In the paper,in vitro degradation of DL polylactic acid (PDLLA) film was studied.Regulation and tendency of degradation were showed by molecular weight regulator and monomer ration mass lossing.Degradation mechanism was discussed in light.It was thought that degradation of PDLLA in vitro was a simple hydrolysis reaction.The hydrolysis reaction was self catalytic reaction caused by terminal carboxyl group.

Lactide一glycolide copolymerization with stannous octanoate as an initiator and dedecanolas regulator was carried out.The effect of reaction condition such as reaction time,temperature, initiatorconcentration, regulator and monomer ratbonpolymerization conversion,molecular weight and its distrbu-tion were investigated.The obtained results show that the finest reaction condition are initiator 0. 075%,ternperature 170℃ and reaction time 6hr.At this reaction condition,both molecular weight and polymer-ization conversion obtained are vecy high.

ObjectiveTo prepare artificial viscoelastic agent used in ophthalmic operation as a substitute of Healon. MethodsPolyacrylamide was synthesized in aqueous solution of acrylamide. Residual monomer(Am) was separated from polymer by a novel method, extraction by semi permeable film. Results and ConclusionsArtificial viscoelastic agent prepared has advantages on cost of manufacture, processing repeatability and stability of storage comparing to Healon.

BACKGROUND: The water molecules and biological macromolecules in human tissue may combine to form hydrate composite. Different types of macromolecules show different approaches to combine with water molecules. OBJECTIVE: To discuss the basic form of water molecules combined with biological macromolecules. METHODS: The theoretical hypothesis of texture composite hydration system was proposed. The relevant literatures were retrieved through the computer to discuss these issues. RESULTS AND CONCLUSION: According to the role of water in the hydrate composite, the composite ways can be divided into the following 4 groups. ①Surfaca composite: Hydrated membrane layers can form on the surface of globular protein or DNA molecules. The hydrated membrane layer shows that the speed of water molecular and hydrate density were reduced gradually from surface to inside. The hydrated layer makes the shape and physical state of the macromolecules stabilized, and it plays important role in forming of TCHS.②Swelling composite: As a result of the strong hydration of glycosaminoglycans, the hydrated proteoglycan often swells and shows high viscosity and hydrogel character. The hydrated proteoglycan play some mechanicalroles in connective tissue. For example, it can make the cartilage have a strong deformation-resistibility.③Hydrophobic composite: Hydr0phobic effect drives structural rearrangement, including the formation of bilayers (Bio-membrane). This hydrophilic-hydrophobic-hydrophilic "sandwich" structure is conducive to the self-stability in mechanics, combination with membrane protein and transmembrane transport. ④Slit composite: A lot of slit spaces with nano scale were existing inside and outside of the cells. Aqueous solution in the slit spaces shows some abnormal characters such as higher viscosity and lower ice point, because of the rearrangement of water molecules. Slit composite and surface composite have some universality, and it can be regarded the former as a special case of the latter. The classification way mentioned above has not any absolute connotations. However, the rational utilization of these hydration composite ways will be conducive to research the theory on textural composite hydrate system.

ObjectiveTo approach the taxonomy of polymer hydrogels prepared with composite material science methods.MethodsThe research results which have been obtained were synthesized and analysed in the light of multiscale design viewpoint,and the hydrogel composite materials were classified by the composite ways and its structural levels.Results and ConclusionA kind of taxonomy system was advanced in which new concepts of intermolecular composite,textural composite etc.were induced.Apply-ing these concepts and methods will be helpful to research on composite biomaterials.

Two types of catheter made of polymeric hydrogel were prepared and their mechanical properties were studied. The results showed PVA hydrogel catheter was prepared by repeated freezing-thawing cycles of PVA solution in mould. Another type of catheter (PVA-DMSO - hydrogel ) was prepared by cooling the PVA solution containing 10%wt DMSO in mould. The tensile strength (30～40MPa)and elongation(380 %～400%) of these two types of catheter were comparable with those of commercial PVC catheter and silicone rubber catheter. But the elastic modulus of PVA-DMSO hydrogel catheter was 10MPa,near to silicone rubber catheter and that of PVA hydrogel catheter was only 4MPa. γ-ray irradiation for sterile made 40%～50% loss of tensile strength for both catheter. Dipping in hibitane aqueous solution didn\'t affect mechanical properties.The obvious difference in mechanical properties was due to the difference in the orientation of PVA molecule chain and crystalline structure.

A new kind of medical sponges,ionic polyvinyl alcohol sponges(i-PVA sponges)were prepared by surface-grafting of acrylic acid onto acetal-PVA sponges.i-PVA sponges obtained show excellent hydrophilicity and water-absorption.The i-PVA sponges are three dimentional porous network.Because there are great amount of carboxyl and sodium carboxylate groups on PVA molecule chains,the speed of water absorption and water-absorptivity is >2.9mm/s and >15 times respectively.That is,in the case of the cataract-extraction,the polyion-modified sponges much more advantageous than any traditional nonionic polymer sponges.

ObjectivePolyamidoamine(PAMAM) dendrimers enhance the solubility of nicotinic acid. MethodsPAMAM dendrimers of generation 1 to 6 were prepared and the effect of pH and concentration of the dendrimers on the solubility enhancement of nicotinic acid was investigated. ResultsThe pH and concentration of the dendrimers influence the solubility enhancement of nicotinic acid. Conclusions Electrostatic interaction between the carboxyl group of the nicotinic acid and the amine groups of the dendrimers is involved.