Direct imaging of non-classical triblock copolymer blend and GEL morphologies in the dilute regime
- North Carolina State Univ., Raleigh, NC (United States)
- Procter & Gamble Company, Cincinnati, OH (United States); and others
Two families of copolymers were examined in this work. The first series consisted of poly[styrene-b-(styrene-r-isoprene)-b-isoprene] extended block copolymers (EBCs), in which the S/I midblock fraction ({Phi}) varied from 0.0 to 0.4 in 0.1 increments. These materials were synthesized via living anionic polymerization with sec-butyllithium and a potassium alkoxide (to control monomer sequencing). At 50/50 (w/w) S/I and the molecular weights (M) examined here 120-160 kDa, they all exhibited the lamellar morphology. Blends of the EBCs were prepared with a 20 kDa homopolystyrene (hPS) by solution casting from toluene. The second series of copolymers was comprised of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) triblock copolymers. The compositions of these materials were about 31-33 wt% styrene, and they ranged in M from 150 to 240 kDa. Blends were prepared with several homopolyisoprenes (HPIs) varying in M and a Witco 380 PD saturated aliphatic oil. Films were prepared by two routes: (i) solution casting from cyclohexane and (ii) mechanical mixing at 100{degrees}C. Resultant films and gels were sectioned at -100{degrees}C in a Reichert-Jung Ultracut-S ultramicrotome using a cryodiamond knife. Electron contrast was enhanced upon exposure to the vapor of OsO{sub 4}(aq) (to stain the isoprene in EBC blends) for 90 min or RuO{sub 4}(aq) (to stain the styrene in SEBS blends) for 5 min. Images were acquired with a Zeiss EM902 electron microscope at 80 kV and {Delta}E between 50 and 100 eV.
- OSTI ID:
- 468790
- Report Number(s):
- CONF-960877--
- Country of Publication:
- United States
- Language:
- English
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