Morphology of Segmented Polyether Based Poly(urea-urethane) Thermoplastic Elastomers

Abstract

ABSTRACT:New aniline-containing segmented poly(urea-urethane) (PUU-OPA) based on polyether polyurethane prepolymer and an oligomer of amine-terminated polyaniline (OPA) were prepared as a conductive material. The amine-terminated functional groups of OPA were introduced into the poly(urea-urethane) (PUU) structure as a chain extender to form the hard segment of the copolymer with urea-linkage. The morphology of PUU-OPA was examined by the transmission electron microscopy (TEM) and solid-state 13 C NMR approaches. The conductivity of the copolymers is found to be ranged from 0.83 S/cm for the neat OPA to 1:96 Â 10 À6 S/cm for the resultant copolymers. TEM measurements clearly reveal the microphase separation. Various contact time CP experiments indicate that T CH and T 1 (H) of the soft segment carbons declined as the OPA content increased. These results indicate that the chain mobility and the domain size of the soft segment in the copolymer on the nanophase scale gradually decreased as the OPA content increased. [doi:10.1295/polymj.PJ2005204] KEY WORDS 13 C NMR / TEM / Poly(urea-urethane) / Morphology / Polyurethane / Polyaniline (PANI), one of the most promising intrinsically conducting polymers, has been attracted considerable attention in recent years because it has a relatively high conductivity and potential application in electronic devices.1,2 Polyaniline is generally prepared by oxidative the polymerization of aniline in acid media using an external oxidant such as ammonium peroxydisulfate, (NH 4 ) 2 S 2 O 8 , and can exist as a number of unique structures, characterized by the oxidation state, which determines the ratio of amine to imine nitrogens, and the extent of protonation. 3 The emeraldine base (EB) is one of the several possible structures. The conducting form of polyaniline can be easily prepared by doping the EB with a protonic acid resulting in a complex acid salt. The members of the polyaniline family are difficult to handle because of their brittleness and poor solubility in polar organic solvents. The processing of emeraldine base is difficult, because EB decomposes below its softening or melting temperature.4-7 Therefore, the processibility of EB has been the subject of several investigations over the last few years. [8][9][10][11] The earlier attempts at processing polyaniline focused on modifying the chain structure by copolymerization or derivation with hydrophilic or alkyl groups. These attempts resulted in a first successful step toward the so-called soluble polymer. Recently, attempts have been made to synthesize aniline oligomers with well-defined structures and amine end-groups and thus improve their solubility and capacity to undergo further polymerization have been reported.12-18 Polyurethanes (PU), comprising a polyether or polyester soft (flexible) segment and a diisocyanate-based hard (rigid) segment, are well known to be tough materials and are typically employed as additives to improve the toughness of brittle materials. The incompatibility between the hard segment and the ...