Thermal Tranesterification of Bis(hydroxymethyl)propane-1,3-diyl Units in (Poly(ethyl terephthalate) and Poly(butylene terephthalate):  A Route to Thermoset Polyesters

Kriegel, Robert M.; Collard, David M.; Liotta, Charles L.; Schiraldi, David A.

doi:10.1021/ma9710949

Cited by 9 publications

(9 citation statements)

References 17 publications

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“…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., 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 detail and compared the dynamic network formed by this novel processing‐induced method with that from a common TFA‐promoted deprotection method.…”

Section: Methodscontrasting

confidence: 98%

“…Normally, the deprotection step to obtain the linear copolyester with pendent hydroxyl groups, as shown in Scheme , involves an acid‐promoted deprotection of the benzal group at room temperature and an acid used often is trifluoroacetic acid (TFA) . 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.…”

Section: Methodsmentioning

confidence: 99%

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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: Methodscontrasting

confidence: 98%

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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“…Monomers 1-7 were copolymerized with PET (0.04 mol % FBA) by a standard melt-polymerization procedure (285-290°C) 17 on a 4 mole scale. Polymers were characterized by fluorescence and intrinsic viscosity (IV).…”

Section: Copolymerization Of Fba With Petmentioning

confidence: 99%

“…1). 17 Incorporation of the comonomers into the backbone of the polymers was shown by precipitation of the polymer from a solution in trifluroacetic acid upon addition to methanol, followed by extensive extraction with a variety of solvents in a soxhlet extractor. Table I summarizes the absorption characteristics of the FBA monomers 1-7.…”

Section: Polymerizationmentioning

confidence: 99%

Pyrene and anthracene dicarboxylic acids as fluorescent brightening comonomers for polyester

Connor

Kriegel

Collard

et al. 2000

J. Polym. Sci. A Polym. Chem.

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“…The thermal methods involve the copolymerization with the crosslinkable comonomers of polyfunctional alcohols or acids in a standard PET synthesis of ethylene glycol and terephthalic acid or dimethyl terephthalate. The copolymerization of 5,5‐bis(hydroxymethyl)‐2‐phenyl‐1,3‐dioxane and trans‐esterification produced a thermoset polyesters . The copolymerization of dimethyl 2,6‐anthracenedicarboxylate and successive Diels–Alder cycloaddition with bis(maleimide) can form a thermally reversible crosslinked polyester .…”

Section: Introductionmentioning

confidence: 99%

Acetophenone‐assisted main‐chain photocrosslinking of poly(ethylene terephthalate)

Yun

Jang

2013

J of Applied Polymer Sci

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Maximum gel fraction of 99.1% was obtained under continuous UV irradiation of a UV energy of 200 J cm−2 on poly(ethylene terephthalate) (PET) containing only in presence of 2.9%(w/w) acetophenone (AP). The fragmented AP radicals abstract the hydrogen atoms of methylene units in PET, producing secondary methine radicals which couples to main‐chain crosslinks. The crystal structure of the crosslinked PET became disordered remarkably. The glass transition temperature disappeared and the peak thermal decomposition temperature was significantly retarded as much as 85°C. The crosslinking density and molecular weight between crosslinks reaches up to 0.129 mol g−1 and 7.7 g mol−1, respectively. Also tensile modulus and strength increased by 200 and 72% compared with those of the pristine PET respectively, resulting in more toughened PET. The solid‐state photocrosslinking may extend high‐temperature applications of PET with enhanced thermal and mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39802.

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Thermal Tranesterification of Bis(hydroxymethyl)propane-1,3-diyl Units in (Poly(ethyl terephthalate) and Poly(butylene terephthalate): A Route to Thermoset Polyesters

Cited by 9 publications

References 17 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

Pyrene and anthracene dicarboxylic acids as fluorescent brightening comonomers for polyester

Acetophenone‐assisted main‐chain photocrosslinking of poly(ethylene terephthalate)

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