The Study On The Phase Separation And Gelation Transition In Physically Associating Polymer Solution

Phase separation and gelation transition of polymer solution are always interesting topic in polymer science field. Due to the temperature sensitivity of the incompatible between polymer and solvent, the separation consisting of different stage in polymer solution takes place. Therefore phase separation has wide applications in polymer purity and industries production. Gelation which has much excellent function is very important in polymer material field. Sol-gel transition always polymer science extremely active topic, especially to sol-gel method in chemistry sample preparation and actual production. So phase separation and sol-gel transition theory research of associating polymer solution is very significant, especially to promotion of new method in research field.The paper work is carries on under the field theory frame. We study phase transition and gelation of physically associating polymer solution using lattice self-consistent field method.The paper is arranged as followed: In order to understand well we give the simple conception of phase separation and gelation transition in the first chapter; In the second chapter, the advantage of our method are compared with disadvantage of several methods, and proposed chapter, and so. Further we demonstrate validation of the model in the third chapter. And then we will discuss the phase separation and gelation transition in the forth chapter and the fifth our method, model and formula of calculation. Finally, conclusion and expectation will be given.First,study of phase separation: Firstly we construct polymer system partition function,obtaining stable state using the conjugate relation between chemical potential field and polymer volume fraction through iteration solution. To confirm our method we construct the phase diagram for polymer solution, selecting several initial value, change lattice size and degree of polymerization, The results have showed that our model for the study of polymer solution is feasible and convenient.The system is characterized by volume fractionφpand interaction parameterχ, which is the inverse of the temperature. With the polymer volume fraction increasing the changing curve, i.e. the separation line, is parabola-like. However, for solvent and the polymer mixture the polymerization degree is asymmetrical, the phase diagram is not symmetric, the critical point deviates the direction of small polymer volume fraction. We have already given particular result. The result obtained is consistent with theory existent result. Further we studied different polymer chain structure, the calculation indicated that the parameterχof the onset of phase separation increases when the non-stickers are inserted into polymer chains consisting of stickers in some interval and the interval number is increased. The changing extent is proportional the interval number, nearly equaling the changing extent interval number between monomers. The smaller is the interval number between monomers, the smaller the interaction parameter. And the polymer concentration of critical point is changeless. However, when stickers are inserted into the polymer consisting of non-stickers ,the interaction parameter of the onset of separation increases with increasing the interval number between stickers, for the total number of stickers from polymer decreases. The polymer concentration of critical point tends to the direction of low polymer solution.Second, sol-gel transition: In our model system, sol-gel transition occur when the concentration of associating polymer solution increase to some extent. In many studies the stress variation is used to determinating the onset of sol-gel transition, but we use heat capacity as the thermodynamics signature when gelation takes place. We obtained a sequence of results through the calculation. The sol-gel transition line obtained indicates interaction parameterχremains changeless when polymer solution concentration is in the high range. Further, when the interval number between stickers decreases the interaction parameter of the onset of gelation also decreases, equaling increasing the polymer solution concentration. Various system of the transform from chemical energy to mechanical energy is conceived using the sensitivity of gelation deformation to the external environment, it is conceived a wide range of chemical energy transit to mechanical. Such as, artificial muscle-based model, Chemical valve, drug delivery systems etc. Recently the research in this area is in rapid progress in many countries of the world, especially in Japan. In addition to this, gelation is applied in the governance of the desert, soil improvement, solution of the problem of water and soil moisture.Based on the limitations of Calculation conditions and time ,Presently, the study is only confined to the two-dimensional system and small lattice size, but out results is in reasonable agreement with the existent theory. Because of the low amount of calculation for this method, it has specially advantage in application.