The shape memory polyurethane (PU) copolymers cross-linked by celite, a porous inorganic material with enormous surface area and hydroxyl groups on the surface, were prepared to see if the shape memory effect and the mechanical properties were improved. The PU copolymers with different celite contents were compared and characterized by IR, DSC, DMA, and UTM. The melting temperatures of PU soft segment were around 20 o C independent of celite content. The shape memory effect and mechanical properties were dependent on the celite content, and the celite addition into the reaction mixture should be made in the middle of polymerization to get the best shape memory and mechanical properties. The best mechanical properties were found at 0.2 wt% celite content and its shape retention rate went up to 98 %. The inclusion of celite as a cross-linker increased both shape memory effect and mechanical properties. The reasons underlining the improvements by adopting celite as a cross-linker are discussed in this paper.

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Multi-walled carbon nanotubes (MWNTs) were covalently functionalized with poly(e-caprolactone) (PCL) using click chemistry. First, chlorine moiety-containing PCL was synthesized by the copolymerization of a-chloro-ecaprolactone with e-caprolactone monomer using ring opening polymerization, and further converted to azide moietycontaining PCL. The alkyne-functionalized MWNTs were prepared with the treatment of p-amino propargyl ether using a solvent free diazotization procedure. The covalent functionalization of alkyne-derived MWNTs with azide moiety-containing PCL was accomplished using Cu(I)-catalyzed [3þ2] Huisgen dipolar cycloaddition click chemistry. The PCL-functionalization of MWNTs was confirmed by the measurements of Fourier transform infra-red, NMR, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy.

Shape memory polyurethane (SMPU) grafted using polyethyleneimine (PEI) was tested for its electrolytic attraction in aqueous solution and shape memory effect. The PEI was connected through a second 4,4'-diphenylmethane diisocyanate anchored to the carbamate moiety of SMPU. Two series of SMPU that differed in soft segment polytetramethylene glycol and PEI content were prepared to compare their tensile and shape memory properties. Shape recovery was high as 99% and reduced only to 97% after four test cycles. The PEI group attached to the SMPU chain, if converted to the imminium salt form, was designed to work as an electrolyte during water electrolysis and was to be attracted toward the cathode to show SMPU movement in aqueous solution. The electrolytic attraction of SMPU in aqueous solution was demonstrated in an experiment in which a specimen moved to the cathode only when voltage above a minimum was applied. The mechanism and application of this finding are discussed.