Morphology of polyurethanes at various length scale: The influence of chain structure

Abstract

Micro-structural investigation of polyurethanes (PUs) with different chain structure has been reported. Polarized optical microscopic studies of aliphatic polyurethanes demonstrate the development of micro clusters with increasing hard segment content (HSC) and crystallization. DSC and XRD results support the crystalline and amorphous nature of aliphatic and aromatic PUs, respectively. Self-assembled biphasic morphology is discernible in aliphatic polyurethane while nanometer size domains are observed in aromatic PUs. The dimension of micro-domain has been measured by using AFM and established its size as independent of hard segment content. The self-assembly is greater for higher HSC aliphatic PUs leading to the formation of bigger domain while the meager hydrogen bond formation restricts the domain size of aromatic polyurethanes. Segmented morphology of surface as well as in bulk of aliphatic polyurethanes is evident from SEM and TEM images and grows with increasing HSC. In contrast, homogeneous and amorphous nature has been observed for aromatic PUs. In situ segregation of phases in aliphatic PUs have been captured through light transmittance and optical images which is categorically absent in aromatic polyurethane.

Structure–property relationships of polycarbonate diol‐based polyurethanes as a function of soft segment content and molar mass

“…In the phase images (parts a, c and e) clear and bright areas corresponding to the hard segment domains and dark areas corresponding to the soft segment are observed. This morphology, spherulite type, is similar to the one obtained by other authors . These spherulites vary with the molecular weight of the soft segment and hard segment content.…”

Numerical study of smart honeycomb core using shape memory polymers

“…Shape memory polymers (SMPs) are a class of intelligent materials that have the capacity to recover original shape from the deformed one by different external stimulations, such as heat, electricity, magnetism, light, and moisture . The shape memory effect of SMPs is the result of glass transition or melting transition of the molecular chains unit .…”

Synthesis, Characterization and O2Permeability of Shape Memory Polyurethane Films for Fresh Produce Packaging

“…10,11 The hard segments function as both physical cross links and reinforcing fillers dispersed in the soft segment matrix. 12,13 These structures determine their unique physical, mechanical and thermal properties as well as gas permeabilities of polyurethane films. 14,15 SMPUs possess flexibility, high shape-recovery ratio, ease of manufacture, strong resistance to organic solvents and aqueous solutions, excellent and consistent elastic properties and biocompatibility.…”