Temperature‐Induced Chiroptical Changes in a Helical Poly(phenylacetylene) Bearing N,N‐Diisopropylaminomethyl Groups with Chiral Acids in Water

A stereoregular poly(phenylacetylene) bearing an N,N‐diisopropylaminomethyl group as the pendant (poly‐ 1 ) changed its structure into the prevailing one‐handed helical conformation upon complexation with optically active acids in water. The complexes exhibited induced circular dichroism (ICD) in the UV/Vis region of the polymer backbone. Poly‐ 1 is highly sensitive to the chirality of chiral acids and can detect a small enantiomeric imbalance in these acids, in particular, phenyl lactic acid in water. For example, a 0.005 % enantiomeric excess of phenyl lactic acid can be detected by CD spectroscopy. The observed ICD intensity and pattern of poly‐ 1 were dependent on the temperature and concentration of poly‐ 1 , probably due to aggregations of the polymer at high temperature as revealed by dynamic light scattering and AFM. On the basis of the temperature‐dependent ICD changes, the preferred chiral helical sense of poly‐ 1 was found to be controlled by noncovalent bonding interactions by using structurally different enantiomeric acids.     

Helicity induction on a poly(phenylacetylene) derivative bearing aza‐18‐crown‐6 ether pendants in water

A stereoregular poly(phenylacetylene) bearing the bulky aza‐18‐crown‐6 ether as the pendant (poly‐ 1 ) formed a predominantly one‐handed helical conformation upon complexation with various chiral compounds, such as amino acids, peptides, aminosugars, amines, and amino alcohols in water. The complexes exhibited an induced circular dichroism (ICD) in the UV–visible region of the polymer main chain. Therefore, poly‐ 1 can be used as a novel probe for determining the chirality of chiral compounds in water. The assay of 19 common free L ‐amino acids gave the same ICD sign at 0 °C except for L ‐phenylalanine. The effects of pH, temperature, guest concentration, and organic solvent content on the ICD during the complexation of poly‐ 1 with chiral compounds were also investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1004–1013, 2003     

Synthesis of sulfonated poly(diphenylacetylene)s with high CO2 permselectivity

High‐molecular‐weight poly[1‐phenyl‐2‐(4‐t‐butylphenyl)acetylene], poly[1‐phenyl‐2‐(4‐trimethylsilylphenyl) acetylene], and their copolymers were synthesized by the polymerization with TaCl₅–n‐Bu₄Sn. The obtained polymers were sulfonated by using acetyl sulfate to give sulfonated poly(diphenylacetylene)s with different degrees of substitution. The degrees of sulfonation of poly[1‐phenyl‐2‐(4‐t‐butylphenyl)acetylene] and copolymers were in the range of 0.57–0.85. When poly[1‐phenyl‐2‐(4‐trimethylsilylphenyl)acetylene] was sulfonated, the sulfonated poly(diphenylacetylene) with the highest degree of sulfonation was obtained among all the polymers in this study. Its degree of sulfonation was 1.55. All the sulfonated polymers exhibited high CO₂ permselectivity, and their CO₂/N₂ separation factor were over 31. The sulfonated poly(diphenylacetylene) with the highest degree of sulfonation showed the highest CO₂/N₂ separation factor of 75. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6463–6471, 2009     

Synthesis and properties of azobenzene‐containing poly(1‐alkyne)s with different functional pendant groups

