro-1-methylpyridinium p-toluenesulfonate had no effect on the polymerization speed, suggesting that tBuS did not serve as the photo-acid generator for the photo-NMP. It was found that the acceleration of the polymerization was based on the electron transfer from MTEMPO into tBuS in the excited state to temporarily generate a free radical propagating chain end and an oxoaminium salt (OAS), the one-electron oxidant of MTEMPO. This electron transfer mechanism was verified on the basis of the fact that the photo-NMP in the presence of tBuS was still accelerated by triphenylamine, the electron transfer inhibitor, to partly produce a polymer with an uncontrolled molecular weight. The formation of an uncontrolled molecular weight polymer indicated the generation of a free radical propagating chain end due to the deactivation of the OAS by the triphenylamine. It was deduced that tBuS served as the electron acceptor from MTEMPO in the excited state to temporarily produce a free radical propagating chain end along with OAS, resulting in the acceleration of the polymerization.
Cite this paper
Yoshida, E. (2014) Elucidation of Acceleration Mechanisms by a Photosensitive Onium Salt for Nitroxide-Mediated Photocontrolled/Living Radical Polymerization. Open Journal of Polymer Chemistry, 4, 47-55. doi: 10.4236/ojpchem.2014.43006. 
 

[1] Liu, Y., Klep, V. and Luzinov, I. (2006) To Patterned Binary Polymer Brushes via Capillary Force Lithography and Surface-Initiated Polymerization. Journal of American Chemical Society, 128, 8106-8107.
http://dx.doi.org/10.1021/ja061646f
[2] Zhou, F., Zheng, Z., Yu, B., Liu, W. and Huck, W.T.S. (2006) Multicomponent Polymer Brushes. Journal of American Chemical Society, 128, 16253-16258. http://dx.doi.org/10.1021/ja0654377
[3] Scales, C.W., Huang, F., Li, N., Vasilieva, Y.A., Ray, J., Convertine, A.J. and McCormick, C.L. (2006) Corona-Stabi-lized Interpolyelectrolyte Complexes of SiRNA with Nonimmunogenic, Hydrophilic/Cationic Block Copolymers Prepared by Aqueous RAFT Polymerization. Macromolecules, 39, 6871-6881.
http://dx.doi.org/10.1021/ma061453c
[4] Giacomelli, C., Schmidt, V. and Borsali, R. (2007) Nanocontainers Formed by Self-Assembly of Poly(Ethylene Oxide)-b-Poly(Glycerol Monomethacrylate)—Drug Conjugates. Macromolecules, 40, 2148-2157.
http://dx.doi.org/10.1021/ma062562u
[5] Ting, S.R.S., Min, E., Escalé, P., Save, M., Billon, L. and Stenzel, M.H. (2009) Lectin Recognizable Biomaterials Synthesized via Nitroxide-Mediated Polymerization of a Methacryloyl Galactose Monomer. Macromolecules, 42, 9422-9434. http://dx.doi.org/10.1021/ma9019015
[6] Zhang, F., Shi, Z.L., Chua, P.H., Kang, E.T. and Neoh, K.G. (2007) Functionalization of Titanium Surfaces via Controlled Living Radical Polymerization:? From Antibacterial Surface to Surface for Osteoblast Adhesion. Industrial and Engineering Chemistry Research, 46, 9077-9086.
http://dx.doi.org/10.1021/ie070795j?
[7] Werne, T.A., Germack, D.S., Hagberg, E.C., Sheares, V.V., Hawker, C.J. and Carter, K.R. (2003) A Versatile Method for Tuning the Chemistry and Size of Nanoscopic Features by Living Free Radical Polymerization. Journal of American Chemical Society, 125, 3831-3838.
