This study demonstrates an easy way to change surface characteristics, the water contact angle on styrene based shape memory polymer (SMP) surface alters before and after cracking formation and recovery. The contact angle of water on the original SMP surface is about 85 degree, after coating with Al and then kneading from side face at glass transition temperature Tg, cracking appeared both on Al film and SMP; cooling down and removing the Al film, cracks remain on SMP surface while the contact angle reduced to about 25 degree. When reheated above Tg, the cracks disappeared, and the contact angle go back to about 85 degree. The thin Al film bonded on SMP surface was coated by spurting, that constrains the deformation of SMP. Heating above Tg, there are complex interactions between soft SMP and hard metal film under kneading. The thin metal film cracked first with the considerable deformation of soft polymer, whereafter, the polymer was ripped by the metal cracks thus polymer cracked as well. Cracks on SMP can be fixed cooling down Tg, while reheated, cracks shrinking and the SMP recovers to its original smooth surface. Surface topography changed dramatically while chemical composition showed no change during the deformation and recovery cycle, as presented by SEM and EDS. Furthermore, the wetting cycle is repeatable. This facile method can be easily extended to the hydropobicity/hydrophilicity modification of other stimuli-responsive polymers and put forward many potential applications, such as microfluidic switching and molecule capture and release.
To date, majority shape adaptations of shape memory polymer (SMP) are thermo responsive. A desire for isothermal,
remotely controlled shape adaptations of SMP has motivated examinations of other stimulus. We successfully construct
novel TiO2-polystyrene shape memory nanocomposites and investigate influence of the ultraviolet irradiation on the
shape memory effect. This material is facilely fabricated by introducing TiO2 into polystyrene SMP. The properties of
TiO2-polystyrene shape memory nanocomposites are characterized by X-ray powder diffraction (XRD), Fourier
transform infrared spectra (FT-IR), dynamic mechanical analysis (DMA), and diffused reflectance spectrum (DRS).
Deriving from photoelectric foundational properties of TiO2, the TiO2-polystyrene shape memory nanocomposites can
absorb light energy and undergo intra-molecular or inter-molecular physical or chemical transformations. Furthermore,
the results of this work provide a useful baseline upon which researchers could explore more interesting behaviors of
photosensitive SMP composite and investigate other more challenging actuation problems.
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