Takashi Ishizone

Recent advance in living anionic polymerization of functionalized styrene derivatives

Abstract This review covers recent advance of living anionic polymerization of styrene derivatives with functional groups. Although there have so far been reported several successful systems of living anionic polymerization of functionalized styrene derivatives, most useful functional groups are not amenable to the conditions of living anionic polymerization of styrene. Therefore, we herein present two generalized strategies to be able to achieve the living anionic polymerization of styrenes with such functional groups that are normally incompatible with carbanionic species. The first strategy involves protection of the functional group and living anionic polymerization of the resulting protected monomer, followed by deprotection to regenerate the original functional group after the polymerization. In the second strategy, an electron-withdrawing functional group is introduced into the benzene ring of styrene to purposefully lower the reactivity of the generated chain-end carbanion, thereby allowing the functional group and the carbanion to coexist. The living anionic polymerization of a number of styrene derivatives with functional groups became indeed possible by employing two proposed strategies. Their scopes, limitations, and possibilities are also discussed.

Nonvolatile organic field-effect transistor memory devices using polymer electrets with different thiophene chain lengths

We report the synthesis of poly(5-hexyl-2-vinylthiophene) (PVT) and poly(5-hexyl-5′′-vinyl-2,2′:5,2′′-terthiophene) (PVTT) as charge storage electrets for nonvolatile organic field effect transistor (OFET) memory devices of n-type semiconducting N,N′-bis(2-phenylethyl)perylene-3,4,9,10-bis(dicarboximide) (BPE-PTCDI). The effects of the conjugated thiophene chain length on the morphology, OFET mobility and memory characteristics are explored and compared to those of the styrene or fluorene side chain. The mobility of the OFET memory device using PVTT as an electret is significantly smaller compared with that of PVT because its large torsional angle hinders the molecular packing of BPE-PTCDI. However, the OFET memory device using the PVTT electret has the largest hysteresis window of 81 V, compared to PVT, polystyrene (PS), and poly(styrene) para-substituted with fluorene (PSt-Fl). The highest HOMO energy level of PVTT facilitates the charge transfer from BPE-PTCDI and leads to the largest memory window. The backbone non-coplanarity prevents the back transfer of the charge for the nonvolatile memory characteristics. The device shows excellent nonvolatile behavior for bistable switching and the write–read–erase–read (WRER) cycles are operated over 100 cycles. The shifted threshold voltages of the OFET memory devices using PVTT are stable over 104 s, and the ON and OFF states could maintain 104 s with the Ion/Ioff current ratios of 103. This study suggests that the pendent conjugation length and the backbone coplanarity of polymer electrets significantly affect the charge mobility and electrical characteristics of OFET memory devices.

Synthesis of well-controlled graft polymers by living anionic polymerization towards exact graft polymers

This article reviews the synthesis of well-controlled graft polymers by living anionic polymerization towards exact graft polymers. The structure of a graft polymer is defined by the following three parameters: (1) molecular weight of the main chain, (2) molecular weight of the graft chain, and (3) placement of the graft chain. Based on these three parameters, the extent of the structural control of the graft polymers synthesized so far is described. Finally, the recently synthesized exact graft (co)polymers by stepwise iterative methodologies are introduced. In their structures, the three parameters are perfectly controlled.

Synthesis of well-defined block copolymers containing poly(N-isopropylacrylamide) segment by anionic block copolymerization of N-methoxymethyl-N-isopropylacrylamide

Anionic polymerization of N-methoxymethyl-N-isopropylacrylamide (1) was carried out with diphenylmethyllithium,-potassium and-cesium in the presence of diethylzinc in THF at-78°C for 1-3 h. The resulting poly(1)s possessed the predicted molecular weights based on the molar ratios between monomer and initiators and the narrow molecular weight distributions (M w/M n = 1.1). The methoxymethyl protecting groups were completely hydrolyzed to afford a poly(N-isopropylacrylamide) (poly(NIPAM)), having well-defined chain structures by treatment with aqueous HCl in 1,4-dioxane at room temperature for 12 h. Stereoregularity of the resulting poly(NIPAM) was strongly affected by the counterions of anionic initiator. From the 1H-NMR measurement, the racemo dyad of poly(NIPAM) obtained with diphenylmethyllithium, -potassium and -cesium in the presence of Et2Zn was found to be 75, 50 and 30%, respectively. The sequential copolymerization of styrene or isoprene with 1 and the subsequent deprotection quantitatively gave well-defined block copolymers containing poly(NIPAM) segments. The copolymers had the predicted molecular weights, compositions and the narrow molecular weight distributions, and showed the typical amphiphilic character with regard to solubility.

