Search

We examined the isothermal crystallization kinetics of poly(e-caprolactone) (PCL) homopolymers confined in a cylindrical nanodomain (nanocylinder) with 12.9 nm in diameter. The confined PCL homopolymers were prepared using the microphase separation of PCL-block-polystyrene (PCL-b-PS) diblock copolymers with a photocleavable o-nitrobenzyl group (ONB) at block junctions and the subsequent cleavage of ONB with UV light. Several PCL homopolymers with different end-groups, acetyl group (molecular weight MEG = 43 g/mol, original PCL homopolymer), adamantane (MEG = 163), cholesterol (MEG = 386), methyl 2,3,6-tri-o-benzoyl-α-d-galactopyranoside (MEG = 506), and vitrified PS (MEG = ∞, i.e., PCL blocks in PCL-b-PS), were prepared to gradually change their chain mobility in the nanocylinder. The crystallization rate of corresponding bulk PCL homopolymers (i.e., no spatial confinement imposed) decreased steadily with increasing MEG, suggesting that these end-groups had no extra effect on the crystallization but simpl...

We have examined the crystal orientation of poly (e-caprolactone) (PCL) chains covalently tethered to nanodomain interfaces at both chain-ends (T2-PCL), one chain-end (T1-PCL), and no chain-end (PCL homopolymers, T0-PCL) all confined in an identical lamellar nanodomain (nanolamella). In order to prepare these PCL chains, we synthesized two kinds of lamella-forming polystyrene-block-PCL-block-polystyrene (PS-b-PCL-b-PS) triblock copolymers with photocleavable o-nitrobenzyl groups (ONB) at either or both of block junctions. The chain-ends tethering significantly affected the tilt angle φ between the c axis of PCL crystals and the normal of nanolamella interfaces (ND). That is, the c axis of T2-PCL crystals oriented almost perpendicular to ND (φ ≥ 70°), whereas that of T0-PCL crystals took completely parallel orientation against ND (φ ∼ 0°) at high crystallization temperatures (>32 °C). The T1-PCL crystal showed an intermediate orientation between T2-PCL and T0-PCL crystals (35°

Two photodegradable heterobifunctional linkers (PHBL) connected by a N-(2-nitrobenzyl)imide structure have been developed as tools to obtain photodegradable diblock copolymers with precisely contro...

We have investigated the effects of chain-ends tethering at nanodomain interfaces on the crystallization behavior of poly(e-caprolactone) (PCL) chains spatially confined in lamellar nanodomains. The PCL chains tethered at both chain-ends (T2-PCL), one chain-end (T1-PCL), and no chain-end (i.e., PCL homopolymers) (T0-PCL) were prepared from polystyrene-block-PCL-block-polystyrene (PS-b-PCL-b-PS) triblock copolymers having a photocleavable o-nitrobenzyl (ONB) group at either or both of block junctions. The lamellar nanodomain was provided by the microphase separation of PS-b-PCL-b-PS copolymers, in which T2-PCL was inherently confined. Subsequently, the ONB group was cleaved by the irradiation of ultraviolet light to yield T1-PCL or T0-PCL from T2-PCL without perturbing the lamellar nanodomain. T2-PCL showed an extremely low melting temperature and crystallinity as compared with T1-PCL and T0-PCL, indicating that the crystallization was significantly affected by chain mobility imposed by chain tethering at ...

The crystallization behavior of poly(e-caprolactone) (PCL) homopolymers and PCL blocks confined in identical lamellar nanodomains (L-domains) has been examined using differential scanning calorimetry and synchrotron small-angle X-ray scattering as a function of PCL layer thickness d and crystallization temperature. The PCL homopolymers confined in the L-domains with d = 8.7 nm (small L-domain) and 15.8 nm (large L-domain) were prepared using microphase separation of PCL- block -polystyrene (PCL- b -PS) copolymers with a photocleavable o -nitrobenzyl group (ONB) between PCL and PS blocks, followed by the photocleavage of ONB with UV-irradiation. The PCL crystallinity showed a conventional sigmoidal evolution both for PCL blocks and PCL homopolymers confined in the large L-domain. However, it increased monotonously with no induction time for PCL blocks but sigmoidally for PCL homopolymers confined in the small L-domain. The substantial differences in crystallization mechanism between PCL blocks and PCL homopolymers confined in the small L-domain are discussed on the basis of chain mobility during crystallization.

The crystallization behavior of poly(e-caprolactone) (PCL) chains (i.e., PCL block + PCL homopolymer systems) spatially confined in nanocylinders with different diameters D has been investigated as a function of the mole fraction of PCL homopolymers fhomo existing in the PCL chains. The nanocylinders with PCL chains inside were prepared using the microphase separation of PCL-block-polystyrene (PCL-b-PS) diblock copolymers with a photocleavable o-nitrobenzyl group (ONB) between PCL and PS blocks, and subsequently ONB was cleaved by a controlled irradiation of UV light to get the PCL chains with various fhomo. In the isothermal crystallization process, the crystallinity of PCL chains showed an exponential time evolution (or first-order kinetics) for all the systems investigated. The half-time of crystallization of PCL chains with 0 < fhomo < 1 was found to be intermediate between those of PCL blocks (fhomo = 0) and PCL homopolymers (fhomo ∼ 1); it decreased moderately with increasing fhomo in a smaller nano...

