Abstract: In order to reduce the swelling ratio of calcium alginate beads，vinyl acetate (VAc) was grafted on sodium alginate (SA) by free radical copolymerization，and vinyl acetate grafted calcium alginate (Ca-SA-PVAc) beads with low swelling ratio were prepared. FTIR indicated that new chemical bond was formed in modified alginate molecule. TGA showed that the rate of bound moisture loss of modified alginate beads was changed and its heat stability was improved. SEM showed that Ca-SA-PVAc beads had well-developed pore structure. The effects of reaction conditions，such as grafting reaction temperature，monomer and initiator concentrations，percentage of alginate and calcium chloride，grafting reaction time on swelling ratio in 0.9%NaCl solution were studied. By changing reaction conditions and consequently grafting reaction parameters，the swelling ratio of grafted beads could be controlled.

Key words: sodium alginate, vinyl acetate, grafting reaction, swelling ratio, hydrogel microsphere

摘要： 为了降低海藻酸钙凝胶微球的溶胀度，以乙酸乙烯酯（VAc)对海藻酸钠进行自由基接枝共聚，进而制备具有较低溶胀度的聚乙酸乙烯酯改性海藻酸钙(Ca-SA-PVAc)凝胶微球。红外光谱表明，改性之后海藻酸钙的分子上生成新的化学键；热重分析表明，改性微球受热失水行为发生变化，热稳定性提高；扫描电镜表明，改性微球结构孔隙结构发达；接枝反应条件如反应温度、VAc的浓度、引发剂用量、海藻酸钠浓度、钙离子浓度及反应时间等对改性凝胶微球在生理盐水中的抗溶胀性具有不同程度的影响。通过改变反应条件以控制接枝反应参数，可以获得溶胀行为可控的改性海藻酸钙凝胶微球。

关键词: 海藻酸钠, 乙酸乙烯酯, 接枝反应, 溶胀度, 凝胶微球