Novel approach to well‐defined polyester by living anionic alternating copolymerization of ethylphenylketene with 4‐methoxybenzaldehyde

A living anionic alternating copolymerization of ethylphenylketene (EPK) with 4‐methoxybenzaldehyde (MBA) was achieved. When n‐butyllithium was added to a mixture of EPK and MBA in tetrahydrofuran at ?40 °C in the presence of an excess amount of lithium chloride, the copolymerization of these monomers proceeded via complete 1:1 alternating manner to afford the polymer with a narrow molecular weight distribution. A linear relationship was observed between the molecular weight and the monomer/initiator ratio, keeping a narrow molecular weight distribution. The structure of the obtained polymer was determined to be a polyester by IR spectroscopy together with the reductive degradation of the polymer by lithium aluminum hydride, which quantitatively afforded the corresponding diol to the repeating unit of the expected polyester structure. Both conversions of EPK and MBA agreed to a first‐order kinetic equation with linear evolution between the molecular weight and conversion. These observations along with the successful results in two‐stage polymerization indicate that the present copolymerization proceeded through a living mechanism. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2078–2084, 2001     

Application of ketenes to well‐defined polyester synthesis (4): End‐capping reactions in living anionic polymerization of ethylphenylketene

End‐capping reactions of a living polyester, obtained by anionic polymerization of ethylphenylketene (EPK), were carried out. As end‐capping reagents, electrophiles such as alkyl halide and acyl halide were successfully used. Reactivity of the terminal enolate and the resulting terminal structures were elucidated by model reactions, using lithium enolates having low molecular weights, obtained by an equimolar reaction of EPK with butyllithium. Polymerization of EPK by lithium alkoxide and the subsequent end‐capping reaction afforded the corresponding polyester having functional groups at both chain ends and a narrow molecular weight distribution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3103–3111, 2002     

Application of ketenes to well‐defined polyester synthesis. II. Synthesis of reactive polyester by living anionic polymerization of (4‐halophenyl)ethylketene

Novel ketenes, (4‐chlorophenyl)ethylketene and (4‐bromophenyl)ethylketene, were synthesized by dehydrochlorination of 2‐(4‐halophenyl)butanoyl chlorides, and their anionic polymerizations by lithium (4‐methoxyphenoxide) in tetrahydrofuran at ?20 °C were carried out to afford the corresponding polyesters with narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.3) quantitatively. Polymerizations with various feed ratios afforded the corresponding polyesters with predictable molecular weights and narrow molecular weight distributions. Kinetic studies of the polymerizations at ?78 °C revealed that the polymerization rates were apparently larger than that of ethylphenylketene, which is considered to be responsible for the enhanced electrophilicities of the monomers via the introduction of electron‐negative halogen atoms. Monomer conversion agreed with the first‐order kinetic equation. These results strongly support the living mechanism of this polymerization. The obtained polyesters were modified by a palladium‐catalyzed coupling reaction of the side‐chain 4‐halophenyl group with 4‐methoxyphenylboronic acid, demonstrating their potential as reactive polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2093–2102, 2001     

Living anionic polymerization of N‐methoxymethyl‐N‐isopropylacrylamide: Synthesis of well‐defined poly(N‐isopropylacrylamide) having various stereoregularity

Anionic polymerization of N‐methoxymethyl‐N‐isopropylacrylamide ( 1 ) was carried out with 1,1‐diphenyl‐3‐methylpentyllithium and diphenylmethyllithium, ‐potassium, and ‐cesium in THF at ?78 °C for 2 h in the presence of Et₂Zn. The poly( 1 )s were quantitatively obtained and possessed the predicted molecular weights based on the feed molar ratios between monomer to initiators and narrow molecular weight distributions (M_w/M_n = 1.1). The living character of propagating carbanion of poly( 1 ) either at 0 or ?78 °C was confirmed by the quantitative efficiency of the sequential block copolymerization using N,N‐diethylacrylamide as a second monomer. The methoxymethyl group of the resulting poly( 1 ) was completely removed to give a well‐defined poly(N‐isopropylacrylamide), poly(NIPAM), via the acidic hydrolysis. The racemo diad contents in the poly(NIPAM)s could be widely changed from 15 to 83% by choosing the initiator systems for 1 . The poly(NIPAM)s obtained with Li⁺/Et₂Zn initiator system possessed syndiotactic‐rich configurations (r = 75–83%), while either atactic (r = 50%) or isotactic poly(NIPAM) (r = 15–22%) was generated with K⁺/Et₂Zn or Li⁺/LiCl initiator system, respectively. Atactic and syndiotactic poly(NIPAM)s (42 < r < 83%) were water‐soluble, whereas isotactic‐rich one (r < 31%) was insoluble in water. The cloud points of the aqueous solution of poly(NIPAM)s increased from 32 to 37 °C with the r‐contents. These indicated the significant effect of stereoregularity of the poly(NIPAM) on the water‐solubility and the cloud point in water © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4832–4845, 2006     

