Iron(III)-Catalyzed Chain Growth Reactions of Polymeric Methylene Diphenyl Diisocyanate

Abstract

The overall goal of the present study was to identify the high molecular weight species formed during the synthesis and processing of polymeric methylene diphenyl diisocyanate (PMDI) and determine the root cause of the viscosity buildup in these materials. Initial studies focused on the use of MALDI-TOF mass spectrometry to examine the PMDI mixture and MALDI-TOF/TOF CID fragmentation for elucidating the degradation mechanisms of the identified compounds. The low molecular mass portion of the MALDI spectrum was observed to contain the expected PMDI and small quantities of carbodiimides (CDIs). The high molecular mass portion of the spectrum primarily contained 1,3-diazetidine branched carbodiimide dimers, uretonimine branched CDIs, and imino-s-triazine along with low levels of guanidine branched CDIs. The results of this study indicate that the root cause of the observed CDI defects was extensive branch formation through unexpected side reactions catalyzed by iron(III). These reactions lead to a buildup of viscosity which poses a significant challenge during the processing of these materials.

Characterization of microstructures and reaction mechanisms of Tröger's base polymers of intrinsic microporosity

“…ESI requires solubility, and conventional MALDI and direct laser desorption methods have only been marginally successful for intractable polymers . However, the evaporative‐grinding (E‐G) MALDI sample preparation method was developed to overcome solubility problems, and will be our analysis technique of choice for the present study of Tröger's base PIMs.…”

“…This report serves as an update on new developments and applications of the E‐G MALDI sample preparation method, combined with collision‐induced dissociation (CID) fragmentation, for improved rapid microstructure characterization of poorly soluble/insoluble Tröger's base PIMs . Examples will be presented of the use of enhanced data mining with ultrahigh‐resolution MS and statistical analysis for examining the various distributions in molecular mass, chemical connectivity, and end groups generated during synthesis of Tröger's base PIMs.…”

Mass spectrometry and ion mobility study of poly(ethylene glycol)‐based polyurethane oligomers

“…6 Gies et al published a MALDI-MS/MS study of carbodiimide branching reactions 7 and used MALDI and MS/MS to identify the cause of increased viscosity observed in processing of poly-MDI. 8 Lastly, Lattimer et al combined MALDI with pyrolysis to study the structure of segmented PURs formed from MDI and poly(butylene adipate). 9 Nearly all the aforementioned work has used fragmentation as the primary method of PUR structure characterization.…”