Ha Hongfei

Pre-irradiation grafting of temperature sensitive hydrogel on cotton cellulose fabric

Abstract Temperature sensitive polymer (poly-N-isopropylacrylamide)was grafted on the surface of cotton cellulose fabric by γ -pre-irradiation-induced grafting. The effect of absorbed dose, dose rate, grafting temperature and concentration of monomer on grafting yields were investigated. In order to explain the characteristic of active points and the location of grafting site, the peroxides formed during irradiation in air and the effects of store time at various temperatures after irradiation were measured. It was found that grafting reaction was induced mainly by trapped radicals located in the interphase between crystal and amorphous regions, but for the monomer of N-isopropylacrylamide the peroxides also made some contribution to grafting yields. The results showed that the surface of grafted fabric has temperature sensitivity as well.

Effect of kappa-carrageenan on the properties of poly(N-vinyl pyrrolidone)/kappa-carrageenan blend hydrogel synthesized by γ-radiation technology

Abstract A series of hydrogels in the form of rods were prepared from kappa-carrageenan (KC) and poly ( N -vinyl pyrrolidone) (PVP) by gamma radiation with 60 Co γ source at room temperature. The properties of the prepared hydrogels, such as the gel strength, gel fraction and swelling behavior were investigated. Incorporation of KC into the PVP/water system increased obviously the gel strength and equilibrium degree of swelling (EDS) of PVP hydrogel. The experimental analyses showed that the crosslinking reaction of PVP was quicker than the degradation of KC at a low dose (less than 30 kGy), and the degradation of KC was inhibited in the PVP/KC mixture system. So an interpenetrating polymer network (IPN) hydrogel composed of PVP (a chemical crosslinking network) and KC (a physical crosslinking network) was proposed here. The existence of different classes of water in this IPN system was shown by water melting curves using DCS.

Radiation preparation and thermo-response swelling of interpenetrating polymer network hydrogel composed of PNIPAAm and PMMA

Abstract Interpenetrating polymer network (IPN) hydrogel composed of hydrophilic poly( N -isopropylacrylamide) (PNIPAAm) and hydrophobic poly(methyl methacrylate) (PMMA) were synthesized by sequential IPN method using γ -rays from 60 Co source. Compared with pure PNIPAAm hydrogel, PNIPAAm/ PMMA IPN hydrogel not only behaved with obvious temperature sensitivity, but also had higher mechanical strength. The shrinking rate of the prepared IPN hydogel was slower than that of PNIPAAm hydrogel and the relative shrinkage was higher than that of PNIPAAm hydrogel. The IPN hydrogel with less PMMA was not stable while with more PMMA it was quite stable. In addition, the release of Methylene Blue (MB) from the IPN hydrogel was slower than that from PNIPAAm hydrogel as well.

Radiation synthesis and characteristic of IPN hydrogels composed of poly(diallyldimethylammonium chloride) and Kappa-Carrageenan

Abstract A new system of IPN hydrogels composed of diallyldimethylammonium chloride (DADMAC) and natural macromolecule, Kappa-Carrageenan (KC) were prepared by γ-irradiation. Their gel fraction and swelling behavior were studied. Elemental analysis and gel strength measurement results showed that there was an amount of KC that remained in the gels and the gel strength was enhanced obviously.

Solvent effect on grafting polymerization of NIPAAm onto cotton cellulose via γ-preirradiation method

Grafting polymerization of N-isopropylacrylamide (NIPAAm) onto cotton cellulose preirradiated in air by 60Co-γ-rays was accomplished in mixed solvents of water and alcohols or acetone. The grafting yields changed with different ratios of water and organic solvents. In the system of solvents comprised of water and methanol, the Trommsdorff effect appeared in the curve of the grafting yields vs. the concentrations of the monomer. In the same system, the dependence of the grafting yield of NIPAAm on the grafting temperature was different from that of acrylamide (AAm). The relation between the grafting yields of the samples and their crystallinities measured by X-ray diffraction could be regarded as a proof of the ‘third-phase’ conception.

