Irreversible helix rearrangement from Cis‐transoid to Cis‐cisoid in poly(p‐n‐hexyloxyphenylacetylene) induced by heat‐treatment in solid phase

Polymerization of p‐n‐hexyloxyphenylacetylene (pHPA) by using a [Rh(norbornadine)Cl]₂‐triethylamine catalyst was carried out at room temperature to afford stereoregular helical poly(p‐n‐hexyloxyphenylacetylene)s (PpHPAs). When ethanol and n‐hexane were used as polymerization solvents, a bright yellow PpHPAs, poly( Y ) with M_n = 8.5 × 10⁴ and its purple red polymer, poly( R ) with M_n = 5.3 × 10⁴ were obtained in 95% yields and 84% yields, respectively. Diffuse reflective UV–vis spectra of poly( Y ) and poly( R ) in solid phase showed different broad absorption peaks at 445 and 575 nm, respectively. X‐Ray diffraction patterns of poly( Y ) and poly( R ) showed typical columnar structures assignable to cis‐transoid and cis‐cisoid structures, respectively, which were also supported by molecule mechanics calculation. Poly( Y ) was irreversibly transformed to a reddish‐black polymer, poly( Y‐B ), which columnar diameter was nearly the same as that of poly( R ). Further, poly( Y ) showed an exothermic peak in the differential scanning calorimetry trace at 80 °C for 1 h in N₂ gas. Thus, these findings suggest a thermally irreversible rearrangement from an unstable cis‐transoid form, poly( Y ) with a stretched cis‐transoid helix to a stable cis‐cisoid form, poly( R ), with a contracted cis‐cisoid helix in the solid phase to give poly( Y → B ) with the cis‐cisoid form. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Contracted helix to stretched helix Rearrangement of an aromatic polyacetylene prepared in n‐hexane with [Rh(norbornadiene)Cl]2‐triethylamine catalyst

p‐n‐Heptylphenylacetylene (pHepPA) was stereoregularly polymerized in n‐hexane at 25 °C using [Rh(nbd)Cl]₂ catalyst (nbd: norbornadiene) and NEt₃, affording the purple‐red Poly( R ) in 97% yield. A 80 °C heat treatment transformed Poly( R ) to the black Poly( B ). The Poly( R ) X‐ray diffraction (XRD) pattern revealed a hexagonal crystal structure comprising contracted cis‐cisoid helices [ ^Hexa Poly( R ) ^CC ]. The 80 °C heat treatment generated two tetragonal crystals: ^Tetra Poly( B ) ^CC containing contracted cis‐cisoid helices and ^Tetra Poly( B ) ^CT containing stretched cis‐transoid helices. The helical diameters before and after heat treatment were estimated using XRD and were consistent with molecular mechanics calculations (MMFF94 force field method). When heated at 80 °C in the solid phase, the λ_max in the diffuse reflective UV–vis spectra of ^Hexa Poly( R ) ^CC shifted from 482 to 560 nm. Additionally, an endothermic transition occurred in the ^Hexa Poly( R ) ^CC differential scanning calorimetric trace at ～80 °C. Therefore, these data corroborated the assertion that ^Hexa Poly( R ) ^CC thermally converted to ^Tetra Poly( B ) ^CC and ^Tetra Poly( B ) ^CT . © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5177–5183     

Synthesis,structural, and retrostructural analysis of helical dendronized poly(1‐naphthylacetylene)s

Structural and retrostructural analysis of chiral, nonracemic ( poly [(3,4,5)dm8G1‐1EN] ), and achiral ( poly[(3,4,5)12G1‐1EN] ) poly(1‐naphthylacetylene)s demonstrates new design principles for helical dendronized polyarylacetylenes. The oblate cylindrical dendronized polymers self‐organize in a c2mm centered rectangular columnar (Φ_r‐c) lattice. An all cis‐polyene backbone microstructure with very high cisoid character is introduced to rationalize features from small‐ and wide‐angle X‐ray diffraction experiments. More compact helical conformations are ideal for efficient communication or amplification of chirality over long distances. Peripheral chiral tails select a preferred helical screw sense of the polyene backbone. In solution, the preferred helical conformation persists over a wide temperature range. In bulk, the naphthyl moiety facilitates a longer correlation length for helical order compared to an analogous minidendritic poly(phenylacetylene). These attributes suggest that the naphthyl moiety may be better suited for expressing helical chirality in monolayer domains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4974–4987, 2007     

