Recyclable Polydimethylsiloxane Network Crosslinked by Dynamic Transesterification Reaction

Zhang, Huan; Cai, Chao; Liu, Wen‐Xing; Li, Dongdong; Zhang, Jiawei; Zhao, Ning; Xu, Jie

doi:10.1038/s41598-017-11485-6

Cited by 84 publications

(79 citation statements)

References 66 publications

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“…These dynamic cross‐linked networks follow an associative exchange mechanism, in which exchange reactions under certain stimuli permit the change of network topology while keeping the number of bonds and cross‐links constant . Since their discovery, research has been directed toward the development of new types of associative exchangeable chemistries, and practical applications for high‐performance or functional material innovations . Previously, we developed poly(butylene terephthalate) (PBT) vitrimers via the incorporation of glycerol into PBT in the solid state .…”

Section: Methodsmentioning

confidence: 99%

In Situ Network Formation in PBT Vitrimers via Processing‐Induced Deprotection Chemistry

Zhou

Goossens

Bergen

et al. 2018

Macromol. Rapid Commun.

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in the solid state. [38,45] In general, the terminal relaxation behavior of PBT vitrimers above the melting temperature was rarely observed at angular frequencies down to 10 −2 s −1 in the temperature range from 250 to 270 °C. [37,38,45] Considering that typical shear rates during injection molding are as high as 10 000 s −1 and the viscosity of PBT vitrimers can be up to 10 7 Pa s at 250 °C, these PBT vitrimers cannot be processed like neat PBT during the short residence times typical for extrusion and injection molding. [52] Here, we propose a controllable way to process PBT vitrimers (based on transesterification exchange reactions) via controlling the network formation with the help of protection-deprotection chemistry. In this way, we can overcome the relatively long relaxation times and high viscosities associated with PBT vitrimers and maintain the high production rates of final parts by injection molding as for neat PBT. The strategy is schematically shown in Scheme 1: pentaerythritol is first converted into 5,5-bis(hydroxymethyl)-2-phenyl-1,3-dioxane (BPO, melting point 135-137 °C) via benzaldehyde protection chemistry. [53] Subsequently, this diol is incorporated into the PBT backbone via solid-state (co)polymerization to form a linear copolyester in line with earlier work from our group on PBT modification in the solid state. [54][55][56][57][58][59][60] The linear polymer chain is then transformed into a network via deprotection of the benzal group to afford a linear polymer chain with pendent-free hydroxyl groups for further thermal transesterification of the linear copolyester catalyzed by the Zn(II) catalyst. If deprotection and subsequent cross-linking takes place during processing, we can combine an initial low viscosity with final vitrimer characteristics.Normally, the deprotection step to obtain the linear copolyester with pendent hydroxyl groups, as shown in Scheme 1, involves an acid-promoted deprotection of the benzal group at room temperature and an acid used often is trifluoroacetic acid (TFA). [53] Accidentally we discovered that compression molding of the linear copolyester with benzal protection groups resulted in a cross-linked material with vitrimer characteristics, even without deprotection with TFA. This observation is in contrast to results previously reported by Collard et al., [53] who obtained thermoset materials after incorporation of BPO into PBT and poly(ethylene terephthalate) (PET) and repeated subsequent cycling to 300 °C in differential scanning calorimetry (DSC). Driven by this intriguing result and its practical relevance, we investigated the in situ network formation in more Vitrimers Although the network dynamics and mechanical properties of poly(butylene terephthalate) vitrimers can to some extent be controlled via chemical and physical approaches, it remains a challenge to be able to process PBT vitrimers with the same processing conditions via, for example, injection molding as neat PBT. Here, it is shown that the use of protected pentaerythritol as a latent cross...

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Section: Methodsmentioning

confidence: 99%

In Situ Network Formation in PBT Vitrimers via Processing‐Induced Deprotection Chemistry

Zhou

Goossens

Bergen

et al. 2018

Macromol. Rapid Commun.

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“…In order to identify the possible contribution of the latter factor to the electrorheological and dielectric properties of the obtained elastomers, we assessed a degree of polymer crosslinking in composites vulcanized in an electric field or without it. The crosslinking degree was evaluated gravimetrically by determining the degree of swelling [ 53 , 54 ].…”

Section: Resultsmentioning

confidence: 99%

Electrorheological Properties of Polydimethylsiloxane/TiO2-Based Composite Elastomers

et al. 2020

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Electrorheological elastomers based on polydimethylsiloxane filled with hydrated titanium dioxide with a particle size of 100–200 nm were obtained by polymerization of the elastomeric matrix, either in the presence, or in the absence, of an external electric field. The viscoelastic and dielectric properties of the obtained elastomers were compared. Analysis of the storage modulus and loss modulus of the filled elastomers made it possible to reveal the influence of the electric field on the Payne effect in electrorheological elastomers. The elastomer vulcanized in the electric field showed high values of electrorheological sensitivity, 250% for storage modulus and 1100% for loss modulus. It was shown, for the first time, that vulcanization of filled elastomers in the electric field leads to a significant decrease in the degree of crosslinking in the elastomer. This effect should be taken into account in the design of electroactive elastomeric materials.

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“…On the contrary, the glass transition temperatures (Tg) of PBZ-SA3 (138 °C) and PBZ-SA4 (133 °C), which could be reflected by the tanδ peaks, were apparently lower than that of PBZ-SA1 (148 °C) and PBZ-SA2 (144 °C). One of possible reasons for this was that the crosslink density of the thermoset increased by adding SA 36 , however, more transesterification reaction would happen, which might improve the flexibility of the network simultaneously 37 . In addition, by only increasing the Zn(Ac) 2 content, it was noted that the E ′ of the PBZ-SA2 and PBZ-SA4 had no marked change when compared to PBZ-SA1 and PBZ-SA3, respectively, while the Tg values showed a slightly decrease.…”

Section: Resultsmentioning

confidence: 99%

Thermally assisted self-healing behavior of anhydride modified polybenzoxazines based on transesterification

Huang

Zhang

et al. 2018

Sci Rep

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A self-healing polybenzoxazine is synthesized solely based on dynamic ester bonds. For this purpose, an anhydride (succinic anhydride) was added into bisphenol F derived benzoxazine monomer before thermocuring. Owing to the transesterification of newly formed ester bonds, the thermoset network behaves as a thermoplastic at 140 °C in the presence of Zn (Ac)2, and shows self-healing properties even after multiple damage-healing cycles. Furthermore, kinetics study indicates that the transesterification is a first-order reaction and the activation energy is about 135.4 kJ/mol. This study proposes a facile and economical way to prepare self-healing polybenzoxazine. It has promising applications in coating, adhesive, and other smart materials that rely on structurally dynamic polymers.

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Recyclable Polydimethylsiloxane Network Crosslinked by Dynamic Transesterification Reaction

Cited by 84 publications

References 66 publications

In Situ Network Formation in PBT Vitrimers via Processing‐Induced Deprotection Chemistry

In Situ Network Formation in PBT Vitrimers via Processing‐Induced Deprotection Chemistry

Electrorheological Properties of Polydimethylsiloxane/TiO2-Based Composite Elastomers

Thermally assisted self-healing behavior of anhydride modified polybenzoxazines based on transesterification

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