The crystallization behavior and crystal orientation of poly(e-caprolactone) (PCL) homopolymers and PCL blocks spatially confined in identical nanocylinders have been investigated using differential scanning calorimetry (DSC) and two-dimensional wide-angle X-ray diffraction (WAXD) as a function of cylinder diameter D. The PCL homopolymers confined in nanocylinders were prepared using microphase separation of PCL-block-polystyrene (PCL-b-PS) copolymers with a photocleavable o-nitrobenzyl group (ONB) between PCL and PS blocks and the subsequent cleavage of ONB by irradiating UV light. The time evolution of PCL crystallinity χPCL showed a first-order kinetics for both PCL blocks and PCL homopolymers confined in all the nanocylinders investigated. However, the D dependence of crystallization rates for PCL blocks was more drastic than that for PCL homopolymers, and consequently various D-dependent interrelations were observed between crystallization rates of PCL blocks and PCL homopolymers. The crystal orienta...

Stable potassium enolates of N,N-diethylacetamide [α-potassio-N,N-diethylacetamide (1)], N,N-diethylpropionamide [α-potassio-N,N-diethylpropionamide (2)], and N,N-diethylisobutyramide [α-potassio-N,N-diethylisobutyramide (3)] were prepared by the proton abstraction of the corresponding N,N-diethylamides with diphenylmethylpotassium (Ph2CHK) or potassium naphthalenide in THF. The relative nucleophilicity of 1–3 was estimated to be in the order of 1 < 3 < 2 from the results of the alkylation reaction with methyl iodide. N,N-diethylacetamide transferred its α-proton to 2 quantitatively in THF at 0 °C, whereas no reaction occurred between N,N-diethylisobutyramide and 2; this indicated the relative basicity to be 1 < 2 ∼ 3. Anionic polymerizations of N,N-diethylacrylamide (DEA) and methyl methacrylate were quantitatively initiated with 2 in THF at −78 °C, whereas the initiation efficiencies of 2 for styrene and 2-vinylpyridine were about 2 and 67%, respectively. The initiation of DEA with 1–3 at −78 or 0 °C in THF gave poly (DEA)s having broad molecular weight distributions (MWDs; Mw/Mn = 2) and ill-controlled molecular weights. In contrast, poly(DEA)s of narrow MWDs (Mw/Mn < 1.2) and predicted Mn's were obtained with 2 in the presence of diethylzinc (Et2Zn) at −78 °C, whereas the initiations with 1/Et2Zn and 3/Et2Zn at −78 °C resulted in poor control of the molecular weights. At the higher temperature of 0 °C, all the binary initiator systems (1–3/Et2Zn) induced controlled polymerizations of DEA in terms of the conversion, molecular weight, and MWD. The poly(DEA)s produced with 1–3/Et2Zn at 0 °C showed mr-rich configurations (mr = 76–89%), as observed for the poly(DEA) generated with Ph2CHK/Et2Zn. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1260–1271, 2007

A novel heterobifunctional linker 1 connected with photocleavable N-(2-nitrobenzyl)imide has been developed. Hydrophobic polystyrene (PS), hydrophilic poly(ethylene oxide) (PEO), and thermosensitiv...

The anionic polymerizations of p-pentamethyldisilylstyrene (1), p-heptamethyltrisilylstyrene (2), and p-nonamethyltetrasilylstyrene (3) were carried out under various conditions. The polymerizations of 1 and 2 proceeded in a living manner in THF at −78 °C to quantitatively afford polymers with predictable molecular weights and narrow molecular weight distributions. Suitable initiators for these living anionic polymerizations were sec-BuLi, lithium, sodium, and potassium naphthalenides, cumylpotassium, and living oligomers of α-methylstyrene lithium, sodium, and potassium salts. Well-defined diblock copolymers, poly(1)-block-polystyrene, poly(2)-block-polystyrene, polystyrene-block-poly(1), and polystyrene-block-poly(2) were successfully synthesized under similar conditions by a two-step sequential monomer addition, namely, styrene followed by 1 or 2, or vice versa. In contrast, the polymerization of 3 was problematic. No polymer was obtained in the polymerization of 3 in either THF at −78 °C or benzene at...

