Synthesis And Properties Of Amino Polysiloxane Carboxylate

Amino polysiloxane has the flexible silica bonds on the main chain, the methyl group linking to the silicon atom outwards, and the interaction between chains is weak, the molar volume is big, so it shows a low surface tension, high flexibility and good gas permeability. It is because of their high ductility and the resulting low viscosity can sometimes be a defect in the practical application. Due to the defects, for example, polysiloxane is difficult to be processed into fibers or the stable membranes. So it is necessary to introduce some effective modification, such as crosslinking. Over the past decade, scientists were trying to improve the defects, but the modification reaction processes are usually very complex. So we thought of using the simplest organic acids to react with the amino polysiloxane. The process can introduce in the electrostatic force, improve the interaction in the whole system, this can increase the viscosity of the system, improve its physical properties and mechanical properties. Further, we can think of the introducing of organic di-acids, which can make the adjacent of two contiguous polymer chains to form a network. This can lead the interaction between polymer chains increasing, to improve the rheology properties. Finally, we introduce the unsaturated carboxylic acid to amino polysiloxane, following by photo polymerization, we believe all the properties can be enhanced.It has been found in research that the thermodynamic properties changes of amino polysiloxane carboxylate that detected by differencial scanning calorimeter, such as phase transition, glass transition are not observed. While the thermo gravity analyzing shows the different weight loss ratio between mono acid and di acid. There is tremendous increasing of the viscosity, storage moduli, loss moduli and adhesive force.Mono acid can form electrostatic forces in the system. Carboxylic acid ions can make fast exchange between the protonation amino groups. Viscosity can be changed by using different acidity and structure of acid, the big structure and strong acid is not easy to move, leads to more stable system, bigger viscosity and bigger moduli at particular strain. Base on the study of adding different ratio of acid, we learn that when the molar ratio of acid and amino group is1.1to1, viscosity and moduli properties of the systems reach the maximum. If it is lower than that,there is not enough electrostatic, if it is more than that, the extra acid ion works like lubrication.Di acid salts system can form crosslinked network structure. Rheological properties are significantly higher than that of mono acid system. The length of the alkyl chain of the di acid can control the salts rheological properties, length is shorter, structure is more stable. But to the oxalate, malonate, succinate and glutarate, the molecular configuration also have an impact on the nature. The explanation needs further study.After photo polymerization, the unsaturated acid salts system has greatly enhanced in rheological properties, because they forms more stable and closer three dimensional polymer networks.