聚脲-聚酰亚胺嵌段共聚物的制备及表征

以4,4′-二氨基二苯醚(ODA)、4,4′-二苯甲烷二异氰酸酯(MDI)、3,3′,4,4′-联苯四甲酸二酐(BPDA)为原料,首先合成端氨基聚酰胺酸和端异氰酸酯基聚脲,然后将2个均聚物偶联,制备3种聚脲链段含量不同的聚脲-聚酰亚胺嵌段共聚物。通过红外分析、X射线衍射、热重分析、差示扫描量热分析和热膨胀系数测试对嵌段共聚物的结构和性能进行了表征。结果表明,聚脲-聚酰亚胺嵌段共聚物具有较好的热稳定性,失重5%的温度T5%在330℃以上;热失重曲线出现2个失重台阶;聚脲链段含量的增加,使玻璃化转变温度升高,热膨胀系数降低;聚脲-聚酰亚胺嵌段共聚物在酸性介质中比在碱性介质中更稳定。

Preparation and Representation of Polyurea-Polyimide Block Copolymer

Though prepolymerization method,three polyurea-polyimide block copolymers with different polyurea segment contents were synthesized using 4,4'-diaminodiphenyl ether(ODA),4,4'-diphenylmethane diisocyanate(MDI),3,3',4,4'-diphenyl tetracarboxylic anhydride(BPDA).Firstly,amino terminated polyamic acid and isocyanate terminated polyurea were obtained,and then polyurea solutions were added into poly(amic acid).The structure and properties of the block polymer were characterized by FT-IR,WAXD,TG,DSC and TMA.The results show that the polyurea-polyimide block copolymer has good thermal stability,the temperature of 5%mass loss is above 330℃.Two mass loss steps exit in the thermogravimetric curve.With the increase of polyurea chain content,the glass transition temperature(Tg)increases and the thermal expansion coefficient decreases.Polyurea-polyimide block copolymers are more stable in an acidic medium than in an alkaline medium.