Phase behavior of poly(4-hydroxystyrene-block-styrene) synthesized by living anionic polymerization of an acetal protected monomer

(Graph Presented) We have synthesized a series of poly(4-(2-tetrahydropyranyloxy)styrene) [P(OTHPSt)] homopolymers by living anionic polymerization of the protected monomer (OTHPSt) in tetrahydrofuran at -78°C, with excellent control over molecular weight and dispersity. The high T_g of P(OTHPSt) led to facile purification and isolation of the polymer as a powder. Characterization of the POTHPSt homopolymer by nuclear Overhauser effect spectroscopy confirms the strong preference for the axial position of the relatively sterically demanding alkoxy phenyl group. By sequential monomer addition, a series of low to high molecular weight P(OTHPSt-b-styrene) BCPs with narrow dispersities were synthesized. Quantitative deprotection of the THP groups yielded poly(4-hydroxystyrene-b-styrene) with tunable molecular weights and compositions. The solid-state and melt-phase self-assembly of these diblocks was investigated using synchrotron small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Mean-field theory analysis of the temperature-dependent correlation-hole scattering for a disordered diblock was used to determine the interaction parameter as X_HS/S(T) = (4.39 ± 0.83)/T + (0.109 ± 0.002), which is approximately 4 times larger than that of poly(styrene-b-methyl methacrylate) with the same disproportionately high contribution of entropy to the free energy of mixing.