Zhai Maolin

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.

Study on radiation-induced grafting of styrene onto chitin and chitosan

Abstract Radiation-induced grafting of styrene onto chitin and chitosan powder was performed at room temperature. The effect of various conditions such as absorbed dose, solvent and oxygen on grafting was investigated. The grafting yield increased with the increase in absorbed dose. At the same dose, the grafting yield of styrene on chitosan was higher than that on chitin. The grafting reaction was promoted in the presence of methanol, and oxygen delayed the grafting reaction but did not inhibit it completely. In order to study the mechanism of grafting reaction and analyze the grafted samples, the grafted products were extracted first by benzene, then they were hydrolyzed in the presence of acid and separated by thin layer chromatography (TLC). Three different kinds of polystyrene (PS), i.e. PS grafted onto chitin, PS embedded in chitin and PS in grafting solution were gained. The variation of their molecular weight (MW) and width index of molecular weight distribution (Mw/Mn) determined by gel permeation chromatography (GPC) at different grafting conditions is discussed.

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.

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.

Radiation preparation and diffusion behavior of thermally reversible hydrogels

Abstract Temperature sensitive PolyNIPAAm hydrogels in the form of rod were prepared from the binary system of NIPAAm/water and ternary system of NIPAAm/Bis/water by γ-irradiation with 60 Co source at room temperature, respectively. The prepared hydrogels had obvious temperature sensitivity (LCST is about 35.0 °C) and suitable mechanical properties. The incorporation of cross-linking agent, N, N′-methylene-bisacrylamide (Bis), into the binary system of monomer/water reduced the gelation dose. The maximum swelling ratio of hydrogels was decreased with the increasing of dose or the incorporation of Bis. The diffusion behavior of water in hydrogels obtained in this work was investigated. In addition, the drug delivery of fluoro uracili (Fu-5) from the hydrogels was investigated.

Radiation synthesis of a water-soluble temperature sensitive polymer, activated copolymer and applications in immobilization of proteins

Abstract In this work the radiation polymerization of N-isopropylacrylamide (NIPAAM) in aqueous solutions has been carried out and a water-soluble, temperature sensitive polymer and copolymer were obtained by using γ-rays from Co-60 source at room temperature. We have gained the optimum dose and dose—rate of radiation synthesis of linear polyNIPAAM through determining conversion yield and viscosity. In order to immobilize protein (BSA) and enzyme (HRP) into this water-soluble polymer, we prepared an activated copolymer, poly ( N-isopropylacrylamide-co-N-acryloxysuccinimide). The BSA and HRP has been immobilized onto the activated copolymer. The BSA (HRP) / copolymer conjugates still kept the original thermally sensitive properties of the linear polyNIPAAM. The conjugation yield of BSA to the activated copolymer decreased with increasing of dose. The thermal stability of the immobilized HRP was stable at 0 °C for a long time and has, at least, 4 days stability at room temperature. Immobilized HRP activity was lowered when the temperature was raised above its LCST. This phenomenon was reversible and the immobilized HRP regained activity below its LCST. The optimum pH of the immobilized HRP shifted from ca.5 upward to ca.7.

Influencing factors and measuring method of the heat conducting performance of UHMWPE single fiber

The fiber with higher thermal conductivity is rare and it is difficult to measure the thermal conductivity of a single fiber. In this paper, the composite samples of ultra-high molecular weight polyethylene (UHMWPE) fiber and epoxy resin were prepared in order to study the heat conducting properties of the UHMWPE fiber. The specific heat capacity and thermal conductivity of the samples were tested by the transient plane source method. Based on the serial–parallel equivalence theory model, the axial and radial thermal conductivities of the UHMWPE filament were calculated. Effects of the volume fraction of fiber, fineness and drawing ratio on thermal conductivity were explored. Also, the relationship between the structure and thermal conductive capacity was revealed. The results showed that the volume fraction of fibers should be large to obtain a relative accurate value. Moreover, the difference in fineness led to different thermal conductivity of the UHMWPE fiber, the cruder the fiber, the higher the thermal conductivity. Besides, as the drawing ratio increased, the crystallinity and orientation of the fibers also increased. Thus, the results were that the axial equivalent thermal conductivity of the filament was dramatically increased, while the radial equivalent thermal conductivity grew a little. The paper showed that UHMWPE fibers had much higher thermal conductivity than other fibers, and also provided a new method to get the thermal conductivity of UHMWPE single fiber.