Preparation of nano composite from dendrimer-grafted carbon black with crystalline polymer and its application as gas sensor

1.通过重复两个过程成功地在炭黑表面接枝了聚酰胺胺树枝状大分子：(1)将丙烯酸甲酯作为引发剂核引入到炭黑表面的氨基上进行Michael加成反应；(2)用烷基二胺对生成的酯基进行末端酰胺化。然而，由于接枝的树枝状大分子的空间位阻，理论上无法实现树枝状大分子从炭黑表面繁殖，并在表面接枝了超支化的聚酰胺胺。在N，N‘-二环己基碳二亚胺(DCC)存在下，通过树枝状大分子末端氨基与炭黑表面羧基的直接缩合反应，在炭黑表面接枝了具有理想结构的聚酰胺胺类树枝状大分子。在DCC的存在下，端羧基聚乙二醇(PEG)很容易与接枝在炭黑表面的树枝状大分子的末端氨基反应，然后再接枝到炭黑表面。由聚乙二醇接枝碳黑制备的纳米复合材料在酒精蒸气中的电阻急剧增加到初始电阻的103~104倍，在干燥空气中转移后立即恢复到初始电阻。电阻的对数与乙醇蒸气的分压成线性关系。将聚乙烯(PE)与聚环氧乙烷(PEO)的嵌段共聚物(PE-BLOCK-PEO)通过嵌段共聚物的端羟基与表面的羧基反应，接枝到炭黑表面。PE-嵌段-PEO接枝炭黑制备的纳米复合材料对卤代烃的蒸气具有良好的电阻响应。在含烷基卤化物的正己烷中，复合材料的电阻增大。因此，这些化合物可用作正己烷中的气体传感器和溶质传感器。

1. Poly (amidoamine) dendrimer was successfully grafted onto carbon black surface by repeating two processes : (1) Michael addition of methyl acrylate to amino groups introduced onto the surface as initiator core, and (2) terminal amidation of the resulting ester moieties with an alkyl diamine. The propagation of dendrimer from carbon black surface, however, was not achieved theoretically and hyper-branched poly (amidoamine) was grafted onto the surface, because of steric hindrance of grafted dendrimer.2. Poly (amidoamine) dendrimer having ideal structure was grafted onto carbon black surface by direct condensation of terminal amino groups of dendrimer with carboxyl groups on carbon black surface in the presence of N,N'-dicyclohexylcarbodiimide (DCC).3. Carboxyl-terminated poly (ethylene glycol) (PEG) was readily reacted with terminal amino groups of dendrimer grafted on carbon black surface in the presence of DCC as a condensing agent and PEG was postgrafted onto the surface.4. The electric resistance of a nano composite prepared from PEG-postgrafted carbon black drastically increased to 10^3-10^4 times of initial resistance in vapor of alcohol and returned immediately to initial resistance when it was transferred in dry air. The logarithm of electric resistance was linearly proportional to partial pressure of alcohol vapor.5. Block copolymer of polyethylene (PE) with poly (ethylene oxide) (PEO), PE-block-PEO, was grafted onto carbon black surface by the reaction of carboxyl groups on the surface with terminal hydroxyl groups of the block copolymer. The electric resistance of a nano composite prepared from PE-block-PEO -grafted carbon black has good responsibility to vapor of alkyl halides. The electric resistance of the composite increased in hexane containing alkyl halides. Therefore, these composite can be used as a gas sensor and a solute sensor in hexane.