Chemistry Reference
In-Depth Information
The thermal properties were characterised by DSC. The thermal behaviours of CL
and AEDA diblock copolymers depended mainly on the length and fraction of the
PCL block in the diblock copolymers. The high fraction of AEDA can suppress the
crystallisation of CL so that the DSC curve (
Figure 4.24
) only showed the
T
g
of the
PAEDA block at approximately 50
o
C. However, a conspicuous endothermic peak at
approximately 50
o
C was observed for diblock copolymers with a high fraction of the
PCL block (PAEDA
50
-
b
-PCL
500
), which coincided with the
T
g
of the PAEDA block.
The thermal behaviours were further confirmed by atomic force microscopy (AFM)
experiments (
Figure 4.25
). The film with a shorter length of PCL block is smoother
than that with a longer PCL block. AFM height images of block copolymers with
high fractions of the PCL block (PAEDA
50
-
b
-PCL
500
) revealed the formation of small
crystals with an average size of a half micron and a roughness of approximately 20
nm. In contrast, thin films of block copolymers with a short length of the PCL block
(PCL
41
-
b
-PAEDA
41
) appeared to be very smooth with an average of roughness below
5 nm.
PCL
41
-
b
-PAEDA
41
-Br
25
50
75
100
125
150
175
200
0
PAEDA
50
-
b
-PCL
500
-Br
PCL
41
-Br
0
25
50
75
100
125
150
175
200
Temperature (°C)
Figure 4.24
DSC curves of polymers PCL-Br, PAEDA-
b
-PCL-OH and PCL-
b
-
PAEDA-Br. Reproduced with permission from P.A. Wilbon, Y. Zheng, K. Yao, C.
Tang,
Macromolecules
, 2010,
43
, 21, 8747. ©2010 American Chemical Society [4]
