本研究以DMF為溶劑在室溫下配製PNIPAAm溶液。並藉由流變儀以動態測試量測不同濃度溶液下的G’與G”與*對關係圖、 與o等流變特性。藉由毛細管黏度計的量測，可得PNIPAAm的本質黏度[]為1.98 dL/g。

以常溫電紡絲設備製備PNIPAAm奈米纖維，從對w關係圖的結果可得PNIPAAm溶液的entanglement濃度為7 wt%，但當溶液濃度高於14 wt%才可電紡得到均勻的纖維。本研究探討在不同操作條件下，如：溶液黏度()與流量(Q)對cone、jet形態、液柱直徑(dj)及纖維直徑(df)的影響。實驗發現改變黏度與流量，對液柱、纖維直徑均造成影響，並遵循scaling law的關係式如下：dj ~o0.02、df ~o0.80、dj ~Q0.38、df ~Q0.12。

本研究以快速轉動的滾輪可有效收集順向電紡纖維膜。藉由FTIR以偏光板偏極化IR光的方式量測計算dichroic ration(D)，對於1545與1657 cm-1兩個代表PNIPAAm的特徵官能基，D皆大於1，代表纖維內高分子鏈排列方向平行於纖維方向。

本研究以雷射繞射方式量測電紡過程中jet從Taylor cone尖端到開始whipping位置之間液柱直徑的變化趨勢。在不同流量下，液柱直徑對於距Taylor cone尖端距離(z)的變化呈現scaling law的關係式: dj~z -a，a的範圍在0.31~0.48之間。假設溶劑只在whipping區域揮發，可計算得到流體速度(Vj)隨z的關係圖。Vj隨z的上升而上升，當流體速度到達某個值之後就不再變化。

Electrospinning solutions of PNIPAAm/DMF with different concentrations were prepared at room temperature. Prior to electrospinning, the rheological properties of solutions were investigated by using an ARES rheometer. From the log-log plot of complex viscosity versus solution concentration, the entanglement concentration of the PNIPAAm solution was determined to be 7 wt%. In addition, the intrinsic viscosity was determined to be 1.98 dL/g using a capillary viscometer. Room-temperature electrospinning was carried out to obtain PNIPAAm fibers. Based on our findings, a stable process and bead-free fibers could be obtained from solutions with a concentration higher than 14 wt%. The effects of processing parameters, i.e. solution viscosity (), flow rate (Q) on the Taylor cone, jet length, jet diameter (dj), and fiber diameter (df), were investigated. Some scaling laws were discovered: dj ~o0.02、df ~o0.80、dj ~Q0.38、df ~Q0.12. Aligned PNIPAAm fibers were collected by a rotating roller with a high linear velocity. The chain orientation in the as-spun fibers was characterized by the dichroic ratio (D) obtained from the polarized FTIR spectra. For the 1545 and 1657 cm-1 bands, the calculated D was larger than 1, indicating that polymer chains were parallel to the fiber direction. Laser diffraction was carried out to measure the dj at different positions (z) from the apex of Taylor cone to jet whipping regime. A scaling law was discovered to be dj~z-a, where the exponent a was about 0.31-0.48. Assuming that no solvent evaporation took place in the straight jet region, the jet velocity (Vj) could be calculated by: . It was found that Vj increased with z and finally reached an asymptotic value despite of different Q applied.