http://dx.doi.org/10.1021/ja028866n
[8] Teare, D.O.H., Schofield, W.C.E., Garrod, R.P. and Badyal, J.P.S. (2005) Rapid Polymer Brush Growth by TEMPO-Mediated Controlled Free-Radical Polymerization from Swollen Plasma Deposited Poly(maleic anhydride) Initiator Surfaces. Langmuir, 21, 10818-10824. http://dx.doi.org/10.1021/la051566+
[9] Saleh, N., Phenrat, T., Sirk, K., Dufour, B., Ok, J., Sarbu, T., Matyjaszewski, K., Tilton, R.D. and Lowry, G.V. (2005) Adsorbed Triblock Copolymers Deliver Reactive Iron Nanoparticles to the Oil/Water Interface. Nano Letters, 5, 2489-2494. http://dx.doi.org/10.1021/nl0518268
[10] Pyun, J. and Matyjaszewski, K. (2001) Synthesis of Nanocomposite Organic/Inorganic Hybrid Materials Using Controlled/“Living” Radical Polymerization. Chemistry of Materials, 13, 3436-3448.
http://dx.doi.org/10.1021/cm011065j
[11] Andruzzi, L., Hexemer, A., Li, X., Ober, C.K., Kramer, E.J., Galli, G., Chiellini, E. and Fischer, D.A. (2004) Control of Surface Properties Using Fluorinated Polymer Brushes Produced by Surface-Initiated Controlled Radical Polymerization. Langmuir, 24, 10498-10506. http://dx.doi.org/10.1021/la049264f
[12] Idota, N., Nagase, K., Tanaka, K., Okano, T. and Annaka, M. (2010) Stereoregulation of Thermoresponsive Polymer Brushes by Surface-Initiated Living Radical Polymerization and the Effect of Tacticity on Surface Wettability. Langmuir, 26, 17781-17784. http://dx.doi.org/10.1021/la1024229
[13] Matyjaszewski, K. and Xia, J. (2001) Atom Transfer Radical Polymerization. Chemical Reviews, 101, 2921-2990.
http://dx.doi.org/10.1021/cr940534g
[14] Kamigaito, M., Ando, T. and Sawamoto, M. (2001) Metal-Catalyzed Living Radical Polymerization. Chemical Reviews, 101, 3689-3746. http://dx.doi.org/10.1021/cr9901182
[15] Moad, G., Rizzardo, E. and Thang, S.H. (2008) Toward Living Radical Polymerization. Accounts of Chemical Research, 41, 1133-1142. http://dx.doi.org/10.1021/ar800075n
[16] Yamago, S. (2009) Precision Polymer Synthesis by Degenerative Transfer Controlled/Living Radical Polymerization Using Organotellurium, Organostibine, and Organobismuthine Chain-Transfer Agents. Chemical Reviews, 109, 5051-5068. http://dx.doi.org/10.1021/cr9001269
[17] Hawker, C.J., Bosman, A.W. and Harth, E. (2001) New Polymer Synthesis by Nitroxide Mediated Living Radical Polymerizations. Chemical Reviews, 101, 3661-3688. http://dx.doi.org/10.1021/cr990119u
[18] Otsu, T. (2000) Iniferter Concept and Living Radical Polymerization. Journal Polymer Science, Part A, Polymer Chemistry, 38, 2121-2136.
http://dx.doi.org/10.1002/(SICI)1099-0518(20000615)38:12<2121::AID-POLA10>3.0.CO;2-X
[19] Tatemoto, M., Yutani, Y. and Fujiwara, K. (1988) Novel Iodine-Containing Compound, Preparation Thereof and Block Copolymer Comprising the Same. European Patent 272698 A2.
[20] David, G., Boyer, C., Tonnar, J., Ameduri, B., Lacroix-Desmazes, P. and Boutevin, B. (2006) Use of Iodocompounds in Radical Polymerization. Chemical Reviews, 106, 3936-3962.
http://dx.doi.org/10.1021/cr0509612
[21] Yamago, S., Ukai, Y., Matsumoto, A. and Nakamura, Y. (2009) Organotellurium-Mediated Controlled/Living Radical Polymerization Initiated by Direct C-Te Bond Photolysis. Journal of American Chemical Society, 131, 2100-2101.
http://dx.doi.org/10.1021/ja8099689
[22] Tasdelen, M.A., Uygun, M. and Yagci, Y. (2011) Photoinduced Controlled Radical Polymerization. Macromolecular Rapid Communications, 32, 58-62. http://dx.doi.org/10.1002/marc.201000351
[23] Mosnácek, J. and Ilcíková, M. (2012) Photochemically Mediated Atom Transfer Radical Polymerization of Methyl Methacrylate Using ppm Amounts of Catalyst. Macromolecules, 45, 5859-5865.
