The Role of Non-Rubber Components on Molecular Network of Natural Rubber during Accelerated Storage

Zhang, Huifeng; Zhang, Lu; Chen, Xu; Wang, Yueqiong; Zhao, Fuchun; Luo, Ming‐Chao; Liao, Shuangquan

doi:10.3390/polym12122880

Cited by 22 publications

(20 citation statements)

References 53 publications

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“…4d and S7 †), which is ascribed to the high temperature, salt, acid and base environments, which caused further cross-linking reactions of the unsaturated bonds in SFPCMs. 79,80 One prominent feature is the reduction effect of saturated NaCl on the elongation at break of the SFPCMs because of the decrease in the mobility of the NR chains originating from the penetration of the high-salt ion solution in the NR matrix. Although the SFPCMs are in a phase transition state during the 120 h accelerated stability experiments, the elongation at break of the SFPCMs was maintained over 350% aer these treatments.…”

Section: Salient Stability Of Sfpcmsmentioning

confidence: 99%

Super-flexible phase change materials with a dual-supporting effect for solar thermoelectric conversion in the ocean environment

et al. 2023

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Section: Salient Stability Of Sfpcmsmentioning

confidence: 99%

Super-flexible phase change materials with a dual-supporting effect for solar thermoelectric conversion in the ocean environment

et al. 2023

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“…In order to magnify the chemical and mechanical properties of IRs, the molecular insights of the association of terminal ends of polyisoprene chains of NR are needed. The raw latex of NR extracted from the Hevea brasiliensis tree comprises rubber particles, protein, metal ions, carbohydrates, lipids, and others. − Hevea NR predominantly comprises cis polyisoprene as a main chain and two types of end functional groups. , The fundamental structure of the polymer chain of NR is constituted by cis -1,4-polyisoprene as a main chain structure, ω-end, and α-end. The ω-end consists of a single unit of dimethyl allyl (DMA) and two to three trans -1,4-isoprene units. ,, The α-terminal consists of hydroxy, ester, ,,,, and phosphate groups .…”

Section: Introductionmentioning

confidence: 99%

Role of Terminal Groups of cis-1,4-Polyisoprene Chains in the Formation of Physical Junction Points in Natural Rubber

Dixit

Taniguchi

2023

Biomacromolecules

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The terminal structures of cis-1,4-polyisoprene (PI) chains play a vital role in the excellent comprehensive performance of Hevea natural rubber (NR) with properties such as high toughness, tear-resistance, and wet skid resistance. The cis-1,4polyisoprene chain constituting NR exhibits a distinct composition of terminal groups comprising two distinct types, namely, the ω and α terminal groups. The structures of the ω terminal [dimethyl allyl (DMA)-(trans-1,4-isoprene) 2 ] and six kinds of α end groups of the polymer chain of NR have been explored by utilizing a newly developed 2D NMR method. In the present work, we examine different kinds of PI melt systems, and we choose various combinations of terminal groups: Hydrogen, one DMA unit with two trans isoprene units as ω end groups and ester-terminated isopentene (α1), hydroxy-terminated isopentene (α2), ester-terminated isobutane (α3), hydroxy-terminated isobutane (α4), esterterminated 1,4-cis-isoprene (α5), and hydroxy-terminated 1,4-cis-isoprene (α6), i.e., H PI H (PI 0 )−pure PI (Hydrogen terminal), ω PI α1 (PI I ), ω PI α2 (PI II ), ω PI α3 (PI III ), ω PI α4 (PI IV ), ω PI α5 (PI V ), and ω PI α6 (PI VI ). We evaluated dynamic and static properties of PI chains such as the end-to-end vector autocorrelation function (C(t)), its average relaxation time (τ), end-to-end distance (R ee ), and radius of gyration (R g ). We also estimated the diffusion coefficients of polyisoprene chains and pair correlation functions [radial distribution functions (RDFs)], potentials of mean force (PMFs) in between end residues, and survival probability (P(τ)) of end groups around the end group by analyzing the equilibrated trajectories of full-atom MD simulations. As per the examination of C(t), rotational relaxation time τ, and RDFs, we discovered that the existence of a strong hydrogen bond in α2−α2, α4−α4, and α6−α6 residues makes the dynamics of hydroxy-terminated polyisoprene chains in ω PI α2,α4,α6 melt systems slower. From the analyses of RDFs and PMFs (W(r)), the association between [α2]−[α2], [α4]−[α4], and [α6]−[α6] terminals in ω PI α2,α4,α6 melt systems is significantly stronger than in [ISO]−[ISO] [Hydrogen terminated 1,4-cis-isoprene:(ISO)] in H PI H and ω−ω, [α1]−[α1], [α3]−[α3], and [α5]− [α5] in ω PI α1,α3,α5 systems. We quantified the fraction of cluster formation of terminal groups of a given size in the seven PI melt systems by employing the criteria of PMFs. It is revealed that no stable cluster exists in the H PI H , ω PI α1 , ω PI α3 , and ω PI α5 melt systems. Conversely, in the ω PI α2 , ω PI α4 , and ω PI α6 systems, we perceived stable clusters of [(α2) p ] [(α4) p ] and [(α6) p ] end groups where p (2 ≤ x ≤ 6). These stable clusters validate the presence of physical junction points in between hydroxy-terminated polyisoprene chains through their α2, α4, and α6 terminals. These physical junction points might be crucial for superior properties of NR such as high toughness, crack growth resistance, and strain-induced crystallization.