[1] J. M. Dealy, K. F. Wissbrun, “Melt rheology and its role in plastics processing, theory and application”, Springer (1999).
[2] 林坤賢, “以電紡絲法製備PBO纖維”, 國立成功大學碩士論文 (2005).
[3] D. N. Rockwood, D. B. Chase, R. E. Akins, Jr. , J. F. Rabolt, ”Characterization of electrospun poly(N-isopropyl acrylamide) fibers”, Polymer 49, 4025 (2008).
[4] J. Zhang, R. D. K. Misra, “Magnetic drug-targeting carrier encapsulated whit thermosensitive smart polymer: Core-shell nanoparticle carrier and drug release response”, Acta Biomaterialia 3,838 (2007).
[5] S. Fujishige, K. Kubota, I. Ando,”Phase transition of aqueous solutions of poly(N-isopropylacrylamide) and poly(N-isopropylmethacrylamide)”, Journal of Physical Chemistry 93, 3311 (1989).
[6] M. K. Jaiswal, R. Banerjee, P. Pradhan, D. Bahadur, “Thermal behavior of magnetically modalized poly(N-isopropylacrylamide)-chitosan based nanohydrogel”, Colloids and Surfaces B: Biointerfaces 81, 185 (2010).
[7] S.-Y. Gu, Z.-M. Wang, J.-B. Li, J. Ren, “Switchable wettability of thermo-responsive biocompatible nanofibrous films created by electrospinning”, Macromolecular Materials and Engineering 295,32 (2010).
[8] Y. Okada, F. Tanaka, “Cooperative hydration, chain collapse, and flat LCST behavior in aqueous poly(N-isopropylacrylamide) solutions”, Macromolecules 38, 4465 (2005).
[9] M. Heskins, J. E. Guillet, ”Solution properties of poly(N-isopropylacrylamide)”, Journal of Macromolecular Science: Part A-Chemistry 2, 1441 (1968).
[10] Y. Matsuda, Y. Miyazaki, S. Sugihara, S. Aoshima, K. Saito, T. Sato, “Phase separation behavior of aqueous solutions of a thermosensitive polymer”, Journal of Polymer Science Part B: Polymer Physics 43,2937 (2005)
[11] . C. Boutris, E. G. Chatzi, C. Kiparissides, “Characterization of the LCST behavior of aqueous poly(N-isopropylacrylamide) solutions by thermal and cloud point techniques”, Polymer 38, 2567 (1997).
[12] Y. Maeda, T. Higuchi, I. Ikeda, “FTIR Spectroscopic and Calorimetric Studies of Phase Transition of N-isopropylacrylamide Copolymer in Water”, Langmuir 17, 7535 (2001).
[13] I. Lynch, I. A. Blute, B. Zhmud, P MacArtain, M. Tosetto, L. T. Allen, ”Correlation of the adhesive properties of cells to N-isopropylacrylamide/N-tert-butylacrylamide copolymer surfaces with changes in surface structure using contact angle measurement simulations, and Raman spectroscopy”, Chemistry of Materials 17, 3889 (2005).
[14] J. Zeleny, “The electrical discharge from liquid points, and a hydrostatic method of measuring the electric intensity at their surfaces”, Journal of Physical Review 3, 69 (1914).
[15] A. Formhals, US patent No. 1975504 (1934).
[16] D. H. Reneker, I. Chun, “Nanometer diameter fibers of polymer, produced by electrospinning”, Nanotechnology 7, 216 (1996).
[17] C. Wang, Y-W Cheng, C-H Hsu, H-S Chien, S-Y Thou, “How to manipulate the electrosunning jet with controlled properties to obtain uniform fibers with the smallest diameter? A brief discussion of solution electrospinning process”, Journal of Polymer Research 18, 111 (2011).
[18] H. Okuzaki, K. Kobayashi, H. Yan, “Non-woven fabric of poly(N-isopropylacrylamide) nanofibers fabricated by electrospinning”, Synthetic Metals 159, 2273 (2009).
[19] Y. Konosu, H. Matsumoto, K. Tsuboi, M. Minagawa, A. Tanioka,”Enhacing the effect of the nanofiber network structure on thermoresponsive wettability switching”, Langmuir 27, 14716 (2011).
[20] J. W. Park, T. Tanaka, Y. Doi, T. Iwata, ”Uniaxial drawing of poly[(R)-3-hydroxybutyrate]/cellulose acetate butyrate blends and their orientation behavior”, Macromolecular Bioscience 5, 840 (2005).
[21] C. Wang, H. S. Chien, K. W. Yan, C. L. Hung, K. L. Hung, S. J. Tsai, H. J. Jhang,”Correlation between processing parameters and microstructure of electrospun poly(D,L-lactic acid) nanofibers”, Polymer 50, 6100 (2009).
[22] J. Doshi, D. H. Reneker,”Electrospinning process and applications of electrospun fibers”, Journal of Electrostatics 35, 151 (1995).