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O
O
Cl
(
O
n
Cl
HO
O
R
R
R=H, CH
3
COOH
C
O
O
(
n
O
O
Cl
NaBH
2
O
COOH
O
O
Figure 4.9
Synthesis of vinyl monomers derived from DHAA. Reproduced with
permission from Y. Zheng, K. Yao, J.S. Lee, D. Chandler, J. Wang, C. Wang,
F. Chu and C. Tang,
Macromolecules
, 2010,
43
, 14, 5922. ©2010 American
Chemical Society [5]
4.4.2 Atom Transfer Radical Polymerisation of Acrylic Monomers
In order to vary the steric effect, different spacers were placed between the vinyl group
and the hydrophenanthrene group, which has a significant influence on the control
of polymerisation. Copper-catalysed ATRP of vinyl monomers in the presence of
tris[2-(dimethylamino)ethyl]amine (Me
6
Tren) [111, 112] as the ligand was found to
have a strong dependence on the solvents used (
Figure 4.11
). For the monomer with
the shortest spacer (DAMA), the polymerisation was not controlled, probably due
to an overwhelming steric effect. For other acrylates including AEDA and ABDA,
relatively polar solvents promoted the control of polymerisation, while nonpolar
solvents resulted in a better control in the polymerisation of a methacrylate (MAEDA).
In both cases, polar solvents achieved faster polymerisation. We obtained both types
of polymers with polydispersity indexes below 1.3 with molecular weight in the
range of 10,000 to 100,000 g/mol, as indicated by gel permeation chromatography
(GPC) (
Figure 4.12
). Higher molecular weight was obtained for polymers with longer
spacers between the rosin moiety and the vinyl group, further indicating the steric
effect on polymerisation.
1
H NMR spectra (
Figure 4.12
) of these polymers show
the disappearance of characteristic signals of vinyl protons from vinyl monomers
and the appearance of broad peaks corresponding to -CH
2
-CH- protons from the
polymer backbone.