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“…The natural rubber from Hevea brasiliensis consists of rubber particles, protein, lipid, carbohydrates, metal ions, and others. − Hevea natural rubber is mainly composed of cis -1,4-polyisoprene and two kinds of functional terminal groups. , The basic structure of natural rubber consists of cis -1,4-polyisoprene, ω-terminal and α-terminal. ω-Terminal contains a dimethylallyl group and two to three trans -isoprenes. ,, α-Terminal consists of hydroxy, ester, and phosphate groups. ,,− The resistance of rubber to the deformation and fracture before vulcanization is called the green strength .…”

Section: Introductionmentioning

confidence: 99%

“…Tanaka et al − have thoroughly investigated these functional groups using NMR and presumed that lipid molecules associate with α-terminal via a hydrogen bond or an ionic bond . In a recent experimental study, it was assumed that the formation of branching points in between terminal groups of molecular chains of NR plays a vital role in the strain-induced crystallization of NR. ,− The structural mechanism of branching-point formation is still missing. In the present work, we investigate the role of ω-terminal and α-terminal in the formation of branching points between terminal groups of polyisoprene chains but without any carbohydrates, metal ions, proteins, and lipids by performing coarse-grained and all-atom molecular dynamics simulations.…”

Section: Introductionmentioning

confidence: 99%

Substantial Effect of Terminal Groups in cis-Polyisoprene: A Multiscale Molecular Dynamics Simulation Study

Dixit

Taniguchi

2022

Macromolecules

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Hevea natural rubber (NR) consists of 99% cis-polyisoprene with dimethyl allyl-(trans-1,4-isoprene)2 (ω) and α terminal groups. These terminal groups provide excellent mechanical and physical properties to NR. Oochi et al. (Oouchi, M.; Ukawa, J.; Ishii, Y.; Maeda, H. Biomacromolecules 2019, 20, 1394–1400) have elucidated the structures of six types of α terminals of NR by using a solid -state NMR study. We examine four types of cis-1,4-polyisoprene (PI) melt systems with different combinations of dimethyl allyl-(trans-1,4-isoprene)2 (ω) and hydroxylated isoprene (α6) terminal groups, i.e., pure PI (no terminal) (PII), ω-PI-ω (PIII), ω-PI-α6 (PIIII), and α6-PI-α6 (PIIV). From the obtained equilibrated systems, we computed the end-to-end vector autocorrelation function (C(t)), average relaxation time (τ), end-to-end distance (R e), radius of gyration (R g), self-diffusion coefficients of polymer chains, radial distribution functions (RDFs) between terminal residues, and survival probability (P(τ)) for terminal groups. From the analysis of C(t), τ, and self-diffusion coefficients, we found that the presence of a hydrogen bond between α6 residues makes the dynamics of polymer chains slower in PIIII and PIIV melt systems. From the analyses of RDFs and the potentials of mean force (W(r)), the association between α6 terminals in ω-PI-α6 and α6-PI-α6 is significantly stronger than the isoprene–isoprene association in PII and the ω–ω association in PIII. By the analysis based on the obtained potential of the mean field, we calculated the cluster-formation fraction of terminal groups associated in clusters of a given size in the four systems. We found that in the PII and PIII systems no firm cluster formation is observed, but in the ω-PI-α6 and α6-PI-α6 systems, stable clusters of α6 terminals with a size s (2 ≤ s ≤ 5) are observed, which supports the formation of multiple branching points in between polyisoprene chains through their α6 terminals. We also found that the cluster-formation fraction in the α6-PI-α6 system is significantly enhanced compared to that in the ω-PI-α6 system.

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The Role of Non-Rubber Components on Molecular Network of Natural Rubber during Accelerated Storage

Cited by 22 publications

References 53 publications

Super-flexible phase change materials with a dual-supporting effect for solar thermoelectric conversion in the ocean environment

Super-flexible phase change materials with a dual-supporting effect for solar thermoelectric conversion in the ocean environment

Role of Terminal Groups of cis-1,4-Polyisoprene Chains in the Formation of Physical Junction Points in Natural Rubber

Substantial Effect of Terminal Groups in cis-Polyisoprene: A Multiscale Molecular Dynamics Simulation Study

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