Synthesis and DSC study of model hard segments from diphenyl methane diisocyanate and butane diol

Model hard segments having different chain length and chain terminating groups, such as methyl, ethyl, octyl, and octadecyl, have been synthesized from diphenyl‐methane diisocyanate (MDI) and butanediol and studied by DSC. In the case of short chain ends (i.e., methyl, ethyl, and octyl), hard segments having up to three MDI units show an increase of melting temperature T m , while those with octadecyl chain end have T m increase continuously with the number of MDI units. Enthalpy and entropy decrease with the augmentation of the hard‐segment length. Side groups on the chain ends have a great influence on the melting properties.