The effect of cucurbit[n]uril on the solubility,morphology, and the photophysical properties of nonionic conjugated polymers in an aqueous medium

The effects of cucurbit[n]uril on the dissolution and the photophysical properties of nonionic conjugated polymers in water are described. For this purpose, a fluorine‐based polymer, namely, poly[9,9‐bis{6(N,N‐dimethylamino)hexyl}fluorene‐co‐2,5‐thienylene (PFT) was synthesized and characterized by spectroscopic techniques including 1D and 2D NMR, UV–vis, fluorescent spectroscopy, and matrix‐assisted laser desorption mass spectrometry (MALDI‐MS). For the first time, it was demonstrated that a nonionic conjugated polymer can be made soluble in water through an inclusion complex formation with CB8. The structure of the complex was elucidated by NMR experiments including ¹H and selective 1D‐NOESY. This complex emits green and is highly fluorescent with fluorescent quantum yield of 35%. In contrast, CB6 or water‐soluble CB7 although they are chemically identical to CB8 do not have any effect on the dissolution and photophysical properties of PFT. By preparing a protonated version of PFT, the optical properties of PFT in methanol, protonated PFT and PFT@CB8 in water have been studied and compared. It was also observed that the morphology of the polymer PFT was affected by the presence of CB8. Thus CB8‐assisted self‐assembly of polymer chains leads to vesicles formation; these structures were characterized by DLS, AFM, SEM, and TEM fluorescent optical microscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Remarkably stable amphiphilic random copolymer assemblies: A structure–property relationship study

Synthesis of a library of amphiphilic random copolymers from a single reactive pre‐polymer and their self‐assembly is reported. Post‐polymerization modifications of the parent polymer containing pendant N‐hydroxy succinimide (NHS) ester groups with various oligooxyethylene (OE) amines produce amphiphilic random copolymers with same degree of polymerization and equal extent of randomness. ¹H‐NMR and FT‐IR data indicate quantitative substitution in all cases. The critical aggregation concentration (CAC) for all the polymers is estimated to be in the range of 10^?5 M. Stability of these nano‐aggregates is studied by photoluminescence using time dependent F—rster Resonance Energy Transfer (FRET) between co‐encapsulated lipophilic dyes namely DiO and DiI in the hydrophobic pocket of the aggregates. These studies suggest remarkably high stability for all systems. However those with shorter hydrophilic pendant chains are found to be even more robust. Morphology is examined by high resolution transmission electron microscopy (HRTEM) which reveals multi‐micellar clusters and vesicles for polymers containing short and longer OE segments, respectively. Encapsulation efficacy is tested with both hydrophobic and hydrophilic guest molecules. All of them can encapsulate hydrophobic guest pyrene while a hydrophilic dye Calcein can be sequestered only in vesicle forming polymers. Lower critical solution temperature (LCST) is exhibited by only one polymer that contains the shortest OE chains. All polymers exhibit excellent cell viability as determined by MTT assay. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4932–4943     

Polymer electrolyte membranes based on p‐toluenesulfonic acid doped poly(1‐vinyl‐1,2,4‐triazole): Synthesis,thermal and proton conductivity properties

Throughout this work, the synthesis, thermal as well as proton conducting properties of acid doped heterocyclic polymer were studied under anhydrous conditions. In this context, poly(1‐vinyl‐1,2,4‐triazole), PVTri was produced by free radical polymerization of 1‐vinyl‐1,2,4‐triazole with a high yield. The structure of the homopolymer was proved by FTIR and solid state ¹³C CP‐MAS NMR spectroscopy. The polymer was doped with p‐toluenesulfonic acid at various molar ratios, x = 0.5, 1, 1.5, 2, with respect to polymer repeating unit. The proton transfer from p‐toluenesulfonic acid to the triazole rings was proved with FTIR spectroscopy. Thermogravimetry analysis showed that the samples are thermally stable up to ～250 °C. Differential scanning calorimetry results illustrated that the materials are homogeneous and the dopant strongly affects the glass transition temperature of the host polymer. Cyclic voltammetry results showed that the electrochemical stability domain extends over 3 V. The proton conductivity of these materials increased with dopant concentration and the temperature. Charge transport relaxation times were derived via complex electrical modulus formalism (M*). The temperature dependence of conductivity relaxation times showed that the proton conductivity occurs via structure diffusion. In the anhydrous state, the proton conductivity of PVTri1PTSA and PVTri2PTSA was measured as 8 × 10^?4 S/cm at 150 °C and 0.012 S/cm at 110 °C, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1016–1021, 2010     

