![]() For instance, a spiroacetal epoxy monomer has been used to produce cellulose nanofiber composites with chemical recyclability. Furthermore, spirocyclic acetal structures are sensitive to acidic conditions, which can be utilized to design polymers with degradability or chemical recyclability. (11−15) These structures are rather rigid, which can effectively enhance the thermal and mechanical properties of the polymers. Spirocyclic acetal structures have received growing attention in the development of biobased polymers because they can be produced from various biobased polyols (e.g., pentaerythritol, glycerol, xylitol, xylose, etc.) and aldehydes (e.g., 5-hydroxymethyl furfural, levulinic acid, vanillin, glyoxylic acid, etc.). In this work, we have demonstrated that these telechelic polyesters can be conveniently converted back into poly(acetal-ester)s via cycloacetalization reactions with pentaerythritol. After acidic hydrolysis, telechelic polymers exclusively terminated by two aldehyde end groups were obtained. We found that the acetal units in the copolyesters could be selectively hydrolyzed under acidic conditions while virtually retaining all of the ester bonds in the polymer backbone. The presence of the spiroacetal units in the polyesters not only enhanced the T g (up to 103 ☌) and thermal stability ( T 5 ≥ 300 ☌) but also the oxygen barrier of solution-cast films. ![]() ![]() Up to 50 mol % of spirocyclic diol (with respect to DMT) could be incorporated in the copolyesters, but a reasonably high molecular weight was only achieved when ≤30 mol % of the spirocyclic diol was used. In the present work, a vanillin-based diol with a spirocyclic acetal structure was incorporated in a series of rigid amorphous polyesters based on neopentyl glycol and dimethyl terephthalate (DMT). Spirocyclic acetal structures have recently received growing attention in polymer science due to their dual potential to raise the glass transition temperature ( T g) and enable chemical recycling of biobased polymers. ![]()
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