Asymmetric radical polymerization and copolymerization of N‐(1‐phenyldibenzosuberyl)methacrylamide and its derivative leading to optically active helical polymers

N‐(1‐Phenyldibenzosuberyl)methacrylamide (PDBSMAM) and its derivative N‐[(4‐butylphenyl)dibenzosuberyl]methacrylamide (BuPDBSMAM) were synthesized and polymerized in the presence of (+)‐ and (?)‐menthols at different temperatures. The tacticity of the polymers was estimated to be nearly 100% isotactic from the ¹H NMR spectra of polymethacrylamides derived in D₂SO₄. Poly(PDBSMAM) was not soluble in the common organic solvents, and its circular dichroism spectrum in the solid state was similar to that of the optically active poly(1‐phenyldibenzosuberyl methacrylate) (poly(PDBSMA)) with a prevailing one‐handed helicity, indicating that the poly(PDBSMAM) also has a similar helicity. Poly(BuPDBSMAM) was optically active and soluble in THF and chloroform. Its optical activity was much higher than that of the poly[N‐(triphenylmethayl)methacrylamide], suggesting that one‐handed helicity may be more efficiently induced on the poly(BuPDBSMAM). The copolymerization of BuPDBSMAM with a small amount of optically active N‐[(R)‐(+)‐1‐(1‐naphthyl)ethyl]methacrylamide, particularly in the presence of (?)‐menthol, produced a polymer with a high optical activity. The prevailing helicity may also be efficiently induced. The chiroptical properties of the obtained polymers were studied in detail. The chiral recognition by the polymers was also evaluated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1304–1315, 2007     

Demonstration of isospecific free radical polymerization of acrylate controlled by conformation and chirality of monomer

Radical polymerization of lactic acid‐based chiral and achiral methylene dioxolanones, a model for conformationally s‐cis locked acrylate, was carried out with AIBN to demonstrate an isospecific free radical polymerization controlled by chirality and conformation of monomer. Polymerization of the dioxolanones proceeded smoothly without ring opening to give a polymer with moderate molecular weight and 100% of maximum isotacticity. ESR spectrum indicated a twisted conformation of the growing poly(methylene dioxolanone) radical in contrast to an acyclic analogous radical, suggesting a restriction of the free rotation around main chain C_α? C_β bond of the growing radical center. Chirality as well as the polarity and bulkiness of monomer affected the polymer tacticity, and chiral alkyl substituent would afford a high isotactic polymer, in which higher the enantiomeric excess of the monomer was, higher the isotacticity of the polymer was. While, achiral or polar substituents including dibenzyl and trichloromethyl groups would afford an atactic polymer. In addition, glass transition temperature (T_g) of the resulting polymers was significantly high, ranging from 172.2 to 229.8 °C, and even for an isotactic polymer T_g was as high as 206.8 °C. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2007–2016     

Reactivity of styrene and substituted styrenes in the presence of a homogeneous isospecific titanium catalyst

The isospecific polymerization of several para‐substituted styrenes was performed in the presence of the catalyst dichloro[1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)]titanium activated by methylaluminoxane. All the polymers were highly regioregular and isotactic with narrow molecular weight distributions. The presence of electron‐donating substituents on the aromatic ring had a positive effect on the catalyst activity, whereas electron‐withdrawing substituents affected the polymerization activity negatively. Binary copolymerizations of the various substituted styrenes showed an inversion of the reactivity with respect to that observed in the homopolymerization. These results suggested that the last monomer unit of the polymer chain coordinated to the metal center, influencing the reactivity of the catalyst with respect to the incoming monomer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1486–1491, 2006     

Stereocontrol during the free‐radical polymerization of methacrylamides in the presence of Lewis acids

The effects of Lewis acids, that is, rare earth metal trifluoromethanesulfonates, on the free‐radical polymerization of N‐methylmethacrylamide (MMAM), N‐isopropylmethacrylamide (IPMAM), N‐tert‐butylmethacrylamide (tBMAM), N‐phenylmethacrylamide (PMAM), and methacrylamide were examined under various conditions. A catalytic amount of Yb(OSO₂CF₃)₃ significantly affected the stereochemistry during the radical polymerization. Polymerization solvents strongly influenced the effect of the Lewis acids. Methanol was the best solvent for increasing the isotactic specificity during the polymerization of MMAM and IPMAM, whereas tetrahydrofuran was more effective for the tBMAM and PMAM polymerizations. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1027–1033, 2003     

Anionic polymerization of methyl methacrylate by initiating systems based on lithium amides of various secondary amines

The anionic polymerization of methyl methacrylate in toluene at −78 °C with lithium amides of various secondary amines (diisopropylamine, N‐isopropylaniline, N‐n‐butylaniline, indoline, and N‐ethyl‐o‐toluidine) as initiators was studied. The tacticity of the resulting poly(methyl methacrylate)s (PMMAs) was dependent on the kind of secondary amine, and highly isotactic PMMAs (91–93% mm) were obtained when lithium amides of N‐isopropylaniline and N‐n‐butylaniline were employed. The isotacticity of the PMMAs further increased up to 98% mm with initiating systems composed of the lithium amides, n‐butyllithium, and transition‐metal halides (WCl₆, MoCl₅, and NbCl₅). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4405–4411, 2005     