Anionic polymerizations of 1-adamantyl methacrylate (1) and 3-methacryloyloxy-1,1'-biadamantane (2) were carried out in THF at -50 to -78°C for 24 h. The initiator employed was either [1,1-bis(4'-trimethylsilylphenyl)-3-methylpentyl]lithium (3)/lithium chloride, or diphenylmethylpotassium. The polymerizations of 1 and 2 proceeded quantitatively to afford the polymers having the predicted molecular weights based on the molar ratios of monomers and initiators and the narrow molecular weight distributions (M w /M n = 1.05-1.18), indicating the living character of the polymerization systems of 1 and 2. Novel well-defined block copolymers, poly[2-block-(tert-butyl methacrylate)], poly[2-block-isoprene-block-2), and poly[[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate]-block-2], were anionically synthesized by the sequential copolymerization of 2 and comonomers. The poly(2) had the significantly higher glass transition temperature (T g ) of 236°C and decomposed over 370°C, while poly(1) started to decompose at around 320°C before its T g was reached. This thermal stability can be explained by the substituent effects of the bulky adamantyl and 1,1'-biadamantyl moieties.

Surface glass transition behaviors of monodisperse α,ω-diamino-terminated and α,ω-dicarboxy-terminated polystyrenes (α,ω-PS(NH2)2 and α,ω-PS(COOH)2) were studied by scanning force microscopy and were compared with the results of proton-terminated polystyrene (PS−H). All surface glass transition temperatures, Tgs, of PS−H, α,ω-PS(NH2)2, and α,ω-PS(COOH)2 were discernibly lower than each corresponding bulk glass transition temperature, Tgb. However, the magnitude of Tgs was strongly dependent on the chemical structure of chain end groups, because the surface concentration of chain ends varied with the surface free energy difference between the main chain part and the chain end portion, via the surface segregation or surface depletion of chain ends. This result makes it clear that chain end chemistry is one of determining factors on the magnitude of Tgs. On the basis of the time−temperature superposition principle applied to the scanning rate dependence of lateral force as a function of temperature, the appa...

N,N-Dimethylacrylamide (DMA) and N,N-diethylacrylamide (DEA) were polymerized with various Grignard reagents in tetrahydrofuran at -78 °C in the presence of diethylzinc (Et 2 Zn). Highly isotactic poly(DEA) was produced in quantitative yield with tert-butylmagnesium bromide and Et 2 Zn, whereas atactic poly(DEA) was generated in the absence of Et 2 Zn. No stereospecific polymerization of DMA proceeded with Grignard reagent in the presence of Et 2 Zn. The highly isotactic poly-(DEA) obtained was soluble in water and showed the characteristic coil-globule transition phenomenon.

We have synthesized the AB type diblock copolymer with polystyrene and poly(6-[4-(4′-methoxyphenyl)phenoxy]hexyl methacryrate) by sequential anionic living polymerization. The copolymers were prepared with quantitative yields, possessing the predictable M n values, compositions and narrow molecular weight distributions. The thermotropic phase behavior and structures were examined for six copolymers with the weight fraction of LC segments from 24wt% to 45wt%. All copolymers exhibit the crystal-SmA and the SmA-isotropic phase transitions. Microphase separations were examined as a function of the weight fraction of two segments and in a relation with the micro structure of LC segment.

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.

Anionic polymerizations of N,N-dimethylacrylamide (DMA) and N,N-diethylacrylamide (DEA) proceeded slowly and steadily with 1,1-diphenyl-3-methylpentyllithium (DPPLi) and with diphenylmethylpotassium (Ph2CHK) in the presence of triethylborane (Et3B) in THF even at 30 °C to afford the polymers having the predicted molecular weights and very narrow molecular weight distributions in quantitative yields. The result of the postpolymerization of DEA with Ph2CHK/Et3B confirmed the formation of a living polymer with heterotactic configuration at 30 °C. The poly(DMA) and poly(DEA) produced with DPPLi/Et3B were highly syndiotactic, while the isotactic polymers were formed in the absence of Et3B. The additive effects of Et3B on retarded reaction rate and stereospecificity of the polymerization are attributed to the coordination of Et3B with the propagating enolate anion.

The microdomain structure of an ABC triblock copolymer consisting of poly(2-hydroxyethyl methacrylate), poly(tert-butyl methacrylate) and poly(2-(perfluorobutyl) ethyl methacrylate) was investigated by means of small-angle X-ray scattering (SAXS) and energy-filtered transmission electron microscopy (EF-TEM) which is based on inelastically scattered electrons by a specific element (F atoms in this case) and known as element spectroscopic imaging (ESI). A three-phase lamellar structure was observed with good contrast for an unstained ultrathin section of the as-cast film of the triblock copolymer by imaging the inelastically scattered electrons at energy-loss of 100 eV. The microdomain structure can be interpreted in accordance with the EF-TEM result. A peculiar SAXS profile where the intensity of the first-order peak was weaker than that of the second-order was observed for the triblock copolymer. Theoretical calculation of the SAXS intensity with a paracrystal model of the four-layer lamellae successfully reproduced the observed SAXS profile.