Raman Optical Activity (ROA) as a New Tool to Elucidate the Helical Structure of Poly(phenylacetylene)s

Poly(phenylacetylene)s are a family of helical polymers constituted by conjugated double bonds. Raman spectra of these polymers show a structural fingerprint of the polyene backbone which, in combination with its helical orientation, makes them good candidates to be studied by Raman optical activity (ROA). Four different well‐known poly(phenylacetylene)s adopting different scaffolds and ten different helical senses have been prepared. Raman and ROA spectra were recorded and allowed to establish ROA‐spectrum/helical‐sense relationships: a left/right‐handed orientation of the polyene backbone (M_helix/P_helix) produces a triplet of positive/negative ROA bands. Raman and ROA spectra of each polymer exhibited the same profile, and the sign of the ROA spectrum was opposite to the lowest‐energy electronic circular dichroism (ECD) band, indicating a resonance effect. Resonance ROA appears then as an indicator of the helical sense of poly(phenylacetylene)s, especially for those with an extra Cotton band in the ECD spectrum, where a wrong helical sense is assigned based on ECD, while ROA alerts of this misassignment.     

Synthesis and chiroptical properties of L‐valine‐containing poly(phenylacetylene)s with (a)chiral pendant terminal groups

Poly(phenylacetylene)s containing L ‐valine residues (P 1 ) with (a)chiral pendant terminal groups R^(*) [?(HC?C{C₆H₄CONHCH[CH(CH₃)₂]COO? R^(*)})_n?]; R^(*) = 1‐octyl (P 1 o), (1S,2R,5S)‐(+)‐menthyl [P 1 (+)], (1R,2S,5R)‐(?)‐menthyl [P 1 (?)] are designed and synthesized. The polymers are prepared by organorhodium catalysts in high yields (yield up to 88%) with high molecular weights (M_w up to ?6.4 × 10⁵). Their structures and properties are characterized by NMR, IR, TGA, UV, and circular dichroism analyses. All the polymers are thermally fairly stable (T_d ≥ 320 °C). The chiral moieties induce the poly(phenylacetylene) chains to helically rotate in a preferred direction. The chirality of the pendant terminal groups affects little the helicity of the polymers but their bulkiness stabilizes the helical conformation against solvent perturbation. The backbone conjugation and chain helicity of the polymers can be modulated continuously and reversibly by acid. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2117–2129, 2006     

Synthesis and helicity of optically active poly(N‐propargylphosphonamidates) having chiral phosphorus center

Novel chiral N‐propargylphosphonamidate monomers (HC?CCH₂NHP(?O)R? O? menthyl, 1 : R = CH₃, 2 : R = C₂H₅, 3 : R = n‐C₃H₇, 4 : R = Ph) were synthesized by the reaction of the corresponding phosphonic dichlorides with menthol and propargylamine. Pairs of diastereomeric monomers 1 – 4 with different ratios were obtained due to the chiral P‐center and menthyl group. One diastereomer could be separated from another one in the cases of monomers 1 and 2 . Polymerization of 1 – 4 with (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃] as a catalyst in CHCl₃ gave the polymers with number‐average molecular weights ranging from 5000 to 12,000 in 65–85%. Poly( 1 )–poly( 4 ) exhibited quantitative cis contents, and much larger specific rotations than 1 – 4 did in CHCl₃. The polymers showed an intense Cotton effect around 325 nm based on the conjugated polyacetylene backbone. It was indicated that the polymers took a helical structure with predominantly one‐handed screw sense, and intramolecular hydrogen bonding between P?O and N? H of the polymers contributed to the stability of the helical structure. Poly( 1a ) and poly( 2a ) decreased the CD intensity upon raising CH₃OH content in CHCl₃/CH₃OH. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1515–1524, 2007     

Synthesis of graft copolymer by ATRP of MMA from poly(phenylacetylene)

The present report describes the synthesis of a densely grafted copolymer consisting of a rigid main chain and flexible side chains by the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from an ATRP initiator‐bearing poly(phenylacetylene) [poly(BrPA)]. Poly(BrPA) was obtained by the polymerization of 4‐ethynylbenzyl‐2‐bromoisobutyrate using [Rh(NBD)Cl]₂ in the presence of Et₃N. The ¹H NMR spectrum showed that poly(BrPA) was in the cis‐transoid form. Upon heating at 30 °C for 24 h the cis‐transoid form was maintained. ATRP of MMA from the poly(BrPA) was carried out at 30 °C using CuX (X = Br, Cl) as the catalyst and N,N,N′,N′,N′‐pentamethyldiethylenetriamine as the ligand, and the resulting graft copolymers were investigated with ¹H NMR and SEC. To analyze the graft structure in more detail, the graft copolymers were hydrolyzed with KOH and the resultant poly(MMA) part was investigated with ¹H NMR and SEC. The polydispersity indexes of 1.25–1.45 indicated that the graft copolymers have well‐controlled side chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6697–6707, 2006     

