Nanostructured poly(urethane)s and poly(urethane-urea)s from reactive solutions of poly[styrene-b-butadiene-b-(methyl methacrylate)]-triblock copolymers

Poly[Styrene-b-Butadiene-b-(Methyl Methacrylate)], SBM triblock copolymers have been incorporated in different polyurethane, PU formulations in order to prepare nanostructured materials. Macrodiols used for PU synthesis were based on a central bis-phenol A, BPA unit with two hydroxyl-terminated oligo(oxypropylene), BPA-POx or oligo(oxyethylene), BPA-EO chains with varying lengths. The initial solubility of the three blocks and the rheological behavior of the solutions in macrodiols and also in two diisocyanates, isophorone diisocyanate, IPDI, and 1,3-xylylene diisocyanate, XDI have been first characterized. The PMMA block is the most soluble and its role during the reaction is to stabilize the initial nanostructure or to control the reaction-induced microphase separation. Block copolymers can be dissolved first in the macrodiol, or preferably in the diisocyanate. With BPA-POx and low SBM content (<10 wt%), transparent linear or crosslinked PU with well dispersed triblock nanoparticles have been prepared, depending on the molar mass of the macrodiol and on the concentration of diblock SB impurities present in the triblock. For high SBM concentrations (>50 wt%), a twin screw extruder had to be used for the blending. Under well-defined conditions, transparent linear PUs and linear segmented polyurethane-ureas have been prepared. This study confirms that for designing a nanostructured material from a reactive mixture with a triblock additive, one block, called “the nanostructuring block” has to remain soluble up to the end of the reaction.