Authors:C. V. Chaudhari, Y. K. Bhardwaj, and S. Sabharwal
Grafting ofmethyl methacrylate (MMA) on radiation crosslinked natural rubber (NR) film has been investigated by mutual radiation
grafting. The effect of experimental parameters like radiation dose, dose-rate, additives like acids and inorganic salts,
solvents, monomer concentration, cross-linking density of the natural rubber film on the grafting extent has been studied.From
the kinetic studies, a kinetic equation showing almost parabolic and linear dependence of grafting on concentration and dose
rate, respectively, was deduced.Preliminary thermal stability studies of grafted films indicated that grafting of MMA does
not enhance the thermal stability of NR.
Authors:C. Chaudhari, K. Dubey, Y. Bhardwaj, Virendra Kumar, N. Goel, and S. Sabharwal
Radiation induced grafting of acrylonitrile (ACN) on ethylene-propene diene terpolymer (EPDM) rubber film was investigated
by mutual radiation grafting technique. Effect of experimental variables viz. radiation dose, dose rate, type of solvent and
monomer content on extent of grafting was studied. From the kinetic studies a mathematical relation Rgα[M]0.7D0.68 showing non-linear relationship for rate of grafting with monomer concentration and dose was deduced. The grafted samples
showed increased hardness and oil resistance.
Authors:Giancarlo Angelini, Ornella Ursini, and Franco Cataldo
Fullerene/silica hybrid materials were obtained by radiation grafting on silica surface of toluene or decalin solutions of
C60. As determined by thermogravimetric analysis, the amount of C60 grafted on silica surface was dependent from the radiation dose administered and independent from the C60 concentration and the nature of the organic solvent. In absence of air, a dose of 48 kGy was sufficient to ensure a grafting
level of 30% by weight of C60 in the hybrid material. The fullerene/silica hybrid material shows a remarkable thermal stability, since the early decomposition
starts above 300 °C as measured by DTG and DTA. The chemical structure of the fullerene/silica hybrid material was determined
by FT-IR spectroscopy and with solid state 13C CP-MAS NMR. The potential application of such materials has been outlined.
Authors:Ricardo Neri, Guillermina Burillo, and Susana Castillo-Rojas
A pH-sensitive comb-type hydrogel was obtained by gamma radiation polymerization and crosslinking of acrylic acid (AAc) in
solution. The pH-sensitive 4-vinylpyridine (4VP) was then grafted to the poly acrylic acid (PAAc) hydrogel using gamma radiation
from a 60Co source. The comb type graft polymers obtained (net-PAAc)-g-4VP has been studied through determination of graft yield and swelling behavior. The critical pH value was found to
be 5.6. The apparent mechanical properties appear to be qualitatively better than hydrogels of PAAc upon swelling. The new
comb-type system presents faster swelling response (30 h) than the polyacrylic acid hydrogel (50 h). The increase in dose
rate from 7.3 to 11.3 kGy h−1, increase the radiation grafting percentage of 4VP in the system. Comb-type polymers were also characterized by DSC, TGA
A new anti-thrombosis dialytic membrane with a hydrophilic-hydrophobic microphase structure was prepared by pre-irradiation grafting of -hydroxyethyl methacrylate (HEMA) and styrene (St) onto polyethylene (PE) membranes. The effects of reaction conditions on the degree of grafting were determined, and the properties of the grafted films were investigated. Compared with PE grafted with hydrophilic monomer, the antithrombogenicity and permeability of the PE-g-(HEMA-co-St) were 30 and 15 times higher than that of the ungrafted films, respectively, if the volume ratio (HEMA:St) is about 1:1.
Authors:Wu Minghong, Chen Jie, Qian Qun, and Bao Borong
Interpenetrating polymer network (IPN) hydrogels were prepared by grafting of acrylamide (AAm), N-methylol acrylamide (NMA) and acrylic acid (AAc) onto preirradiated polypropylene (PP) membrane. To obtain PP-g-AAc/AAm/NMA IPN hydrogels, at first, AAc were grafted onto preirradiated PP and then AAm were grafted onto the PP-g-AAc membranes. Finally NMA were grafted onto PP-g-AAc/AAm membranes. In the different stages of grafting under different reaction conditions, trapped radicals in the membrane samples were probed by electron spin resonance (ESR). The temperature response behaviors of the IPN hydrogels were studied. Reversible behavior and controlled release of drug tests made reflecting the switching to on state at higher temperatures and to off state at lower temperatures were achieved. By increasing the grafted content of NMA, higher transition temperature of the hydrogel could be attained.
A series of condensed ethylene glycol acrylate monomers with differentmolecular weight was grafted to polyethylene films by means of pre-irradiation.The effect of the molecular weight of monomer and co-solvent system on thegrafting reaction and the properties of the grafted sample were studied. Theexperimental results showed that the initial rate of grafting reaction decreasedand the molar degrees of grafting linearly decreased with the increment ofmolecular weight of the monomer. The grafting degree was increased with theswelling degree of the grafted film. The biocompatibility and blood compatibilityof the grafted PE films were evaluated by the determination of hydrophilicityand anti-thrombus.
of the grafted poly(methyl methacrylate) (PMMA) side chains was in the range of 430 000 (for a dose of 10 kGy) and practically independent of grafting degree. However, the number of branches per graft copolymer molecule increases from 0.3 to 0.8 when the degree of grafting increases from 32% to 88%. Similarly, the radiation yield, i.e. the number of branches formed per 100 eV of energy absorbed in the substrate polymer increases from 0.75 to 1.94. The value and meaning of molecular weight of graft copolymer is discussed along with the mechanism of polymer chain termination.
Preparation of membranes of poly-(tetrafluoroethylene-perfluorovinylether (TFA) and poly-tetrafluoroethylene-polyethylene
(ET) films grafted with 4-vinylpyridine using γ-rays has been carried out. The appropriate reaction conditions were selected.
Furthermore, quaternization of the pyridine of the grafted chains was conducted. The effect of monomer concentration on the
rate of grafting was also investigated. The order of the grafting rate gram per hour depending on monomer concentration was
found to be 0.94 and 1.0 for TFA and ET films, respectively. Some selected properties of the grafted films such as swelling
behavior, dimensional stability, mechanical and electrical properties were investigated. The grafted film of TFA and ET showed
a marked decrease in elongation with a significant increase in the tensile strength.
Thioglycolic acid is an efficient agent for controlling the lengths of poly(methyl methacrylate) (PMMA) chains grafted onto collagen. The addition of 0.006 mol of thioglycolic acid per one mol of methyl methacrylate (MMA) has no effect on the yield of grafting, but brings about a decrease in the molecular weight of grafted PMMA by about 50%. The mechanism of the grafting reaction in the presence of the chain transfer agent thioglycolic acid is discussed on the basis of the results.