Chemistry Reference
In-Depth Information
HS
R
O
R
O
LiAlH
4
OH
HO
R
HO
S
O
S
OH
O
TH F
DM PA/ h
ν
n
n
HS
R
O
O
OH
HO
OH
R
S
O
S
O
DM PA/ h
ν
n
n
Oleic:
n
=6,R=
n
-C
8
H
17
;
Und ecy lenic :
n
=7,R=H
Scheme 4.11 Preparation of diols from oleic and undecylenic acids.
44
In the case of
oleic acid, only one of the two isomers is shown. THF
¼
tetrahydro-
furan, DMPA
¼
2,2-dimethoxy-2-phenylacetophenone,
a
photo-
initiator.
O
S
S
+
H
R'
H
O
O
6
DT: R' =
O
UDA
hv, DMPA
CH
3
CN, RT
O
S
S
O
O
R'
6
6
O
x
UDA-A
S
hv, DMPA
CH
3
CN, RT
R = OH, COOH, CH
2
-
Si(OMe)
3
H
R
O
S
S
O
S
O
R'
S
6
6
R
O
x
UDA-R
R
Scheme 4.12 The synthesis of telechelic polymers.
42
DT is 3,6-dioxa-1,8-octanedithiol.
The resulting diols were polymerized with 4,4
0
-methylenebis(phenyl-
isocyanate), in a dimethylformamide (DMF) solution using tin(II) 2-ethyl-
hexanoate as the catalyst. The synthesized PUs utilizing the LiAlH
4
reduction, had higher T
g
values than the ones utilizing the allylic alcohol
route. The PUs synthesized from undecylenic acid had higher T
g
values than
the ones from oleic acid. The PUs synthesized from undecylenic acid showed
stress-strain curves, indicating the presence of rigidity increasing crystalline
domains. The PUs synthesized from oleic acid showed behavior similar to
lightly cross-linked rubbers.
Lluch et al.
42
reported on the synthesis of telechelic polymers (polymers
where both ends possess the same reactive functionality). As a starting
material, they utilized allyl 10-undecenoate (UDA). UDA has a high reactivity
towards thiols, since both olefinic double bonds are primary. The two-step
reactions (Scheme 4.12) were successfully carried out in one pot. Telechelics
