Temperature‐dependent changes in the hydrogen bonded hard segment network and microphase morphology in a model polyurethane: Experimental and simulation studies. Issue 2 (31st October 2017) - Yildirim, Erol
ABSTRACT: Hydrogen bonding between hard segments has a critical effect on the morphology and properties of polyurethanes. Influence of temperature on hydrogen bonded urethane network and melting behavior of a model semicrystalline segmented polyurethane was investigated by experiments and simulations. Polyurethane was synthesized by the stoichiometric reaction between p ‐phenylene diisocyanate and poly(tetramethylene oxide) (PTMO) with a molecular weight of 1000 g/mol. Simulations were carried out using dissipative particle dynamics (DPD) and molecular dynamics (MD) approaches. Experimental melting behavior obtained by various techniques was compared with simulations. DPD simulations showed a room temperature microphase morphology consisting of a three‐dimensional hydrogen‐bonded urethane hard segment network in a continuous and amorphous PTMO matrix. The first‐order melting transitions of crystalline urethane hard segments observed during the continuous isobaric heating in DPD and MD simulations (340–360 K) were in reasonably good agreement with those observed experimentally, such as AFM (320–340 K), WAXS (330–360 K), and FTIR (320–350 K) measurements. Quantitative verification of the melting of urethane hard segments was demonstrated by sharp discontinuities in energy versus temperature plots obtained by MD simulations due to substantial decrease in the number of hydrogen bonds above 340 K. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2018, 56, 182–192 Abstract : This research employs FTIR, AFM, and WAXS with dissipative particle dynamics (DPD) and molecular dynamics (MD) simulation methods to understand the temperature‐dependent changes in the structure and microphase morphology of hydrogen‐bonded urethane hard segments in a model polyurethane (PU) at macroscopic and atomistic levels. PU was prepared by the stoichiometric reaction of 1, 4‐phenylene diisocyanate and poly(tetramethylene oxide) (1000 g/mol). The first‐order melting transition was identified as the complete breakdown of the hydrogen‐bonded network above 343 K.