[24] Koumura, K., Satoh, K. and Kamigaito, M. (2008) Manganese-Based Controlled/Living Radical Polymerization of Vinyl Acetate, Methyl Acrylate, and Styrene: Highly Active, Versatile, and Photoresponsive Systems. Macromolecules, 41, 7359-7367. http://dx.doi.org/10.1021/ma801151s
[25] Jiang, W., Lu, L. and Cai, Y. (2007) Highly Efficient and Well-Controlled Ambient Temperature RAFT Polymerization under Solar Radiation. Macromolecular Rapid Communications, 28, 725-728.
[26] Otsu, T. and Kuriyama, A. (1984) Living Monoand Biradical Polymerizations in Homogeneous System Synthesis of AB and ABA Type Block Copolymers. Polymer Bulletin, 11, 135-142.
http://dx.doi.org/10.1007/BF00258020
[27] Doi, T., Matsumoto, A. and Otsu, T. (1994) Elucidation of Mechanism for Living Radical Polymerization of Styrene with N,N-Diethyldithiocarbamate Derivatives as Iniferters by the Use of Spin Trapping Technique. Journal of Polymer Science, Part A: Polymer Chemistry, 32, 2241-2249.
http://dx.doi.org/10.1002/pola.1994.080321205
[28] Guillaneuf, Y., Bertin, D., Gigmes, D., Versace, D., Lalevee, J. and Fouassier, J. (2010) Toward Nitroxide-Mediated Photopolymerization. Macromolecules, 43, 2204-2212. http://dx.doi.org/10.1021/ma902774s
[29] Guillaneuf, Y., Versace, D., Bertin, D., Lalevee, J., Gigmes, D. and Fouassier, J. (2010) Importance of the Position of the Chromophore Group on the Dissociation Process of Light Sensitive Alkoxyamines. Macromolecular Rapid Communications, 31, 1909-1913. http://dx.doi.org/10.1002/marc.201000316
[30] Versace, D., Lalevee, J., Fouassier, J., Guillaneuf, Y., Bertin, D. and Gigmes, D. (2010) Photodissociation Rate Constants of New Light Sensitive Alkoxyamines. Macromolecular Rapid Communications, 31, 1383-1388.
http://dx.doi.org/10.1002/marc.201000144
[31] Versace, D., Lalevee, J., Fouassier, J., Gigmes, D., Guillaneuf, Y. and Bertin, D. (2010) Photosensitized Alkoxyamines as Bicomponent Radical Photoinitiators. Journal of Polymer Science, Part A: Polymer Chemistry, 48, 2910-2915.
http://dx.doi.org/10.1002/pola.24071
[32] Hu, S., Malpert, J.H., Yang, X. and Neckers, D.C. (2000) Exploring Chromophore Tethered Aminoethers as Potential Photoinitiators for Controlled Radical Polymerization. Polymer, 41, 445-452.
http://dx.doi.org/10.1016/S0032-3861(99)00188-3
[33] Goto, A., Scaiano, J.C. and Maretti, L. (2007) Photolysis of an Alkoxyamine Using Intramolecular Energy Transfer from a Quinoline Antenna—Towards Photo-Induced Living Radical Polymerization. Photochemical & Photobiological Sciences, 6, 833-835. http://dx.doi.org/10.1039/b705671k
[34] Yoshida, E. (2008) Photo-Living Radical Polymerization of Methyl Methacrylate by a Nitroxide Mediator. Colloid and Polymer Science, 286, 1663-1666. http://dx.doi.org/10.1007/s00396-008-1930-y
[35] Yoshida, E. (2009) Photo-Living Radical Polymerization of Methyl Methacrylate by 2,2,6,6-Tetra-Methylpiperidine-1Oxyl in the Presence of a Photo-Acid Generator. Colloid and Polymer Science, 287, 767-772.