Anionic polymerization of monomers containing functional groups, 11. Anionic polymerizations of alkynyl methacrylates

SUMMARY: Anionic polymerization of 2-propynyl methacrylate (1), 3-trimethylsilyl-2-propynyl methacrylate (2), 2-butynyl methacrylate (3), and 3-pentynyl methacrylate (4) was carried out in tetrahydrofuran at ‐788C for 1 h. The employed initiator systems were (diphenylmethyl)potassium/diethylzinc (Et2Zn) and 1,1bis(49-trimethylsilylphenyl)-3-methylpentyllithium/lithi um chloride (LiCl). Although poly( 1) was obtained quantitatively with each initiator system, the observed molecular weights were always higher than the predicted values and the molecular weight distributions were rather broad (M — w/M — n A 1.3), indicating a side reaction at the acidic acetylenic proton. On the other hand, the polymerization of 2 ‐4, i. e., methacrylate monomers having no terminal acetylenic protons in the ester moieties, proceeded quantitatively under similar conditions. The resulting poly(2 ‐4)s were found to possess the predicted molecular weights and narrow molecular weight distributions (M — w/M — n a 1.1), indicating the living character of the polymerization systems. The trimethylsilyl protecting group of poly(2) was completely removed to form a poly(1) having well-defined chain structures by treating it with potassium carbonate in a mixed solvent of THF and methanol at room temperature for 1 h.

Thermally robust nanocellular thin films of high-Tg semifluorinated block copolymers foamed with supercritical carbon dioxide

Nanoscopic porous and cellular materials with high thermal stability are demanded for a variety of applications. We fabricated thermally robust nanocellular thin films using block copolymer templated carbon dioxide foaming (BCTCF). We synthesized semi-fluorinated block copolymers having a CO2-philic fluorine containing block and high glass transition temperature (Tg) blocks, such as poly[4-(1-adamantyl)styrene-b-perfluorooctylethyl methacrylate] (P(AdSt-FMA)) and poly[α-methylstyrene-b-perfluorooctylethyl methacrylate] (P(AMSt-FMA)). In particular, PAdSt has a Tg close to 250 °C due to the bulky adamantyl group attached to the polystyrene backbone. Although high-Tg blocks (polymers) lack processability in general, CO2 effectively plasticizes and reduces the Tg of the high-Tg blocks, swells the fluorinated block domains, and leaves empty nanocells in the fluorinated block domains after CO2 was removed. We optimized process conditions, such as saturation temperature (Ts), CO2 pressure and depressurization temperature (Td), to introduce nanoscopic cells in such high-Tg matrices, and achieved porosities as high as 0.25, average diameter about 20 nm and remarkable thermal robustness up to more than 200 °C.

Synthesis of tetramers of 1,3-adamantane derivatives

Abstract Novel tetramers of 1,3-adamantane and 5,7-dibutyl-1,3-adamantane were synthesized by the coupling reaction of 3-bromo-1,1′-biadamantane or 3-bromo-5,5′,7,7′-tetrabutyl-1,1′-biadamantane with sodium in n -octane or with magnesium in diethyl ether. Although the former 1,3-adamantane tetramer showed poor solubility in organic solvents, the latter tetrameric 5,7-dibutyl-1,3-adamantane was readily soluble in THF, chloroform and benzene and was successfully characterized by NMR, IR, SEC and elemental analyses.