N,N-Dimethylacrylamide (DMA), N,N-diethylacrylamide (DEA), N,N-dipropylacrylamide (DPA), N-ethylmethylacrylamide (EMA), N-acryloylpyrrolidine (APY), N-acryloylpiperidine (API), and N-acryloylmorpholine (AMO) were polymerized with 1,1-bis[(4‘-trimethylsilyl)phenyl]-3-methylpentyllithium (1) and with 1,1-bis[(4‘-trimethylsilyl)phenyl]-3,3-diphenylpropylpotassium (2) in THF in the presence of additives. Although the polymers produced directly with 1 or 2 have broad molecular weight distributions, the addition of Et2Zn to the polymerization systems leads to slow propagation reaction and narrow molecular weight distributions of the polymers. The poly(N,N-dialkylacrylamides) produced with 1 are rich in isotactic configuration, while the addition of Et2Zn reduces isotacticity and increases the degree of syndio- and heterotacticity. In particular, the poly(DEA)s generated with 1/Et2Zn and 1/LiCl are highly syndiotactic and isotactic, respectively. Although the broad distributions of triad sequence are observed fo...

Three different ω−α-substituted styryl macromonomers with well-controlled structures were synthesized by directly terminating either polystyryllithium or polyisoprenyllithium with 4-(3-halopropyl)-α-methylstyrenes (2), α-(3-halopropyl)styrenes (3), and 1-[4-(3-halopropyl)phenyl]-1-phenylethylenes (4). With uses of their bromo and iodo derivatives as terminating agents, the reactions proceeded in a desired manner in THF at −78 °C to afford well-controlled ω-styryl polystyrene and polyisoprene macromonomers quantitatively. On the other hand, the synthetic utility of chloride derivatives as terminators was much dependent on both their polymerizable styryl groups and living polymers to be reacted. By comparison of these results with our previous results using 4-(3-halopropyl)styrenes (1), the scope and limitation of the methodology developed here were discussed from a viewpoint of quantitative synthesis of various ω-styryl macromonomers with well-controlled structures.

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, res...

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...

Anionic polymerizations of four styrenes protected with bicyclic ortho ester moieties, 1-(4-vinylphenyl)methyl-4-methyl-2,6,7-trioxabicyclo[2.2.2]octane (1), 1-[2-(4-vinylphenyl)ethyl]-4-methyl-2,6,7-trioxabicyclo[2.2.2]octane (2), 1-(3-vinylphenyl)-4-methyl-2,6,7-trioxabicyclo[2.2.2]octane (3), and 1-(4-vinylphenyl)-4-methyl-2,6,7-trioxabicyclo[2.2.2]octane (4), were carried out in THF at −78 °C for 0.5 h with oligo(α-methylstyryl)lithium and -dipotassium and potassium naphthalenide. Poly(1)−(3) were quantitatively obtained, and the resulting polymers possessed the predicted molecular weights based on the molar ratios of monomers to initiators and narrow molecular weight distributions (MWDs, Mw/Mn < 1.1). By contrast, polymerization of 4 did not go to completion and gave insoluble polymeric product in low yield due to the side reactions under the similar conditions. The substituent position in the monomer was very important for the success of the polymerization, although the bicyclic ortho ester was foun...

We performed the anionic living polymerization of 6-[4-(4‘-cyanophenyl)phenoxy]hexyl methacrylate. By a selection of suitable initiations, the cyano group was completely stable toward the propagating enolate anion, and the anionic polymerization proceeded with a living nature. The homopolymers could thus be prepared with a wide range of molecular weights from 6000 to 20 000, a narrow molecular weight distribution of less than 1.14, and different tacticities. All the polymers exhibited the smectic A phase in which two mesogenic groups were included within a smectic layer of thickness 36.0 A. The isotropization temperature of the smectic A phase increased with the increase of the molecular weight and leveled off at around 15 000. No crystallization took place so that the smectic A phase was glassified. Well-controlled block copolymers with methyl methacrylate and styrene were also prepared by living anionic polymerization, and their thermotropic phase behavior and structures are described in a relation to a...

The anionic polymerization of 2,3-diphenyl-1,3-butadiene (1) was investigated in THF at -78 °C as well as in benzene at 40 °C. Compound 1 was found to undergo anionic living polymerization in THF with cumylpotassium or s-BuLi to afford quantitatively the polymers of well-controlled molecular weights and narrow molecular weight distributions (M w /M n < 1.1). Each of the microstructures of the polymers was observed to be only the 1,4-addition product of poly(2,3-diphenyl-1,3-butadiene). Furthermore, the polymer consisted of 90% cis and 10% trans 1,4-structures, although the assignment of these configurations was tentative. It was observed by DSC that the polymer showed a glass transition temperature of 98 °C and a melting point of 170 °C. Surprisingly, on standing for a few hours the polymer precipitated completely from the polymer solution in THF. The polymer thus precipitated became insoluble in most organic solvents except for hot toluene and o-dichlorobenzene. This may therefore be due to the crystallization of the polymer, but not cross-linking as previously reported.

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 (Mw/Mn < 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 (Mw/Mn = 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 con...

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.

