Transport-morphology relationships in segmented polybutadiene polyurethanes: 2. Analysis

Abstract

An analysis of the transport properties in a series of segmented polybutadiene polyurethanes described in Part 1 is presented in terms of the effective medium theory (EMT) and simple transport models involving ordered microstructures. The 75 wt% hard segment (HS) sample is assigned a dispersed morphology of soft segment (SS) spheres in a glassy matrix of hard segment. A lamellar morphology is indicated at 55 wt% HS by all methods of analyses: TEM, SAXS and transport models. Based on sorption studies and the results from SAXS, cylindrical domains of hard segment in a rubbery matrix of soft segment are believed to exist in the dilute range ( < 40 wt%) of hard segment content. Complex sorption kinetics indicate the inadequacy of Fick's law to describe the transport in copolymer samples of rubbery and glassy materials. Relaxational effects dominate the transport ofC0 2 in polybutadiene polyurethanes. In this case, a simple transport model using EMT involving coupled diffusion and relaxation is used to describe the anomalous sorption kinetics.

Characterizing the nanoclay induced constrained amorphous region in model segmented polyurethane–urea/clay nanocomposites and its implications on gas barrier properties

“…The objective of the present work is to understand the mechanistic origin of the barrier properties of the nanoclay filled segmented polybutadiene polyurethane-urea matrix. This system can be considered as a model for the investigation of transport and morphology relationships in segmented block copolymers [35][36][37] because of (a) the absence of hydrogen bonding between the soft and hard segments (b) a higher degree of micro-phase separation and the amorphous nature of the soft segments and (c) the possibility of direct visualization of hard domain morphology by microscopic techniques. There are several reports on the morphology-gas transport correlations of these model systems.…”

Estimation of Hard Segment Content in Polyurethane from Solvent Absorption

“…1 -3 However, it has been pointed out that the detailed domain structure and its unification are not completely possible from any of the above mentioned techniques. 4 Diffusion of small molecules on the other hand is shown to provide insight into the intricacy of the microstructure since these types of diffusants scales with the domain sizes in polyurethanes. To date most of the diffusion studies in polyurethanes are aimed either to understand the overall morphology of the polymer or to elucidate the diffusion mechanism in these polymers.…”