Computer simulation of urethane formation

Abstract

Computer model calculations have been used to simulate the reaction of polyoxypropylene triol with hexamethylene diisocyanate. Various molecular weight distributions and degrees of polymerisation are used in the calculation. The effect of side reactions is investigated and compared with experiment. Good agreement for both cyclisation and gel points is found for bulk and concentrated solutions. The model can be used to simulate random polycondensation reactions with a reliability approaching that of experiments, and it gives crucial results that cannot be obtained in any other way.

Molecular Dynamics Simulation of the Formation of Polymer Networks

“…The average between the upper and lower bounds gives the critical reaction extent p c at the gel point. Using this upper-lower bound method to estimate the gel point, they obtained results with very good agreement between simulations [32] and measurements. [33] Figure 2 shows the reaction extent dependence of DP w and RDP w for f ¼ 0.3, r ¼ 1 and N 0 ¼ 20.…”

Forced Gelation in an Off‐Stoichiometric Copolymerization of A2 and B3 Monomers

“…Much preferred became the off-lattice models. [19][20][21][22][23][24] The most theoretically studied gelling system was the model of step-growth homopolymeri-zation of an A f monomer ( f ¼ 3, 4,..). [17,[25][26][27] Another widely studied system was the one comprising A f and B g (or RA f and R'B g ) monomers (f > 1, g > 2), which is more relevant to real systems (A and B denote the kinds of functional groups that are capable to react with each other, e.g.…”

“…Unfortunately, most of the assumptions made in the first percolation experiments were hard to accept by chemists studying real polymerization systems. Much preferred became the off‐lattice models 19–24. The most theoretically studied gelling system was the model of step‐growth homopolymeri‐zation of an A f monomer ( f = 3, 4,..) 17, 25–27.…”

Formation of Poly(dimethylsiloxane) Gels

“…If the distances between reactive groups are large, the Gaussian approximation is adequate; if they are short, sampling from RIS configurations will more accurately represent the correlations between reactive groups. The coordinates of the reactive groups do not change as the reaction proceeds, and bond formation is effected by the use of “capture spheres.” − A capture sphere represents the average volume through which a reactive site would diffuse in a unit of time. The reaction is controlled by allowing bond formation between polymer and end-linker reactive sites when the distance between them is within the capture radius.…”

“…The coordinates of the reactive groups do not change as the reaction proceeds, and bond formation is effected by the use of "capture spheres." [40][41][42][43] A capture sphere represents the average volume through which a reactive site would diffuse in a unit of time. The reaction is controlled by allowing bond formation between polymer and endlinker reactive sites when the distance between them is within the capture radius.…”