在低pH 值条件下采用NaIO₄氧化羧甲基纤维素( CMC) ，制备了二醛羧甲基纤维素( DACMC) ，通过 FT- IR、¹³C NMR、XRD 和AFM 等研究了pH 值对 NaIO₄ 氧化CMC 程度的影响，以及pH 值对DACMC 结晶结构、形貌结构、热稳定性的影响．结果表明: pH 值对 NaIO₄氧化CMC 的程度有显著的影响，但缺乏规律性，当pH 值为1．5 时其氧化程度最高( 醛基含量最大为54．35%) ; FT- IR和 ¹³C NMR结果证实了在CMC 分子链上有羰基产生; DACMC 的结晶度均大于CMC，且随反应体系pH 值的增加而增大; 由于失水葡萄糖环的断裂，DACMC 的分子链更加柔软，相互缠结得更加紧凑、规整，表面Z向尺寸随着醛基含量的增大而降低; DACMC 的热稳定性差于CMC，pH =1．5 的条件下制备的DACMC 的热稳定性最差．

Dialdehyde carboxymethyl cellulose (DACMC) was synthesized by oxidizing carboxymethyl cellulose (CMC) with periodate NaIO₄ at low pH value,and the effects of pH value on the oxidation degree of CMC,as well as on the crystal structure,morphology and thermal stability of DACMC,were investigated by means of FT- IR,¹³C NMR,XRD and AFM.The results show that (1) pH value significantly and irregularly affects the oxidation degree of DACMC,and the oxidation degree reaches its maximum at pH 1.5,with an aldehyde content of 54.35%; (2) carbonyl groups are introduced into the molecular chain of CMC,which is verified by FT- IR and ¹³C NMR results; (3) the crystallinity of DACMC is higher than that of CMC and increases with pH value; (4) due to the break of glucopyranose rings，the molecular chain of DACMC becomes softer,entangles with each other more compactly and arranges more regularly,while the Z dimension of DACMC surface decreases with the increase of aldehyde content; and (5) the thermal stability of DACMC is poorer than that of CMC,especially in the condition of pH 1.5.