Anionic polymerizations of 2-[2-(4-ethenylphenyl)ethenyl]-4,4-dimethyl-2-oxazoline (1), 2-[2-(4-isopropenylphenyl)ethenyl]-4,4-dimethyl-2-oxazoline (2), and 2-[1-methyl-2-(4-ethenylphenyl)ethenyl]-4,4-dimethyl-2-oxazoline (3) were carried out in tetrahydrofuran at −78 °C with (1,1,4,4-tetraphenylbutanediyl)dipotassium. Poly(1) was quantitatively obtained after 24 h but the molecular weight distribution (MWD) of the polymer was relatively broad (Mw/Mn = 1.3−1.4). The 1H NMR analysis of the polymer suggested that side reactions toward the conjugated CC−oxazoline linkage occurred during the polymerization. No apparent polymerization of 2 was observed under similar condition. On the other hand, the polymerization of 3 proceeded rather rapidly within 1 h and quantitatively gave poly(3) having a narrow MWD (Mw/Mn < 1.1) and the predicted molecular weight based on the molar ratio of monomer to initiator. The living character of the propagating carbanion of poly(3) was confirmed by the quantitative initiation eff...

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 (Mw/Mn = 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 o...

The anionic polymerization of 4-cyano--methylstyrene 1 was carried out in THF with (diphenylmethyl)potassium (Ph2CHK) as an initiator. At the various temperature ranging from 0 to 78 C, conversion and equilibrium monomer concentration, [M]e, were obtained from the GLC analysis of the residual monomer. From the plot of ln [M]e against reciprocal temperature, the thermodynamic parameters, H and S, and the ceiling temperature, Tc, of the anionic polymerization of 1, were determined to be 7.64 0.5 kcal mol-1, 25.5 1.3 cal mol-1 K-1, and 27 3 C, respectively. The apparent rate constant and the activation energy of the anionic polymerization for 1 were determined as follows: ln kpap = 1.83 103/T + 5.74 L mol-1 s-1 and Ea = 3.6 0.2 kcal mol-1, respectively. Depolymerization of the living poly(1) proceeded to give a low molecular weight oligomer and starting monomer when the temperature of the polymerization system was raised from 78 to 0 C. The resulting poly(1)s produced at low temperatures (30 to 78 C) possess...

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.

We have synthesized the A-B block copolymer with polystyrene as A segment and side-chain liquid crystal (LC) polymer as B segment by a sequential living polymerization. The copolymers were successfully prepared with quantitative yields, possessing the predictable Mn values, compositions, and narrow molecular weight distributions. The thermotropic phase behavior and structures were examined for nine copolymers with the fraction of segments around 50 w% and with the various molecular weights ranged from 8000 to 34000. All the polymers exhibit the well-defined lamellar type of segregation and the side-chain LC segment in the microdomain forms crystal, smectic A (SA) and isotropic phases with increasing temperature. The lamellar segregation is maintained over the whole temperature region from crystal to isotropic phases, and the crystal and SA structures are formed with a preferential orientation to the microdomain interface such that the mesogenic side-chain groups lie parallel to the interface. The lamellar thickness depends on the SA temperatures. It gradually decreases from the value of crystal phase to that of isotropic phase. The reduction is around 20–25%, which can be explained in terms of the change in main-chain conformation of the LC block.

Four 2-[(N,N-dialkylamino)silyl] substituted 1,3-butadiene derivatives, 2-[(N,N-diethylamino)dimethylsilyl]-1,3-butadiene (1), 2-[(N,N-dibutylamino)dimethylsilyl]-1,3-butadiene (2), 2-[(1-pyrrolidinyl)dimethylsilyl]-1,3-butadiene (3), and 2-[[N-[2‘-(N‘,N‘-dimethylamino)ethyl]-N-methylamino]dimethylsilyl]-1,3-butadiene (4), were newly synthesized and polymerized under various conditions of anionic polymerization. Under the condition of THF at −78 °C, all the monomers, 1−4, underwent living polymerization to afford the polymers of predictable molecular weights and narrow molecular weight distributions. On the other hand, side reactions occurred to some extent in the polymerizations of 1−4 carried out in heptane at 40 °C, although yields of polymers were quantitative in all cases within 1 h. The polymers obtained in THF consisted mainly of 1,4 (83−91%) and 1,2 (9−17%) linkages, while all the polymers obtained in heptane were structurally pure 1,4-addition products. There were mixtures of 1,4-E (16−32%) and 1...

