Chemistry Reference
In-Depth Information
THF and hexafluoroisopropanol; the one formed from DTL was soluble in
THF. The melting temperature of the polymers was increased by 40-50 1Cby
oxidizing the sulfide groups to sulfone groups.
4.4.3.3 Synthesis of Polymers from Polyfunctional Enes and
Thiols
Wu et al.
54
reported the kinetic study of the formation of bio-based thiols by
reacting SBO with an excess of polyfunctional thiol (Scheme 4.29). Dif-
ficulties were reported with the miscibility of the thiols with SBO. Since the
formed bio-based thiols had better miscibility with SBO than with the
starting thiols, further reaction with SBO molecules led to oligomeric
products with lower thiol functionalities.
Echeverri et al.
62
reacted SBO with glycerine to obtain a mixture of mono-,
di- and triglycerides. The mixture was reacted with maleic anhydride to
obtain mixed malonate-FA glycerides (see Scheme 4.30). The resulting
product was reacted with stoichiometric amounts of tri- and tetrafunctional
thiols, with DMPA as an initiator, and under UV irradiation. Within 12 h, the
percentage of the soluble fraction dropped to 11% and the spectroscopy data
indicated all the thiol groups and malonate double bonds had reacted,
however, some FA double bonds remained unreacted. The T
g
values of the
polymers were
7-8 1C, and the thermal degradation in air (thermogravi-
metric analysis, 5%) started at
B
B
260 1C.
4.5 Bio-based Products of H-Phosphonate-ene
Reactions
The reaction of H-phosphonates with double bonds is similar to the
thiol-ene reaction, with the exception that cis-trans isomerization of
double bonds has not been reported, which implies that the formation of
the P-C bond may be irreversible.
63
UV light alone cannot initiate the
H-phosphonate-ene reaction, however a g-radiation-initiated reaction has
been reported.
64
On the other hand, the phosphor-centered radicals are
probably more reactive, as there are reports of these radicals abstracting
allylic hydrogens the same way that thiyl radicals are reported to abstract
bis-allylic hydrogens.
65
We are not aware of a report where the
H-phosphonate-ene reaction has been successfully carried out to com-
pletion with compounds having bis-allylic hydrogens (linoleic acid, lino-
lenic acid, their esters, or vegetable oils). Our attempts showed the reaction
of H-phosphonates with methyl linoleate to be sluggish: the best achieved
conversion was 30% in 48 h. In addition, the reaction was accompanied by
transesterification of the different alkoxy groups, especially at higher
reaction temperatures.
66
Nevertheless, there are reports where esters of
oleic acid have been successfully modified using the general reaction of
Scheme 4.31.
