聚苯噁唑(PBO)纖維可藉由前驅物聚羥醯胺(PHA)溶入溶劑後，經電紡絲及高溫環化製備得到，所得之纖維具有優越的機械性質及纖維配向性。不過使用之溶劑THF具有高度揮發性，常導致Taylor cone在形成前即生成阻塞物於針端。因此藉由飽和的溶劑蒸氣以氮氣引導至針端避免阻塞的問題，使過程能連續運作。

　　本研究中將PHA溶入THF/DMAc之混合溶劑中，藉由改變THF與DMAc之比例可得不同形態的收集物。此外溶液濃度、溶劑性質、氮氣流量及環化條件均會影響纖維之成型及形態上的變化。

　　藉由高速攝影機的拍攝，可以觀察到cone及液柱運動的過程。其中在低濃度時，cone會以高頻率上下振動並形成droplet快速滴落。高濃度時，液柱在bending instability過程中以折曲、螺旋狀且成圈之方式展開，同時發現液柱會有糾結的現象發生。

　　以THF/DMAc=9/1之co-solvent系統中，溶液濃度20wt%，可製備出纖維直徑719 209nm之PHA纖維，經高溫環化後可得643 212nm之PBO纖維。

　　雙針電紡絲實驗中，針與針間的距離、針到收集網的距離、電壓均會影響實驗。其中以針距之影響最為重要，由於電場受彼此斥力作用，使得液柱產生偏移，發現各溶液系統針距越小時，液柱偏移的角度越大。

　Polybenzoxazole(PBO) fibers with submicron-scale diameter have been fabricated from the PBO precursor polyhydroxyamide(PHA) by using electrospinning and thermal cyclization processes. The resulting fibers have exceptional mechanical properties and birefringent. In systems a common solvent we used tetrahydrofuran(THF), which evaporates rapidly at room temperature, the solution droplet at the tip dries out very quickly during the formation of the Taylor cone, thereby blocking the tip and making the collection process discontinuous. Several alternatives have been proposed to overcome this problem, we used nitrogen gas to carry saturated gas surrounding the Taylor cone against volatile solvent evaporates immediately. This method can stabilize the system and make process continuous.

　In this study, PHA was dissolved in the mixture of dimethylacetamide (DMAc) and THF. The results indicate that the morphology of the fibers are dependent on the ratio of DMAc and THF mixture. Besides the solution concentration, solvent properties, and nitrogen gas flow rate, and even the condition of thermal cyclization also can affect the formation and morphology of the fibers.

　Using high speed videography , we can observe the rapid motion of cone and jet splaying. In low solution concentration, the cone vibrated up and down very quickly, and produced spheres. In high solution concentration, the liquid jet followed a bending, winding, spiraling and looping path，and the loops formed immediately on the jet.

　The average diameter of electrospun fibers was 719 209nm from a 20wt% solution of PHA in THF/DMAc=9/1. After thermal cyclization processes, PBO fibers can be fabricated and the fiber diameter is 643 212nm.

　In multi-jet electrospinning, the experiment results were dependent on the distance between needles, the distance between needle and collector and the applied voltage. Due to the electric field effect, it can be observed that the deflection of jet increases with decreasing the distance between needles.

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