Chemistry Reference
In-Depth Information
of molecular chains, hydrophilic-hydrophobic capability, complexing capacity,
stimuli-responsive ability, and rheological behavior of gums, and so the applica-
tion domain of gums was greatly extended. But, the derivatization of gum can
only improve the properties to a finite degree because the number of introduced
functional groups is less and the molecular weight of gum fails to be increased by
the simple modification with small molecules. Graft polymerization is anticipated
to be a quite promising technique for modifying the properties of a polymer, and
the modification of natural polymer materials by graft copolymerization offers the
opportunity to tailor their physical and chemical properties, functionalize
biopolymers to impart desirable properties onto them, and combine the
advantages of both natural and synthetic polymers [
16
-
19
]. Several grafting
modification techniques have been reported, involving with “grafting-from”
(growth of polymer chains from initiating sites on the polysaccharide backbone)
and “grafting-to” methods (coupling of preformed polymer chains to the polysac-
charide) [
20
]. “Grafting-from” is the most common procedure with the initiating
sites generated by various chemical or high-energy irradiation methods. Different
from the derivative modification by active small molecules, the graft reaction may
introduce polymer chains with large amounts of functional groups to form a
“brush-like” structure around the main chains. Correspondingly, the properties
of gums, such as flocculation efficiency, complexing, stimuli-responsive, viscos-
ity, controlled biodegradation, and shear resistance characteristics, were greatly
changed by the new functional groups for extending the application domains of
gums [
21
-
23
]. The results of graft polymerization are to improve the intrinsic
properties of gums or bring gums with new properties. For example,
Cassia
javahikai
seed gum is a better coagulant, but the graft of PAM chains onto the
gum can further enhance its coagulant properties [
24
]. The graft of PAN onto
Ipomoea seed
gum may clearly enhance its viscosity (the maximum value reaches
10.56 folds of the gum) and stability [
25
]. The AG does not have conducting
capability, but the graft of PANI results in good processability along with the
electrical conductivity, and used to develop biopolymer-based electronic materials
for the environmental favorable technologies [
26
]. By virtue of the excellent
intrinsic properties and the adjustable character of the structure and properties
of gums, their graft copolymers play vital role in almost each chemical industrial
field, especially in wastewater treatment, controlled release of agricultural
chemicals or pharmaceutics, petroleum industry, papermaking, daily chemicals,
dyeing, thickener, smart materials and biomaterials, etc.
The properties of a gum-g-copolymer are highly dependent on the intrinsic
structure and nature of gums, the sort of grafted monomer, grafting ratio, and
efficiency. Over the past decades, researchers devoted many efforts to explore the
graft mechanism, the structure-activity relation of graft copolymer, and the key
influence factors of graft ratio and efficiency, and greater progress was made. So,
the introduction about the types, structure, and derivatives of gums, the synthesis
method, properties, and applications of gum-g-copolymer will be attractive.