Application of ketenes to well-defined polyester synthesis. III. Living anionic polymerization of ethyl(4-methoxyphenyl)ketene—Development of polyester having masked phenol side chain

A novel ketene, ethyl(4-methoxyphenyl)ketene (EMPK), was synthesized by the dehydrochlorination of 2-(4-methoxyphenyl)butanoyl chloride. The anionic polymerizations of EMPK by butyllithium in tetrahydrofuran at −20 °C were carried out with a varying feed ratio to give the corresponding polyesters having predictable molecular weights and narrow molecular weight distributions, quantitatively. The selective formation of the polyester was confirmed by IR analysis, and the reductive degradation of the polymer was supported by lithium–aluminium hydride. The second feed of the monomer (after the first stage of polymerization) resulted in the formation of the polymer with the expectedly increased molecular weight and low polydispersity to strongly support the living mechanism of this polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1596–1600, 2001     

Synthesis of well‐defined polymers end‐functionalized with crosslinkable aziridine groups by living anionic polymerization

Well‐defined end‐functionalized polystyrene, poly(α‐methylstyrene), and polyisoprene with polymerizable aziridine groups were synthesized by the termination reactions of the anionic living polymers of styrene, α‐methylstyrene, and isoprene with 1‐[2‐(4‐chlorobutoxy)ethyl]aziridine in tetrahydrofuran at ?78 °C. The resulting polymers possessed the predicted molecular weights and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.1) as well as aziridine terminal moieties. The cationic ring‐opening polymerization of the ω‐monofunctionalized polystyrene having an aziridinyl group with Et₃OBF₄ gave the polymacromonomer, whereas the α,ω‐difunctional polystyrene underwent crosslinking reactions to afford an insoluble gel. Crosslinking products were similarly obtained by the reaction of the α,ω‐diaziridinyl polystyrene with poly(acrylic acid)‐co‐poly(butyl acrylate). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4126–4135, 2005     

Precise synthesis of well‐defined dendrimer‐like star‐branched polymers by iterative methodology based on living anionic polymerization

Dendrimer‐like star‐branched polymers recently developed as a new class of hyperbranched polymers, which resemble well‐known dendrimers in branched architecture, but comprise polymer chains between junctions, are reviewed in this highlight article. In particular, we focus on the precise synthesis of various dendrimer‐like star‐branched polymers and block copolymers by the recently developed methodology based on iterative divergent approach using living anionic polymers and 1,1‐bis(3‐tert‐butyldimethylsilyloxymethylphenyl)ethylene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6659–6687, 2006     

Silyl‐protected hydroxystyrenes: Living anionic polymerization at room temperature and selective desilylation

Both 4‐ and 3‐(tert‐butyldimethylsilyl)oxystyrene (MSOST) undergo living anionic polymerization at room temperature with sec‐butyllithium (sBuLi) in cyclohexane or methylcyclohexane upon injection of a small amount of tetrahydrofuran. Desilylation can be conveniently afforded with hydrogen chloride or tetra(alkyl)ammonium fluoride to provide poly(hydroxystyrene) (PHOST) with a narrow molecular weight distribution, which could be further transformed to other polystyrene derivatives. ¹³C NMR spectra of poly(tert‐butyldimethylsilyloxystyrene) (PMSOST) and PHOST prepared under different conditions (tetrahydrofuran vs. cyclohexane, −78 °C vs. 20 °C) have indicated that the room temperature living polymerization in the hydrocarbon‐rich solvent produces polymers with high syndiotacticity. Similarly, 4‐(tert‐butyldiphenylsilyl)oxystyrene (PhSOST), a new monomer, provides living anionic polymerization at room temperature. Desilylation of this polymer can be achieved using tetra(n‐butyl)ammonium or tetraethylammonium fluoride. Inertness of the phenylsilyl ether to HCl allows selective desilylation of the dimethylsilyl ether with HCl in the presence of the phenylsilyl ether group, providing a new route to interesting macromolecules. Application of the selective desilylation technique to the synthesis of a block copolymer of HOST and 4‐tert‐butoxycarbonyloxystyrene (BOCST) is described. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2415–2427, 2000     

