In this research, a novel solvent exchange method has allowed
the primarily exfoliated dispersion of unmodified clay platelets
into an elastomeric polyurethane matrix containing a polar hard
block and polar, hydrophilic soft block (PEO-PPO-PEO). This
investigation of unmodified clay/polyurethane nanocomposites
extends the wealth of literature addressing the complex behavior
of PEO and PEO-PPO-PEO when intercalated and/or exfoliated
with unmodified Laponite. Thermomechanical and morphological
behavior were explored to confirm the preferred
interactions between the polyurethane blocks and the layered
silicates. The hydrophilic, polar soft block (PEO-PPO-PEO)
dominated the clay-polyurethane interactions in the PEOPPO-
PEO:HDI-BDO nanocomposites. POM suggests that
strain-induced alignment of the soft segment chains is suppressed
within the nanocomposite, which resulted in a substantial
reduction in toughness and extensibility. By comparison, the
silicate layers in segmented polyurethanes containing a hydrophobic
soft block (PTMO) and MDI-BDO or HDI-BDO hard
domains were preferentially embedded within the hard block,
enhancing toughness and initial modulus, while preserving the
elastomeric nature of the materials. These observations may
serve as guides in the selective tailoring of the properties of
polyurethane nanocomposites for a variety of applications by
moderating the clay/segment interactions through calculated
material design.