Functionalized multi‐walled carbon nanotubes with poly(N‐(2‐hydroxypropyl)methacrylamide) by RAFT polymerization

In this study, we grafted water‐soluble biocompatible polymer, poly(N‐(2‐hydroxypropyl)methacrylamide) (PHPMA), onto the surface of multi‐walled carbon nanotubes (MWNTs). The reversible addition‐fragmentation chain transfer (RAFT) agents, dithioesters, were successfully immobilized onto the surface of MWNTs first, PHPMA chains were then subsequently grafted onto MWNTs via RAFT polymerization by using dithioesters immobilized on MWNTs as RAFT agent. FTIR, XPS, ¹H NMR, Raman and TGA were used to characterize the resulting products and to determine the content of water‐soluble PHPMA chains in the product. The MWNTs grafted with PHPMA chains have good solubility in distilled water, PBS buffer, and methanol. TEM images of the samples provide direct evidence for the formation of a nanostructure that MWNTs coated with polymer layer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2419–2427, 2006     

Self‐assembly of star‐shaped polystyrene‐block‐polypeptide copolymers synthesized by the combination of atom transfer radical polymerization and ring‐opening living polymerization of α‐amino acid‐N‐carboxyanhydrides

The self‐assembling nature and phase‐transition behavior of a novel class of triarm, star‐shaped polymer–peptide block copolymers synthesized by the combination of atom transfer radical polymerization and living ring‐opening polymerization of α‐amino acid‐N‐carboxyanhydride are demonstrated. The two‐step synthesis strategy adopted here allows incorporating polypeptides into the usual synthetic polymers via an amido–amidate nickelacycle intermediate, which is used as the macroinitiator for the growth of poly(γ‐benzyl‐L ‐glutamate). The characterization data are reported from analyses using gel permeation chromatography and infrared, ¹H NMR, and ¹³C NMR spectroscopy. This synthetic scheme grants a facile way to prepare a wide range of polymer–peptide architectures with perfect microstructure control, preventing the formation of homopolypeptide contaminants. Studies regarding the supramolecular organization and phase‐transition behavior of this class of polymer‐block‐polypeptide copolymers have been accomplished with X‐ray diffraction, infrared spectroscopy, and thermal analyses. The conformational change of the peptide segment in the block copolymer has been investigated with variable‐temperature infrared spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2774–2783, 2006     

Side‐chain glycylglycine‐based polymer for simultaneous sensing and removal of copper(II) from aqueous medium

Since glycylglycine (Gly‐Gly) residue in the N‐terminal region of human prion protein, a copper binding protein, binds with Cu(II), N‐terminus Gly‐Gly side‐chain containing water soluble block copolymer was synthesized and used for simultaneous sensing and removal of Cu(II) ion from aqueous medium. The polymer has amide nitrogen atom and ester carbonyl group as potential binding sites in the side‐chain Gly‐Gly pendants. Job's plot experiment confirms 2:1 binding stoichiometry of polymer with Cu(II). This polymer is able to sense parts per billion level of Cu(II) very selectively in an aqueous medium and remove Cu(II) ions quantitatively by precipitating out the Cu(II) via complex formation in the pH range 7–9. The binding mode of polymer with Cu(II) in polymer‐Cu(II) complex was characterized by ¹H NMR, FTIR, and UV–vis spectroscopy. The attachment of Cu(II) in the polymer‐Cu(II) complex was confirmed by cyclic voltammetry experiment. Cu(II) release from the complex was achieved at pH 5 due to the protonation of amide nitrogen atoms in the Gly‐Gly moiety. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 914–921     

