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Title: Sustainable polyacetals from erythritol and bioaromatics

The polymerization of biorenewable molecules to polymers with hydrolyzable main‐chain functionality is one approach to identifying sustainable replacements for common, environmentally unsound packaging plastics. Bioaromatic polyacetals were synthesized via acid‐catalyzed acetal formation from dialdehydes and tetraols. Ethylene linked dialdehyde monomersVVandSSwere constructed from bioaromatics vanillin and syringaldehyde, respectively. Tetraol monomers included biogenic erythritol (E), along with pentaerythritol (P), and ditrimethylolpropane (D). Four copolymer series were prepared with varying tetraol content:E/PVV;E/DVV;E/PSS; andE/DSS. Number average molecular weights (Mn) ranged from 1,400 to 27,100 Da. Generally, the copolymerization yields were inversely proportional to the feed fraction of erythritol (E), implying that tetraolsPandDreact more readily. The materials were typically amorphous and exhibited glass transition temperatures (Tg) ranging from 57 to 159 °C, suitably mimicking theTgvalues of several commodity plastics. The syringaldehyde‐based copolymers exhibited a higherTgrange (71–159 °C) than the vanillin‐based copolymers (57–110 °C). Accelerated degradation studies in aqueous HCl (3M, 6M, concentrated) over 24 h showed that degradation (Mndecrease) was proportional to the acid concentration. A one‐year degradation study ofE50/D50‐SS(from 50% feed of erythritol) in seawater, deionized water, tap water, or pH 5 buffer showed noMndecrease; but in pH 1 buffer, the decrease was 40% (18,800 to 11,200). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 44089.

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Author(s) / Creator(s):
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Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Journal of Applied Polymer Science
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Abstract

    Linear polyphosphonates with the generic formula –[P(Ph)(X)OR′O]n– (X = S or Se) have been synthesized by polycondensations of P(Ph)(NEt2)2and a diol (HOR′OH = 1,4‐cyclohexanedimethanol, 1,4‐benzenedimethanol, tetraethylene glycol, or 1,12‐dodecanediol) followed by reaction with a chalcogen. Random copolymers have been synthesized by polycondensations of P(Ph)(NEt2)2and mixture of two of the diols in a 2:1:1 mol ratio followed by reaction with a chalcogen. Block copolymers with the generic formula –[P(Ph)(X)OR′O](x + 2)–[P(Ph)(X)OR′O](x + 3)– (X = S or Se) have been synthesized by the polycondensations of Et2N[P(Ph)(X)OR′O](x + 2)P(Ph)NEt2oligomers with HOR′O[P(Ph)(X)OR′O](x + 3)H oligomers followed by reaction with a chalcogen. The Et2N[P(Ph)(X)OR′O](x + 2)P(Ph)NEt2oligomers are prepared by the reaction of an excess of P(Ph)(NEt2)2with a diol while the HOR′O[P(Ph)(X)OR′O](x + 3)H oligomers are prepared by the reaction of P(Ph)(NEt2)2with an excess of the diol. In each case the excess, x is the same and determines the average block sizes. All of the polymers were characterized using1H,13C{1H}, and31P{1H} NMR spectroscopy, TGA, DSC, and SEC.31P{1H} NMR spectroscopy demonstrates that the random and block copolymers have the expected arrangements of monomers and, in the case of block copolymers, verifies the block sizes. All polymers are thermally stable up to ~300°C, and the arrangements of monomers in the copolymers (block vs. random) affect their degradation temperatures andTgprofiles. The polymers have weight average MWs of up to 3.8 × 104 Da.

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    Thermomechanical properties of polymers highly depend on their glass transition temperature (Tg). Differential scanning calorimetry (DSC) is commonly used to measureTgof polymers. However, many conjugated polymers (CPs), especially donor–acceptor CPs (D–A CPs), do not show a clear glass transition when measured by conventional DSC using simple heat and cool scan. In this work, we discuss the origin of the difficulty for measuringTgin such type of polymers. The changes in specific heat capacity (Δcp) atTgwere accurately probed for a series of CPs by DSC. The results showed a significant decrease in Δcpfrom flexible polymer (0.28 J g−1K−1for polystyrene) to rigid CPs (10−3J g−1K−1for a naphthalene diimide‐based D–A CP). When a conjugation breaker unit (flexible unit) is added to the D–A CPs, we observed restoration of the ΔcpatTgby a factor of 10, confirming that backbone rigidity reduces the Δcp. Additionally, an increase in the crystalline fraction of the CPs further reduces Δcp. We conclude that the difficulties of determiningTgfor CPs using DSC are mainly due to rigid backbone and semicrystalline nature. We also demonstrate that physical aging can be used on DSC to help locate and confirm the glass transition for D‐A CPs with weak transition signals. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2019, 57, 1635–1644

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    This work was partially supported by the U.S. National Science Foundation (NSF) Award No. ECCS-1931088. S.L. and H.W.S. acknowledge the support from the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 22011044) by KRISS.

    Figure 1


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