A2+CBn approach to hyperbranched polymers with alternating ureido and urethano units

Various hyperbranched polymers with alternating ureido and urethano units in their backbones were synthesized by direct polycondensation of diisocyanates (A(2)-type monomers) with compounds containing one amino group and multihydroxyl groups (CBn-type monomers). Because of the commercial availability of the monomers and the simplicity of the synthesis process, hyperbranched poly-(urea-urethane) materials can be large scale accessed. The reaction between an A group and a C group is much faster than that between an A group and a B group, resulting in the formation of AB(n)-type intermediates in the initial stage of the reaction. Further self-polycondensation of the intermediates gives hyperbranched macromolecules. The influence of reaction conditions such as temperature and concentration on the polymerization was discussed in detail.