Chemistry Reference
In-Depth Information
5.5.3 UV-Vis Spectra
UV-vis spectra are simple and accurate approach to identify the existence of
aromatic groups. In the families of gum-g-copolymers, many used monomers
(such as styrene, aniline, sodium 4-vinylbenzenesulphonate) have benzene rings,
and so the corresponding graft copolymers possess aromatic characteristic. Thus,
UV-vis spectra were developed as an effective approach to prove the graft of these
monomers onto the gum backbone. The the grafting copolymers of gum with
aniline has focused much attention because it can introduce electrical properties
into gum. In the UV-vis spectra of AG-g-PANI polymer [
26
], AG showed a broad
absorption band at 298 nm due to the presence of arabinogalactan components in
the AG. Furthermore, the characteristic peaks of both arabinogalactan components
and PANI were observed in the graft copolymer, and it confirmed the grafting of
PANI onto AG backbone. In addition, UV-vis spectra are effective for a hydrogel
based on graft-copolymer of gum. Wang et al. [
193
] introduce styrene in the GG-g-
PAA/muscovite hydrogel system and the properties were obviously improved. In
the UV-vis spectra of the swollen gel, the E band absorption of phenyl rings was
observed, but it is absent in the spectra of sample without addition of styrene. This
proved styrene participates in graft copolymerization. The UV-vis spectra are
suitable for solution, solid, film, and gel.
5.5.4 Elemental Analysis
Elemental analysis is an identification method based on the difference of elements
between gum backbone and graft copolymers in a type or content of special
elements. The main characteristic elements are N and S. The monomers containing
N elements (i.e., acrylamide,
N
-vinyl-2-pyrrolidone, aniline,
N
-isopropyla-
crylamide, 4-vinylpyrridine) or containing S elements (i.e., 2-acrylamido-2-methyl
propane sulfonic acid, sodium 4-vinylbenzenesulphonate) were grafted to the gum
backbone; the elemental analysis may show the change of contents of N or S
elements (for the gums containing N or S elements) or the appearance of N or S
elements in the graft copolymer (for the gums without N or S elements). This
provides direct evidence that these elements were grafted onto the gum backbone
[
132
,
152
,
155
]. According to the change of elemental contents, the graft amount of
monomers may also be roughly calculated, and this is also the advantages of
elemental analysis method.
5.5.5 NMR Analysis
The
1
H-NMR and
13
C-NMR analyses are accurate approach to identify the molec-
ular structure. By comparing with the change of special groups before and after
grafting reaction,
the occurrence of graft copolymerization reaction can be
