Structure, Morphology, and Transport Relationships in Segmented Polyurethanes: A Molecular Simulation Approach
Abstract
In the last funding period, we continued to focus on the formation of polyurethanes by controlling the relative kinetics of crosslinking versus phase separation of hard segments. These materials exhibit interesting mechanical behavior and controllable barrier properties. A series of polyurea urethanes was isothermally synthesized from toluene diisocyanate (TDI), water, and trifunctional poly(propylene oxide) in the temperature range of 50 - 150 deg C. Morphologies of the samples vary significantly as a function of reaction temperature. in this system, phase separation competes with polymerization and crosslinking. Both transmission electron microscopy and atomic force microscopy have displayed a network type structure for the 50 deg C samples; the 150 deg C samples appear to be homogeneous. Infrared analysis reveals that samples prepared at 150 deg C possess a morphology that is less strongly hydrogen bonded and with a broader distribution of hydrogen bonded states in comparison to those prepared at lower temperatures. From this combination of techniques, it can be inferred that phase separation occurs more rapidly than crosslinking at low temperatures; consequently, a phase separated morphology results. In contrast, crosslinking occurs more rapidly than phase separation at higher reaction temperatures.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1998
- Accession Number
- ADA358503
Entities
People
- Samuel P. Gido
- Shaw L. Hsu
- William J. Macknight
Organizations
- University of Massachusetts Amherst