Radiation synthesis and characterization of polyDMAEMA hydrogel

Abstract Poly N, N-dimethylaminoethyl methacrylate (polyDMAEMA) hydrogels were synthesized by γ-irradiation technology, and the conditions of synthesis, such as total dose, dose rate, concentration of monomer and crosslinker in aqueous solution, were investigated. The property measurements of the hydrogels showed that they exhibited temperature sensitivity in a temperature range of 38–40°C and pH sensitivity at pH=2.5. They also had electric responsive behavior although it was not typical. The hydrogels synthesized were transparent and elastic and displayed good swelling behavior in water, therefore, they can be used as a kind of carrying material in drug delivery systems.

Study on interpenetrating polymer network hydrogel of diallyldimethylammonium chloride with kappa-carrageenan by UV irradiation

Interpenetrating polymer network hydrogels composed of diallyldimethylammonium chloride and the natural polysaccharide, kappa-carrageenan (KC), were prepared by UV irradiation; gel strength and swelling behavior were studied. The results showed that the degradation of KC was not induced by UV irradiation over a 3 h period; moreover, addition to the hydrogels enhanced the strength markedly.

Radiation preparation of PVA-g-NIPAAm in a homogeneous system and its application in controlled release

Abstract Thermosensitive PVA-g-NIPAAm copolymers were prepared by graft copolymerization of N -isopropylacrylamide (NIPAAm) onto poly (vinyl alcohol) (PVA) in homogeneous system of dimethyl sulfoxide (DMSO) by 60 Co- γ irradiation at room temperature. The factors of affecting the grafting yield, such as radiation dose, dose rate, acid concentration, were investigated. It was found that the grafting yield was increased with dose up to 30 kGy, but decreased slightly with dose rate from 61.2 to 50.1 Gy/min. The acid concentration also had influence on the grafting yield. Then the hydrogel of PVA-g-NIPAAm copolymer was made through a freezing–thawing process. The PVA-g-NIPAAm hydrogel exhibited obvious thermal sensitivity, which was observed from the differences of swelling behavior in water at different temperatures (below or above LCST). In addition, the release of Methylene Blue (MB) from this kind of hydrogel was studied. The release rate of MB from PVA-g-NIPAAm copolymer hydrogel at 48°C was faster than that at 15°C due to the shrinkage of the hydrogel at 48°C.

The swelling behavior of radiation prepared semi-interpenetrating polymer networks composed of polyNIPAAm and hydrophilic polymers

Abstract In this study, semi-interpenetrating polymer networks (semi-IPNs) composed of polyNIPAAm and hydrophilic polymers were prepared by Co-60 γ -rays to investigate the effect of hydrophilic polymers on the properties of semi-IPNs. The linear hydrophilic polymers used in this study were PVA, PVP, poly(NaAAc) and PAAc, which can form hydrogen bonds in the semi-IPNs. It was found that the incorporation of linear hydrophilic polymers led to various changes in swelling behavior compared with pure polyNIPAAm hydrogel.

Study on oxidation of polymers treated by high let radiation

Abstract The oxidation of medical silicone rubber and segmented polyether urethane which were bombarded with 1∼1.2 MeV Si + or F + at the dose of 5 × 10 14 ions/cm 2 was studied. In XPS measurements, it was found that the oxygen concentration on the surface of the implanted polymeric membranes had been increasing in three months at least. ESR measurement showed that some free radicals existed in these membranes and their quantities decreased with time. Chemical analysis proved that peroxides were generated in the γ irradiated membranes. The reason for the increasing of oxygen concentration was that free radicals combined with oxygen in the air and produced peroxides on the membrane surface. Moreover, in order to demonstrate the radiation mechanism, low LET (γ rays) radiation of such polymeric membranes was carried out for comparison