Influence of stereoregularity and linkage groups on chiral recognition of poly(phenylacetylene) derivatives bearing L‐leucine ethyl ester pendants as chiral stationary phases for HPLC

Stereoregular poly(phenylacetylene) derivatives bearing L ‐leucine ethyl ester pendants, poly‐1 and poly‐2a , were, respectively, synthesized by the polymerization of N‐(4‐ethynylphenylcarbamoyl)‐L ‐leucine ethyl ester ( 1 ) and N‐(4‐ethynylphenyl‐carbonyl)‐L ‐leucine ethyl ester ( 2 ) using Rh(nbd)BPh₄ as a catalyst, while stereoirregular poly‐2b was synthesized by solid‐state thermal polymerization of 2 . Their chiral recognition abilities for nine racemates were evaluated as chiral stationary phases (CSPs) for high‐performance liquid chromatography (HPLC) after coating them on silica gel. Both poly‐1 and poly‐2a with a helical conformation showed their characteristic recognition depending on coating solvents and the linkage groups between poly(phenylacetylene) and L ‐leucine ethyl ester pendants. Poly‐2a with a shorter amide linkage showed higher chiral recognition than poly‐1 with a longer urea linkage. Coating solvents played an important role in the chiral recognition of both poly‐1 and poly‐2a due to the different conformation of the polymer main chains induced by the solvents. A few racemates were effectively resolved on the poly‐2a coated with a MeOH/CHCl₃ (3/7, v/v) mixture. The separation factors for these racemates were comparable to those obtained on the very popular CSPs derived from polysaccharide phenylcarbamates. Stereoirregular poly‐2b exhibited much lower chiral recognition than the corresponding stereoregular, helical poly‐2a , suggesting that the regular structure of poly(phenylacetylene) main chains is essential to attain high chiral recognition. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and liquid crystalline behavior of bulky poly(methacrylamide)s

N‐(Bis(4‐(2‐ethylhexyloxy)phenyl)(phenyl)‐methyl)methacrylamide was synthesized and polymerized via reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. The chain‐transfer agent (4‐cyano‐4‐(phenylcarbonothioylthio) pentanoic acid (CPADB)), combined with a chiral additive, and a radical initiator yielded polymers with dispersities between 1.2 and 1.4. At low concentrations, the polymers are soluble in hexanes and chloroform while at higher concentrations they swell in these solvents. Characterization of the polymers by wide‐angle X‐ray scattering (WAXS) revealed an interplanar distance of 19.0 Å. The WAXS data combined with polarized optical microscopy support a lamellar crystallization and lyotropic liquid crystalline behavior in hexanes and chloroform. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2563–2568     

Synthesis and bifunctional asymmetric organocatalysis of helical poly(phenylacetylene)s bearing cinchona alkaloid pendants via a sulfonamide linkage

Four novel helical poly(phenylacetylene)s with amino‐functionalized cinchona alkaloid pendant groups connecting to the phenyl rings through a sulfonamide linkage were synthesized by the polymerization of the corresponding phenylacetylene monomers using Rh⁺(2,5‐norbornadiene)[(η⁶‐C₆H₅)B^?(C₆H₅)₃] (Rh(nbd)BPh₄) as the catalyst. The optically active sulfonamide‐linked polymers adopted a helical conformation with an excess of one‐handedness as supported by the appearance of the induced Cotton effects in the main‐chain chromophore regions, and efficiently catalyzed the enantioselective methanolytic desymmetrization of a cyclic anhydride and aza‐Michael addition of aniline to chalcone, thereby producing the corresponding optically active products up to 86% enantiomeric excess. However, their enantioselectivities from the methanolytic desymmetrization were slightly lower than those catalyzed by the corresponding cinchona alkaloid‐bound monomers. On the other hand, during the asymmetric aza‐Michael addition, a unique enhancement of the enantioselectivity was observed for several sulfonamide‐linked helical polymers, and thus affording a remarkably higher enantioselectivity compared to those of the corresponding monomers and nonhelical polymers bearing the identical cinchona alkaloid residues. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2869–2879     