Micellar behavior of well‐defined polystyrene‐based block copolymers with triethoxysilyl reactive groups and their hydrolysis–condensation

Block copolymers of acryloxy propyl triethoxysilane and styrene were prepared through nitroxide‐mediated polymerization using alkoxyamine initiators based on N‐tert‐butyl‐1‐diethylphosphono‐2,2‐dimethylpropyl nitroxide. The copolymers were characterized by ¹H NMR, size exclusion chromatography and differential scanning calorimetry. Their micellar behavior in dioxane/methanol solutions was examined through static light scattering and transmission electron microscopy (TEM). TEM indicated the successful formation of spherical micelles which were subsequently frozen by the sol–gel process. Hydrolysis–condensation of the reactive ethoxysilyl side groups was followed by FTIR, ¹H NMR, and ²⁹Si NMR. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 784–793, 2010     

Microporous polyurethanes: Synthesis and investigation of the mechanism of the pore formation

A new approach for microporous polymeric material is developed utilizing the secondary interactions such as hydrogen bonding in the polymer chains in polyurethane systems at ambient conditions. A new series of highly rigid, thermally stable, and readily soluble cycloaliphatic polyurethanes were designed and synthesized for this purpose, based on new tricyclodecanedimethanol and 1,4‐cyclohexanedimethanol. The hydrogen‐bonding interactions induce phase separation in solution, which leads to polymer‐rich and solvent‐rich domains; subsequent evaporation of the solvent molecules results in micropores. The phase‐separation process in the polyurethane is found to be highly dependent on the chemical structures of the polymer chain backbone. ¹H NMR titration experiments were carried out to understand the mechanism of the micropore formation and its dependence on different structural subunits. The hydrogen‐bonding association constant (K) obtained from the titration experiments revealed that higher the K‐value more the tendency to form micropores. A fully cycloaliphatic polyurethane produces micropores of sizes ranging from 1 to 8 μm, and each pore is separated by 10^?20 μm, whereas the replacement of one of the cyclic unit in the backbone disturbs the entire phase‐separation process and results in nonporous morphology. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1296–1308, 2006     

Hydrogen‐bonding‐aided synthesis of novel ladderlike organobridged polysiloxane containing side‐chain naphthyl groups

With a hydrogen‐bonding template, a novel soluble aryl amide‐bridged ladderlike polysiloxane, containing naphthyl as the side‐chain group, has been successfully synthesized via a stepwise coupling polymerization. It is proposed that the monomer, N,N′‐di(3‐naphthyldiethoxylsilyl‐propyl)‐[4,4′‐oxybis(benzyl amide)], prepared by Grignard and hydrosilylation reactions, undergoes self‐assembly first via amido hydrogen bonding and then via hydrolysis, followed by condensation under controlled reaction conditions to yield a high molecular weight, soluble, dark yellow polymer. The analytical results (Fourier transform infrared, ¹H NMR, ²⁹Si NMR, X‐ray diffraction, differential scanning calorimetry, and vapor pressure osmometry) show that the polymer possesses an ordered ladderlike architecture. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 636–644, 2003     

Effects of different acid functional groups on proton conductivity of polymer‐1,2,4‐triazole blends

Proton transfer reactions under anhydrous conditions have attracted remarkable interest due to chemical energy conversions in polymer electrolyte membrane fuel cells. In this work, 1H‐1,2,4‐triazole (Tri) was used as a proton solvent in different polymer host matrices such as Poly(vinylphosphonic acid) (PVPA), and poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) (PAMPS). PVPATri_x and PAMPSTri_x electrolytes were investigated where x is the molar ratio of Tri to corresponding polymer repeat unit. The interaction between polymer and Tri was studied via FTIR spectroscopy. Thermogravimetry analysis and differential scanning calorimetry were employed to examine the thermal stability and homogeneity of the materials, respectively. PVPATri_1.5 showed a maximum water‐free proton conductivity of 2.3 × 10^?3 S/cm at 120 °C and that of PAMPSTri₂ was 9.3 × 10^?4 S/cm at 140 °C. The results were interpreted in terms of different acidic functional groups and composition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3315–3322, 2006     

