材料期刊网

为了提高环梯形聚苯基硅倍半氧烷(Cyclic Ladder Polyphenylsilsesquioxane,CL-PPSQ)在聚合物中的相容性,使用多种硝化试剂,包括发烟硝酸、HNO3-H2SO4、KNO3-H2SO4、HNO3-KNO3、CH3COOH-KNO3、(CH3 CO)2O-HNO3,在不同的条件下对其进行硝化,制备得到含硝基基团的NO2-PPSQ.使用FTIR、元素分析、GPC、TGA、1H NMR等对硝化产物进行表征.结果表明:发烟硝酸、HNO3-H2SO4、KNO3-H2 SO4对CL-PPSQ的硝化能力最强,产物中硝基数目最多,但产物分子量降低,硅氧烷链段发生断裂;而HNO3-KNO3和CH3 COOH-KNO3对CL-PPSQ没有硝化能力;(CH3CO)2O-HNO3硝化过程温和,硝化能力适中,制备得到分子链不断裂的硝化产物.对不同硝化试剂的硝化机理进行了分析,在发烟硝酸、HNO3-H2SO4、KNO3-H2SO4体系中,NO2+为硝化活化剂;对于(CH3 CO)2 O-HNO3体系,CH3 COONO2为主要的硝化活化剂.

Several nitration reagents including fuming nitric acid,HNO3-H2SO4,KNO3-H2SO4,HNO3-KNO3,CH3COOH-KNO3,(CH3CO)2O-HNO3 were used to nitrate cyclic ladder polyphenylsilsesquioxane (CL-PPSQ) in different conditions in order to enhance the compatibility of the CL-PPSQ in polymers,the NO2-PPSQ was obtained.FTIR,element analysis,GPC,TGA and 1 H NMR were used to characterize the structures of the nitrated products.The results show that the nitrating abilities of the fuming nitric acid,HNO3-H2 SO4 and KNO3-H2 SO4 are very strong.Many nitro groups can be linked with phenyl groups in CL-PPSQ,but with low molecular mass,fracture occurs in siloxane segment.However,the Mn of the product NO2-PPSQ sharply drops by 50％ compared with that of CL-PPSQ,so the nitration reagents can break the cyclic structure of CL-PPSQ.The nitrating reagents of HNO3-KNO3 and CH3COOH-KNO3 have no nitration effects on CL-PPSQ.At last,NO2-CL-PPSQ was prepared using (CH3 CO)2O-HNO3 because of the moderate nitration process and ability.The cyclic structure of PPSQ is remained,although the number of-NO2 group is not too much.At the same time,the nitration mechanism using different nitration reagents was analyzed.A certain amount of NO2-,which is a kind of activator owning strong nitration ability,can be found in the fuming nitric acid and H2SO4-HNO3(KNO3 systems.As to the (CH3CO)2O-HNO3 system,the main activator is CH3 COONO2.