Summary (PP-g-DMAEMA)-g-NIPAAm was synthesized using gamma radiation from a 60Co
source. Graft polymerization of N,N’-dimethylaminoethylmethacrylate (DMAEMA) onto polypropylene (PP)
was accomplished in about 100 percent yield by the mutual irradiation technique at a dose of 10 kGy.
Grafting of N-isopropylacrylamide (NIPAAm) onto PP-g-DMAEMA was carried out by the pre-irradiation method
with doses from 20 to 100 kGy. The influence of temperature, reaction time, and monomer concentration
on grafting yield was studied. Grafting processes were confirmed by infrared spectroscopy (FTIR-ATR).
(PP-g-DMAEMA)-g-NIPAAm films were characterized by thermogravimetric analysis (TGA) and differential
scanning calorimetry (DSC). The lower critical solution temperature (LCST) and critical pH point of
the films were obtained by water contact angle and percent swelling measurements. The LCST was also
determined by DSC. We report here hare a new binary graft copolymer which shows two LCST values, synthesized
in two steps. 相似文献
A study has been made of radiation-induced grafting of vinyl acetate (VAc) on to (tetrafluoroethylene–perfluorovinyl ether) copolymer (PFA). Effects of grafting conditions such as inhibitor and monomer concentrations and irradiation dose on the grafting yield were investigated. In this grafting system, ammonium ferrous sulphate (Mohr′s salt) was added to the monomer-solvent mixture to minimize the homopolymerization of VAc and the most suitable concentration was found to be 2.0 wt%. It was found that the dependence of the initial grafting rate on monomer concentration is of the order 1.5. The degree of grafting tends to level off at high irradiation doses due to the recombination of formed free radicals without initiating graft polymerization. Some properties of the prepared graft copolymer such as swelling behaviour, electrical conductivity, thermal and mechanical properties were also investigated. The electrical conductivity was improved by hydrolysis of poly(vinyl acetate) in the grafted chains to their respective vinyl alcohols. The tensile properties were improved by grafting; however, the elongation percent decreased. The DTA data showed thermal stability of such graft copolymers for temperatures up to 300°C, but stability decreased at higher temperatures. 相似文献
Summary: N‐Isopropylacrylamide (NIPAAm) was graft‐polymerized from its acetone solution onto poly(propylene) (PP) films, after electron‐beam irradiation in the presence of air oxygen. The effects of pre‐irradiation dose as well as monomer concentration, reaction temperature and reaction time on the grafting efficiency were investigated. Typical conditions for achieving maximum grafting yield were observed for 1 M monomer concentration, after PP pre‐irradiation with a 300 kGy dose and a reaction temperature of 50 °C. The location of the graft polymerization was examined by different methods including measurements of dimensional variations, calorimetry, SEM and AFM. The temperature‐responsive behavior of grafted copolymer was studied by swelling and contact angle measurements at different temperatures.