1‐Alkynes containing azobenzene mesogenic moieties [HC?C(CH₂)₉? O? ph? N?N? ph? O? R; R = ethyl ( 1 ), octyl ( 2 ), decyl ( 3 ), (S)‐2‐methylbutyl ( 4 ), or (S)‐1‐ethoxy‐1‐oxopropan‐2‐yl ( 5 ); ph = 1,4‐phenyl] were synthesized and polymerized in the presence of a Rh catalyst {(nbd)Rh⁺[B(C₆H5)₄]^?; nbd = 2,5‐norbornadiene} to yield a series of liquid‐crystalline polymers in high yields (e.g., >75%). These polymers had moderate molecular weights (number‐average molecular weight ≥ 12,000), high cis contents in the main chain (up to 83%), good thermal stability, and good solubility in common organic solvents, such as tetrahydrofuran, chloroform, and dichloromethane. These polymers were thoroughly characterized by a combination of infrared, nuclear magnetic resonance, thermogravimetric analysis, differential scanning calorimetry, polarized optical microscopy, and two‐dimensional wide‐angle X‐ray diffraction techniques. The liquid‐crystalline behavior of these polymers was dependent on the tail group attached to the azobenzene structure. Poly‐ 1 , which had the shortest tail group, that is, an ethyl group, showed a smectic A mesophase, whereas poly‐ 2 , poly‐ 3 , and poly‐ 5 , which had longer or chiral tail groups, formed smectic C mesophases, and poly‐ 4 , which had another chiral group attached to the azobenzene structure, showed a chiral smectic C mesophase in both the heating and cooling processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4532–4545, 2006     

Macromolecular helicity inversion of poly(phenylacetylene) derivatives induced by various external stimuli

Unique macromolecular helicity inversion of stereoregular, optically active poly(phenylacetylene) derivatives induced by external achiral and chiral stimuli is briefly reviewed. Stereoregular, cis-transoidal poly(phenylacetylene)s bearing an optically active substituent, such as (1R,2S)-norephedrine (poly- 1 ) and β-cyclodextrin residues (poly- 2 ), show an induced circular dichroism (ICD) in the UV-visible region of the polymer backbone in solution due to a predominantly one-handed helical conformation of the polymers. However, poly- 1 undergoes a helix-helix transition upon complexation with chiral acids having an R configuration, and the complexes exhibit a dramatic change in the ICD of poly- 1 . Poly- 2 also shows the inversion of macromolecular helicity responding to molecular and chiral recognition events that occurred at the remote cyclodextrin residues from the polymer backbone; the helicity inversion is accompanied by a visible color change. A similar helix-helix transition of poly((R)- or (S)-(4-((1-(1-naphthyl)ethyl)carbamoyl)phenyl)acetylene) is also briefly described.     

Solvent-induced switching of the macromolecular helicity of poly[(4-carboxyphenyl)acetylene] induced by a single chiral amino alcohol

Cis–transoidal poly[(4-carboxyphenyl)acetylene] (poly- 1 ) complexed with optically active amines and amino alcohols showed an induced circular dichroism (ICD) in the ultraviolet–visible region because of a predominantly one-handed helix formation in water and in dimethyl sulfoxide (DMSO). The Cotton effect signs of the poly- 1 /chiral amino alcohol complexes were inverted in the presence of water, whereas the ICD pattern of the poly- 1 /chiral amine complexes showed no change, regardless of the water content. These results demonstrated that the helix sense of poly- 1 induced by optically active amino alcohols through noncovalent acid–base interactions could be switched by changes in the solvent ratio in the DMSO–water mixtures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3625–3631, 2003     

Synthesis and asymmetric polymerization of (S)‐N‐maleoyl‐L‐leucine propargyl ester

A kind of N‐substituted maleimide (RMI), chiral (S)‐N‐maleoyl‐L ‐leucine propargyl ester ((S)‐PLMI) with a specific rotation of [α]₄₃₅ = ?27.5° was successfully synthesized from maleic anhydride, L ‐leucine, and propargyl alcohol. (S)‐PLMI was polymerized by three polymerization methods to obtain the corresponding optically active polymers. Asymmetric anionic, radical, and transition‐metal‐catalyzed polymerizations were carried out using organometal/chiral ligands, 2,2′‐azobisisobutyronitrile (AIBN) and (bicyclo [2,2,1]hepta‐2,5‐diene) chloro rhodium (I) dimer ([Rh(nbd) Cl]₂), respectively. Poly((S)‐PLMI) obtained by [Rh(nbd)Cl]₂ in DMF showed the highest specific rotation of ?280.6°. Chiroptical properties and structures of the polymers obtained were investigated by GPC, CD, IR, and NMR measurements. Two types of poly((S)‐PLMI)‐bonded‐silica gels as the chiral stationary phase (CSP) were prepared for high‐performance liquid chromatography (HPLC). Their optical resolution abilities were also elucidated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3722–3738, 2007     

