Polyurethanes have a broad range application such as foams, fibers, coatings, sealants, elastomers and others. This versatility is attributed to the ease with which their chemistry is tuned by changing stoichiometry or monomer type resulting in various interesting morphological features. Because of the different structures present, Polyurethanes generally exhibit a phase-separated structure. This originates from their multi-blocked chain structure composed of the relatively flexible soft segment and relatively rigid hard segment with short chain extenders. In this study, we seek to understand how changing the symmetry of the chain extender can influence the morphological development kinetics. 1,2-propanediol based chain extender was compared to other more traditional chain extenders on the kinetics of morphological evolution. The presence of the pendant group (methyl or phenyl) in the asymmetric chain extender structure altered the local segmental mobility of the hard segment structure. The different categories of chain extended polyurethanes have been characterized using thermal analysis, infrared and low field NMR. There are a large number of studies dealing with the formation of phase-separated morphology in polyurethanes. However, we found the low field NMR technique provided new information dealing with phase separation kinetics that complement with the well-established DSC and infrared analysis.

The role of chain extender in controlling the kinetics of morphology development of polyurethane elastomers

255th National Meeting (2018)

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