Peptide‐poly(2‐(dimethylamino)ethyl methacrylate) conjugates: Synthesis and aqueous/nonaqueous self‐aggregation into nanostructures of dendritic and spherical morphologies

Peptide–polymer conjugate consisting of a sequence‐defined tripeptide and poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) is synthesized by a simple “grafting from” atom transfer radical polymerization (ATRP) approach. The ATRP of PDMAEMA using peptide‐macroinitiator and CuBr/1,1,4,7,10,10‐hexamethyltriethylenetetramine system in anisole follows pseudo first order kinetics up to a conversion of about 25% within a time span of 125 min. The attachment of peptide moiety at the end of PDMAEMA chain is confirmed from MALDI‐TOF‐MS and circular dichroism analyses. The self‐assembly of as‐synthesized peptide‐PDMAEMA conjugate in organic solvents leads to the formation of spherical nanoparticles as observed through FESEM. Peptide‐PDMAEMA conjugate become soluble in water due to the protonation of the pendent —N(CH₃)₂ moiety of DMAEMA group of the conjugate. Owing to the amphiphilic nature of the protonated conjugate (peptide‐PDMAEMAH), it also undergoes self‐aggregation in water into nanostructures of various morphologies such as dendrite, small sphere and large sphere at pHs of 2, 8, and 10, respectively. Peptide‐PDMAEMA‐IBu conjugate obtained by the post‐modification of —N(CH₃)₂ moiety of DMAEMA group of the conjugate with n‐butylbromide also undergoes self‐aggregation into dendritic nanostructures in water. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3286–3297     

Supramacromolecular chemistry: Self‐assembly of polystyrene‐based multi‐armed pseudorotaxane star polymers from multi‐topic C60 derivatives

Multitopic dibenzylammonium derivatives ( 4 ) of C₆₀ were prepared by Bingel reactions of C₆₀ with a malonate diester ( 2 ) containing two t‐BOC protected dibenzylamine moieties, followed by deprotection and protonation. Self‐assembly of model pseudorotaxanes 5 from the multidibenzylammonium C₆₀ derivatives with dibenzo‐24‐crown‐8 was studied by ¹H NMR spectroscopy and mass spectrometry. Self‐assembly of linear and star‐shaped pseudorotaxanes 8 with up to 12 arms based on polystyrenes bearing terminal DB24C8 host units ( 7 ) and the guest functionalized C₆₀ salts was demonstrated by ¹H NMR spectroscopy and solution phase viscometry. These studies provide further evidence of the potential of supramacromolecular chemistry in construction of complex polymeric architectures. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6472–6495, 2009     

A new soluble conducting polymer and its electrochromic devices

A new polythiophene derivative was synthesized by both chemical and electrochemical oxidative polymerization of 1‐(1‐phenylethyl)‐2,5‐di(2‐thienyl)‐1H‐pyrrole (PETPy). Of which the chemical method produces a polymer that is completely soluble in organic solvents. The structures of both the monomer and the soluble polymer were elucidated by nuclear magnetic resonance (¹H and ¹³C NMR) and Fourier transform infrared (FTIR) spectroscopy. The average molecular weight has been determined by gel permeation chromatography to be M_n = 3.29 × 10³ for the chemically synthesized polymer. Polymer of PETPy was synthesized via potentiostatic electrochemical polymerization in acetonitrile (AN)/NaClO₄/LiClO₄ (0.1 M) solvent–electrolyte couple. Characterizations of the resulting polymer were performed by cyclic voltammetry, FTIR, scanning electron microscopy, and UV–vis spectroscopy. Four‐probe technique was used to measure the conductivities of the samples. Moreover, the spectroelectrochemical and electrochromic properties of the polymer films were investigated. In addition, dual‐type polymer electrochromic devices based on P(PETPy) with poly(3,4‐ethylenedioxythiophene) were constructed. Spectroelectrochemistry, electrochromic switching, and open circuit stability of the devices were studied. They were found to have good switching times, reasonable contrasts, and optical memories. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2215–2225, 2006     