Samarium enolate on crosslinked polystyrene beads. II. An anionic initiator for the well‐defined synthesis of poly(allyl methacrylate) on a solid support

A samarium enolate, supported on a crosslinked polystyrene resin, successfully initiated the living anionic polymerization of allyl methacrylate (AMA) to afford the corresponding poly(AMA) with well‐controlled molecular weights. Diblock, triblock, and tetrablock copolymerizations with methyl methacrylate (MMA) were also successfully performed. The formed polymers, supported on the resin by a benzyl ester linker, were quantitatively isolated from the resin by selective cleavage of the linker with trifluoroacetic acid (TFA). Allyl ester in the side chain was not affected by this isolation step. The allyl group of the immobilized poly(AMA‐b‐MMA) on the resin was transformed into a 2,3‐dihydroxypropyl group by osmium oxidation. The resulting copolymer was isolated by TFA treatment of the resin, and it showed amphiphilicity. In both the polymerization and side‐chain modification, the formed polymers were easily washed from excess reagents only by filtration, and this demonstrated the feasibility of the automated synthesis of functional polymers based on this solid‐supported polymerization technique. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 853–860, 2003     

Samarium enolate on crosslinked polystyrene beads. III. Anionic initiator for well‐defined synthesis of poly(hydroxyethyl methacrylate) on solid support

A solid‐supported samarium enolate successfully initiated the polymerization of 2‐(trimethylsilyloxy)ethyl methacrylate (TMS‐HEMA) through the living anionic process. In addition, the silyl group was readily removed by treatment of the beads with a weak acid to afford the corresponding well‐defined poly(methacrylate) having a hydroxyethyl group in the side chain (PHEMA). The hydroxyl group of the immobilized PHEMA on the beads was successfully acetylated to give poly(2‐acetoxyethyl methacrylate), which could be quantitatively isolated from the beads by trifluoroacetic acid treatment. Moreover, the hydroxyl group of the immobilized PHEMA could be utilized as an initiator for acid promoted ring opening polymerization of lactone to yield the corresponding graft copolymer. In this method, the residual and excess reagents could be removed by filtration, which demonstrated the applicability of the present technique to a novel method for construction of functional polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4417–4423, 2004     

Living tert‐butyllithium initiated anionic polymerization of 2‐vinylnaphthalene in toluene‐tetrahydrofuran mixtures

The tert‐butyllithium (t‐BuLi) initiated polymerization of carefully purified 2‐vinylnaphthalene in toluene containing small amounts of tetrahydrofuran with respect to t‐BuLi proceeds on a timescale of several hours without significant deactivation and allows the synthesis of very narrow molecular weight distribution poly‐(2‐vinylnaphthalene) (P2VN) (polydispersities as low as 1.04) and molecular weights between 1000 and 20,000. The absence of P2VN‐Li deactivation at these conditions is also indicated by high degrees of trimethylsilyl end functionalization (>95%) and coupling with dibromoxylene. The respective polymerizations of conventionally purified monomer reveal a complex polymerization profile consistent with deactivation by 2‐acetylnaphthalene during the early stages of the reaction. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3034–3041, 2001     

Synthesis and properties of a well‐defined glycopolymer via living radical polymerization

A well‐defined glycopolymer was synthesized to investigate its properties. The glycopolymer was obtained with a narrow polydispersity by nitroxide‐mediated radical polymerization of styrene carrying acetylated lactose and by the subsequent deprotection. The cylindrical structure and helical conformation of the polymer were measured by circular dichroism (CD) spectra. The affinities of the polymers towards lectins depended on the degree of polymerization (DP), and the polymers with higher DP showed stronger affinity. Copyright © 2007 John Wiley & Sons, Ltd.     

