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

1. 通过在炭黑表面引入的氨基基上加成丙烯酸甲酯作为引发剂核，再通过烷基二胺末端酰胺化，成功地将聚氨基胺枝状大分子接枝到炭黑表面。然而，由于枝状分子的位阻作用，枝状分子在炭黑表面的延伸在理论上是不可能实现的，因此枝状分子被接枝到炭黑表面。在N，N'-双环己基碳二酰亚胺（DCC）存在下，将树状大分子末端氨基与炭黑表面羧基直接缩合，得到了结构理想的聚胺胺类树状大分子。在DCC的作用下，端羧基聚乙二醇（PEG）与接枝在炭黑表面的枝状大分子末端氨基发生反应，并将其接枝到炭黑表面。由聚乙二醇接枝炭黑制备的纳米复合材料的电阻在酒精蒸气中急剧增加到初始电阻的10^3-10^4倍，并在干燥空气中转移时立即恢复到初始电阻。电阻的对数与酒精蒸气的分压成线性关系。聚乙烯（PE）与聚环氧乙烷（PEO）嵌段共聚物PE-嵌段PEO通过嵌段共聚物表面羧基与末端羟基的反应接枝到炭黑表面。由聚乙烯嵌段-聚氧乙烯接枝炭黑制备的纳米复合材料的电阻对烷基卤化物的蒸气有良好的响应。在含有烷基卤化物的己烷中，复合材料的电阻增加。因此，这些复合材料可以用作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.