丙烯腈-丙烯酰胺溶液共聚合及其产物热性能研究

Solution polymerization and thermal properties of acrylonitrile(AN)-acrylamide(AM) copolymer

通过改变原料中丙烯腈(AN)与丙烯酰胺(AM)的配比,获得不同共聚组成的聚丙烯腈。结合凝胶渗透色谱(GPC),X射线衍射(XRD),核磁共振(NMR),失重差热联用(DSC TG)等考察了AM对聚合反应的影响,剖析了聚合物的结构特征,评价了共聚产物在50℃～500℃氮气中的热性能。研究结果表明:反应物料中AN与AM的配比对产物分子量、转化率、共聚组成、共聚物的晶态结构和立体结构以及放热行为有着极大的影响。AM的加入对共聚产物分子量和聚合转化率的影响趋势相反。当AN与摩尔分数为0.75%的AM反应时,转化率最高,分子量最低。在AM的摩尔分数为0%～3.78%的条件下,随着AM加入量的增多,共聚组成中AM量也增多,聚合物的规整度增高,结晶度变大,晶粒尺寸增加。AM的引入能够使PAN/AM环化提前,降低放热速率。并且,环化机理受共聚组成影响。AM的引入使得共聚物存在两种环化增长方式(离子增长和自由基增长)。随着AM引入量的增多,氰基的自由基环化增长越来越少,离子环化增长越来越多,存在自由基机理向离子机理过渡的趋势。

Copolymerization of AN and AM with azobisisobutyronitrile (AIBN) as the initiator and AM varying from 0 to 3.78 mol% was carried out in dimethylsulfoxide (DMSO) solution at 60degreesC under nitrogen flow, and copolymers were characterized by elemental analysis (EA), gel permeation chromatography (GPC), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and C-13-NMR. Results indicated that the amount of AM had a strong influence on the molecular weight, the polymerization conversion, the composition, the crystalline properties, the stereoregularity, and the thermal properties of the copolymers. The tacticity, the crystallinity and the crystallite size increased with the amount of AM. The presence of AM induced an ionic cyclization mechanism to the copolymers in the stabilization process and the cyclization reaction mechanism gradually changed from free radical to ionic with the increased amount of AM.