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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Well-defined end-functionalized polystyrenes and polyisoprenes with monosaccharide residues were synthesized by the termination reactions of the anionic living polymer of styrene or isoprene with benzyl chloride derivatives containing acetal-protected glucofuranose (1), fructopyranose (2), galactopyranose (3), and sorbofuranose (4). Furthermore, novel well-defined end-functionalized polymers with two, three, and four monosaccharide residues were successfully synthesized by reacting polystyryllithium with 1,1-bis{3‘-[(1,2;5,6-di-O-isopropylidene-α-d-glucofuranose-O-3-yl)methyl]phenyl}ethylene (5), followed by treating with methanol, 1 (or 3), and the octyliodide containing two acetal-protected glucofuranoses (6), respectively. The end-functionalized polystyrenes with one and two glucose residues thus synthesized were found by static light scattering measurements to form reverse micelles in cyclohexane by aggregating several polymer chains.

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Anionic polymerizations of seven styrenes para-substituted with N-arylimino groups were carried out in THF at −78 °C with oligo(α-methylstyryl)dipotassium and -dilithium as the initiators. The N-aryl functionalities contained phenyl (1), 2-(tert-butyl)phenyl (2), 2,6-dimethylphenyl (3), 2,6-diethylphenyl (4), 2,6-diisopropylphenyl (5), 4-cyanophenyl (6), and 2,3,4,5,6-pentafluorophenyl (7) groups. The monomers 3−5 underwent anionic polymerization quantitatively to produce the polymers having predicted molecular weights based on molar ratios of monomers to initiators and narrow molecular weight distributions, the M w/M n values being around 1.1. On the other hand, no polymeric products were obtained from the polymerization mixture of 1, 2, 6, and 7 under identical conditions. The bulkiness of the two ortho alkyl substituents on the N-aryl moiety was necessary to achieve the anionic living polymerization of styrenes bearing N-arylimino groups. Well-defined new block copolymers having poly(5) segments were synthesized by the sequential addition of 5 and styrene or tert-butyl methacrylate. The resulting poly(3−5) could be quantitatively transformed into the poly(4-formylstyrene) having tailored chain structures by the acid hydrolysis of N-arylimino moieties.

Hydrophilic−hydrophobic diblock copolymers composed of 2-hydroxyethyl methacrylate (HEMA) and 4-(7‘-octenyl)styrene with 26, 47, and 82 wt % of poly[4-(7‘-octenyl)styrene], HO-30, -50, and -80, respectively, were synthesized by anionic living polymerization. The surface structures of their solvent-cast films under dry and wet conditions were analyzed by contact angle measurements, transmission electron microscopic (TEM) observation, and X-ray photoelectron spectroscopic (XPS) measurements. The analytical results of HO-30 and HO-50 substantiate surface restructuring in response to environmental change. When the films were soaked in water, very quick hydration of the surface was observed. However, dehydration of the surface occurred slowly even by annealing in air. TEM observation was successfully performed by staining technique with OsO4 and introduction of a carbon−carbon double bond in the hydrophobic segment. Cross sectional TEM images of near film surfaces suggested that the phase restructuring at the outermost surface corresponding to environmental change occurred at the microdomain scale of the block copolymer. The block copolymer film of HO-80 retained a hydrophobic surface under various conditions and never experienced surface restructuring.