本論文以二甲基甲醯胺(DMF)為溶劑，配製不同濃度聚(異丙基丙烯醯胺)高分子(PNIPAM)溶液，量測溶液性質以決定overlap與糾結濃度和各濃度下的鬆弛時間。探討溶液黏度、流量與施加電壓對於電紡過程中泰勒錐(Taylor cone)/液柱/電紡纖維形態的影響。
定義針底中心為(z,x)=(0,0)，以直徑為1 mm的雷射光束打擊電紡液柱不同位置，掃描不同位置的散射圖案，將第一個強度極大值的散射向量(qm,1)代入R.G.B.理論的式子:dj=10.22/qm,1，建構不同操作參數下的液柱直徑分佈圖。在泰勒錐-液柱區間內溶劑揮發可忽略的假設下計算得液柱速度分佈圖(vj(z)=4Q/dj(z)2)，圖中斜率為液柱受到的拉伸速率。依拉伸速率的大小可在針底至液柱末端處之間分成三個區間，從針底至液柱起始處，液柱受到拉伸速率為最大值，直徑有明顯的變化，此為regime I，液柱內糾結結構的網路可被有效拉伸。液柱直徑隨距針底距離呈指數形式的縮減行為，關係式為dj(z)~z-n，為regime II。溶液黏度的改變對n值的影響最為明顯。液柱直徑會在近液柱末端處縮減至一漸近值(dj,e)，此平坦區域為regime III，有鬆弛現象發生，regime III的存在可用液柱所受到的空氣阻力與電斥應力的力平衡來解釋，且由應力平衡推導所得結果(dj,e~Q0.41)與實驗結果相符合(~Q0.37)，代表jet whipping行為是受電斥力與空氣阻力共同作用而形成的。dj,e受流量的影響，而幾乎與溶液黏度無關。
最後，以高速攝影機觀察電紡7、9與17 wt%溶液時，液柱在jet whipping起始區域中的運動行為，運動模式為波形外觀，只有17 wt%溶液存在高頻率與低頻率震動組成的週期性運動。分別量測不同濃度的液柱在側向與軸向上的運動速率。並量測波長與在軸向方向上的速率以計算液柱在此區間的運動頻率。探討溶液黏度對於運動行為與頻率的影響。

The electrospinning of poly(N-isopropylarylamide)/dimethylformamide (PNIPAM/DMF) solutions with various concentrations was performed at room temperature. Prior to electrospinning, the rheological properties were investigated which used to determine the relaxation time, solution viscosity, overlap and entanglement concentrations. In this study, we reveal the effects of solution properties and processing parameters on the morphologies of Taylor cone/jet/as-spun fibers.
Light scattering technique with He-Ne laser source was carried out to measure the jet diameter (dj(z)) at different positions (z) from needle-end to the jet-end position. The jet diameter profile was constructed from the magnitude of scattering vector of first intensity maximum (qm,1) which obtained from the equatorial intensity profiles by R.G.B. theory: dj(z)=10.22/qm,1. Based on the assumption that no solvent evaporation took place in the cone-jet region, the jet velocity (vj(z)) could be calculated by mass balance (vj(z)=4Q/dj(z)2). The slope in the jet velocity profiles represent the strain rate that applied on the electrospinning jet. According to the derived strain rate, three distinct regions could be identified. Regime I is from the needle-end to the initial jet section. The liquid element was stretched significantly by the highest strain rate in the straight jet section, thus the jet diameter decreased significantly in this region. Due to the high strain rates in regime I, the chain orientation even chain stretch may occur. Along the jet, dj keep decreasing as a scaling law: dj(z)~z-n in this range, which named region II. The derived exponent n is a function of solution viscosity, not a function of flow-rate and applied voltage. Near the jet-end position, jet diameter finally reached an asymptotic value (dj,e) despite of the parameters applied, named region III. Because the derived strain-rate in region III is around 0 s-1, the chain relaxation process would occur. The jet diameter on the jet-end (dj,e) is a function of flow-rate, but independent of solution viscosity. The existence of regime III could be explained by the force balance between air drag stress and electrical stress which induced by the surface charges on the jet in the electrical field. The derived result, dj,e~Q0.41, was consistent with our experimental results. Based on our finding, the resistant force by air friction is not negligible at the straight jet-end and progressively becomes the key factor in determining dj,e and the initial jet whipping behavior.
In the last section, we used a high speed camera to study the effect of solution viscosity on the vibration process of electrospinning jet in the initial jet whipping region for 7, 9 and 17 wt% solutions. There are wave-like morphologies for electrospinning jet in the initial jet whipping region despite of solution concentration. But only 17 wt% solution has a periodicity motion which composed by high frequency and low frequency vibrations. The effects of solution viscosity on the jet velocities on the lateral and axial directions and vibration frequency were investigated by the measurement of wavelength in wave-like motion and the jet velocity in the axial direction.

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