MODELING OF STEP-GROWTH INTERFACIAL POLYMERIZATION: THE KINETICS AND POLYMER FILM STRUCTURE

摘要

Step-growth alternating interfacial polymerization (IP) between miscible or immiscible monomer melts is studied theoretically and by dissipative particle dynamics simulations. The kinetics for an initially bilayer system passes from the reaction to diffusion control. The polymer composed of immiscible monomers precipitates at the interface forming a film. In linear IP, the film is nearly uniform and the reaction proceeds in a narrow zone, which expands much slower than the whole film. It leads to a ehemical extrusion" of newly formed polymer from the reaction zone. This concept is used to predict the degree of polymerization (DP) and end-group distribution within the film in close agreement with the simulations. Increasing the comonomer incompatibility leads to thinner and more uniform films with the higher average DP. The final product is considerably more polydisperse than expected for the homogeneous step-growth polymerization. Crosslinking in the case of branched IP drastically changes the mechanism of polymer film development and makes the theoretical model inapplicable. The simulations demonstrate that the extrusion effect is suppressed and polymerization proceeds like in a homogeneous system until the gel-point is attained. Growth of the comonomer immiscibility postpones the gel transition and, oppositely to the linear IP, decreases the final number-average DP. The obtained film is highly inhomogeneous with a dense core and loose shell regardless of the comonomer interactions. The results extend the previous theoretical reports on IP and provide new insights into the internal film structure and polymer characteristics, which are important for membrane preparation, microencapsulation, and 3D-printing technologies. The financial support from Russian Foundation of Basic Research (Project 12-03-00817a) is appreciated. We thank Moscow State University Supercomputer Center for providing the computational resources.