Linear and hyperbranched poly(ester amine)s (PEAs) were used as additives in electrospinning of low concentration poly(methyl methacrylate) solutions to eliminate beads and improve the fiber uniformity.With only 1 wt% PEA

no matter linear or hyperbranched

the electrospinnability was all improved

and uniform fibers without beads were obtained.Compared to linear PEA

hyperbrchched PEA has better ability in improving the fiber uniformity.The average fiber diameter decreases significantly (from 1.9 μm to 1.0 μm) compared to those obtained at high concentration without PEA.The principle of the improvement in electrospinnability was investigated by measuring the solution properties (viscosity

conductivity and surface tension)

and it was attributed to the significant increase in solution conductivity.The solution viscosity and surface tension only change slightly

while solution conductivity increases greatly with the addition of 1 wt% PEA (including linear and hyperbranched).The hyperbranched PEAs have higher conductivity than the linear PEA because they have more polar endgroups resulted from the multiple branches

and therefore the hyperbranched PEAs have better performance than the linear PEA in improving the electrospinnability of low concentration PMMA solutions.The method reported in this paper could be generalized and provides a good alternative to the existing methods.