http://dx.doi.org/10.1007/s00396-009-2023-2
[36] Yoshida, E. (2010) Effect of Azoinitiators on Nitroxide-Mediated Photo-Living Radical Polymerization of Methyl Methacrylate. Colloid and Polymer Science, 288, 341-345. http://dx.doi.org/10.1007/s00396-009-2163-4
[37] Yoshida, E. (2010) Stability of Growing Polymer Chain Ends for Nitroxide-Mediated Photo-Living Radical Polymerization. Colloid and Polymer Science, 288, 1027-1030. http://dx.doi.org/10.1007/s00396-010-2230-x
[38] Yoshida, E. (2010) Nitroxide-Mediated Photo-Living Radical Polymerization of Methyl Methacrylate in Solution. Colloid and Polymer Science, 288, 1639-1643. http://dx.doi.org/10.1007/s00396-010-2287-6
[39] Yoshida, E. (2012) Photo-Controlled/Living Radical Polymerization Mediated by 2,2,6,6-Tetramethylpiperidine-1Oxyl in Inert Atmospheres. Colloid and Polymer Science, 290, 1087-1091.
http://dx.doi.org/10.1007/s00396-012-2668-0
[40] Yoshida, E. (2012) Effects of Illuminance and Heat Rays on Photo-Controlled/Living Radical Polymerization Mediated by 4-Methoxy-2,2,6,6-Tetramethylpiperidine-1-Oxyl. International Scholarly Research Network (ISRN) Polymer Science, 2012, Article ID: 102186.
[41] Yoshida, E. (2012) Photo-Controlled/Living Radical Polymerization of tert-Butyl Methacrylate in the Presence of a Photo-Acid Generator Using a Nitroxide Mediator. Colloid and Polymer Science, 290, 661-665.
http://dx.doi.org/10.1007/s00396-012-2605-2
[42] Yoshida, E. (2012) Photo-Controlled/Living Radical Polymerization of 2-(Dimethylamino)ethyl Methacrylate Using 4-Methoxy-2,2,6,6-Tetramethylpiperidine-1-Oxyl as a Mediator. Colloid and Polymer Science, 290, 965-969.
http://dx.doi.org/10.1007/s00396-012-2641-y
[43] Yoshida, E. (2010) Nitroxide-Mediated Photo-Living Radical Polymerization of Vinyl Acetate. Colloid and Polymer Science, 288, 73-78. http://dx.doi.org/10.1007/s00396-009-2123-z
[44] Yoshida, E. (2011) Nitroxide-Mediated Photo-Controlled/Living Radical Polymerization of Ethyl Acrylate. Colloid and Polymer Science, 289, 1127-1132. http://dx.doi.org/10.1007/s00396-011-2435-7
[45] Yoshida, E. (2009) Synthesis of Poly(methyl methacrylate)-block-poly(tetrahydrofuran) by Photo-Living Radical Polymerization Using a 2,2,6,6-Tetramethylpiperidine-1-Oxyl. Colloid and Polymer Science, 287, 1417-1424.
http://dx.doi.org/10.1007/s00396-009-2105-1
[46] Yoshida, E. (2011) Graft Copolymerization of Methyl Methacrylate on Polystyrene Backbone through Nitroxide-Mediated Photo-Living Radical Polymerization. Colloid and Polymer Science, 289, 837-841.
http://dx.doi.org/10.1007/s00396-011-2385-0
[47] Yoshida, E. (2011) Nitroxide-Mediated Photo-Controlled/Living Radical Dispersion Polymerization of Methyl Methacrylate. Colloid and Polymer Science, 289, 1625-1630. http://dx.doi.org/10.1007/s00396-011-2487-8
[48] Yoshida, E. (2010) Nitroxide-Mediated Photo-Living Radical Polymerization of Methyl Methacrylate in the Presence of (η6-Benzene)(η5-cyclopentadienyl)FeII Hexafluorophosphate. Colloid and Polymer Science, 288, 1745-1749.
