The presence of different functional groups of the NR-gPMMA
and E(NR-g-PMMA) can be seen from their FT-IR
spectra, as shown in Fig. 1, as compared to that of NR.
The characteristic peaks of the isoprene units can be
observed at wave numbers of 1663 and 835 cm1
, assigned
to C@C stretching and @CAH out of plane deformation,
respectively. The graft copolymer demonstrates absorption
peaks at wave numbers of 1732 and 1140 cm1 which indicate
the presence of C@O and CAO, respectively. The presence
of CAO in the modified polymer also introduces the
double bound weak peak in the region of 800–700 cm1
due to its symmetric deformation. This peak is appeared
together with the strong peak of CAO stretch at
1140 cm1
. After epoxidation, E(NR-g-PMMA) displays
additional peaks at a wave numbers of 870 cm1
, which
can be attributed to epoxide asymmetric stretching. A
higher epoxide contents on the epoxidized graft copolymer
structure results in the stronger characteristic absorption
peaks of the epoxide ring, as shown in Fig. 2.
A typical 1
H NMR spectrum of the modified graft
copolymers is shown in Fig. 3 in comparison with that of
virgin NR, NR-g-PMMA and ENR-30. The absorption bands
at the chemical shifts of 2.7, 3.6 and 5.1 ppm, which indicate
the signals of the methine proton of the epoxidized
unit, the AOCH3 proton of the PMMA and the @CH proton
of the polyisoprene, respectively, can be clearly observed.
These peaks confirm the occurrence of the epoxide group
and grafted PMMA on the NR structure. With increasing
epoxide contents, the peak intensity at 2.7 ppm was clearly
increased, as shown in Fig. 4. The characterization data
from both FT-IR and 1
H NMR techniques agree well, and
the modified graft copolymers with various epoxide contents
were successfully prepared in the latex state