Synthesis of poly(vinylene arsine)s through the ring‐collapsed radical alternating copolymerization of an organoarsenic homocycle with aliphatic acetylenes and their properties

Poly(vinylene arsine)s with no aromatic substituent ([? CH?CR? AsMe? ]_n) were prepared through a radical alternating copolymerization of acetylenic compounds having an alkyl substituent with an organoarsenic homocycle as an arsenic‐atomic biradical equivalent. The radical reaction between 1‐octyne and pentamethylcyclopentaarsine, with a catalytic amount of 2,2′‐azobisisobutyronitrile without a solvent (60 °C, 10 h), produced the corresponding poly(vinylene arsine)s (45% yield). The copolymers obtained were soluble in tetrahydrofuran, chloroform, hexane, and so on. The copolymers were characterized with ¹H and ¹³C NMR spectra. The number‐average molecular weights of the copolymers were estimated with gel permeation chromatography (chloroform and polystyrene standards) to be 6500. The copolymers showed an emission property attributable to the n–π* transition in the main chain. Irradiation by an incandescent lamp of a mixture of 1‐octyne and 1 also produced poly(vinylene arsine)s. The conversion rate of 1‐octyne during the copolymerization with 2,2′‐azobisisobutyronitrile was measured with gas chromatography analysis and was found to be much slower than that of phenylacetylene. A radical terpolymerization of cyclo‐(AsMe)₅ with 1‐octyne and styrene was carried out to yield the terpolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3604–3611, 2004     

Recyclable helical poly(phenylacetylene)‐supported catalyst for asymmetric aldol reaction in aqueous media

A novel one‐handed helical poly(phenylacetylene) bearing L‐hydroxyproline pendants (poly(PA‐P)) was synthesized as an eco‐friendly polymer‐supported catalyst for asymmetric reactions. The helical poly(PA‐P) catalyzed the asymmetric aldol reactions of cyclohexanone with p‐nitrobenzaldehyde, and showed good recyclability and higher enantiomeric excess (ee) in aqueous medias than that in organic medias. The one‐handed helicity of poly(PA‐P) was clearly affected by the water content in the aqueous media. The helical poly(PA‐P) showed the higher enantioselectivity (ee = 99%) than its monomer PA‐P (ee = 54%) in THF/H₂O (H₂O vol % = 25.0 vol %). After the one‐handed helical structure of poly(PA‐P) was destroyed by grinding treatment, the ee of the reaction clearly decreased from 99 to 49%. These indicate that the one‐handed helical structure of poly(PA‐P) played an important role in the high enantioselectivity of the asymmetric aldol reactions in the aqueous media. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1024–1031     

Synthesis of end‐functionalized poly(phenylacetylene)s with well‐characterized palladium catalysts

End‐functionalized poly(phenylacetylene)s were synthesized by the polymerization of phenylacetylene (PA) using the well‐defined palladium catalysts represented as [(dppf)PdBr(R)] {dppf = 1,1′‐bis(diphenylphosphino)ferrocene}. The Pd catalysts having a series of R groups such as o‐tolyl, mesityl, C(Ph)?CPh₂, C₆H₄‐o‐CH₂OH, C₆H₄‐p‐CN, and C₆H₄‐p‐NO₂ in conjunction with silver triflate polymerized PA to give end‐functionalized poly(PA)s bearing the corresponding R groups in high yields. The results of IR and NMR spectroscopies and MALDI‐TOF mass analyses proved the introduction of these R groups at one end of each polymer chain. The poly(PA) bearing a hydroxy end group was applied as a macroinitiator to the synthesis of a block copolymer composed of poly(PA) and poly(β‐propiolactone) moieties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Aromatic poly(benzoxazole)s from multiring diacids containing (phenylenedioxy)diphenylene or (naphthalenedioxy)diphenylene groups: Synthesis and thermal properties