http://dx.doi.org/10.1007/s00396-010-2292-9
[49] Yoshida, E. (2010) Nitroxide-Mediated Photo-Living Radical Polymerization of Methyl Methacrylate Using (4-tert-Butylphenyl)diphenylsulfonium Triflate as a Photo-Acid Generator. Colloid and Polymer Science, 288, 239-243. http://dx.doi.org/10.1007/s00396-009-2161-6
[50] Yoshida, E. (2010) Effects of Initiators and Photo-Acid Generators on Nitroxide-Mediated Photo-Living Radical Polymerization of Methyl Methacrylate. Colloid and Polymer Science, 288, 901-905.
http://dx.doi.org/10.1007/s00396-010-2220-z
[51] Yoshida, E. (2010) Photo-Living Radical Polymerization of Methyl Methacrylate Using Alkoxyamine as an Initiator. Colloid and Polymer Science, 288, 7-13. http://dx.doi.org/10.1007/s00396-009-2113-1
[52] Yoshida, E. (2012) Aqueous Photo-Living Radical Polymerization of Sodium Methacrylate Using a Water-Soluble Nitroxide Mediator. International Scholarly Research Network (ISRN) Polymer Science, 2012, Article ID: 630478.
[53] Yoshida, E. (2013) Nitroxide-Mediated Photo-Controlled/Living Radical Polymerization of Methacrylic Acid. Open Journal of Polymer Chemistry, 3, 16-22. http://dx.doi.org/10.4236/ojpchem.2013.31004
[54] Miyazawa, T., Endo, T., Shiihashi, S. and Ogawara, M. (1985) Selective Oxidation of Alcohols by Oxoaminium Salts (R2N=O+ X-). Journal of Organic Chemistry, 50, 1332-1334. http://dx.doi.org/10.1021/jo00208a047
[55] Yoshida, E., Nakamura, K., Takata, T. and Endo, T. (1993) Oxoaminium Salts as Initiators for Cationic Polymerization of Vinyl Monomers. Journal of Polymer Science, Part A: Polymer Chemistry, 31, 1505-1512.
http://dx.doi.org/10.1002/pola.1993.080310620
[56] Kita, Y., Gotanda, K., Murata, K., Suemura, M., Sano, A., Yamaguchi, T., Oka, M. and Matsugi, M. (1998) Practical Radical Additions under Mild Conditions Using 2,2’-Azobis(2,4-dimethyl-4-methoxyvaleronitrile) [V-70] as an Initiator. Organic Process Research & Development, 2, 250-254. http://dx.doi.org/10.1021/op970059z
[57] Crivello, J.V., Lam, J.H.W., Moore, J.E. and Schroeter, S.H. (1978) Triarylsulfonium Salts: A New Class of Photoinitiators for Cationic Polymerization. Journal of Radiation Curing, 5, 2-17.
[58] Devoe, R.J., Sahyun, M.R.V., Serpone, N. and Sharma, D.K. (1987) Transient Intermediates in the Photolysis of Iodonium Cations. Canadian Journal of Chemistry, 65, 2342-2349.
http://dx.doi.org/10.1139/v87-391
[59] Crivello, J.V. and Sangermano, M. (2001) Visible and Long-Wavelength Photoinitiated Cationic Polymerization. Journal of Polymer Science, Part A: Polymer Chemistry, 39, 343-356.
http://dx.doi.org/10.1002/1099-0518(20010201)39:3<343::AID-POLA1001>3.0.CO;2-J
[60] Odell, P.G., Veregin, R.P.N., Michalak, L.M., Brousmiche, D. and Georges, M.K. (1995) Rate Enhancement of Living Free-Radical Polymerizations by an Oraganic Acid Salt. Macromolecules, 28, 8453-8455.
http://dx.doi.org/10.1021/ma00128a073
[61] Golubev, V.A., Rozantsev, E.G. and Neiman, M.B. (1965) Some Reactions of Free Iminoxyl Radicals with Unpaired Electron Participation. Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, 1927-1936.