Two derivatives of ω-hydroxy carboxylic ionophore 2-[[2-[2-[2-[2-[2-[2-[2-(2-hydroxyethoxy)phenoxy]ethoxy]phenoxy]ethoxy]phenoxy]ethoxy]phenoxy]methyl]benzoic acid 1, 2-[[3-[2-[2-[2-[2-[2-[3-(2-hydroxyethoxy)-2-naphthyloxy]ethoxy]phenoxy]ethoxy]phenoxy]ethoxy]-2-naphthyloxy]methyl]benzoic acid 2 and 2-[[3-[2-[2-[2-[3-[2-[2-(2-hydroxyethoxy)phenoxy]ethoxy]-2-naphthyloxy]ethoxy]phenoxy]ethoxy]-2-naphthyloxy]methyl]benzoic acid 3, were prepared. Both compounds exhibited high K+ selectivity over Na+, as did 1. The structures of the Rb salt of 2 and the K salt of 3 were determined by single-crystal X-ray analyses. Both ionophores formed psuedocycles by a head-to-tail hydrogen bond between the hydroxy and carboxylato groups and enclosed each cation like the seam of a tennis ball to make lipophilic complexes. However, the three-dimensional structures of the two hydrophobic salts differed from each other in spite of the similarity of the primary structures, which might be due to the interaction of the aromatic rings.

In order to prepare well-defined polymers with halogen end groups, anionic living polymers of isoprene and styrene were allowed to react with excess amounts of α,ω-dihaloalkanes in THF at −78 °C. The monosubstitution reactions of 1,3-dichloropropane with these anionic living polymers proceeded cleanly to afford quantitatively the polymers with chlorine end groups that possessed controllable molecular weights and narrow molecular weight distributions. On the other hand, the reactions of the anionic living polymers with either α,ω-dibromoalkanes or α,ω-diiodoalkanes proceeded competitively with side reactions leading to dimer formation of the starting living polymers. Thus, the bromine- and iodine-terminated polymers were obtained in 12−93% yields along with undesirable dimers. As side reaction candidates, we speculated on metal−halogen interchange and/or single electron transfer pathways followed by coupling reactions between the reaction intermediates generated by both pathways. By end-capping the polysty...

The anionic polymerization of 4-cyano-α-methylstyrene (1) was carried out in THF at −78 °C with (1,1,4,4-tetraphenylbutanediyl)dipotassium and -dilithium, (diphenylmethyl)potassium, and (triphenylm...

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 Mw/Mn 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 syn...

The anionic polymerization of 4-vinylphenyl methyl sulfide (1), (4-vinylphenyl)methyl methyl sulfide (2), and 2-(4'-vinylphenyl)ethyl methyl sulfide (3) were carried out in THF at -78 °C. Monomers 1 and 3 were found to undergo anionic living polymerization with typical initiators such as lithium and potassium naphthalenides, sec-butyllithium, and sec-butyllithium capped with a-methylstyrene. The resulting polymers possessed molecular weights predictable from [monomer] to [initiator] ratios and narrow molecular weight distributions, the values of M w /M n being less than 1.1. In contrast, attempts to polymerize 2, which has a benzyl sulfide structure, failed. No appreciable polymerization occurred with 2 under the identical conditions used for the successful polymerizations of and 3. For this reason, we proposed the reaction mechanism based on a 1,6-elimination of anion, followed by the formation of the very reactive p-xylylene intermediate.

本論文では電子吸引性基を有するスチレン誘導体のアニオンリビング重合による鎖構造の規制された反応性ポリマーの合成について報告する. スチレン骨格に導入した電子吸引性基は, N, N-ジアルキルアミド基, オキサゾリン環, エステル基, N-アルキルイミノ基, (トリメチルシリル) エチニル基, N, N-ジアルキルスルホンアミド基, シアノ基である. これらのモノマーのアニオン重合はリビング的に進行し, 設計どおりの分子量と狭い分子量分布をもつポリマーを定量的に与えた. 成長鎖末端アニオンの反応性を生かして, さまざまなモノマー類との構造の明確なブロック共重合体の合成にも成功した. また, ヒ記モノマー類のアニオン重合性は, 電子吸引性基によってビニル基上の電子密度が低められることにより, 無置換のスチレンよりも大きく高められ, 逆に同様の置換基効果によって, 生成したリビングポリマーの成長鎖末端アニオンは求核性が低下していることが確かめられた.

Anionic living polystyrene and polyisoprene were allowed to react with six tern-butyldimethylsilyl ethers of ω-halo-1-alkanols 1-6, the trimethylsilyl ether of bromohydrin (7), the tert-butyldimethylsilyl ether of 4-bromophenol (8), and tert-butyldimethylsilyl 3-chloropropyl sulfide (9), followed by acid-catalyzed cleavage of Si-O and Si-S bonds to afford polystyrene and polyisoprene, respectively, with hydroxy or mercapto end groups. The alcoholic hydroxy groups were introduced quantitatively to the polymer chain end regardless of the kind of halogen atom, length of methylene spacer separating the protected hydroxy group from the halogen, and structure of protecting groups. The tert-butyldimethylsilyl ether of 4-bromophenol (8) was not suitable for this reaction, since most (90%) of the original living polyisoprene was dimerized due to metal-halogen exchange followed by the coupling reaction of the polymeric allyl bromide derivatives thus formed with remaining living polyisoprene. Polystyrene and polyisoprene with tert-butyldimethylsilyl sulfide end group were obtained quantitatively by the reaction of their anionic living polymers with 9. Generation of mercapto groups through deprotection was confirmed by I 2 oxidation and reaction with acrylonitrile.

