Transmission electron microscopy triblock copolymer

The use of lightly crosslinked polymers did result in hydrophilic surfaces (contact angle 50°, c-PI, 0.2 M PhTD). However, the surfaces displayed severe cracking after 5 days. Although qualitatively they appeared to remain hydrophilic, reliable contact angle measurements on these surfaces were impossible. Also, the use of a styrene-butadiene-styrene triblock copolymer thermoplastic elastomer did not show improved permanence of the hydrophilicity over other polydienes treated with PhTD. The block copolymer film was cast from toluene, and transmission electron microscopy showed that the continuous phase was the polybutadiene portion of the copolymer. Both polystyrene and polybutadiene domains are present at the surface. This would probably limit the maximum hydrophilicity obtainable since the RTD reagents are not expected to modify the polystyrene domains. 

Triblock terpolymers PS-b-PBd-b-P2VP and PBd-b-PS-b-P2VP, where PBd is polybutadiene (mostly 1,2-PBd), were prepared in order to study the microphase separation by transmission electron microscopy, TEM and SAXS. In the first case the triblocks were synthesized by the sequential addition of monomers in THF using s-BuLi as the initiator [26]. For the second type of copolymers, living PBd-b-PS diblocks were prepared in benzene at 40 °C in the presence of a small quantity of THF in order to obtain the desired 1,2-content and to accelerate the crossover reaction as well. DPE was then added to decrease the nucleophilicity of the active centers in order to avoid side reactions with the THF, which in combination with benzene was the solvent of the final step. 

A controversy has arisen as to whether the observations by POM and those by transmission electron microscopy reflect the same morphological features or not. In fact, Kim et al. [125] demonstrated that the same block copolymer can exhibit different morphologies depending on sample thickness, this being a possible reason for the sometimes contradictory results found in several works. Nevertheless, before this aspect can be properly treated in this section, we present a review of the morphological investigations carried out in semicrystalline ABC triblock copolymers at a nanoscopic scale. 

The submicroscopic structure of spherulites, especially the location of the Is phase within the spherulites as a function of EO content, was examined by transmission electron microscopy. The fine structure of the EO-Is-EO triblock copolymers cast from 0.1% benzene solutions at 30 °C is revealed in Figure 2. These figures represent typical textures of copolymers with EO segments of more than 75 wt % (Figures 2a and 2b), of 40-75 wt % (Figures 2c and 2d), and of less than ca. 40 wt % (Figures 2e and 2f). 

Fayt et al. [259, 260] used transmission electron microscopy (TEM) to study the localization of the copolymer at the polymer-polymer interface. Staining a short mid-block (isoprene) with OSO4 permitted the direct observation of the location of the added PS-6-PI-6-PBDH triblock copolymer to the interface between PS and low density PE TEM images showed the localization of the copolymer to the blend... 

Transmission electron microscopy was used to study high temperature pol3rimide-based nanofoams derived from triblock copolymers for applications in microelectronics packaging, storage cells, and high temperature polymer membranes [192]. Films before and after forming were prepared for microtomy by sub-... 

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