Study On The Properties And Mechanism Of Aminopropyl Polysiloxane Carboxylate Electrostatic Gel

Amino polysiloxane has been widely used in industry and daily life due to the advantages of high flexibility and high hydrophilicity.However,its low mechanical properties and low viscosity limit its application as a matrix material.Most of the existing modification methods involve complex synthetic steps,which are complicated and costly.Electrostatic interaction is a very strong non-covalent interaction.It plays an important role in polymer aggregation systems and supramolecular chemistry,and can control the properties of materials to a large extent.In the previous work,aliphatic carboxylic acid was used to modify aminopropyl polysiloxane with amine content of 6-7%.The method is simple and the effect is obvious.The viscosity and modulus of polysiloxane are greatly improved,which is attributed to the strong intermolecular electrostatic interaction of polysiloxane ammonium carboxylate.In order to further understand and explain this phenomenon,a variety of polysiloxane ammonium carboxylate were prepared by using polysiloxanes with different amine content,different molecular weights and carboxylic acids with different carbon chain structure.The viscosity and modulus of different polysiloxane ammonium carboxylate were studied.It was found that some polysiloxane ammonium carboxylate can form electrostatic gels while greatly increasing the viscosity and modulus.Through experiments and theoretical calculations,the influencing factors and laws of electrostatic gel formation were studied.It was found that the viscosity and modulus of the high molecular weight aminopropyl polysiloxane mono aliphatic carboxylate increased with acidity,and showed up to a hundred-fold increase compared to the corresponding aminopropyl polysiloxane.But it cannot form an electrostatic gel.Compared with the corresponding aminopropyl polysiloxane,aminopropyl polysiloxane dicarboxylate has a viscosity and modulus up to 109 times.Whether it can form an electrostatic gel is influenced by various factors.Higher molecular weight and larger amine content of polysiloxane can promote the formation of electrostatic gel.The ability to form an electrostatic gel is also related to the parity of the spacer carbon chain of the dicarboxylic acid within a certain range.Even-numbered carbon chains have a better ability to form an electrostatic gel.Due to the different symmetry of diacids with different parity,the dipole moments are different.The even-numbered carbon chain diacid has high symmetry,and the formed four-dipole center has a small dipole moment,which makes the surrounding low-polarity polysiloxane chain wrap it tighter.Thereby increase the packing density of the polymer crosslinking network and promote the formation of electrostatic gel.In addition,the aminopropyl polysiloxane anthramate in the aminopropyl polysiloxane monoaromatic carboxylate system can form an electrostatic gel with good strength.Because the polymer chain of polysiloxane can further undergo physical cross-linking through the π-π stacking between aromatic carboxylic acid molecules,resulting in a rise in the density of the cross-linked network,to a certain extent similar to the dicarboxylic acid effect.The role of anthracene formic acid is greater than that of naphthoic acid.The anthracene ring has a higher probability of forming a π-π stacking effect than the naphthalene ring,because anthracene has two benzene rings that can participate in the π-π stacking effect,while naphthalene has only one.Moreover,the benzene rings located on both sides of anthracene formic acid can interact with the benzene rings of the other two anthracene formates respectively,which has a chance to form a structure of continuous alternating stacking,forming a more dense cross-linked network.