Reactions of anionic living polymers of styrene, tert-butyl methacrylate, and 2-(trimethylsiloxy)ethyl methacrylate with perfluoroalkyl (Rf) halides, such as C 4 F 9 (CH 2 ) 3 I (1), (CF 3 ) 2 CF(CF 2 ) 6 I (2), C 4 F 9 (CH 2 ) 2 I (3), C 8 F 17 (CH 2 ) 2 O(CH 2 ) 4 Br (4), were investigated to synthesize well-defined polymers with Rf groups at the chain end. Nucleophilic attack of living polystyryl anions on 1 and 4 quantitatively proceeds to give the Rf-terminated polystyrenes with predictable molecular weights and narrow molecular weight distributions, while low functionalities (0-50 mol-%) were obtained in the cases of 2 and 3, on account of electron transfer and β-proton elimination. The anionic propagating ends of the methacrylates with potassium countercation react with 1 and 4 to afford the Rf-terminated poly(methacrylate)s in high efficiency. Poly[2-(trimethylsiloxy)ethyl methacrylate] produced was deprotected under acidic conditions to give poly(2-hydroxyethyl methacrylate) bearing the Rf-terminal group. However, the reactions of the propagating enolate with lithium countercation with 1 and 4 result in low yields of the Rf-terminated polymers. From the surface analyses of the Rf-terminated polymer films by X-ray photoelectron spectroscopy and contact angle measurements, a remarkable enrichment of the Rf group at the dry surface and a surface restructuring corresponding to the environmental change are indicated.

Anionic polymerization of 4-(4′-trimethylsilyl-3′-butynyl)styrene (2) was carried out in THF at −78°C for 0.5 h with oligo(α-methylstyryl)lithium, -dilithium, and -dipotassium. Poly(2)s possessing predicted molecular weights and narrow molecular weight distributions (Mw/Mn < 1.11) were quantitatively obtained in all cases. By sequential anionic copolymerization of 2 and styrene, novel block copolymers, polystyrene-block-poly(2) starting either from living polystyrene or living poly(2), were synthesized. After completion of the polymerization, there occurred some gradual deactivation of the propagating carbanion of poly(2) at −78°C. This deactivation reaction could be almost completely suppressed at −95°C. The deprotection of poly(2) was performed by treating with Bu4NF in THF at 0°C for 1 h. The trimethylsilyl protecting group of poly(2) was completely removed to afford a poly[4-(3′-butynyl)styrene] of a controlled molecular structure.

The surface composition of anionic polymerized poly(2-hydroxyethyl methacrylate) (PHEMA) films cast onto glass coverslips was examined with x-ray photoelectron spectroscopy (XPS). The elemental composition determined from a survey scan was 68.3 at. % carbon and 31.7 at. % oxygen. This composition is within experimental error of the composition expected based on the structure of PHEMA (66.7 at. % carbon and 33.3 at. % oxygen). The C 1s spectrum was fit using four components corresponding to C–H/C–C, beta-shifted C–H, C–O, and O=C–O species. The O1s spectrum was fit using three components corresponding to C=O, C–OH, and C–O–C species. The assignment, binding energies, and relative areas are all consistent with the structure of PHEMA and previous XPS studies of methacrylates [D. G. Castner and B. D. Ratner, Surf. Interface Anal. 15, 479 (1990) and G. P. Lopez, D. G. Castner, and B. D. Ratner, 17, ibid. 267 (1991)]. The surface composition of PHEMA after reaction of the hydrdoxyl groups with (CH3Si)2NHSi(CH3)...

In order to synthesize end-functionalized polymers with 4-vinylphenyl group (so-called ω-styryl macromonomers), anionic living polymers of styrene and isoprene were allowed to react with five 4-(ω-...

Anionic polymerizations of 2-, 3-, and 4-fluorostyrenes (2-, 3-, and 4-FSt) were carried out at -78 °C in THF with see-butyllithium, oligo(a-methylstyryl)lithium, -dipotassium, and (1,1-diphenyl-3-methyl-pentyl)lithium as initiators to give the respective polymers in quantitative yields. The propagating carbanion derived from 2-FSt is found to survive at least for 5 min at -78 °C, affording the anionic living poly(2-FSt) with predictable molecularweight and very narrow molecular weight distribution. The addition of styrene to the anionic living poly(2-FSt) in THF affords poly(2-FSt)-block-polystyrene in quantitative efficiency, indicating the high nucleophilicity of the propagating carbanion of 2-FSt. During the polymerization of3-FSt, the benzyne intermediate is formed probably due to meta-fluoro substitution to cause polymer coupling reaction. Poly(4-FSt) produced has narrow molecular weight distribution and slightly higher molecular weight than the calculated one. The results of the polymerizations of2-FSt and 4-FSt suggest that persistency of the propagating carbanionic species of 4-FSt is slightly lower than that of 2-FSt at -78 °C.

