SBS Thermoplastic Elastomer Based on Dynamic Metal‐Ligand Bond: Structure, Mechanical Properties, and Shape Memory Behavior

Abstract

A Cooper(II) (Cu2+)‐nitrogen coordination‐crosslinked network is designed in poly(styrene‐co‐butadiene‐co‐styrene) (SBS) to change commercial elastomers into advanced soft materials. Herein, ligand groups into SBS molecular chains by the 3,6‐di(2‐pyridyl)‐1,2,4,5‐tetrazine (DPT) click reaction are first introduced. The results from fourier transform infrared (FT‐IR), 1H‐nuclear magnetic resonance, and X‐ray photoelectron spectroscopy (XPS) are verified the successful modification of SBS. The DPT‐grafted SBS could then coordinate with copper sulfate (CuSO4) to form a Cu2+‐nitrogen bond, which is further characterized using FT‐IR, XPS, atomic force microscope, scanning electron microscope, and geometric structure calculations. After modifying SBS to form an SBS‐DPT/CuSO4 composite (SBS‐DPT2‐Cu10), the tensile stress is improved from 11.43 to 23.25 MPa, while the elongation at break is remained almost unchanged, and the corresponding toughness is increased from 33.21 to 63.26 MJ m–3. Moreover, the dynamic nature of the Cu2+‐nitrogen coordination bonds enables the SBS‐DPT/CuSO4 composite to exhibit sustained thermoplastic performance and excellent shape memory behavior under an external thermal stimulus.

Renewable and Degradable Triblock Copolymers Produced via Metal-Free Polymerizations: From Low Sticky Pressure-Sensitive Adhesive to Soft Superelastomer

“…The PGM–PHL–PGM(15–60–15) triblock copolymer specimen also displayed relatively superior tensile behaviors, with a Young’s modulus ( E ) of 2.07 MPa, an ultimate strength at break (σ b ) of 4.63 MPa (or 3.12 MPa corrected for slip ), and a toughness (γ) of 88.8 MJ m –3 (or 29.6 MJ m –3 corrected for slip ) in the S–S curves. Furthermore, an elongation at break (ε b ) of greater than 3000% (or 1757% corrected for slip ) was shown beyond the low elastic area, even though the sustainable PGM–PHL–PGM(15–60–15) had a little smaller or similar M n,SEC value of 90.0 kg mol –1 , compared to those of commercially petroleum-derived TPEs based on a triblock copolymer architecture (ABA-type), including SIS (Kraton D1107 with 15 wt % PS and 15 wt % diblock content, M n,SEC = 106.0 kg mol –1 ), SBS (Kraton D1101 with 31 wt % PS, M n,SEC = 135.0 kg mol –1 ), and MBM (Kuraray LA2140e with 23 wt % PMMA, M n,SEC = 67.0 kg mol –1 ). ,, The significantly improved elongation at break may suggest the potential to be employed as a superelastomer, , when compared to the elongations at break of the above-stated commodity TPEs (ε b for SIS, SBS, and MBM = 1300%, 726%, and 543%, respectively), ,, and even poly­(isobutylene)– graft –acetylated poly­( l -lactide) superelastomer with a f PLLA of 0.18 as we previously reported (ε b = 2560%) (Figure ). …”

“…It demonstrated a linear response tensile modulus (E = 1.21 MPa) at relatively low strains (<10%), a tensile strength at break (σ b ) of 0.59 MPa (or 0.44 MPa corrected for slip ), a strain at break (ε b ) of 910% (or 526% corrected for slip ), and a work to fraction (γ) of 3.9 MJ m −3 (or 1.6 MJ m −3 corrected for slip ). The PGM−PHL− PGM(15−60−15) triblock copolymer specimen also displayed 50,61,62 The significantly improved elongation at break may suggest the potential to be employed as a superelastomer, 3,63 when compared to the elongations at break of the above-stated commodity TPEs (ε b for SIS, SBS, and MBM = 1300%, 726%, and 543%, respectively), 24,64,65 and even poly(isobutylene)−graf t−acetylated poly(L-lactide) superelastomer with a f PLLA of 0.18 as we previously reported (ε b = 2560%) (Figure 6). 66 It is well-known that a hard block fraction composed of glassy amorphous or semicrystalline polymeric blocks 23 and the entanglement molar mass of the midblock in ABA-type triblock copolymers have a significant influence on mechanical characteristics.…”

Styrene‐butadiene‐styrene‐based shape memory polymers: Evolution and the current state of art

“…Elastomers have proved to be excellent materials in the purview of shape memory behavior with high deformation, excellent shape fixity, and recovery along with a quick recovery rate 159,160 . SBS in this context has proved to be an excellent thermoplastic for metamorphosing into a shape memory polymer 161,162 . The research on SBS‐based shape memory polymers has exceptionally risen by 68% since 2014 and is projected to evolve in the upcoming years (Figure 10).…”

“…159,160 SBS in this context has proved to be an excellent thermoplastic for metamorphosing into a shape memory polymer. 161,162 The research on SBS-based shape memory polymers has exceptionally risen by 68% since 2014 and is projected to evolve in the upcoming years (Figure 10). Moreover, the application of SBS-based shape memory elastomers has widened since its inception in the shape memory realm (Figure 26).…”

Shape-Memory Composites Based on Ionic Elastomers

“…Other approaches include the use of noncovalent supramolecular interactions, such as multiple hydrogen bonding [ 22 ], hydrophobic interactions, π–π stacking, metal–ligand coordination [ 23 ], and ionic interactions [ 24 ]. Among the latter group, different ionomers featuring the shape-memory effect have been reported [ 25 ].…”