Optically active polyacrylamides bearing an oxazoline pendant: Influence of stereoregularity on both chiroptical properties and chiral recognition

Enantiopure acrylamide derivatives, N‐[o‐(4‐methyl‐4,5‐dihydro‐1,3‐oxazol‐2‐yl) phenyl]acrylamide (MeOPAM), N‐[o‐(4‐isopropyl‐4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenyl]acrylamide (PrⁱOPAM), and N‐[o‐(4‐phenyl‐4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenyl]acrylamide (PhOPAM), were synthesized and radically polymerized in the presence of rare earth metal trifluoromethanesulfonates (Ln(OTf)₃, Ln = La, Nd, Sm, and Y) to yield corresponding optically active polymers. Among these Lewis acids, Y(OTf)₃ was found to be most effective for increasing the isotactic specificity during the radical polymerizations when using n‐butanol as solvent. Also, the effect of the Lewis acids was significantly influenced by the ratio of Ln(OTf)₃ to monomer. The relationship of both chiroptical property and the chiral recognition with the stereoregularity was then examined for the resulting polymers having various tacticity by spectroscopic techniques such as NMR, fluorescence, and circular dichroism. The results indicated that the polymers rich in isotacticity exhibited a favorable enantioselective discrimination ability toward 1,1′‐bi‐2‐naphthol as evidenced by ¹H NMR study, where the characteristic hydroxyl proton signal was split into two peaks that ascribed respectively to the levo‐ and dextro‐isomer; furthermore, the splitting magnitude was linearly correlated with the diad isotacticity of the polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and crosslinking reaction of polyacetylenes substituted with benzoxazine rings: Thermally highly stable benzoxazine resins

Novel polyacetylenes, poly( 1 ) and poly( 2 ) substituted with benzoxazine rings were synthesized by the polymerization of the corresponding acetylene monomers 1 and 2 using Rh catalysts, [(nbd)RhCl]₂, and (nbd)Rh⁺B^–Ph₄ (nbd = 2,5‐norbornadiene). The polymers were heated at 250 °C under N₂ to obtain the corresponding polybenzoxazine resins, poly( 1 )′ and poly( 2 )′ possessing polyacetylene main chains via the ring‐opening polymerization of the benzoxazine moieties. The polyacetylene backbones were maintained after crosslinking reaction at 250 °C, which were confirmed by Raman spectroscopy. The benzoxazine resins were thermally highly stable as evidenced by differential scanning calorimetry and thermogravimetric analysis. The surface of poly( 1 )′ film became hydrophilic compared to that of poly( 1 ), while the surfaces of poly( 2 ) and poly( 2 )′ films showed almost the same hydrophilicity judging from the water contact angle measurement. Poly( 1 )′ and poly( 2 )′ exhibited refractive indices smaller than those of poly( 1 ) and poly( 2 ). © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1884–1893     

Helicity Induction and Memory of the Macromolecular Helicity in a Polyacetylene Bearing a Biphenyl Pendant

A novel, cis‐transoidal poly‐(phenylacetylene) bearing a carboxybiphenyl group as the pendant (poly‐ 1 ) was prepared by polymerization of (4′‐ethoxycarbonyl‐4‐biphenylyl)acetylene with a rhodium catalyst followed by hydrolysis of the ester groups. Upon complexation with various chiral amines and amino alcohols in dimethyl sulfoxide (DMSO), the polymer exhibited characteristic induced circular dichroism (ICD) in the UV/Vis region due to the predominantly one‐handed helix formation of the polymer backbone as well as an excess of a single‐handed, axially twisted conformation of the pendant biphenyl group. Poly‐ 1 complexed with (R)‐2‐amino‐1‐propanol showed unique time‐dependent inversion of the macromolecular helicity. Furthermore, the preferred‐handed helical conformation of poly‐ 1 induced by a chiral amine was further “memorized” after the chiral amine was replaced with achiral 2‐aminoethanol or n‐butylamine in DMSO. In sharp contrast to the previously reported memory in poly((4‐carboxyphenyl)acetylene), the present helicity memory of poly‐ 1 was accompanied by memory of the twisted biphenyl chirality in the pendants. Unprecedentedly, the helicity memory of poly‐ 1 with achiral 2‐aminoethanol was found to occur simultaneously with inversion of the axial chirality of the biphenyl groups followed by memory of the inverted biphenyl chirality, thus showing a significant change in the CD spectral pattern.     

