Design and Synthesis of Multigraft Copolymer Thermoplastic Elastomers: Superelastomers

Abstract

worldwide elastomer market, as sealants, coatings, adhesives, sporting good components, automotive parts, footwear, and as biomedical materials. [1] Prepared by living anionic polymerization, styrenic thermoplastic elastomers (S-TPEs), including polystyrene-blockpolyisoprene-block-polystyrene (SIS) and polystyrene-block-polybutadiene-blockpolystyrene (SBS), were first developed by Holden and Millkvich in the early 1960s and have since then become widely used in our daily life. [2,3] The exceptional mechanical properties of S-TPEs are attributed to the microphase separation between the two chemically incompati ble domains where hard polystyrene (PS) domains serve as physical cross-links for the soft polybutadiene (PB) or polyisoprene (PI) matrix. Mechani cal properties, such as tensile strength, Young's modulus, and elasticity, are tunable based on volume fractions of hard and soft domains. One limitation of S-TPEs is the restricted upper service temperature (UST), which is limited by the glass transition temperature (T g ) of polystyrene (T g ≈ 100 °C). When the service temperature is approaching 100 °C, softening of PS domains disrupts the physical cross-links, leading to a sharp drop of storage modulus. Numerous studies have been carried to increase the UST of S-TPEs by either replacing polystyrene with another higher T g polymer [4][5][6][7][8] or using catalytic hydrogenation to fully saturate PS into polyvinylcyclohexane (T g ≈ 150 °C). [9] With recent advances in living/controlled polymerization, various nonlinear architectures, including star, [10][11][12][13][14] graft, and cyclic [15,16] architectures, or their combinations, [17][18][19][20] have been synthesized during the past three decades. These nonlinear macromolecular architectures deliver additional parameters for chemists to use in tuning mechanical properties, as well as incorporating additional functionality to TPEs [21] (Figure 1).In this short review, we focus on the progress in design and synthesis of well-defined multigraft copolymers and their application as thermoplastic elastomers. Progress in precise synthesis of graft copolymers and mechanical properties of multigraft copolymers is first summarized. Recent work on all-acrylic graft copolymer TPEs and a low-cost emulsion polymerization approach to prepare multigraft copolymers are introduced subsequently. Finally, we finish the review with conclusions and some future prospectives. Living Anionic PolymerizationsThermoplastic elastomers (TPEs) have been widely studied because of their recyclability, good processibility, low production cost, and unique performance. The building of graft-type architectures can greatly improve mechanical properties of TPEs. This review focuses on the advances in different approaches to synthesize multigraft copolymer TPEs. Anionic polymerization techniques allow for the synthesis of well-defined macromolecular structures and compositions, with great control over the molecular weight, polydispersity, branch spacing, number of branch points, and branch point ...

Triblock polyester thermoplastic elastomers with semi-aromatic polymer end blocks by ring-opening copolymerization

“…Compared to these samples, TBPE-5 has more linear stress-strain behaviour, a lower E y (18 AE 3 MPa) and higher elastic recoverythese properties correlate with SAXS data showing a cylindrical hard-block morphology. 80,81 For TBPE-2 to -5, the Young's Modulus decreases (E y ¼ 226 to 18 MPa) with increasing molar mass (M n ¼ 61 to 102 kg mol À1 , Đ $ 1.1) and this is likely attributed to phase morphology changes. It is expected that for this volume fraction, i.e.…”

“…5 For example, commercial SIS/SBS TPEs typically have a polystyrene content f hard ¼ 0.2-0.4. 80,81 Highly transparent and completely colourless free-standing lms of the triblock polymers were prepared by solvent casting from dichloromethane solutions of the polymer (Fig. S17 †).…”

Syndiospecific Coordination Polymerization of Si‐H‐Containing Styrenes Catalyzed by Scandium Complex and Synthesis of Styrene‐Based Triblock Copolymers

“…So far, the reports on sPS block copolymers mainly concentrate on diblock or multi‐block copolymers obtained by one‐step monomer feeding process via coordination polymerization, basing on the different properties (for example, the reactivity) of monomers. However, there are few reports on sPS block copolymer synthesis strategy of sequential monomer feeding process, although this pathway has been widely used in living anionic polymerization technology to obtain traditional thermoplastic elastomers such as SBS and SIS . Recently, crystalline SBS and SIS have been successfully prepared by rare‐earth metal based catalyst systems.…”

Dispersity and architecture driven self-assembly and confined crystallization of symmetric branched block copolymers

“…This is consistent with the observations described for other branched block polymers. 62 This trend may also have contributed with the increased difficulty of capturing TEM micrographs associated with the arachnearm architectures. Likewise, the On the basis of the TEM micrograph in Figure 5a, the average radius of the circular domains ranges from 9-13 nm, which is reasonably consistent with the SAXS analysis.…”