Glass‐transition temperature governs the thermal decrosslinking behavior of Diels–Alder crosslinked polymethacrylate networks

Abstract

A series of Diels–Alder (DA) crosslinked polymethacrylate networks covering a broad range of glass‐transition temperatures (Tg) was prepared to establish the relationship between the Tg and the thermal decrosslinking behavior of these networks. A series of permanently crosslinked and uncrosslinked analogues were also prepared to better understand the thermoset‐to‐thermoplastic transition occurring in the DA networks at elevated temperatures. The network series were studied using dynamic mechanical analysis, which established an inverse relationship between Tg and decrosslinking ability. Differential scanning calorimetry confirmed the viability of the DA linkages in all formulations, and a trapping experiment with 9‐anthracenemethanol demonstrated that even the least responsive network was capable of undergoing decrosslinking given appropriate thermal treatment. While polymer chain mobility has long been understood to be a critical factor in healable materials, this work verifies the importance of this parameter in the decrosslinking of DA networks. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 193–203

Versatile Synthesis of rac‐ and meso‐Hydroxymethyl Cyclohexenoids Containing Phenyl Groups: α‐/β‐Glucosidase Activities, Inhibition Kinetics and Molecular Docking Studies

“…The starting material, rel ‐(3 aR , 4 R , 7 S , 7 aS )‐3a,4,7,7a‐tetrahydro‐4,7‐epoxy isobenzofuran‐1,3‐dione ( 5 ), [17] was prepared quantitatively by furan and maleic anhydride cycloaddition reaction (Scheme 1). It was hydrolyzed after the carbonyl groups were reduced by heating with LiAlH 4 in dry THF using the known reduction method [18] .…”

“…rel ‐(3 aR , 4 S , 7 R , 7 aS )‐3 a,4,7,7 a‐tetrahydro‐4,7‐epoxyisobenzofuran‐1,3‐dione (5) . The compound 5 was synthesized according to the literature [17,37] . Furan (20 mL, 275.35 mmol) and maleic anhydride (5 g, 50.99 mmol) were stirred in diethyl ether (35 mL) for 1 hour at 0 °C and then at room temperature for 24 hours.…”

“…The compound 5 was synthesized according to the literature. [17,37] Furan (20 mL, 275.35 mmol) and maleic anhydride (5 g, 50.99 mmol) were stirred in diethyl ether (35 mL) for 1 hour at 0 °C and then at room temperature for 24 hours. After the reaction was completed, the white precipitates formed were filtered off, washed with ether, the solvent was evaporated to yield 5 as white solid without purification.…”

Reducing the reprocessing and healing temperature of polyurea with piperazine-based hindered urea bonds

“…Generally, polymer chain mobility is significantly decreased below T g , thus the bond exchange will be inhibited. [47][48][49] However, in some cases, segmental motion in glassy states can lead to the interpenetration of polymer chains, facilitating the remolding and/or healing process. 50 Our materials consist of a low-molecular weight polymer linked by dense dynamic urea bonds, similar to the situation in Prof. Aida's work, 50 which is favorable for bond exchange through segmental motion.…”

From gas release to foam synthesis, the second breath of blowing agents

“…105 This reaction is all the more interesting since depending on the substrates, the retro Diels-Alder (rDA) can yield gases such as nitrogen or carbon dioxide. The following techniques could possibly be used with PUs 106,107 , polymethacrylates 108,109 or polyesters 110 because DA reaction is already used for these types of polymers.…”