SHAPE MEMORY EFFECT OF SLIGHTLY-CROSSLINKED POLYETHYLENE

A series of slightly crosslinked polyethylenes (SXLPE) was prepared by a one-step method using dicumyl peroxide as crosslinking agent in a Haake Mixer. The gel contents G (Soxhlet extracted) of the samples are in the range from 5% to 20% by weight. Their shear viscosity, crystallization and melting behavior, dynamic mechanical properties and shape recovery effect were systematically investigated in terms of the content of the crosslinking agent. It shows that under certain experimental conditions the SXLPE's may exhibit good shape fixation ability and shape memory properties, which are similar to those of the commercially available shape memory polyethylenes prepared by gamma-irradiation technique. However the shape memory behavior of these samples is not very stable due to their low crosslinking degree, or gel content. Thus their application is limited in special cases with fast strain fixing procedures. (Author abstract) 9 Refs.

SYNTHESIS, STRUCTURE AND PROPERTIES OF INTERPENETRATING SULFONIC ACID RESINS WITH HIGH CAPACITY

Two series of interpenetrating sulfonic acid resins (ISAR), 10×n and n×10, were prepared by means of the wet method, and the physicochemical, thermodynamic and kinetic properties of the ISAR were measured. The results show: 10×n resins exhibit better properties than n×10 ones, mainly in higher apparent degree of crosslinking and larger conformational entropy effect, among which, 10×1 resin exhibits the best thermodynamic and kinetic properties. In the DTA graphs of n×10 resins, there are two T_g and two T_(ox), but in those of 10×n, only one T_g and one T_(ox). This result well supports the conclusion that 10×n resins have much better interpenetrating structural aspects.

NIR-II live imaging study on the degradation pattern of collagen in the mouse model

The degradation of collagen in different body parts is a critical point for designing collagen-based biomedical products.Here,three kinds of collagens labeled by second near-infrared(NIR-II)quantum dots(QDs),including collagen with low crosslinking degree(LC),middle crosslinking degree(MC)and high crosslinking degree(HC),were injected into the subcutaneous tissue,muscle and joints of the mouse model,respectively,in order to investigate the in vivo degradation pattern of collagen by NIR-II live imaging.The results of NIR-II imaging indicated that all tested collagens could be fully degraded after 35 days in the subcutaneous tissue,muscle and joints of the mouse model.However,the average degradation rate of subcutaneous tissue(k=0.13)and muscle(k=0.23)was slower than that of the joints(shoulder:k=0.42,knee:k=0.55).Specifically,the degradation rate of HC(k=0.13)was slower than LC(k=0.30)in muscle,while HC showed the fastest degradation rate in the shoulder and knee joints.In summary,NIR-II imaging could precisely identify the in vivo degradation rate of collagen.Moreover,the degradation rate of collagen was more closely related to the implanted body parts rather than the crosslinking degree of collagen,which was slower in the subcutaneous tissue and muscle compared to the joints in the mouse model.