可溶性聚硅烷的合成与表征及其热分解特性研究
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摘要
先驱体转化法是制备连续碳化硅纤维的重要方法，该方法包括先驱体聚碳硅烷(PCS)的合成、熔融纺丝、不熔化处理和高温烧成等工序。为解决PCS的原料不纯问题，同时也为了制备近化学计量比的陶瓷先驱体，本文采用了合成可溶性聚硅烷的方法，重点对可溶性PMS的制备过程，组成与结构，以及其热分解特性进行了研究。考察了甲基二氯硅烷均聚反应、二甲基二氯硅烷／甲基二氯硅烷共聚反应以及二甲基二氯硅烷／甲基三氯硅烷共聚反应的产物产率组成情况，采用IR、~1HNMR、GC-MS、GPC等测试手段对可溶性的聚硅烷进行了表征，对样品中杂质氧的引入机制进行了初步研究，并初步探讨了可溶性聚硅烷的反应机理。分别利用热聚合法和乙二胺低温胺解法使可溶性PMS高分子化，对高分子化产物的组成和特性进行了初步研究。采用LPS与PMS共聚改性的方式调节先驱体的碳硅元素比，并对不同比例下的产物特性进行了研究。最后利用IR、TG-DTA、XRD等分析手段对可溶性PMS及其改性产物的热分解过程、结构变化、陶瓷收率进行了研究。
研究表明，从甲基二氯硅烷出发制备的可溶物PMS为主要产物，可以通过降低反应温度和适当增加单体用量，提高可溶物PMS的产率，其最终产率可达83％，与文献报道的水平接近。对PMS的结构分析表明，该聚合物分子量在300-500之间，由大量线形低聚体和环状物组成，且其分子结构中硅氢键含量较高，易于氧化，杂质氧在PMS中的结合方式为硅氧硅结构。在研究中还发现，通过热聚合反应可使PMS分子量长大，同时，利用LPS与PMS共聚，可以降低其热聚合反应的活性且可调节其烧成产物中的碳硅比，PMS与PCS的热分解过程类似，均可在高温下得到β-SiC的结晶。
The organosilicon polymer route offers an innovative approach to the preparation of continuous SiC fiber, in which steps involving synthesis of polycarbosilane(PCS), melt-spinning, curing and firing are usually required. However, the PCS precursor derived from insoluble polydimethylsilane(PDMS) are much carbon-rich and difficult to be purified. Therefore, to prepare soluble near-stoichoimetric preceramic polymer, focus was placed upon the synthesis, composition and structure of soluble polymethylsilane(PMS) as well as its pyrolysis properties.
In the paper, polymerization of metyldiclorosilane(MDCS), co-polymerization of dimetyldiclorosilane and methlydiclorosilane and co-polymerization of dimetyldiclorosilane and metyltriclorosilane were thoroughly studied. Synthesis mechanisms and the introduction of unexpected oxygen were primarily proposed, and characterizations of so-obtained soluble PMS, P(MS-DMS) and P(DMS-TMS) were also performed by using IR, 'HNMR, GO-MS and GPC analysis.
Cross-linking of the soluble PMS could be achieved through heating and ethyldiamine ammonolysis respectively and those cross-linked PMSs were discussed in view of their composition and structure. In addition, adjusting the ratio of carbon/silicon was investigated by co-polymerization of low molecular weigh PDMS (LPS) and PMS as well as the copolymer. Finally, pyrolysis, ceramic yield and structure evolution of the soluble PMS and modified PMS were studied through IR, TG-DTA and XRD analysis.
Results reveal that soluble PMS derived from MDCS are the main product, whose yield, with a maximum value close to that of literature, could be increased by lowering the reaction temperature and properly increasing the amount of monomer. The soluble PMS, with a molecular weight in the range of 300 to 500, are composed of much amount of linear polymers and some
ring-like polymers. However, the PMS are much sensitive to oxygen due to its much content of Si-H bond and the contaminated oxygen formed Si-O-Si bond in the PMS. Results also confirmed the cross-linking of PMS by heat treatment; in addition, co-polymerization of LPS and PMS could successfully reduce the reactivity and adjust the carbon/silicon ratio of the modified PMS. Pyrolysis process of PMS is similar to that of common PCS and both contain 0 -SiC microcrystalline after high temperature pyrolysis.
