Chapter 3 Results and discussion
3.1 Characterization of copolymer of styrene and
maleimide
3.1.1 1H-NMR Spectra
In order to characterize the random styrene-maleimide
copolymer, 1H-NMR measurement was performed on a Bruker 600 MHz
spectrophotometer with DMSO as a solvent.
A typical 1H-NMR spectrum of copolymer Maleimide
Styrene is shown in figure 3-1.
Fig 3-1 1H-NMR spectrum of random
copolymer Styrene-Maleimide at ratio 18.8/1
The characteristic spectrum was found for different ratio of
Styrene-Maleimide
The 1H-NMR spectrum shows the expected resonance
for the aromatic protons of polystyrene (c and e; ä~6.0-7.6 ppm proton
signals of the -CH= group of Styrene ) and imine protons of Maleimide
(b; ä~ 11.2ppm).
The broad signals from 1 to 3 ppm are
assignable to CH (a and f) and CH 2
(d) protons of the main chain. Therefore, this spectrum
confirms the presence of Maleimide-styrene copolymer [15].
All of the 1H-NMR spectra of random copolymer of
Styrene-Maleimide at different compositions have shown the same characteristics
bands.
3.1.2 Copolymer composition
1H NMR spectroscopic analysis has been established
as a powerful tool for the determination of copolymer compositions because of
its simplicity, rapidity and sensitivity. The average composition ratio of the
copolymer samples was determined from the corresponding 1H NMR
spectra. The assignment of the resonance peaks in the 1H NMR
spectrum leads to the accurate evaluation of the content of each kind of
monomeric unit incorporated into the copolymer chains.
Thus, the Copolymer ratio of SMA was calculated by measuring the
integrated peak areas of aromatic protons of styrene unit (signal c and e) and
imine proton of Maleimide (signal b). Let B be the integrated peak areas of
aromatic protons of styrene monomer and A is the integrated peak areas of imine
proton of Maleimide. The polystyrene unit contains five aromatic protons active
in resonance and the maleimide unit contains one imine proton, the following
expression is used to determine the composition of copolymer:
Table 3-1 Calculation of
integrated peak area of protons and mole compositions of copolymers
I-V
|
Copolymer
|
IAromatic
|
IImide
|
A
|
B
|
[Styr]/ [Mal]
|
|
I
|
28.832
14.843
|
1.000
|
1.000
|
43.675
|
8.7
|
|
II
|
1.000
0.5473
|
0.0233
|
0.0233
|
1.5473
|
13.2
|
|
III
|
1.000
0.5741
|
0.0167
|
0.0167
|
1.5741
|
18.8
|
|
IV
|
1.000
0.5581
|
0.0122
|
0.0152
|
1.5581
|
25.5
|
|
IV
|
1.000
0.3540
|
0.0153
|
0.0153
|
1.3540
|
17.7
|
I
Aromatic Integrated peak area of aromatic protons of
styrene unit.
Imide Integrated
peak area of an imine proton of Maleimide.
| 