Poly(arylether benzoxazole)s (PAEBOs) were prepared from a series of fully aromatic dicarboxylic acids containing (phenylenedioxy)diphenylene or (naphthalenedioxy) diphenylene groups and 3,3′‐dihydroxy‐4,4′‐diaminobiphenyl (I) or 4‐4′‐(hexafluoroisopropylidene)bis(2‐aminophenol) (II) through high‐temperature direct polycondensation. A phosphorous pentoxide/methanesulfonic acid mixture or trimethylsilylpolyphosphate was used as a condensing agent. All the PAEBOs were amorphous and soluble in strong acids, and those derived from II were also readily soluble in polar organic solvents. Flexible films were cast from their chloroform solutions. The PAEBOs showed inherent viscosity values of 0.68–2.06 dL/g (CH₃SO₃H, T = 30 °C, c = 0.15 g · dL⁻¹). Thermal analysis indicated glass‐transition temperatures ranging from 236 to 270 °C and thermal stability (5% weight loss) in nitrogen up to 526 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1172–1178, 2000     

Synthesis and chiroptical properties of optically active poly(ethynylcarbazole) derivatives: Substituent effect on the helix formation

Novel chiral acetylene monomers containing carbazole, 2‐ethynyl‐9‐[(S)‐2‐methylbutoxycarbonyl]carbazole ( 1 ), 3‐ethynyl‐9‐[(S)‐2‐methylbutoxycarbonyl]carbazole ( 2 ), 2‐ethynyl‐9‐[(S)‐2‐methylbutyl]carbazole ( 3 ), and 2‐ethynyl‐9‐[(S)‐4‐methylhexyl]carbazole ( 4 ) were synthesized and polymerized with [(nbd)RhCl]₂? Et₃N. The corresponding polyacetylenes with number‐average molecular weights ranging from 68,700 to 310,000 were obtained in good yields. Poly( 1 ) exhibited a large specific rotation and an intense Cotton effect in toluene, indicating that it formed a helix with predominantly one‐handed screw sense, while the other three polymers showed no evidence for taking a helical structure. Poly( 1 ) largely decreased the CD intensity upon heating from ?10 to 60 °C. Poly( 1 ) showed a Cotton effect in film state in a manner similar to solution state. No chiral amplification was observed in the copolymerization of 1 with achiral 2‐ethynyl‐9‐tert‐butoxycarbonylcarbazole ( 5 ). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4450–4458, 2007     

The synthesis of poly(phenylacetylene)s with bulky chiral silyl groups and the thermal stability of their helical conformation

The polymerization of (−)‐p‐[(tert‐butylmethylphenyl)silyl]phenylacetylene (t‐BuMePhSi*PA) and (+)‐p‐[{methyl(α‐naphthyl)phenyl}silyl]phenylacetylene (MeNpPhSi*PA) with the [(nbd)RhCl]₂ Et₃N catalyst yielded polymers with very high molecular weights over 2 × 10⁶ in high yields. The optical rotations of the formed poly(t‐BuMePhSi*PA) and poly(MeNpPhSi*PA) were as high as −356 and −150° (c = 0.11 g/dL in CHCl₃), respectively. The circular dichroism (CD) spectrum of poly(t‐BuMePhSi*PA) in CHCl₃ exhibited very large molar ellipticities ([θ]) in the UV region: [θ]_max = 9.2 × 10⁴ ° · cm² · dmol⁻¹ at 330 nm and −8.0 × 10⁴ ° · cm² · dmol⁻¹ at 370 nm. The [θ]_max values of poly(MeNpPhSi*PA) were also fairly large: [θ]_max = 7.1 × 10⁴ ° · cm² · dmol⁻¹ at 330 nm and −5.3 × 10⁴ ° · cm² · dmol⁻¹ at 370 nm. The optical rotations of poly(t‐BuMePhSi*PA) and poly(MeNpPhSi*PA), measured in tetrahydrofuran, chloroform, and toluene solutions, were hardly dependent on temperature in the range 22–65 °C. The CD effects of these polymers hardly changed in the temperature range 28–80 °C, either. These results indicate that the helical structures of these polymers are thermally appreciably stable. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 71–77, 2001     

Origin of the color of π‐conjugated columnar polymers: Poly(p‐n‐octylthiophenyl)acetylene prepared using a [Rh(norbornadiene)Cl]2 catalyst