Synthesis and properties of carbamate‐ and amine‐containing poly(phenylacetylenes)

The 3‐ and 4‐aminophenylacetylenes protected by t‐butoxycarbonyl (t‐Boc) and 9‐fluorenylmethoxycarbonyl (Fmoc) groups ( 3a – 6a ) were synthesized and polymerized using [(nbd)RhCl]₂ ( 1 ) and [(nbd)Rh⁺‐η⁶‐PhB^?Ph₃] ( 2 ) catalysts. The t‐Boc‐containing polymers [poly( 3a ) and poly( 4a )] were obtained in high yield (82–91%). Among the Fmoc‐protected monomers, the para‐derivative polymerized well [poly( 6a ); yield = 85–94%], whereas its meta‐substituted analogue did not afford high molecular weight polymer in good yield [poly( 5a ); yield = 10–15%]. The use of KN(SiMe₃)₂ as a cocatalyst in conjunction with 1 led to a dramatic increase in the molecular weight of the polymers. The acid‐ and base‐catalyzed removal of the t‐Boc and the Fmoc groups, respectively, generated primary amine‐containing polymers [poly( 3b )–poly( 6b )] which cannot be obtained directly by the polymerization of the corresponding monomers. The solubility characteristics of the polymers bearing protected amino groups were quite different from those of the unprotected ones, the former being soluble in polar solvents, whereas the latter displayed poor solubility even in polar protic or highly polar aprotic solvents. The attempts to accomplish the free‐standing membrane fabrication by solution casting were successful only for poly( 3a ), and an augmentation in the gas permeability and CO₂/N₂ permselectivity was discerned in comparison with the unsubstituted poly(phenylacetylene) and poly(m‐t‐butyldimethylsiloxyphenylacetylene). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1853–1863, 2009     

Synthesis and characterization of chiral poly(alkyl isocyanates) by coordination polymerization using a chiral half‐titanocene complex

A new chiral half‐titanocene complex, [CpTiCl₂(O‐(S)?2‐Bu)], is synthesized and characterized by ¹H and ¹³C NMR spectroscopy. This complex is employed for the coordination polymerization of n‐butyl and n‐hexyl‐ isocyanate leading to chiral polymers, as revealed by their CD spectra. Only the left‐handed helix is produced, due to the chiral (S)?2‐butoxy group, which is bound to the polymer chain end. The polymerization of 3‐(triethoxysilyl)propyl isocyanate produces less soluble polymers. On the other hand, phenyl isocyanate reacts slowly with the complex leading quantitatively and selectively to triphenyl isocyanurate. 2‐Ethylhexyl isocyanate is slowly and selectively cyclotrimerized in the presence of the half‐titanocene complex. However, a statistical copolymer of 2‐ethylhexyl isocyanate and hexyl isocyanate is produced. The reaction of benzyl isocyanate with the complex leads to a mixture of low molecular weight polymer and cyclotrimer. The polymers are characterized using SEC, NMR, and CD spectroscopy and their thermal properties are investigated by TGA/DSC analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2141–2151     

Synthesis and chiral recognition properties of poly(N‐propargylamide) gels derived from ornithine and lysine