Alternating copolymerization of carbon dioxide and epoxide by manganese porphyrin: The first example of polycarbonate synthesis from 1-atm carbon dioxide

The first successful example of the formation of polycarbonate from 1-atm carbon dioxide and epoxide was demonstrated by the alternating copolymerization of carbon dioxide and epoxide with manganese porphyrin as a catalyst. The copolymerization of carbon dioxide and cyclohexene oxide with (porphinato)manganese acetate proceeded under the 1-atm pressure of carbon dioxide to give a copolymer with an alternating sequence. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3549–3555, 2003     

Asymmetric anionic polymerization of optically active N-1-cyclohexylethylmaleimide

Chiral (S)-(−)-N-1-cyclohexylethylmaleimide [(S)-CEMI] and (R)-(+)-N-1-cyclohexylethylmaleimide [(R)-CEMI] were synthesized successfully and then polymerized with chiral complexes of (−)-sparteine or (S,S)-(1-ethylpropylidene)bis(4-benzyl-2-oxazoline) [(S,S)-Bnbox] and organometal as initiators in toluene or tetrahydrofuran to obtain optically active polymers. The effects of the polymerization conditions on the optical activity and structure of poly(N-1-cyclohexylethylmaleimide)s were investigated with gel permeation chromatography, circular dichroism, specific rotation, and ¹³C NMR measurements. Poly[(R)-CEMI] obtained with dimethylzinc (Me₂Zn)/(S,S)-Bnbox had the highest specific rotation ([α]₄₃₅ = +323.7°). Complexes of Bnbox and diethylzinc or Me₂Zn were used very effectively as chiral initiators for the asymmetric anionic polymerization of (S)-CEMI and (R)-CEMI. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4682–4692, 2004     

Stereospecific living radical polymerization for simultaneous control of molecular weight and tacticity

The simultaneous control of the molecular weights and the tacticity was attained even during radical polymerization by the judicious combinations of the living/controlled radical polymerizations based on the fast interconversion between the dormant and active species, and the stereospecific radical polymerizations mediated by the added Lewis acids or polar solvents via the coordination to the monomer/polymer terminal substituents. This can be useful for various monomers including not only conjugated monomers, such as acrylamides and methacrylates, but also nonconjugated ones such as vinyl acetate and N‐vinylpyrrolidone. Stereoblock polymers were easily obtained by the addition of the Lewis acids or by change of the solvents during the living radical polymerizations. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6147–6158, 2006     

Stereocontrol using Lewis acids in radical polymerization

The radical polymerization of various (meth)acrylamides in the presence of Lewis acids such as Yb(OTf)₃ and Y(OTf)₃ was carried out. The polymerization with Lewis acids led to highly isotactic polymers, while the polymers synthesized without Lewis acids were atactic or syndiotactic. The dependence of the polymer properties on the tacticity was also demonstrated.     

Enantioselective,alternating copolymerization of carbon monoxide and olefins

Enantioselective, alternating copolymerizations of carbon monoxide with styrene, dicyclopentadiene, and methylcyclopentadiene dimer were carried out with a palladium catalyst modified by 1,4‐3,6‐dianhydro‐2,5‐dideoxy‐2,5‐bis(diphenyl phosphino)‐L ‐iditol. Chiral diphosphine was proven to be effective at enantioselective copolymerization. In the copolymers, some of the second double bonds of alternating poly(1,4‐ketone) were carbonylated. Optical rotation, elemental analysis, and spectra of ¹H NMR, ¹³C NMR, and IR showed that the copolymers had isotactic, alternating poly(1,4‐ketone) structures. An oxidant and an organic acid were the promoters of the copolymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2919–2924, 2000     

Propylene polymerization by C1‐symmetric {ONNO′}‐type salan zirconium complexes

The activities of C₁‐symmetric dibenzyl zirconium complexes of Salan ligands that bear a halo‐substituted phenolate ring and an alkyl‐substituted phenolate ring in propylene polymerization with methylaluminoxane as cocatalyst were studied. These {ONNO′}ZrBn₂‐type catalysts exhibited moderate‐to‐high activities and yielded polypropylene of low molecular weight. The degree of tacticity was found to depend on the steric bulk of the substituents on both phenolate rings and ranged from practically atactic to substantially isotactic (74–78% [mmmm] for polymerizations at room temperature by Lig⁵ZrBn₂). Hemi‐isotactic polypropylene was not obtained, despite the diastereotopicity of the two positions. The pattern of stereo errors was consistent with the enantiomorphic site control of propylene insertion typically observed for C₂‐symmetric catalysts and implied a facile site‐averaging mechanism. A regular 1,2‐insertion and a β‐H transfer to an incoming monomer correspond to the main propagation and termination processes, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Asymmetric oxidative coupling polymerization affording polynaphthylene with 1,1′-bi-2-naphthol units