β-Butyrolactone polymerization initiated with tetrabutylammonium carboxylates: A novel approach to biomimetic polyester synthesis

The anionic ring-opening polymerizations of (R,S)-β-butyrolactone and (S)-β-butyrolactone initiated with tetrabutylammonium salts of carboxylic acids as initiators were investigated. Poly[(R,S)-3-hydroxybutyrate] and poly[(R)-3-hydroxybutyrate], with relatively high molecular weights (170,000 and 35,000, respectively) and low molecular weight distributions, were synthesized. Moreover, biomimetic poly(3-hydroxybutyrate)s with well-defined microstructures and predictable iso-dyad contents were obtained. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2184–2189, 2002     

Living Anionic Polymerization of 2‐Methyl‐4‐ phenyl‐1‐buten‐3‐yne

The anionic polymerization behavior of 2‐methyl‐4‐phenyl‐1‐buten‐3‐yne (2) was investigated to get information on the effect of substituent at the 2‐position. The polymerization of 2 did not proceed in tetrahydrofuran at –78°C by lithium initiators, while sodium initiators can conduct the polymerization smoothly to give polymers consisting of a specific 1,2‐polymerized unit. The living nature of the polymerization of 2 by diphenylmethylsodium was supported by the post‐polymerization experiment.     

Synthesis of porphyrin‐end‐functionalized polycyclohexane with well‐controlled and defined polymer chain structure

Tetraphenylporphyrin‐end‐functionalized polycyclohexane (H₂TPP‐PCHE) and its metal complexes (MTPP‐PCHE) were synthesized as the first successful example of porphyrin‐end‐functionalized transparent and stable polymers with a well‐controlled and defined polymer chain structure. Chloromethyl‐end‐functionalized poly(1,3‐cyclohexadiene) (CM‐PCHD) was synthesized as prerequisite prepolymer by the postpolymerization reaction of poly(1,3‐cyclohexadienyl)lithium and chloro(chloromethyl)dimethylsilane. CM‐end‐functionalized PCHE (CM‐PCHE) was prepared by the complete hydrogenation of CM‐PCHD with p‐toluenesulfonyl hydrazide. H₂TPP was incorporated onto the polymer chain end by the addition of 5‐(4‐hydroxyphenyl)‐10,15,20‐triphenylporphyrin to CM‐PCHE. The complexation of H₂TPP‐PCHE and Zn(OAc)₂ (or PtCl₂) yielded a zinc (or platinum) complex of H₂TPP‐PCHE. H₂TPP‐PCHE and MTPP‐PCHE were readily soluble in common organic solvents, and PCHE did not inhibit the optical properties of the H₂TPP, ZnTPP, and PtTPP end groups. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of well‐defined photoresist materials by SET‐LRP

Single electron transfer‐living radical polymerization (SET‐LRP) provides an excellent tool for the straightforward synthesis of well‐defined macromolecules. Heterogeneous Cu(0)‐ catalysis is employed to synthesize a novel photoresist material with high control over the molecular architecture. Poly(γ‐butyrolactone methacrylate)‐co‐(methyladamantly methacrylate) was synthesized. Kinetic experiments were conducted demonstrating that both monomers, γ‐butyrolactone methacrylate (GBLMA) and methyl adamantly methacrylate (MAMA), are successfully homopolymerized. In both cases polymerization kinetic is of first order and the molecular weights increase linearly with conversion. The choice of a proper solvent was decisive for the SET‐LRP process and organic solvent mixtures were found to be most suitable. Also, the kinetic of the copolymerization of GBLMA and MAMA was investigated. Following first order kinetics in overall monomer consumption and exhibiting a linear relationship between molecular weights and conversion a “living” process was established. This allowed for the straightforward synthesis of well‐defined photoresist polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2251–2255, 2010     

1,4‐Dilithio‐1,1,4,4‐tetraphenylbutane in diethyl ether: An effective initiator for the living anionic polymerization of dienes

The anionic polymerization of butadiene initiated with 1,4‐dilithio‐1,1,4,4‐tetraphenylbutane (LiTPB) in diethyl ether (DEE) gives polybutadiene (PBD) with high 1,2 content (>70%), narrow polydispersities (1.04 < M_w/M_n < 1.20), and predicted molecular weights. In THF, this polymerization does not work very well. After removal of DEE and addition of THF, the PBD dianion is end capped quantitatively by addition of 1,1‐diphenylethylene (DPE) to give the diphenylalkyl end capped PBD dianion. Subsequent addition of methyl methacrylate at low temperatures results in the formation of well‐defined PMMA‐b‐PBD‐b‐PMMA triblock copolymers. The results are accounted for by taking into account the effects of Li ion solvation on the BD initiation and end capping of the PBD anion by DPE. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2198–2206, 2009