Polyurethane/polyhedral oligomeric silsesquioxane shape memory nanocomposites with low trigger temperature and quick response

Abstract

Ester-based polyurethane (PU) was found to have excellent shape memory properties with low trigger temperature. Polyhedral oligomeric silsesquioxanes (POSS) have drawn considerable interest due to their hybrid organic-inorganic structures consisting of a silica cage surrounded by eight organic groups. Incorporation of functional POSS in polymers normally improves the mechanical properties of polymer matrix. For the purpose of obtaining shape memory materials with low trigger temperature and quick response, octa(3-hydroxypropyl) polyhedral oligomeric silsesquioxane (POSS-(OH) 8 ) was incorporated into polyurethane by solution casting. The chemical structures and microstructures were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD) and field emission scanning electron microscope (FESEM). The thermal properties and dynamic mechanical properties were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The mechanical properties were also evaluated. Shape memory properties were characterized by cyclic thermal mechanical tests and physical shape recovery tests. The results show that the nanocomposites with low POSS-(OH) 8 loading content (1 and 3 wt.%) possess higher breaking strength and elastic modulus, resulting in higher shape fixity, recovery ratios and faster recovery. The nanocomposites might have potential applications for controlling tags or proof marks in the area of low temperature storage.

Thermally and Electrically Triggered Triple-Shape Memory Behavior of Poly(vinyl acetate)/Poly(lactic acid) Due to Graphene-Induced Phase Separation

“…Also, it can be seen from Figure (b) that the unfilled PLA/PVAc blend presented moderate R f values located within 84%–87%, while with incorporation of graphene into the blend, the shape fixing of nanocomposites was noticeably improved, as the nanocomposites with 3 and 4.5 wt % graphene exhibited high R f values of 92.6% and 98.9% in the second cycle, respectively. It is worth noting that a certain fraction of the stretched polymer is unlocked even at a temperature below T g , hence there is an instantaneous retractive force upon loading removal, which causes incomplete shape fixing in SMPs, , while almost no instantaneous retraction occurred immediately after unloading the nanocomposite containing 4.5 wt % graphene. Because the stiff space-filling graphene network completely restricted the stretched frozen polymer molecular chains, hence, inhibited any possible mobility of the polymer molecular chains, and thus provided high shape fixing for the matrix.…”

POSS Moieties with PEG Vertex Groups as Diluent in Polyurethane Elastomers: Morphology and Phase Separation

“…Octaphenyl increased T g significantly, while glycidox­ypropyl POSS increased it to a lesser extent . In another work with octa­(3-chloropropyl) POSS particles in an ester-based thermoplastic polyurethane, increase of T g with increasing POSS content was observed …”

“…20 In another work with octa(3chloropropyl) POSS particles in an ester-based thermoplastic polyurethane, increase of T g with increasing POSS content was observed. 21 Two of us recently wrote a review article on polymer/POSS hybrids 7 and concluded on multiple mechanisms by which POSS particles affect the segmental dynamics depending on the degree of dispersion. POSS dispersed at the molecular level tend to behave as molecules rather than nanoparticles and affect the segmental dynamics in a manner similar to common diluents.…”

Rigid polyurethane foams reinforced with disilanolisobutyl POSS: Synthesis and properties

“…The reason for this phenomenon may be the presence in addition to standard connections isocyanate (hard segment)‐polyols (soft segment)‐isocyanate (hard segment) and few connections isocyanate‐DSIPOSS‐isocyanate (Scheme ). With the increase in content of DSIPOSS, there are a growing number of isocyanate‐DSIPOSS‐isocyanate connections, which contribute to a better fit between the segments, thereby decreasing the distance between them …”

“…which contribute to a better fit between the segments, thereby decreasing the distance between them. [33][34][35]…”