Synthesis of Phosphorus Containing Polymers by Phase Transfer Catalysis (PTC). II. Experimental Design for Polycondensation in Liquid-Vapor System

Abstract

The simultaneous influence of four factors reaction time (I), temperature (T), base concentration (c). molar ratio of the reagents (r)] on the yield (q) and on the inherent viscosity (qIv) of the product has been studied for the liquid-vapor system pol ycondensation of cyclohexyldichlorophosphonate (CDP) with bisphenol A (BA) by second order central composite circumscribed design. For a reasonable domain of the parameters t = 30 ÷ 70 min., T = 20 ÷ 60 °C, c = 1 ÷ 5 mol/l, r = 1 ÷ 3.5 mol(CDP)/mol(BA)], designing the experiments, the η and η_iv values where determined in 31 synthesis (7 center points were used). In order to model the response (hyper)surfaces for η and η_iv, second order equations with interaction terms were used. Analyzing these model equations, T and c appear to be the most important factors, but acting in opposite way. Higher T resulted in greater yield and inherent viscosity. In the above defined domain the hypersurface of η presents a saddle point. From the sequential inspection of the dependence of η and η_iv on the different parameter pairs, using contour plots and 3D-plots see for example the attached figure for the yield fimction of factors x2 (T) and x3 (c)] optimum conditions can be deduced for the desired good yield and great inherent viscosity. These are: long reaction time (70 min), high temperature (60 °C), low base concentration (1 mol/l) and high to moderate CDP excess.