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     

Poly(thienylene‐vinylene‐thienylene) with cyano substituent: Synthesis and application in field‐effect transistor and polymer solar cell

A novel conjugated polymer, poly(thienylene‐vinylene‐thienylene) with cyano substituent ( CN‐PTVT ) was synthesized via Stille coupling for the application in air stable field‐effect transistor and polymer solar cell. The polymer was characterized by ¹H NMR, elemental analysis, UV‐vis absorption and photoluminescence spectroscopy, TGA, cyclic voltammetry and XRD analysis. CN‐PTVT exhibits a good thermal stability with 5% weight loss at 306 °C. The FET hole mobility of the polymer reached 5.9 × 10^?3 cm² V^?1 s^?1 with I_on/I_off ratio of 4.9 × 10⁴, which is one of the highest performance among the air‐stable amorphous polymers. The polymer solar cell based on CN‐PTVT as donor and PCBM as acceptor shows a relatively high open‐circuit voltage of 0.82 V and a power conversion efficiency of 0.3% under the illumination of AM1.5, 100 mW/cm². © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4028–4036, 2009     

Self‐assembling directed synthesis of a novel terephthalamide‐bridged ladderlike polysiloxane

A novel, soluble terephthalamide‐bridged ladderlike polysiloxane ( L ) was synthesized successfully for the first time by stepwise coupling polymerization. The process involved the hydrogen‐bonding self‐assembly of amido groups, which resulted in the formation of a more highly ordered polymeric structure. A novel monomer, bis(3‐methyldimethoxysilylpropyl) terephthalamide ( M ), was prepared by a hydrosilylation reaction in the presence of dicyclopentadienyl platinum dichloride as a catalyst. The structures of the monomer ( M ) and the polymer ( L ) were characterized by Fourier transform infrared, ¹H NMR, ¹³C NMR, ²⁹Si NMR, mass spectrometry, X‐ray diffraction, differential scanning calorimetry, and vapor pressure osmometry. All the characterization data indicated that the synthesized polymer ( L ) possessed an ordered ladderlike structure. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3161–3170, 2002     

Poly(phenylene vinylene)‐based copolymers containing 3,7‐phenothiazylene and 2,6‐pyridylene chromophores: Fluorescence sensors for acids,metal ions,and oxidation

A novel copolymer, poly(N‐hexyl‐3,7‐phenothiazylene‐1,2‐ethenylene‐2,6‐pyridylene‐1,2‐ethenylene) ( P3 ), containing N‐hexyl‐3,7‐phenothiazylene and 2,6‐pyridylene chromophores was synthesized to investigate the effect of protonation, metal complexation, and chemical oxidation on its absorption and photoluminescence (PL). Poly(N‐hexyl‐3,8‐iminodibenzyl‐1,2‐ethenylene‐1,3‐phenylene‐1,2‐ethenylene) and poly(N‐hexyl‐3,7‐phenothiazylene‐1,2‐ethenylene‐1,3‐phenylene‐1,2‐ethenylene) ( P2 ), consisting of 1,3‐divinylbenzene alternated with N‐hexyl‐3,8‐iminodibenzyl and N‐hexyl‐3,7‐phenothiazylene, respectively, were also prepared for comparison. Electrochemical investigations revealed that P3 exhibited lower band gaps (2.34 eV) due to alternating donor and acceptor conjugated units (push–pull structure). The absorption and PL spectral variations of P3 were easily manipulated by protonation, metal chelation, and chemical oxidation. P3 displayed significant bathochromic shifts when protonated with trifluoroacetic acid in chloroform. The complexation of P3 with Fe³⁺ led to a significant absorption change and fluorescence quenching, and this implied the coordination of ferric ions with the 2,6‐pyridylene groups in the backbone. Moreover, both phenothiazylene‐containing P2 and P3 showed conspicuous PL quenching with a slight redshift when oxidized with NOBF₄. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1272–1284, 2004     

