| dc.description |
<p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;text-align:justify;line-height:normal;mso-layout-grid-align:none;text-autospace:none"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">Thermo-responsiveshape memory polymers (SMPs) are commonly used smart materials and shape memorypolyurethanes (SMPUs) are one of the most popular examples. According to therequirements of some end uses, besides temperature sensitivity, waterresponsive SMPs have gained popularity [1]. In this manner, formation ofnanocomposite materials by introducing hydrophilic nanoparticles as switchingelement into polymer matrix is a very useful approach to obtain thewater-responsive SMPs. Among these nanoparticles, nano-Al2O3 have attractedmuch attention due to their availability, stability, hydrophilicity, largeamounts of hydroxyl groups and suitable mechanical strength [2].<o:p></o:p></span></p><p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;text-align:justify;line-height:normal;mso-layout-grid-align:none;text-autospace:none"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">In this study,an applicable method is introduced for fabricating dual responsive (thermal andwater sensitive) shape memory composite nanofibers. Commercially available SMPUwas filled with nano-aluminium oxide (nano-Al2O3) (5-20, wt. %) by simplesolution mixing method and nanofibers were fabricated via electrospinning. Themodification of SMPU by nano-Al2O3 is a simple method for obtaining dualresponsive nanostructures without need for complex synthesis routes. Besidesmorphological (SEM), chemical (FT-IR)/mechanical properties, shape memoryperformances of the composite nanofibrous webs were investigated bymechanical-thermo-aqueous programming tests.<o:p></o:p></span></p><p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;text-align:justify;line-height:normal;mso-layout-grid-align:none;text-autospace:none"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">The resultsshowed that nano-Al2O3 can be well dispersed within the SMPU matrix by asurfactant modification and SMPU nanofibrous webs had good surface morphology.Also, nano-Al2O3 significantly improves tensile strength of SMPU nanofibers anddeteriorates elongation as expected. The strong hydrogen bond interactionsbetween SMPU chains and hydroxyl groups on nano-Al2O3 were identified by FT-IR.According to thermal-aqueous test results, the minimum values of 50% shapefixity belonged to neat SMPU, whereas the composite nanofibers containing 20%nano-Al2O3 had the maximum value of 80%. Furthermore, this sample had a shaperecovery of 96% and 75.41% of this recovery belongs to water-induced shapememory effect. These results are promising and therefore suggest thatmodifications SMPU conducted by nano-Al2O3 could be applicable for obtaining anexcellent thermally-induced and water-induced shape memory effect,simultaneously.<o:p></o:p></span></p><p></p><p class="MsoNormal" style="margin-bottom:0cm;margin-bottom:.0001pt;text-align:justify;line-height:normal;mso-layout-grid-align:none;text-autospace:none"><o:p> </o:p></p> |
|