研究表明，从甲基二氯硅烷出发制备的可溶物PMS为主要产物，可以通过降低反应温度和适当增加单体用量，提高可溶物PMS的产率，其最终产率可达83％，与文献报道的水平接近。对PMS的结构分析表明，该聚合物分子量在300-500之间，由大量线形低聚体和环状物组成，且其分子结构中硅氢键含量较高，易于氧化，杂质氧在PMS中的结合方式为硅氧硅结构。在研究中还发现，通过热聚合反应可使PMS分子量长大，同时，利用LPS与PMS共聚，可以降低其热聚合反应的活性且可调节其烧成产物中的碳硅比，PMS与PCS的热分解过程类似，均可在高温下得到β-SiC的结晶。
The organosilicon polymer route offers an innovative approach to the preparation of continuous SiC fiber, in which steps involving synthesis of polycarbosilane(PCS), melt-spinning, curing and firing are usually required. However, the PCS precursor derived from insoluble polydimethylsilane(PDMS) are much carbon-rich and difficult to be purified. Therefore, to prepare soluble near-stoichoimetric preceramic polymer, focus was placed upon the synthesis, composition and structure of soluble polymethylsilane(PMS) as well as its pyrolysis properties.
In the paper, polymerization of metyldiclorosilane(MDCS), co-polymerization of dimetyldiclorosilane and methlydiclorosilane and co-polymerization of dimetyldiclorosilane and metyltriclorosilane were thoroughly studied. Synthesis mechanisms and the introduction of unexpected oxygen were primarily proposed, and characterizations of so-obtained soluble PMS, P(MS-DMS) and P(DMS-TMS) were also performed by using IR, 'HNMR, GO-MS and GPC analysis.
Cross-linking of the soluble PMS could be achieved through heating and ethyldiamine ammonolysis respectively and those cross-linked PMSs were discussed in view of their composition and structure. In addition, adjusting the ratio of carbon/silicon was investigated by co-polymerization of low molecular weigh PDMS (LPS) and PMS as well as the copolymer. Finally, pyrolysis, ceramic yield and structure evolution of the soluble PMS and modified PMS were studied through IR, TG-DTA and XRD analysis.
Results reveal that soluble PMS derived from MDCS are the main product, whose yield, with a maximum value close to that of literature, could be increased by lowering the reaction temperature and properly increasing the amount of monomer. The soluble PMS, with a molecular weight in the range of 300 to 500, are composed of much amount of linear polymers and some
ring-like polymers. However, the PMS are much sensitive to oxygen due to its much content of Si-H bond and the contaminated oxygen formed Si-O-Si bond in the PMS. Results also confirmed the cross-linking of PMS by heat treatment; in addition, co-polymerization of LPS and PMS could successfully reduce the reactivity and adjust the carbon/silicon ratio of the modified PMS. Pyrolysis process of PMS is similar to that of common PCS and both contain 0 -SiC microcrystalline after high temperature pyrolysis.
引文
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[2] M.E.Buch,Mater.Res.l987,8(5) :272
[3] G.C.Wei,P.F.Becher,Am.Ceram.Soc.Bull.,1985,64(2) :298
[4] 王玲森编著.特种陶瓷,长沙:中南工业大学出版社, 1994
[5] S.Yajima, J.Hayashi, M.Omori,Continuous Silicon Carbide Fiber of Tensile Strength.Chem.Lett., 1975,(9) :931-934
[6] S.Yajima, k.Okamura, J.Hayashi,Structure Analysis in Continuous Silicon Carbide Fiber of High Tensile Strength, Chem.Lett.,1975,(12) :1209-1212
