Chemistry Reference
In-Depth Information
O
R
O
n
UV 250 to 450 nm
HSCH
2
CH
2
OH
R=H(
=1),
R=Me(
n
=1),or
R=CH
2
-
CH
-
CH
2
(
n
=3)
n
O
R
O
n
S
OH
Scheme 4.13 Reaction of unsaturated materials with 2ME.
34
In the case of canola
oil, the formed polyol was successfully used to make PU.
with three end-groups (hydroxyl, carboxyl and trimethoxysilane) were re-
ported. One of the end-groups synthesized by this method, macrodiol, was
used for the formation of poly(ester urethane) with 4,4
0
-methylenebis-
(phenylisocyanate) and 1,4-butanediol (as a chain extender). Two T
g
values
(
45 and
รพ
55 1C) and two melting temperatures (
9 and 190 1C) were ob-
served, suggesting the formation of block polymers with a phase-separated
morphology. A further study of analogous poly(ester urethane)s as drug-
release agents was reported by the same group.
49
Desroches et al.
34
reacted 2ME with oleic acid, methyl oleate, methyl
linoleate, and canola oil with irradiation with a UV light (250-450 nm)
without an initiator, with or without solvent (ethanol). The obtained prod-
ucts contained the primary alcohol group from 2ME (Scheme 4.13) and were
used successfully to react with isocyanates to form elastomeric PUs. The PUs,
obtained from 2ME-modified canola oil and isocyanates, had thermal
properties (T
g
, mass loss at 200 1C and residual mass at 500 1C) that are close
to PUs from the same isocyanates and commercial polyols.
Next, the group investigated the same thiol-ene reaction of canola oil
methyl esters with 2ME, followed (or preceded) by an esterification of the
carboxylic ester group with ethylene glycol.
46
The product mixture obtained
by this strategy had a hydroxyl group functionality close to two; cor-
respondingly, the PU formed from it had high fractions soluble in DMF
(76%) and THF (38%).
In a subsequent report, the same group
45
used soybean methyl
esters to form diols. The double bonds were converted to primary -OH
groups using the thermal thiol-ene reaction with 2ME (Schemes 4.14 and
4.15). The carboxylic group was either transesterified with a diol or
amidified with diamine or amine-alcohol. Details of the SBO used for
the synthesis were not described. A typical SBO contains mostly linoleic
acid. Linoleic acid can react with two moles 2ME, and in the following
transesterification would yield a product with 3 -OH groups per molecule.
The reported relatively low numbers (2.01 to 2.63 -OH groups per
molecule) imply that either the high-oleic variety of SBO was used or close
to 50% of the olefinic bonds reacted with 2ME.
When the diols were reacted with Voramer 2093, a series of soft PU
pre-polymers of methylene diphenyl-4,4
0
-diisocyanate, the product started
