A six-membered cyclic carbonate derived from natural sugar ᴅ-mannose was prepared using CO 2 as a C1 building block at room temperature and atmospheric pressure. The monomer was synthesized in two steps from a commercially available mannopyranose derivative. Polycarbonates were rapidly prepared at ambient temperature by controlled ringopening polymerization (ROP) of the monomer, initiated by 4-methylbenzyl alcohol in the presence of 1,5,7-triazabicyclo[5.4.0]dec-5-ene (TBD) as the organocatalyst. Head-to-tail regiochemistry was indicated by NMR spectroscopy and is supported by DFT calculations. These aliphatic polycarbonates exhibit high-temperature resistance and demonstrate potential for post-polymerization functionalization, suggesting future application as high-performance commodity and biomedical materials.
Complete aqueous dissolution of starch
requires the use of temperatures
exceeding 100 °C. During and after cooling of the resultant aqueous
solutions, starch polymers precipitate by aggregation and crystallization.
Low-temperature gelatinization and dissolution of maize starch (MS)
is induced, and the stability of the resultant solutions is enhanced
when they contain the hydrotrope sodium salicylate (NaSal). Differential
scanning calorimetry and optical microscopy evidence showed that MS
gelatinization shifts to lower temperatures and that the associated
enthalpy decreases with increasing NaSal concentrations. The enhanced
gelatinization and dissolution are probably brought about by the association
of NaSal with the more hydrophobic MS structural moieties. The minimum
NaSal content of aqueous mixtures allowing full gelatinization of
MS at room temperature, that is, about 11 wt %, was found to be independent
of MS content (in the range 10–66.7 wt % MS).
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