A new method has been established to graft vinyl monomers onto silk fabrics by ultraviolet rays without any initiator or photosensitizer, in an attempt to improve undesirable properties of the materials with increased wrinkle recovery, better dyeing ability and color-fastness, and higher resistance to photo-yellowing, etc. In this work, ef- fectiveness of different types of UV devices and experimental conditions of the photo-induced graft-copolymeri- zation were investigated to control the influential factors on the grafting yield and properties of the graft-copolymer. Surface characteristics and structure changes, thermal properties and wrinkle resistance of grafted silk fabrics were studied. The grafted silk fabrics showed improved properties in crease resistance, dyeing ability and color-fastness, and heat stability as well. In detail, graft-copolymerization of 2-(Dimethylamino)ethyl methacrylate onto silk fabrics can make silk fabrics undergo from slight to drastic changes in their dyeing behavior, i.e., rate of dyeing and uptake of acid dyes. Different reaction systems of the same monomer can lead to reverse dyeing properties, indicating not only the function but also the structure affects the properties of grafted silk fab- rics, especially the color-fastness. The UV light graft copolymerization method is of significance in silk industrial applications in terms of the facility cost, operation convenience and grafting efficiency, in comparison to Co 60 γ-ray and electron beam irradiation facilities.
Photo-induced Fenton reaction was utilized in this paper to control the sizes of polyethylenimine hydrogels （M-PEIs,M,Fe atom） as gene delivery vector.H2O2 and FeCl2 were mixed with PEI prepolymer in water in a 3-neck quartz flask, and the mixture was stirred vigorously.M-PEIs nanogels dispersed very well in water could be prepared under illumination by use of low-pressure Hg lamps at room temperature.This system was protected from oxygen with N2.By changing reaction conditions,such as the pH value,reaction time and concentrations of solutes,sizes of M-PEIs nanogels could be controlled.It was found that the sizes of M-PEIs decreased with the pH value and the concentrations of FeCl2.The increasing of the initiator （H2O2） concentrations would make the particles more tighten,but might result in crosslinking or degradation of particles.A suitable irradiation time ensured formation of homogeneous nanogel products,but prolonged irradiation would cause degradation of nanogels.After photo crosslinking,the products were purified with membrane filters of 0.45 μm and treated further by dialysis bags with size exclusion below 10 kDa in order to make them more stable for storage.