Highly stereospecific polymerization of a novel sulfur containing aromatic acetylenes, that is, (p‐n‐octylthiophenyl)acetylene (pOctSPA), was successfully performed using the Rh complex, [Rh(norbornadiene)Cl]₂‐TEA, catalyst in the presence of various solvents under mild conditions. The resulting polymers were characterized in detail by ¹H NMR, ESR, laser Raman, diffuse reflective UV‐Vis (DRUV‐Vis), and wide angle X‐ray diffraction methods. The data showed that the resulting polymers bear cis‐transoid form, which can induce the cis‐to‐trans isomerization when the cis polymers are subjected to pressure at room temperature under vacuum, breaking rotationally the cis C?C bonds in the main‐chain giving two kinds of π‐radicals, the so‐called cis radical and trans radical as the origin of a polymer magnet like a novel spin glass material. Further, the resulting cis poly(acetylene)s were found to have a helical main‐chain, which is packed in pseudohexagonal crystal called π‐conjugated columnar or nano π‐conjugated columnar as a novel color controllable material. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2836–2850, 2005     

Application of SSA thermal fractionation and X‐ray diffraction to elucidate comonomer inclusion or exclusion from the crystalline phases in poly(butylene succinate‐ran‐butylene azelate) random copolymers

Poly(butylene succinate‐ran‐butylene azelate) random copolyesters were thermally fractionated by successive self‐nucleation and annealing (SSA). The samples before and after SSA were analyzed by differential scanning calorimetry (DSC) and X‐ray diffraction (WAXS and SAXS). WAXS results indicate that a small degree of comonomer inclusion is present in the crystalline phases that are formed in the copolymers depending on composition: a PBS‐like unit cell or/and a PBAz‐like unit cell, thus confirming the isodimorphic behavior of the samples. SSA on the other hand demonstrated that the degree of comonomer exclusion during crystallization is far larger than comonomer inclusion, as judged by the increase in fractionation degree with compositions leading to the pseudo‐eutectic point. Furthermore, WAXS, SAXS, and SSA results show that the isodimorphic behavior is not highly dependent on kinetic factors, as the degree of comonomer inclusion or exclusion in the samples was not significantly altered by SSA thermal fractionation, a thermal treatment that promotes annealing and molecular segregation of defects to the amorphous regions of the material. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2346–2358     

A solution‐processible poly(p‐phenylene vinylene) without alkyl substitution: Introducing the cis‐vinylene segments in polymer chain for improved solubility,blue emission,and high efficiency

A soluble all‐aromatic poly(2,5‐diphenyl‐1,4‐phenylenevinylene) (2,5‐DP‐PPV) is synthesized by utilizing aromatic phosphonium and aldehyde monomers through Wittig reaction. The H¹ NMR and FTIR measurements indicate that over 50% content of cis‐vinylene units exist in polymer backbone. The diphenyl‐substituted benzaldehyde monomer plays an important role to enhance cis‐products (Z‐selectivity) in Wittig reactions. The twisted cis‐segments in polymer backbone reduce the interchain interactions and enhance the solubility of such all‐aromatic PPV derivative in common organic solvents. 2,5‐DP‐PPV exhibits good solubility in common organic solvents, such as tetrahydrofuran and chloroform. The polymer film exhibits a blue light emission (λ_max = 485 nm) and a very high photoluminescence efficiency of 78%. The cis‐trans photo isomerization of this polymer in solution and the impact on the optical properties are also investigated. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5242–5250, 2008     

Doublet Chirality Transfer and Reversible Helical Transition in Poly(3,5‐disubstituted phenylacetylene)s with Pyrene as a Probe Unit†

A novel doublet chirality transfer (DCT) model was demonstrated in cis poly(3,5‐disubstituted phenylacetylene)s, i.e., S‐I , R‐I , and S‐I‐NMe . The chiral message from the stereocenter of alkylamide substituent at 3‐position induced the polyene backbone to take cis‐transoid helical conformation with a predominant screw sense. And in turn the helical backbone acted as a scaffold to orient the pyrene probes, which was linked to phenyl rings through 5‐position, to array in an asymmetric manner. A combinatory analyses of ¹H NMR, Raman, FTIR, UV‐vis absorption, CD, and computer simulation suggested that the main‐chain stereostructure, solvent nature, and intramolecular hydrogen bonds played important and complex roles on DCT. High cis‐structure content and intramolecular hydrogen bonds were beneficial for the realization of DCT. Reversible helix‐helix transition was observed in S‐I by changing the nature of solvents. In DMF, S‐I adopted a relatively contracted helix, where the main chain exhibited strong optical activity, but that of pyrene was weak. In contrast, a relatively stretched helix formed in CHCl₃, in which the optical activity of pyrene was much larger, whereas that of the polyene backbone was the weakest. This helix‐helix transition was attributed to the intramolecular hydrogen bonds, which was confirmed by solution‐state FTIR spectra and computer calculations.