Temperature dependence of the swelling ratio in water as a function of temperature. 相似文献
Cationic membranes were prepared by direct radiation grafting of methacrylic acid (MAA) onto poly(tetrafluoroethylene) (PTFE) films followed by alkaline treatment to confer ionic character in the graft copolymer. The complete inhibition of homopolymerization of MAA by using ammonium ferreous sulfate (Mohr's salt) failed. However, the addition of 0.5 wt % FeCl3 to the monomer solution effectively inhibited the homopolymerization process and higher grafting yield was obtained. It was found that the graft polymerization proceeded successfully in presence of methanol/water mixture (30/70 wt %), and much higher degrees of grafting were obtained as compared with those in the presence of other diluents used here. The influence of irradiation atmosphere (air, N2 gas, and vacuum) on the grafting process was investigated. The dependence of the grafting rate on MAA concentration was found to be of orders 2.9 and 0.72 in the presence of 0.5 wt % Mohr's salt or 0.5 wt % FeCl3, respectively. This grafting system proceeds by the front mechanism. Investigation of mechanical properties, electrical conductivity, and swelling behavior of the grafted films revealed that such a copolymer could be acceptable in practical use as a cation-exchange membrane. 相似文献
Summary Grafted copolymer of poly(vinyl chloride) (PVC) with N-isopropylacrylamide (NIPAAm) was prepared by radiation-grafting method
using γ-ray source. NIPAAm was graft polymerized from its aqueous solution onto PVC tubes by preirradiation method, all samples
were exposed in the presence of air at room temperature to 60Co. Conditions for achieving maximum grafting yield were observed between 0.5 and 1 moldm-3 of monomer concentration, pre-irradiation dose of PVC from 5 to 110 kGy, and reaction temperature of 323 and 333 K. Characterization
of the grafted copolymer was conducted by various methods: FTIR-ATR, TGA, and SEM. The temperature-responsive behavior of
grafted copolymer was studied by swelling at various temperatures and pH 6.8. 相似文献
A new chelating adsorbent was prepared by grafting glycidyl methacrylate (GMA) onto polystyrene (PS) particles using simultaneous radiation technique and amination of graft copolymers by reacting with diethylenetriamine. The effects of various parameters such as, irradiation doses, inhibitor concentrations, amination temperature, and reaction time were investigated. The grafting yield increased with irradiation dose to reach its maximum value at 15 kGy. The accelerative effect of solvent medium on the grafting yield was higher in THF than DMF. The addition of 0.001 % (wt) inhibitor to the reaction medium led to a sharp increase of grafting yield. The best conversion ratio was obtained at 115 °C during 24 h. By using a column separation technique, the adsorption behaviors of the adsorbent toward Cd2+ and Nd3+ in aqueous solution were examined. The adsorption amount of both Cd2+ and Nd3+ increased with initial ions concentration. The maximum equilibrium of Cd2+ and Nd3+ adsorbed ions were 18.1 and 17.58 mg/g, respectively. It was observed that the functionalized GMA-g-PS was reusable by desorbing with 0.1 M nitric acid almost without losing their adsorption capacity. FTIR test indicates that epoxide and amine groups were introduced onto GMA-g-PS and aminated GMA-g-PS, respectively. The Tg of graft copolymer slightly decreased, and that of aminated GMA-g-PS was higher than graft copolymer. 相似文献
Endowing conventional hydrophobic poly(vinylidene fluoride) (PVDF) films with hydrophilic properties was conducted using electron beam irradiation. Grafting of acrylic acid (AA) in/onto pre-irradiated PVDF films was investigated. Reaction parameters, monomer concentration and inhibitor concentration were examined. Radiation grafted films (PVDF-g-PAA) were synthesized with various grafting yields ranging from 12 to 130 wt % in presence of Mohr's salt (25 wt %). Below 80 wt % of monomer concentration, the degree of swelling was found to increase with the grafting yield. The PAA was arranged randomly in all PVDF matrix (grafting through). Above 80 wt % of monomer concentration, the PAA was grafted only onto the surface of PVDF films leading to a highly dense layer of PAA. Grafting through or surface grafting processes were achieved by varying the water fraction in the initial monomer solution. Water molecule acts not only as a carrier for the monomer but also as a plasticizer expanding the film in the three dimensions. Evidences of grafting through and surface grafting were produced using FTIR in ATR mode, SEM coupled to X-ray detection and XPS. An accurate quantification of AA units was possible up to the micromole via a Cu2+–EDTA complex analyzed by UV–vis spectroscopy. 相似文献
pH-sensitive acrylic acid grafted polyvinylalcohol (AAc-g-PVA) hydrogels has been prepared by gamma irradiation. The maximum grafting yield was at monomer concentration 50% and dose 50 kGy. The swelling, network parameters, thermogravimetric analysis, activation energy and scanning electron microscope of the grafted hydrogels were evaluated. Hydrogel demonstrate high swelling at pH 6.8. The deswelling of the swollen gel in Ni2+ and Cu2+ cations solution was explained on the basis of mono-divalent cation exchange. The release of antihistaminic chlorphenamine maleate hydrochloride (CPM) was faster in gastric fluid (SGF) of pH 1.1 than in intestinal fluid (SIF) of pH 6.8. 相似文献