In order to synthesize ω-epoxy-functionalized 1,4-polyisoprene ω-epoxy- and α,ω-diepoxy-functionalized polystyrenes, anionic living polyisoprene and polystyrene were allowed to react with excess amounts of 2-bromoethyloxirane in THF at −78°C. The resulting polymers were analysed by SEC, 1H and 13C NMR spectroscopy, and thin layer chromatography with flame ionization detection (TLC–FID). Both mono- and di-epoxy terminated polymers of controlled molecular weights (2.5 × 103−2.6 × 104 g/mol) and of narrow molecular weight distributions were obtained quantitatively with high functionalities.

The anionic polymerizations of methyl methacrylate (MMA), isopropyl methacrylate (IPMA), and tert-butyl methacrylate (TBMA) in THF in the presence of diethylzinc were investigated. The addition of diethylzinc to the reaction mixture remarkably lowers the polymerization rates of the methacrylates initiated with potassium diphenylmethanide to afford polymers with the predicted molecular weights and very narrow molecular weight distributions, while PMMA and poly(IPMA) produced with potassium diphenylmethanide in the absence of diethylzinc have rather broad molecular weight distributions. The stereospecificities of PMMA, poly(IPMA) and poly(TBMA) are not affected by diethylzinc. From the result of the block copolymerization of MMA with TBMA, it was found that the presistency of the anionic propagating end of PMMA is significantly enhanced by the addition of diethylzinc. The retardation of the polymerization rates and the enhancement of the persistency of the propagating end in the presence of diethylzinc may be caused by the weak coordination of diethylzinc toward the enolate anions at the propagating end groups.

Anionic polymerization of 4-[(4-(4-vinylphenyl)butoxy)methyl]-1-methyl-2,6,7-trioxabicyclo-[2.2.2]octane (3) was carried out in THF at -78°C for 10 min with oligo(α-methylstyryl)lithium, -dilithium, -potassium, and -dipotassium. Poly(3) was quantitatively obtained in each case, and the resulting polymers possessed predicted molecular weights and narrow molecular weight distributions (M w /M n < 1.1), indicating the living character of the polymerization of 3. By the sequential anionic copolymerization of 3 and styrene, well-defined block copolymers were successfully synthesized. The deprotection of poly(3) was performed by treating with 2 N HCl in THF for 30 min and subsequently with 10% NaOH(aq) in MeOH for 30 min. The bicyclic ortho ester moiety of poly(3) was completely cleaved to give a poly[2-(((4-(4-vinylphenyl)butyl)oxy)methyl)-2-(hydroxymethyl)-1,3-propanediol] bearing three hydroxyl groups in each monomer unit.

The surface structures of poly(HEMA-block-styrene-block-HEMA)s and poly(HEMA-ran-styrene) (where HEMA denotes 2-hydroxyethyl methacrylate) are characterized by TEM observation and contact angle measurements using sessile drop method and Wilhelmy plate technique under the dry and wet conditions. One (T-60) of the triblock copolymers is produced by the addition reaction of telechelic polystyrene with isocyanate terminals and semitelechelic PHEMA with an amino group at one chain end, and the others (L-50, L-60) are synthesized by anionic living polymerization. The random copolymer (R-50) is prepared by radical polymerization. L-50, L-60, T-60, and R-50 contain 45, 61, 63, and 47 wt % of PHEMA segments, respectively. From the TEM observation, the outermost surface of the as-cast L-50 film is found to be completely covered with polystyrene layer, while the microdomains of polystyrene and PHEMA are mixed in the top surface area of the as-cast T-60 film. By use of the staining technique, the wet surface structures of L-60 and T-60 are also observed. At the hydrated top surface, the polystyrene microdomains wrapped with PHEMA segments are stretched toward the water side, while the microphase separated structure in bulk remains intact. The contact angle measurements elucidates that the hydrophobic surfaces are replaced with hydrophilic ones by soaking the L-50 and T-60 films in water and that the hydrated surface of L-50 reverts to the hydrophobic one again by annealing. The surface of R-50 does not show a drastic restructuring in response to the environmental change.

Three styrene derivatives, para-substituted pentamethyldisilyl (Si-Si), heptamethyltrisilyl (Si-Si-Si), and nonamethyltetrasilyl (Si-Si-Si-Si) groups 1 - 3 were synthesized and polymerized in tetrahydrofuran (THF) at −78°C and in benzene at 40°C. The polymerizations of 1 and 2 in THF were found to proceed without transfer and termination reactions to afford stable living polymers. The Si-Si and Si-Si-Si bonds are found to be completely stable under the conditions. Under the same conditions, novel block copolymers with well-defined structures were synthesized by sequential addition of 1 or 2 and styrene. By contrast, side reactions occurred during the polymerizations of 1 and 2 in benzene at 40°C, although polymer yields were quantitative. More seriously, polymer was not obtained in the polymerization of 3 both in THF and in benzene. Thus, the effect of chain length of the oligosilyl group is found to be critical in the anionic polymerization of 1 - 3.