[62] Liu, Y.C., Liu, Z.L., Wu, L.M. and Chen, P. (1985) A Facile Generation of Radical Cations via the Action of Nitroxides. Tetrahedron Letters, 26, 4201-4202. http://dx.doi.org/10.1016/S0040-4039(00)98991-3
[63] Yoshida, E., Ishizone, T., Hirao, A., Nakahama, S., Takata, T. and Endo, T. (1994) Synthesis of Polystyrene Having an Aminoxy Terminal by the Reactions of Living Polystyrene with an Oxoaminium Salt and with the Corresponding Nitroxyl Radical. Macromolecules, 27, 3119-3124.
http://dx.doi.org/10.1021/ma00090a001
[64] Yoshida, E., Takata, T., Endo, T., Ishizone, T., Hirao, A. and Nakahama, S. (1994) Convenient Synthesis of Bis-1,3Dithiolium Salt, the Stable Radical Cation by Oxidation with the Oxoaminium Salt. Chemistry Letters, 23, 1827-1828.
http://dx.doi.org/10.1246/cl.1994.1827
[65] Rozenberg, V.I., Piotrovskii, V.K., Golubev, V.A., Gvon, K.I., Nikanorov, V.A., Bundel, Y.G. and Reutov, O.A. (1975) Evidence of Intermediate Formation of Particles of Homolytic Nature during Reaction of Organometallic Compounds with 2,2,6,6-Tetramethyl-1-Oxopiperidinium Salts. Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, 2617-2618.
[66] Yoshida, E. (2012) Selective Controlled/Living Photoradical Polymerization of Glycidyl Methacrylate Using a Nitroxide Mediator in the Presence of a Photosensitive Triarylsulfonium Salt. Polymers, 4, 1580-1589.
http://dx.doi.org/10.3390/polym4031580                    eww141231lx
标签：

评论

发表评论

此博客中的热门博文

Education Policy Implementation: A Mechanism for Enhancing Primary Education Development in Zanzibar

Education is one of the fundamental rights of individuals; therefore, the government of a country needs to develop and strengthen educational policy and quality as well as to ensure that everyone has equal access to basic education. The improvement of access and quality of education in the world is becoming as an essential factor in development, whereas the basic education (primary school), is acknowledged as a foundation of the higher educational development for every country. To fulfill this goal, governments introduce several policies and procedures; however, it requires some reforms and participation from the politician, policymakers, and other stakeholders to re-examine educational policy so that it can lead to multiplication and betterment of the reforms. Educational reforms actually focus on accountability. A positive educational development and reform is very challenging and needs more effort and strategy on how to use and utilize the resources effectively as such it can achie...
发表评论
阅读全文

Does Immigration Promote the Investment of the Monopolistic Firm?

In the present paper, we examine the effect of increasing uncertainty of immigrants’ growth on the optimal timing of investment of a firm that has a monopolistic power over the labor market. It is revealed that when the uncertainty of immigrants’ growth is more than a threshold level, increasing uncertainty of immigrants’ growth accelerates the optimal timing of firms’ investment and enhances the economic growth, even if the uncertainty of immigrants’ growth is formulated by the geometric Brownian motion, which is in sharp contrast to the standard result that an increase in the uncertainty postpones the optimal timing. With an increase in the immigrants over the past ten years, workforces in the host countries have been growing significantly to the extent that the immigrants represent 70% of the increase in the workforce in Europe, and 47% in the United States as OECD indicates. In the present paper, we attempted to investigate the effect of increased uncertainty caused by the growi...
发表评论
阅读全文

Electron Spin and Proton Spin in the Hydrogen and Hydrogen-Like Atomic Systems

Read full paper at: http://www.scirp.org/journal/PaperInformation.aspx?PaperID=52202#.VIj7tMnQrzE Author(s) Stanisław Olszewski * Affiliation(s) Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland . ABSTRACT The mechanical angular momentum and magnetic moment of the electron and proton spin have been calculated semiclassically with the aid of the uncertainty principle for energy and time. The spin effects of both kinds of the elementary particles can be expressed in terms of similar formulae. The quantization of the spin motion has been done on the basis of the old quantum theory. It gives a quantum number n = 1/2 as the index of the spin state acceptable for both the electron and proton ...
发表评论
阅读全文