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Abstract A bio-based poly (urethane urea) (CIPUU) network comprised of castor oil (CO), isosorbide (IS) and 4-aminophenyl disulfide (APD) was prepared and compared to the corresponding polyurethane (CIPU) consisting of CO and IS. Permanently cross-linked CIPU could not be reprocessed, while CIPUU could be reprocessed, as the network topology could rearrange through an associative disulfide exchange reaction. CIPUU had a higher Young's modulus than CIPU due to the higher rigidity of APD with benzene rings and the formed hydrogen bonding of the urea unit. Stress relaxation measurement indicated that the network topology of CIPUU was stable at temperatures lower than 100 °C due to the inactive disulfide exchange reaction at low temperatures. The exchange reaction became increasingly active with increasing temperature, as evidenced by the gradually reduced relaxation time. CIPUU showed excellent reprocessability, as indicated by the remaining gel fraction and fully recovered mechanical properties after thermal remoulding at 180 °C several times. In addition, CIPUU showed good thermal stability with an onset decomposition temperature (∼260 °C) much higher than the reprocessing temperature. Highlights • Poly (urethane urea) network consists of castor oil, isosorbide and 4-aminophenyl disulfide. • The poly (urethane urea) showed high modulus than the polyurethane without 4-aminophenyl disulfide. • Stress relaxation of the poly (urethane urea) became prominent at elevated temperatures. • The poly (urethane urea) network could be reprocessed without losing mechanical properties. • The poly (urethane urea) network showed good thermal stability. [ABSTRACT FROM AUTHOR]

Castor oil (CO) derived polyurethane networks exhibit poor mechanical properties and non-reprocessibility due to flexible, highly and permanently cross-linked network structures. To overcome these defects, we designed and fabricated a series of poly (urethane urea) (PUU) networks by reacting CO-based polyurethane precursor with different amounts of 4-aminophenyl disulfide (APD). The equilibrium swelling behavior, mechanical properties, stress relaxation and reprocessibility of the COPUU networks were investigated in detail in this study. The swelling ratio increased with increasing APD content due to the reduced crosslink density. The mechanical properties of the COPUU networks are tunable over a broad range (either as elastomers or as plastics) depending on the APD component inputs. The tensile strength, Young's modulus and elongation at break for COPUU composed of CO/APD (W/W, 7:3) were improved by 11.7, 2.7 and 5.2 times, respectively, compared to the control CO-based polyurethane without APD. The COPUU can be reprocessed though thermal compression molding and the mechanical properties recovered completely after reprocessing at 180 °C for several cycles. The stress relaxation of COPUU accelerated with increasing APD content due to the increasing concentration of exchangeable disulfide linkage. [ABSTRACT FROM AUTHOR]

To investigate the influence of main chain structure on the performance of anion exchange membranes (AEMs), crosslinked naphthalene-based block polymer AEMs are synthesized via nucleophilic polycondensation, Williamson reaction, atom transfer radical polymerization (ATRP) reaction, bromination, and quaternization. With a helical structure, the naphthalene-based triblock backbone can provide the ion channels inside AEMs, further enhance the ionic conductivity and dimensional stability. The crosslinked network of long alkyl chains ensures desirable mechanical properties of AEMs. The prepared NAPEK-PVP-X AEMs have a high alkaline stability, a low swelling ratio and a high ionic conductivity. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) are used to confirm the hydrophilic/hydrophobic microphase separated structure of the AEMs. More developed ion transport channels of naphthalene-based AEMs are shown by molecular dynamics (MD) simulations. A power density peak of 160.73 mW cm−2 is obtained by assembling the NAPEK-PVP-10-Q4 AEM into a single cell operating at 60 °C. The study provides a resource for future work on AEMs. [Display omitted] • Naphthalene-based triblock and bisphenol A-based triblock main chain are fabricated. • The long flexible crosslinked chain further enhanced the mechanical property of AEMs. • The naphthalene-based triblock polymer AEMs show efficient ion transport. [ABSTRACT FROM AUTHOR]