Rheological Behaviors Of Complex Membrane Prepartion Soluiton Of Partially Hydrolyzed Poly (2-Ethyl-2-Oxazoline)/Poly(Acrylic Acid)

Polymer composites can be divided into polyelectrolyte composites,hydrogen bonding composites,charge transfer composites,etc.according to different driving forces.Polyelectrolyte complexes and hydrogen-bonded complexes have been widely studied because they can respond to changes in pH,temperature,salt concentration,etc.in a timely manner,and can be applied to the preparation of functional thin films.After partial hydrolysis of poly?2-ethyl-2-oxazoline??PEOX?,random copolymer PEOX-EI can be obtained.The hydrolyzed part can be used as a proton acceptor,and the unhydrolyzed part can be used as a hydrogen bond acceptor.-NH group can be used as a cross-linking site,which can enhance the stability of the material prepared.The ionization degree of-COOH in the molecular structure of polyacrylic acid?PAA?will change at different pH values,so PAA can form a polymer complex with PEOX-EI through hydrogen bonding or electrostatic interaction.The strength and type of intermolecular interactions in the system can be controlled by adjusting the pH of the blended solution.In addition,by studying the rheological behavior of the blend solution,information such as fluid type,viscoelastic performance and intermolecular interaction in the system can be analyzed,and suitable film processing conditions can also be determined by analyzing its rheological behavior,which has theoretical guiding significance for the future preparation of membrane materials by PEOX-EI/PAA blend system.The main research contents of this topic are as follows:1.A series of PEOX-EI with different hydrolysis degrees were prepared by controlling the hydrolysis time.The hydrolyzations of ¹HNMR samples were 25%,38%,59%,67%,85%and 99%,respectively.FTIR spectrum observed that the hydrolysis degree increased,the absorption peak strength of-C=O decreased,and the absorption peak strength of-NH₂⁺increased.TGA was used to test the thermal stability of PEOX-EI samples with different hydrolysis degrees.With the increase of hydrolysis degree,the thermal decomposition temperature of PEOX-EI decreased continuously,and the thermal stability of PEOX-EI samples also decreased significantly.2.P-30^P-120 in PEOX-EI aqueous solution with a degree of hydrolysis of 67%appeared turbid,and P-10^P-120 in a solution with a higher degree of hydrolysis had obvious precipitation,which was due to linear polymerization ethyleneimine?L-PEI?has strong hydrophobicity in high pH aqueous solution,so it is necessary to eliminate the interference of the above factors in the process of subsequent research on the PEOX-EI/PAA blend system.3.In the PEOX-EI/PAA blending system,under the low[NaOH]/[AA]ratio,the hydrogen bonding was dominant,and when the[NaOH]/[AA]ratio increased,the electrostatic interaction was dominant,and the hydrogen bonding was abate The hydrogen bonding was weakened until-COOH is completely ionized,at this time the hydrogen bonding effect disappeared,and the ratio of[NaOH]/[AA]continued to increase.The electrostatic effect was weakened due to the inhibition of the protonation of-NH₂⁺,until-NH₂⁺was completely converted to no charge-NH group,the electrostatic effect disappeared.In addition,when the ratio of[NaOH]/[AA]was the same and the degree of hydrolysis was different,the number of groups that generate precipitates in the blend solution with a high degree of hydrolysis was greater than that with a low degree of hydrolysis,indicating the removal of-NH₂⁺in the blend system with a high degree of hydrolysis Protonation needed to be adjusted to a higher pH.4.Rheological tests were performed on PEOX/PAA and PEOX-EI/PAA homogenized blend solutions with hydrolytic degrees of 25%,38%and 59%,respectively,and the corresponding relationships between their rheological behaviors and the conformation of intermolecular forces and macromolecular chains in the system were analyzed.The steady-state shear rheological behavior of the blending system can be intuitively expressed as that under the condition of the same degree of hydrolysis,the zero shear viscosity will gradually decrease with the increase of pH value due to the weakening of electrostatic effect in the system.When the[NaOH]/[AA]ratios were all 1.2,the zero-shear viscosity of the blend solution with high hydrolysis degree was much higher than that with low hydrolysis degree,indicating that the full protonization of-NH₂⁺in PEOX-EI with high hydrolysis degree should be adjusted to a higher pH value.The amplitude scanning test showed that at the same degree of hydrolysis,the blend solution with a low[NaOH]/[AA]ratio showed mainly elastic deformation,while the blend solution with a high[NaOH]/[AA]ratio showed mainly viscous deformation,and the linear viscoelastic region of the blend solution under different conditions was explored.Frequency scanning test is to explore the response of the blend system with different hydrolysis degree and[NaOH]/[AA]ratio to the frequency change under the condition of constant strain,so as to study the viscoelastic performance of the blend system under different conditions in different frequency ranges.5.The PEOX-EI/PAA homogeneous blend solution without shear thinning can be scraped into a film,and the blend solution with precipitation can be prepared by layer-by-layer self-assembly technology without the formation of precipitation The blend solution with shear thinning property has less intermolecular force in the system,and the shear thinning property of the solution makes it have no processing advantages in high shear film processing,so this condition The blending solution below is not suitable for blade coating or layer-by-layer self-assembly.