Copolymerization of ornithine‐ and lysine‐derived N‐propargylamides, N‐α‐tert‐butoxycarbonyl‐N‐δ‐fluorenylmethoxycarbonyl‐L ‐ornithine N′‐propargylamide ( 1 ), N‐α‐tert‐butoxycarbonyl‐N‐ε‐fluorenylmethoxycarbonyl‐L ‐lysine N′‐propargylamide ( 2 ), N‐α‐fluorenylmethoxycarbonyl‐N‐δ‐tert‐butoxycarbonyl‐L ‐ornithine N′‐propargylamide ( 3 ), and N‐α‐fluorenylmethoxycarbonyl‐N‐ε‐tert‐butoxycarbonyl‐L ‐lysine N′‐propargylamide (4) with dipropargyl adipate was carried out using (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃] as a catalyst in THF to obtain polymer gels in 80–93% yields. The gels adsorbed N‐benzyloxycarbonyl L ‐alanine, N‐benzyloxycarbonyl L ‐alanine methyl ester, and (S)‐(+)‐1‐phenyl‐1,2‐ethanediol preferably than the corresponding optical isomers. The order of chiral discrimination was poly( 1 ) > poly( 4 ) > poly( 2 ), poly( 3 ) gels. The fluorenylmethoxycarbonyl groups of the gels could be partly removed by piperidine treatment, leading to increase of adsorptivity but decrease of chiral recognition ability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4175–4182, 2008     

Preparation of polymer optical fibers doped with nonlinear optical active organic chromophores

We synthesized two novel organic nonlinear optical chromophores—chiral S(+)‐N‐[p‐(4‐nitrostyryl) phenyl] prolinol and non‐chiral [p‐(4‐nitrostyryl) phenyl] piperdine—as potential laser‐active dyes for photonic applications. Both materials show good optical transmittance in the telecommunication frequency region, desirable solubility in acrylic polymer optical fiber matrices, and attractive fluorescence properties that are advantageous for laser‐gain materials and devices. Subsequently, these two chromophores were incorporated into poly(methyl methacrylate) and poly(ethyl methacrylate) and drawn into polymer optical fibers. The relevant properties of these organic dye‐doped fibers have been studied, revealing essential attributes of laser‐active characteristics. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1794–1801, 2001     

Controlled helical orientation of carbazole in amino acid derived poly(N‐propargylamide)s

Novel L ‐alanine and L ‐glutamic acid derivatized, carbazole‐containing N‐propargylamides [N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐alanine N′‐propargylamide and N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] were synthesized and polymerized with (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃] (nbd = norbornadiene) as a catalyst to obtain the corresponding polymers with moderate molecular weights in high yields. Polarimetry, circular dichroism, and ultraviolet–visible spectroscopy studies revealed that both poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐alanine N′‐propargylamide] and poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] took a helical structure with a predominantly one‐handed screw sense in tetrahydrofuran, CHCl₃, and CH₂Cl₂. The helix content of poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐alanine N′‐propargylamide] could be tuned by heat or the addition of a protic solvent, and the helical sense of poly[N‐(9‐carbazolyl) ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] was inverted by heat in CHCl₃ or in mixtures of tetrahydrofuran and CH₂Cl₂. Poly[N‐(9‐carbazolyl) ethyloxycarbonyl‐L ‐alanine N′‐propargylamide] and poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] also took a helical structure in film states. They showed small fluorescence in comparison with the monomers and redox activity based on carbazole. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 253–261, 2007     

Helicity Induction and Its Static Memory of Poly(biphenylylacetylene)s Bearing Pyridine N‐Oxide Groups and Their Use as Asymmetric Organocatalysts

Novel poly(biphenylylacetylene) derivatives carrying different types of pyridine N‐oxide units with a bulky or less‐bulky substituent at a different position as the functional pendant groups (poly‐ 2a and poly‐ 2b ) were synthesized by the rhodium‐catalyzed polymerization of the corresponding monomers. The influence of the steric environment around the catalytically active pyridine N‐oxide sites on the helicity induction and its static memory as well as the asymmetric catalytic activities of the resulting helical polymers with a macromolecular helicity memory was investigated. The polyacetylenes formed an excess one‐handed helical conformation upon noncovalent interactions with optically active alcohols and the induced macromolecular helicities of the polyacetylenes were efficiently memorized after the removal of the chiral inducers. Poly‐ 2b with the macromolecular helicity memory showed an enantioselectivity for the catalytic asymmetric allylation of benzaldehydes, producing optically active allyl alcohols, although their enantioselectivities were low. On the other hand, poly‐ 2a exhibited a negligible catalytic activity probably due to the bulky substituent at the o‐position of the pyridine N‐oxide residues, while poly‐ 2a underwent a unique helix‐inversion with the increasing concentration of chiral alcohols and the opposite helicity of poly‐ 2a was further successfully memorized. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2481–2490     

