Bioinspired Sustainable Polymer with Stereochemistry-Controllable Thermomechanical Properties

Abstract

The regulation of polymer properties based on stereochemistry is essential but rarely studied. Inspired by the isomerization of unsaturated phospholipids in cell membranes, we report a novel method of preparing stereocontrolled polymer using sustainable Eucommia ulmoides gum (EUG) as a raw material. Under the catalysis of thiyl radical, EUG with 100% trans-1,4polyisoprene structure isomerized to cis-configuration partly in a controllable way, thus achieving the rational modulate of thermomechanical properties. The isomerization mechanism was verified by density functional theoretical calculation. The isomerized EUG (IEUG) with low cis content (≤8.7%) can serve as plastics or shape memory materials, while high cis content (≥10.7%) IEUG transferred into elastomer materials. Especially for IEUG-10.7%, its vulcanizates without filler reinforcement shows high tensile strength (15.5 MPa) and elasticity (97%) comparable to natural rubber due to its strain-induced crystallization ability, which has the potential to be the second natural rubber. This paper provides a new strategy for stereocontrol of polymer properties, and the prepared materials have broad application prospects in the intelligent sensing and rubber industry.

Effect of Stereoregularity on Strain-Induced Crystallization and Mechanical Properties of Natural Rubber

“…That is, the iNR contains both cis and trans configurations in the molecular chain. Furthermore, the carbon protons signal at 32.2 ppm (C a ) and 40.0 ppm (C j ) relative to cis and trans configurations are split into two signals, indicating that the cis and trans units are chemically bonded rather than physically blended. , …”

“…37 After isomerization modification, a new trans-configuration absorption peak appeared at 801 cm −1 , which proved the successful preparation of iNR. 36 The absorption peaks at 1739 and 1544 cm −1 correspond to the stretching vibration of C�O and the bending vibration of N−H, respectively, which are derived from nonrubber components such as proteins and phospholipids. 18,23,38 These characteristic peaks are not observed in the FI-TR spectra of IR due to the absence of nonrubber components (Figure S1).…”

“…Furthermore, the carbon protons signal at 32.2 ppm (C a ) and 40.0 ppm (C j ) relative to cis and trans configurations are split into two signals, indicating that the cis and trans units are chemically bonded rather than physically blended. 36,40 The isomerization reaction conditions were studied to control the trans-content of iNR. Based on our previous work, 36 we kept the TG and AIBN dosage constant at 50 and 1 wt %, respectively.…”

“…In addition to intake from unhealthy diets such as hydrogenated vegetable oils, trans fatty acids have also been found to be produced endogenously through thiyl radical-catalyzed cis - trans isomerization of fatty acids. − This particular reaction has been well studied by experiments and simulation calculations. ,− It was found that unsaturated fatty acids preferentially undergo isomerization reactions rather than thiol–ene click reactions at low concentrations of thiyl radicals because the former has a lower energy barrier. , At the same time, the isomerization is reversible, and the opposite reaction accompanies the isomerization of the cis -configuration to the trans -configuration . In our previous work, we applied the isomerization reaction to the modification of Eucommia ulmoides gum ( trans -polyisoprene) for the first time and achieved the stereochemical control of its properties. This modification method lays a foundation for the control of the stereoregularity of the NR.…”

“…34,35 At the same time, the isomerization is reversible, and the opposite reaction accompanies the isomerization of the cis-configuration to the trans-configuration. 34 In our previous work, 36 we applied the isomerization reaction to the modification of Eucommia ulmoides gum (trans-polyisoprene) for the first time and achieved the stereochemical control of its properties. This modification method lays a foundation for the control of the stereoregularity of the NR.…”