Synthesis,characterization, and electrical properties of nanostructural polyaniline doped with novel sulfonic acids (4‐{n‐[4‐(4‐nitrophenylazo)phenyloxy]alkyl}aminobenzene sulfonic acid)

4‐{n‐[4‐(4‐Nitrophenylazo)phenyloxy]alkyl}aminobenzene sulfonic acid (Cn‐ABSA, where n = 2, 4, 6, 8, or 10) as a novel dopant for conducting polymers of polyaniline (PANI) was designed and synthesized. The molecular structure of Cn‐ABSA was characterized with ¹H NMR, Fourier transform infrared, and secondary‐ion mass spectrometry. Nanostructures (nanotubes or nanorods) of PANI–(Cn‐ABSA) were successfully synthesized with a self‐assembly process in the presence of Cn‐ABSA as the dopant. The morphology (shape and size) and conductivity of the resulting nanostructures strongly depended on the number of alkyl groups (n) and, in particular, the addition of water before polymerization. The formed micelles of aniline/Cn‐ABSA/water were proposed to be templatelike in forming PANI–(Cn‐ABSA) nanostructures on the basis of the emulsion properties measured by dynamic light scattering. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3485–3497, 2001     

Nearly monochromatic red electroluminescence from a nonconjugated polymer containing carbazole segments and phenanthroline [Eu(β‐diketonate)3] moieties

A novel nonconjugated copolymer (PVKEu) with carbazole segments and phenanthroline [Eu(β‐diketonate)₃] moieties was synthesized via free radical copolymerization, and characterized by FTIR, ¹H NMR spectroscopy, GPC, ICP, and elemental analysis. The copolymer exhibited good solubility, as well as good thermal stability and high glass transition temperature. The photoluminescence (PL) of this polymer in solution and in solid film has been studied. A multi‐layer device with the configuration of ITO/PEDOT: PSS (40 nm)/PVKEu (70 nm)/BCP (15 nm)/AlQ₃ (30 nm)/LiF/Al exhibited nearly monochromatic red emission at 615 nm and voltage‐independent spectral stability. Our results suggest that enhancing the ligand‐mediated energy transfer between the matrix polymer and europium complex is a potential method to improve the electroluminescence performance of the Eu‐chelated polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 210–221, 2009     

New copolymers of a tautomerizable β‐ketonitrile monomer: Synthesis,characterization and solution tautomerism

The monomer 2‐methyl‐3‐oxo‐5‐phenyl‐4‐pentenonitrile (MOP) was prepared by reaction of ethyl cinnamate and propionitrile in alkaline mixture. This monomer exhibits three possible tautomeric forms. The tautomeric equilibria of MOP and its copolymers with styrene in different solvents were analyzed by ¹H NMR spectroscopy. The bulk and solution radical copolymerization initiated with azobisisobutyronitrile was carried out at 60 °C. The products were characterized by ¹H NMR, ¹³C NMR, HSQC NMR, HMBC NMR, and FTIR spectroscopies. The weight‐average molecular weight and polydispersity index were analyzed with size exclusion chromatography. The monomer reactivity ratios were obtained with the Fineman‐Ross method, obtaining a value of r₁r₂ = 0.286. MOP copolymer composition as well as the nature of the solvent significantly affected the tautomeric equilibrium. Regression analysis of the copolymer composition with solvatochromic parameters showed a good linear correlation, as quantitatively expressed by means of the linear solvation energy relationship using the empirical set of Kamlet‐Taft solvent parameters. This behavior could be attributed to polymer–polymer or polymer‐solvent interactions prevalent in solvents of different polarity, which are responsible for changes in macromolecular chain conformations, as confirmed by FTIR and viscometric studies. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012