[7] S.Yajima, J.Hayashi, M.Omori,etal Development of a silicon carbide fiber with high tensile strength ,Nature,1976,261(5562) :683-685
[8] W.Toreki, C.D.Batch, M.D.Sacks,etal. Polymer-derived silicon carbide fiber with improved Thermo-mechanical stability. Master. Res. Soc. Symp. Proc.,1992(271) :761-769
[9] 樊靖中,新产品世界,9, 57(1990)
[10] 李晓霞.连续碳化硅纤维的制备工艺与基础研究,学位论文, 1998
[11] Kipping, F . S . J . Chem . Soc .,1924,125(2291)
[12] Burkhard, C . J . Am .Chem . Soc.,1949,71(963)
[13] H.Gilman and R.A.Tomasi,J.org.Chem.,1963,28(1651)
[14] Wesson,J.P.andWilliams,T.C.J.Polym.Sci.,Polym.Chem.Ed., 1979,17(2833)
[15] Wesson,J.P.andWilliams,T.C.J.Polym.Sci.,Polym.Chem.Ed., 1980,18(959)
[16] Wesson,J.P.andWilliams,T.C.J.Polym.Sci.,Polym.Chem.Ed., 1981,19(65)
[17] West,R.,U.s.Patent,4,260,780,1981
[18] Trujillo, R.E.J.Organomet.Chem.,1980,198(C27)
[19] W. Y. Ching, Y.-N. Xu, R. H. French, Phy. Rev., 1996,54(13546)
[20] T. Dohmaru, K. Oka, T. Yajima, M. Miyamoto, Y. Nakayama, T. Kawamura, R. West, Phil. Mag. B., 1995,71(1069)
[21] T. Seki, A. Tohnai, T. Tamaki, K. Ueno, J. Chem. Soc., Chem. Commun., 1993,9(1876)
[22] T. Seki, A. Tohnai, T. Tamaki, A. Kaito, Chem. Lett., 1996,293(361)
[23] M. Yoshida, T. Seki, F. Nakanishi, K. Sakamoto, H. Sakurai, Chem. Commun.,1996(1381)
[24] M. Yoshida, F. Nakanishi, T. Seki, K. Sakamoto, H. Sakurai, Macromolecules, 1997, 30(1860)
[25] M. Yoshida, M. Mori, S. Yokokawa, F. Nakanishi, H. Sakurai, Molecular Crystals and Liquid Crystals, 1998, 322(135)
[26] S. Irie and M. Irie, Macromolecules, 1995, 28(922)
[27] T. Dohmaru, K. Oka, T. Nakamura, H. Naito, IS&T's NIP 14: International Conference on Digital Printing Technologies Toronto, 544(Ontario, Canada, October 1998)
[28] 张志毅，陆逸，谭自烈，国防科技大学论文报告资料，1986，86-5040
[29] 吉法祥，叶明泉，陈明华，高分子通报，1992，4(228)
[30] 杜作栋，王勤，陈剑华，高等学校化学学报，1990，11(406)
[31] 陈德本，彭莉，高分子材料科学与工程，1992，5(78)
[32] 李高全，陈德本，高分子材料科学与工程，1993，1(3)
[33] 陈德本，李高全，周宗华，化学研究与应用，1993，5(8)
[34] G. Li, J. Tan, H. Fu. H. Ma, D. Chen. Z. Zhou, J. Appl. polym. Sci.,2000,78(133)
[35] 吉法祥，陈明华，叶明泉，高分子学报，1993，3(348)
[36] 吴俊珺，顾庆超，高分子通报，1995，2(117)
[37] 曹晴，陆云，薛奇，高分子通报，1998，3(41)
[38] 曹晴，陆云，薛奇，高分子通报，1998，6(40)
[39] H. Fu, G. Li, D. Chen, H. Ma M. Xie,S. Chen, J.Appl.polym.Sci.,1997,66(1515)
[40] 王旭东，徐伟箭，化工新型材料，1999，27(8)
[41] 王旭东，徐伟箭，化工进展，2000，19(42)
[42] Kipping, F. S. J. Chem. Soc., 1921,119(830)
[43] H. Sakurai,J. Am. Chem. Soc.,1989,111(7641)
[44] A. Kuriyama,Organometallics.,1995,14(2506)
[45] K. Subramanian, Rev. Macromol.Chem.Phys.,1998,C38(4) (637)
[46] K. Matyjaszewski, J.Am.Chem.Soc.,1988,10(3321)
[47] U.G.Stolberg,Angew.Chem.Intern.Ed.Engl.,1963,2(150)
[48] E.Carberry and R.West,Cyclic Polysilanes.III,J.Am.Chem.Soc., 1969, 91(5440)
[49] West.R and David L.D.Phenylmethylpolysilane,J.Am.Chem.Soc., 1981,103(7352)
[50] West.R and Andris Indriksons,Cyclic Polysilanes.VI., J.Am.Chem.Soc.,1972,94(6110)
[51] Zhang,Z.F.;Scotto,C.S.;Laine,R.M.Ma.Res.Soc.Syn.Proc.,1994,327,207
[52] Matyjaszeeski,K.Polym.Prepr.,1990,31(2) ,224
[53] 宋永才,商瑶,冯春祥,陆逸 高分子材料科学与工程,1992,5(78) 52