Reduced Hydrophobic Interaction of Polystyrene Surfaces by Spontaneous Segregation of Block Copolymers with Oligo (Ethylene Glycol) Methyl Ether Methacrylate Blocks : Force Measurements in Water Using Atomic Force Microscope with Hydrophobic Probes

Reduction of hydrophobic interaction in water is important in biological interfaces. In our previous work, we have found that poly(styrene- b-triethylene glycol methyl ether methacrylate) (PS-PME3MA) segregates the PME3MA block to the surface in hydrophobic environment, such as in air or in a vacuum, and shows remarkable resistance against adsorption or adhesion of proteins, platelets, and cells in water. In this paper, we report that atomic force microscopy (AFM) with hydrophobic probes can directly monitor the reduced hydrophobic interaction of the PS surfaces modified by poly(styrene- b-origoethylene glycol methyl ether methacrylate) (PS-PME NMA), where N is the number of ethylene glycol units. The pull-off forces between the hydrophobic probes that are coated with octyltrichlorosilane (OLTS) and the PS-PME NMA modified polystyrene (PS) surfaces in water were measured. The absolute spring constants and tip-curvatures of the AFM cantilevers were measured to compute the work of adhesion by the Johnson, Kendall, and Roberts (JKR) theory, which relates the pull-off force at which the separation occurs between a hemisphere and a plane to the work of adhesion. The hydrophobic interactions between the hydrophobic tip and polymer surfaces in water were greatly reduced with the segregated PME NMA blocks. The hydrophobic interactions decrease with increasing N of the series of PS-PME NMA and show a correlation with the amount of protein adsorbed.

Anionic polymerization of 2-haloethyl methacrylates

Abstract The anionic polymerizations of 2-chloroethyl methacrylate ( 1 ), 2-bromoethyl methacrylate ( 2 ), and 2-iodoethyl methacrylate ( 3 ) were carried out in THF at −78 °C with 1,1-diphenyl-3-methylpentyllithium in the presence of LiCl. The polymerizations proceeded in a controlled manner to quantitatively afford polymers with predictable molecular weights and narrow molecular weight distributions. Under similar conditions, the anionic block copolymerizations by the sequential addition of methyl methacrylate (MMA) followed by 1 , 2 , and 3 generated the corresponding diblock copolymers with well-defined structures. On the other hand, in the block copolymerization by the reverse addition of monomer, a well-defined diblock copolymer, poly( 1 )- block -PMMA, could be synthesized only by the sequential addition of 1 followed by MMA, whereas the block copolymerizations using 2 and 3 were not successful because of instabilities of the propagating chain-end anions derived from 2 and 3 . The side reactions which occurred during the polymerization were discussed.

Anionic polymerization of monomers containing functional groups, 14. Anionic polymerizations of aryl 4‐vinylbenzoates

Anionic polymerizations of phenyl (2a), 4-methoxyphenyl (2b), 2-methylphenyl (2c), 2-tert-butylphenyl (2d), 3,5-di-tert-butylphenyl (2e), 2,6-dimethylphenyl (1f), 2,6-diisopropylphenyl (2g), 2,6-di-tert-butyl-4-methylphenyl (2h), and 2,6-di-tert-butyl-4-methoxyphenyl (2i) 4-vinylbenzoates were carried out in THF at -78°C with diphenylmethylpotassium and oligo(α-methylstyryl)mithium and -dipotassium. No apparent polymerizations of 2a-2e occured probabaly due to the inherent side reactions such as nucleophilic attack of the anionic initiators toward the ester carbonyl groups. On the other hand, the polymerization of 2f-2i, the monomers possessing bulky aryl ester substituents, certainly proceeded to afford the polymers in quantitative yields. The molecular weight distribution (MWD) of poly(2f) was broad (M w /M n = 1.3-1.8), indicating partial side reactions during the course of the polymerization. By contrast, the resulting poly(2g-2i) possessed narrow MWDs (M w /M n = 1.1) and predicted molecular weights based on the molar ratios between monomers to initiators. It was thus demonstrated that the steric hindrance around the ester carbonyl group was essential to obtain polymers having well-defined chain structures via controlled anionic polymerizations of aryl 4-vinylbenzoates. Novel tailored block copolymers, polyisoprene-block-poly(2h), poly(2h)-block-polystyrene-block-poly(2h), poly(tert-butyl methacrylate)-block-poly(2h), and poly(2h)-block-poly(2-isopropenylbenzoxazole) were synthesised by the sequential copolymerization of 2h and the corresponding comonomers. It was elucidated from the results of block copolymerization that anionic polymerizability of 2h was apparently higher than of styrene because of the electron-withdrawing effect of the COOAr substituent. Our focus is on the anionic polymerization of a series of aryl 4-vinylbenzoates, 2a-2i, the aromatic counterparts of 1 (see Scheme 1) to compare the polymerization behavior with alkyl esters by varying the steric hindrance of the ester moiety.