Polycarbonates Derived from Glucose via an Organocatalytic Approach

An organocatalyzed
ring-opening polymerization methodology was
developed for the preparation of polycarbonates derived from glucose
as a natural product starting material. The cyclic 4,6-carbonate monomer
of glucose having the 1, 2, and 3 positions methyl-protected was prepared
in three steps from a commercially available glucose derivative, and
the structure was confirmed by means of NMR and IR spectroscopies,
electrospray ionization mass spectrometry (MS), and single-crystal
X-ray analysis. Polymerization of the monomer, initiated by 4-methylbenzyl
alcohol in the presence of 1,5,7-triazabicyclo[4.4.0]­dec-5-ene as
the organocatalyst, proceeded effectively in a controlled fashion
to afford the polycarbonate with a tunable degree of polymerization,
narrow molecular weight distribution, and well-defined end groups,
as confirmed by a combination of NMR spectroscopy, gel-permeation
chromatography, and MALDI-TOF MS. A distribution of head-to-head,
head-to-tail, and tail-to-tail regiochemistries was determined by
NMR spectroscopy and tandem MS analysis by electron transfer dissociation.
These polycarbonates are of interest as engineering materials because
of their origination from renewable resources combined with their
amorphous character and relatively high glass transition temperatures
as determined by X-ray diffraction and differential scanning calorimetry
studies.