A Mass Spectrometry Analysis of Hard Segment Length Distribution in Polyurethanes

Abstract

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry was utilized to determine the hard segment length distribution in poly(urea-urethane)s. Although hard segment length is expected to vary with water content in the initial formulations, the actual distribution is rather similar for all samples analyzed. A more detailed analysis, however, revealed that the principal difference is in the region corresponding to hard segments with greater than eight urea repeat units. This finding has implications for both in the origin of phase separation behavior and the mechanical performance of phase separated heterogeneous polymers. The similarity in hard segment distribution suggests that phase separation behavior in these polyurethane foams cannot be due solely to the orientational entropic contribution. The presence of these long hard segments, although not extensive (7% of the total number fraction), may contribute significantly to mechanical performance. MALDI also revealed the presence of side products. The amount of cyclic species, either isocyanurate or cyclic hard segments, varied from 2 to 4% for foams with different urea contents.

Structural investigations of toluene diisocyanate (TDI) and trimethylolpropane (TMP)-based polyurethane prepolymer

“…Majority of positive ions presented in ESI spectra contain Na + and some minor part of them contain K + which has been introduced as KI [37,38]. Additionally, isocyanate products reacted with several methanols employed to dissolve samples, and the MeOH end-capped prepolymer were also observed in the MS spectra depending on the number of isocyanate groups existed.…”

Reaction Monitoring of Toluenediisocyanate (TDI) Polymerization on a Non-Mixable Aqueous Surface by MALDI Mass Spectrometry

“…MALDI time-of-flight (TOF) MS provides a particularly powerful tool for the mass analysis of high-molecular-weight polymers, due its high mass resolution, high sensitivity, and simple sample preparation. [1][2][3] The ability of MALDI TOF MS to monitor the molecular-weight distribution of synthetic polymer samples makes the technique useful for identifying the chemical composition and end-functional groups of polymer samples. [4][5][6] MS techniques have been mainly applied to the investigation of polymer segments, prepared by the hydrolysis of high-molecular-weight polymers.…”

Theoretical modeling of the relationship between Young's modulus and formulation variables for segmented polyurethanes

“…Cylindrical and spherical domains were indeed observed in recent AFM studies of O'Sickey et al25 and Garrett et al21, 22 Notably, in PU elastomers, hard phase cylinders do not assemble into a hexagonal lattice (which is typically the case in monodisperse diblock copolymer melts). It is not clear thus far whether the lack of hexagonal ordering is due to kinetic limitations and/or to the polydispersity of HSs (which, for PUs, is usually quite high34).…”