The oxidative coupling polymerizations of racemic-, (R)-, and (S)-2,2′-dimethoxymethoxy-1,1′-binaphthalene-3,3′-diols were carried out with a copper catalyst with various ligands, such as N,N,N′,N′-tetramethylethylenediamine (TMEDA), (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine, (−)-sparteine, and (S)-(−)-2,2′-isopropylidenebis(4-phenyl-2-oxazoline) [(−)-Phbox], under an O₂ atmosphere. For example, a 10/1 (v/v) MeOH · H₂O-insoluble polymer with a number-average molecular weight of 3.8 × 10³, from a polymerization with CuCl–TMEDA followed by acetylation of the hydroxyl groups, was obtained in a 71% yield. Polymerization with (−)-Phbox proceeded in an S-selective manner to give a polymer with the highest negative specific rotation from the (S)-monomer. The obtained polymer was successfully converted into a polymer with the optically pure 1,1′-bi-2-naphthol unit based on the original monomer structure, which could be used as a polymeric chiral auxiliary and showed catalytic activity for the asymmetric diethylzinc addition reaction to aldehydes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4528–4534, 2004     

Copolymerization of ethylene with isoprene promoted by titanium complexes containing a tetradentate [OSSO]‐type bis(phenolato) ligand

Copolymerization of ethylene with isoprene (IP) catalyzed by 1,4‐dithabutanediyl‐linked bis(phenolato) titanium complexes 1 and 2 and methylaluminoxane (MAO) produced exclusively ethylene‐IP copolymers with good activity. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with IP content ～60%. The copolymer microstructure was fully elucidated by ¹³C‐NMR spectroscopy of the copolymers with various IP content revealing a strong tendency to the alternating microstructure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4200–4206, 2010     

Synthesis and chiral recognition ability of optically active poly{N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide} with various tacticities by radical polymerization using Lewis acids

The radical polymerization of an optically active methacrylamide, N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide, was carried out in the absence and presence of Lewis acids such as yittribium trifluoromethanesulfonate [Yb(OTf)₃] and scandium trifluoromethanesulfonate [Sc(OTf)₃]. Catalytic amounts of the Lewis acids significantly affected the stereoregularity of the obtained polymers. The polymerization with Yb(OTf)₃ in tetrahydrofuran afforded isotactic polymers (up to mm = 87%), whereas the conventional radical method without the Lewis acid produced polymers rich in syndiotacticity (up to rr = 88%). The radical polymerization in the presence of MgBr₂ proceeded in a heterotactic‐selective manner (mr = 63%). Thus, the isotactic, syndiotactic, and heterotactic poly(methacrylamide)s were synthesized by the radical processes. The chiral recognition abilities of the obtained optically active poly(methacrylamide)s were affected by the stereoregularity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3354–3360, 2003     

Palladium catalyzed ethylene-carbon monoxide alternating copolymerization

A new [(PPh₂CH₂CH₂CH₂PPh₂)Pd(CH₃CN)₂](BF₄)₂/CH₃OH catalyst for olefin/carbon monoxide alternating copolymerization has been found which is far more active and more stable than previous monodente phosphine Pd catalysts. Methanol is a coinitiator as well as a chain transfer agent. Protonic acid is not a coinitiator but causes chain transfers. In the absence of methanol, the copolymerization was characterized by long induction period and slow rate © 1992 John Wiley & Sons, Inc.     

Highly Enantioselective Catalytic System for Asymmetric Copolymerization of Carbon Dioxide and Cyclohexene Oxide

A new ligand can be easily prepared, and its intramolecular dinuclear zinc complexes act as a high performance catalyst for the asymmetric alternating copolymerization of cyclohexene oxide and CO₂ under very mild conditions (1 atm CO₂, room temperature), affording completely alternating polycarbonates with up to 93.8 % enantiomeric excess (ee) and 98 % yield. A high M_n value of 28 600 and a relatively narrow polydispersity (M_w/M_n ratio) of 1.43 were also achieved.     

Asymmetric anionic polymerization of N‐1‐naphthylmaleimide with chiral ligand‐organometal complexes in toluene

Asymmetric anionic homopolymerizations of N‐1‐naphthylmaleimide (1‐NMI) were performed with chiral ligand/organometal complexes to form optically active polymers. Poly(1‐NMI)s obtained with methylene‐bridged bisoxazoline derivatives (Rbox)‐diethylzinc (Et₂Zn) complexes showed high specific optical rotations ([α]) from +152.3 to +191.4°. Circular dichroism spectra of the polymers exhibited a split Cotton effect in the UV absorption‐band region. According to the exciton chirality method, the absolute configuration of the polymer main chain was determined according to the following method: (+)‐poly[N‐substituted maleimides (RMI)] main chains can contain more (S,S)‐ than (R,R)‐configurations. (?)‐Poly(RMI) main chains can contain more (R,R)‐ than (S,S)‐configurations. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3556–3565, 2001