The anionic polymerization of tert-butyl acrylate (tBA) was carried out with a binary initiator system prepared from diphenylmethyllithium, -potassium, or -cesium (Ph2CHM) and dimethylzinc or diethylzinc in THF at −78 °C. In the absence of dialkylzinc (R2Zn), the poly(tBA)s produced with Ph2CHM possessed ill-controlled molecular weights and broad molecular weight distributions (MWDs). On the other hand, poly(tBA)s having predicted molecular weights based on the molar ratio of monomer to initiators and narrow MWDs (M w/M n < 1.15) were obtained in quantitative yields by the initiation with Ph2CHK or Ph2CHCs in the presence of 10−20-fold excess R2Zn, although the polymers obtained with Ph2CHLi/R2Zn still possessed broad MWDs (M w/M n = 2). The growing chain end of poly(tBA) associated with cesium counterion is completely stable to reinitiate the further polymerization of tBA in the presence of R2Zn at −78 °C for 1 h, but 56% deactivation occurred after 24 h. It is thus demonstrated that Ph2CHK or Ph2CHCs in conjunction with R2Zn induces the controlled anionic polymerization of tBA in THF at −78 °C. By contrast, addition of R2Zn to the polymerization systems of methyl, ethyl, and isopropyl acrylates showed little effects on the improvement of polymer yields and the molecular weight controls. Well-defined block copolymers, poly(styrene-b-tBA), poly(methyl methacrylate-b-tBA), and poly(tBA-b-N,N-diethylacrylamide), were also anionically prepared by the sequential addition of styrene, methyl methacrylate, or N,N-diethylacrylamide with tBA in the presence of R2Zn.

The hydrophilic−hydrophobic diblock copolymer (2-hydroxyethyl methacrylate, HEMA)41-block-(isoprene)84 was synthesized by anionic living polymerization using a protection technique for the hydroxyl group of HEMA. The surface structures of the block copolymer film under dry and wet conditions were analyzed by transmission electron microscopic observation and contact angle and angle-dependent X-ray photoelectron spectroscopic measurements. The top surfaces of the films cast from DMF/THF and THF/methanol are covered with a polyisoprene microdomain. When the as-cast film is exposed to water, the polyisoprene layer at the top surface disappears and is replaced with a PHEMA microdomain. In particular, the hydrated surface clearly emerges under transmission electron microscopy (TEM) by the double-staining method and reverts again to a hydrophobic polyisoprene layer by annealing the film at 52 °C for 1 h. Such surface rearrangement occurs repeatedly by soaking in water and annealing. The short-time-scale reorientation of the surface microdomain of the film under dry to wet conditions is successively observed with TEM. The difference between the surface rearrangements of the PHEMA-block-polyisoprene and PHEMA-block-polystyrene films in response to environmental change is also investigated.

The anionic polymerizations of 4-, 3-, and 2-(3,3-dimethyl-1-butynyl)styrenes (3a, 3b, and 3c), 4-, 3-, and 2-(1-hexynyl)styrenes (4a, 4b, and 4c), and 4-(phenylethynyl)styrene (5) were carried out in THF at −78 °C with oligo(α-methylstyryl)dipotassium and sec-butyllithium. The polymerizations of these monomers proceeded quantitatively at −78 °C for 0.5 h. The resulting polymers all possessed the predicted molecular weights based on the molar ratios of monomer to initiator and the narrow molecular weight distributions (M w/M n = 1.03−1.15). The living character of the propagating carbanion derived from these monomers was further confirmed by the quantitative initiation efficiency in the second-stage polymerization. A variety of novel block copolymers with well-defined chain structures were synthesized by the sequential block copolymerization of 3a, 4a, 5, and 4-((trimethylsilyl)ethynyl)styrene (1a) with isoprene, styrene, 2-vinylpyridine, and tert-butyl methacrylate. Furthermore, the relative reactivities of the monomers and the resultant living polymers were evaluated from the results of the anionic block copolymerizations. Higher reactivity of 3a, 4a, 5, and 1a and lower nucleophilicity of their living polymers were clearly demonstrated, compared with those of styrene and living polystyrene, respectively. Both of these features can be explained by the electron-withdrawing character of the ethynyl substituents and the extended π-conjugation system including the carbon−carbon triple bond. The anionic polymerizabilities of 3a, 4a, 5, and 1a are estimated to be the same level of 2-vinylpyridine.

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