Versatile ω‐end group functionalization of RAFT polymers using functional methane thiosulfonates

Five different polymers, poly[methyl methacrylate] (PMMA), poly[lauryl methacrylate] (PLMA), poly[diethylene glycol methacrylate] (PDEGMA), poly[N‐isopropylacrylamide] (PNIPA), and poly[styrene] (PS) prepared by the RAFT process and thus terminated with dithioesters were aminolyzed in the presence of S‐3‐butynyl methane thiosulfonate (MTS), which was synthesized in two steps. Analysis of the polymers by 2D NMR, UV–vis absorbance, and gel permeation chromatography revealed them to quantitatively carry acetylene end groups connected with disulfide bridges, indicating that functional MTS reagents can be employed for end group functionalization of RAFT polymers. This versatile method is of advantage compared with conjugations with functional maleimides, where isolation of terminal thiols is often required but inexpedient for poly[(meth)acrylates] because their terminal thiols may undergo backbiting and thus avoid conjugation. The acetylene‐terminated polymers were bound to an azide functionalized glass surface in a Cu(I) catalyzed cycloaddition. The modified surfaces exhibited water contact angles corresponding to the polarity of the attached polymers. In the case of the stimulus responsive polymers PNIPA and PDEGMA, the surfaces showed temperature‐dependent contact angles. The disulfide bond connecting the polymers to the surface could be selectively cleaved and resulted in all surfaces having the same contact angle, independent of the nature of the polymer prior attached to the surface. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3118–3130, 2009     

Synthesis and solution properties of poly(methacrylate)s with semipolar structures on the side chains

Poly{2‐(N,N‐dimethylamino)ethyl methacrylate [poly(DMMA)]}, which was prepared by radical polymerization initiated with dimethyl 2,2‐azobis(2‐methylpropionate), was reacted with hydrogen peroxide, diethyl sulfate, and chloroacetic acid to yield poly[N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)amine N‐oxide] [poly(DMANO)], poly[N‐ethyl‐N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)ammonium ethyl sulfate] [poly(EDMES)], and poly[N,N‐dimethyl‐N‐(2‐methacryloyloxy)ethylammonioacetate] [poly(DMEAA)] as ion‐containing water‐soluble polymers, respectively. The solution properties of these charged polymers were compared via the reduced viscosities of these three charged polymers in aqueous solutions as a function of the concentration. Poly(EDMES) showed typical polyelectrolyte behavior, and the other two polymers [poly(DMANO) and poly(DMEAA)] exhibited antipolyelectrolyte behavior. Furthermore, the antipolyelectrolyte behavior was different for poly(DMANO) and poly(DMEAA); that is, poly(DMANO) was less dependent on small electrolytes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 129–141, 2005     

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     

Tricks of Light on Helices: Transformation of Helical Polymers by Photoirradiation

The following polymer structural transitions were achieved using light: preferred‐handed helix formation for poly(9,9‐di‐n‐octylfluoren‐2,7‐diyl), helix racemization (helix–helix transition) for poly(2,7‐bis(4‐t‐butylphenyl)fluoren‐9‐yl acrylate) and poly(2,5‐bis[4‐((S)‐2‐methylbutyloxy)phenyl]styrene), and helix decomposition for poly(2,7‐bis(4‐t‐butylphenyl)‐9‐methylfluoren‐9‐yl acrylate) and poly(2,7‐bis(4‐t‐butylphenyl)fluoren‐9‐ylmethyl methacrylate). Although these types of transitions and chemical transformations have been studied mainly using heat or chemicals as stimuli, light can also cause these structural alterations. In the helix construction and the helix–helix transition, a key transition is a twist‐coplanar conformational change of a biphenyl or an aryl–aryl unit in the side chain or the main chain of the polymer. Furthermore, the helix–helix transition was caused only by light and not by heat. The examples discussed in this review are expected to trigger off a new direction in synthesis and reaction of chiral polymers.