本研究成功電紡出奈米直徑的同排聚苯乙烯(iPS)纖維，在高溫電紡絲時使用夾套式熱交換器維持溶液的溫度。當電紡流量(Q)改變時，液柱直徑(dj)與纖維直徑(df)會有變化，其關係為dj~Q0.50、df~Q0.13。因iPS溶液於室溫下不易形成凝膠，因此在室溫下亦可進行電紡絲實驗，研究發現高溫電紡所得纖維較室溫電紡所得纖維細。

室溫下利用快速轉動之碟盤收集順向纖維，使用DSC、WAXD與SAXS分析纖維內微結構；WAXD結果可知電紡所得順向纖維膜為amorphous，經由逐步升溫發現晶體於110 oC開始出現，且結晶度隨著溫度的升高增加。由Herman orientation function計算得知溫度上升時晶體c軸之順向度下降。SAXS散射實驗顯示在140 oC可觀察到long period生成，其值隨溫度的上升而變大。藉由一維關聯函數可得iPS順向纖維膜於不同回火溫度之lamellar形態參數。

先前的研究發現iPS纖維可誘導iPP產生beta晶型，而iPP 的beta晶體有很好的韌性，因此本研究進一步研究得知iPS纖維可誘導iPP產生beta晶體的最高等溫溫度為135 oC，且能形成穿晶的最高等溫溫度為138 oC，不同降溫速率結晶條件下，隨著降溫速率越快，iPS纖維能誘導iPP產生beta晶核的數量越多。

Electrospun isotactic polystyrene (iPS) nanofibers were successfully prepared. The scaling laws between Q, dj and df are: dj~Q0.50, df~Q0.13. The cooled solutions remained homogeneous even at room temperature for hours due to the slow process for gel formation and/or crystallization, which led to the feasibility of ambient electrospinning. However, iPS fibers electrospun from the elevated temperature had a smaller diameter than those obtained from room temperature because of reduced viscosity.

The aligned iPS fibers were collected by a rotating disc. By means of wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and differential scanning calorimeter analyses, the internal structure of iPS fibers was characterized. The as-spun iPS fibers were found to be amorphous. WAXD results showed that iPS crystals initially appeared at 110 oC, and fiber crystallinity increased with increasing annealing temperatures. Based on the Herman orientation function, the orientation factor of crystal c-axis decreased with increasing temperature. SAXS results showed that long period initially appeared at 140 oC and increased with increasing annealing temperatures. Using one-dimensional correlation function, lamellar morphological parameters of aligned iPS fibers were determined.

From the previous studies, we found electrospun iPS fibers can induce the beta-crystal form of iPP. For isothermal crystallization, the maximum temperature required for transcrystalline layer to develope is 138 oC. The content of beta-form nuclei increased with increasing cooling rate.

[1] J. Brandup, E. H. Immergut, E. A. Grulke, A. Abe, D. R. Bloch, “Polymer handbook.” Wiley Interscience : New York (1999).
[2] T. Liu, J Petermann, “Multiple melting behavior in isothermally cold-crystallization isotactic polystyrene.” Polymer 42, 6453 (2001).
[3] Y. Duan, J. Zang, D. Shen, S. Yan, “In situ FTIR studies on the cold-crystallization process and multiple melting behavior of isotactic polystyrene.” Macromolecules 36, 4874 (2003).
[4] J. Zang, Y. Duan, D. Shen, S. Yan, I. Noda, Y. Ozaki, “Structure changes during the induction period of cold crystallization of isotactic polystyrene investigated by infrated and two-dimensional infrared correlation spectroscopy.” Macromolecules 37, 3292 (2004).
[5] H. Xu, B. S. Ince, P. Cebe, “Development of the crystallization and rigid amorphous fraction in cold-crystallized isotactic polystyrene.” Journal of Polymer Science, Part B : Polymer Physics 41, 3026 (2003).
[6] H. Xu, P. Cebe, “Transition from solid to liquid in isotactic polystyrene studied by thermal analysis and X-ray scattering.” Polymer 46, 8734 (2005).
[7] M. Tosaka, K.Yamaguchi, M. Tsuji, “Latent orientation in the skin layer of electrospun isotactic polystyrene ultrafine fibers.” Polymer 51, 547 (2010).
[8] A. Phillips, P. W. Zhu, G. Edward, “Polystyrene as a versatile nucleating agent for polypropylene.” Polymer 51, 1599 (2010).
[9] B. Lotz, J. C. Wittmann, A. Lovinger, “Structure and morphology of poly(propylene) : a molecular analysis.” Polymer 37, 4979 (1996).
[10] S. Brűckner, S. V. Meille, V. Petraccone, B. Pirozzi, “Polymorphism in
isotactic polypropylene.” Progress in Polymer Science 16, 361 (1991).
[11] J. Varga, “-Modification of isotactic polystyrene : preparation,
structure, processing, properties, and application.” Journal of Macromolecular Science, Part B 41,1121 (2002).
[12] J. Varga, J. Karger-Kocsis, “Rules of supermolecular structure formation in sheared isotactic polypropylene melts.” Journal of Polymer Science, Part B : Polymer Physics 34, 657 (1996).
[13] J. Varga, J.Karger-Kocsis, “Interfacial morphologies in carbon-fibre-reinforced polypropylene microcomposites.” Polymer 36, 4877 (1995).
[14] F. Luo, C. Geng, K. Wang, H. Deng, F. Chen, Q. Fu, B. Na. “New understanding in tuning toughness ofpolypropylene : the role of -nucleated crystalline morphology.” Macromolecules 42, 9325 (2009).
[15] Z. Su, M. Dong, Z. Guo, J. Yu, “Study of polystyrene and acrylonitrile-styrene copolymer as special -nucleating agents to induce the crystallization of isotactic polypropylene.” Macromolecules 40, 4217 (2007).
[16] G. Natta, P. Corradint, I. W. Bassi, “Crystal structure of isotactic polystyrene.” Nuovo Cimento 15, 68 (1960)
[17] F. J. Balt-Calleja, C. G. Vonk, “X-ray scattering of synthetic polymers.” Elsevier: New York (1989)
[18] C. Wang, T. C. Hsieh, Y. W. Cheng, “Solution-electrospun isotactic polypropylene fibers: processing and microstructure development during stepwise annealing.” Macromolecules 43, 9022 (2010).
[19] C. L. Huang, Y. C. Chen, T. J. Hsiao, J. C. Tsai, C. Wang, “Effect of tacticity on viscoelastic properties of polystyrene.” Macromolecules 44, 6155 (2011).

[20] 吳怡君, “不同電紡纖維對聚丙烯穿晶形成能力的影響”, 國立成功大學碩士論文 (2011).
[21] M. Al-Hussein, G. Strobl, “The melting line, the crystallization line, and the equilibrium melting temperature of isotactic polystyrene.” Macromolecules 35, 1672 (2002).