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The polydiacetylene (PDA) from the bis-n-propylurethane of 5,7-dodecadiyne-1,12-diol (PUDO) undergoes a first order phase transition near 135°C that is associated with a color change from blue at temperatures below the transition to red at temperatures above the transition. We have studied PDA-PUDO by solid state 13C nuclear magnetic resonance (NMR) spectra using cross polarization and magic angle spinning (CP-MAS) techniques at temperatures between 25° and 140°C. As observed previously, the acetylene carbon shift moves up field as the temperature is raised above the transition temperature. In addition, near 130°C, the oxymethylene carbon shows 3 resonances, indicating multiple side chain conformations as the PDA undergoes the phase transition.

Antioxidants are used to protect organic materials from degradation during exposure to heat and/or light in the presence of oxygen. Novel macromolecular antioxidants have been developed which provide superior resistance to oxidative degradation to plastics, lubricants, and cooking oils vs. state‐of‐the‐art commercial antioxidants.

The conformations of azobenzene‐modified poly(α‐L‐glutamate)s (AZOPLGA) with a different degree of functionalization were examined by solid state 13C NMR. The polymer main chain conformations in AZOPLGA powders (precipitated from reaction system) changes from α‐helix to β‐sheet when the degree of functionalization increases from 12% to 56%. In addition, the solvent used for fabricating films plays an important role in organizing AZOPLGA backbones into characteristic conformation. For AZOPLGA56 (AZOPLGA with 56% of functionalization) cast films, the polymer backbones can assume conformations ranging from order state (β‐sheet) to random coil by changing the solvent for fabrication. In contrast, the effect of solvent on the conformation of AZOPLGA23 (AZOPLGA with 23% of functionalization) is not so significant. When compared with AZOPLGA23 powder (precipitated from reaction system), the helical conformation increases for AZOPLGA23 film cast from TFA. However, the fractions of α‐helix and β‐sheet con...

The chiral conducting polyaniline (PANI) nanocomposites [polyacrylic acid/polyaniline/(−) camphorsulphonic acid (CSA)] were synthesized using enzyme, horseradish peroxidase (HRP) in the aqueous buffer solution at pH 4.3. It appears that the enzyme HRP apart being a biocatalyst, plays an important role during the polymerization, which allows PANI to prefer a specific helical conformation whether the induced chirality in the monomer‐CSA complex is either by (+)CSA or (−)CSA. In this paper, we report, the structural characterization of these nanocomposites by solid‐state 13C cross‐polarization with magic angle spinning (CP/MAS) NMR techniques. The structural features of PANI in the conducting form of nanocomposite (as‐synthesized) are similar to that of enzymatically and chemically synthesized PANI. Preliminary data also suggest that some portion of nanocomposite samples are not completely doped. Dedoping of as‐synthesized PANI nanocomposite with aqueous NH4OH shows the spectral features that of the...

The effect of temperature on the concentration of the major reactive species as a function of H2O2 addition in the enzymatic polymerization of 4‐propylphenol was investigated using in situ 1H‐NMR spectroscopy. We have studied the trend of monomer depletion and the formation of predominant dimers with an incremental addition of H2O2 at different temperatures. The trends for depletion of monomer are very similar while the trends for the dimers display dramatic differences at the investigated temperatures. The dynamic equilibrium stage of dimers was observed only in the case of low reaction temperature. The comparison of the in situ spectra recorded at different reaction temperatures suggests that less undesired side reactions occurred at low temperature. #Dedicated to the memory of Professor Sukant K. Tripathy.

A new cellulose based fluorescent polymer has been successfully synthesized by esterificaction of 1‐pyrenebutyric acid and cellulose. This polymer was characterized by solid state 13C cross‐polarization/magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), ultra‐violet‐visible (UV‐VIS) and fluorescence spectroscopic techniques. Spectroscopic results show that the pyrene chromophores have been covalently linked to cellulose. The quenching of fluorescence of by dinitrotoluene (DNT) follows the Stern–Volmer relationship. This suggests the potential use of this polymer in sensor and other applications. #Dedicated to the memory of Professor Sukant K. Tripathy.

Polyanilines (PANI) were synthesized from peroxidase-catalyzed polymerization of aniline with and without the presence of a template in the aqueous buffer solution of pH 4.3. The template used was poly(vinylphosphonic acid) (PVP). Solid-state 13C and 15N CP/MAS NMR techniques were applied to characterize the structure of polyaniline in its self-doped conducting, dedoped base, and redoped conducting form of PANI. The charge distribution along the polymer backbone in the protonated form of the polyaniline is also discussed. The structural features exhibited by a template assisted enzymatically synthesized PANI is the result of linear 1,4-coupling of aniline moiety while the PANI synthesized in the absence of template contains both 1,2- and 1,4-coupled products. Solid-state NMR studies on the enzymatically-synthesized polyaniline with the aid of template (PANI-PVP) confirmed the formation of a linear polymer chain containing alternate benzenoid-quinoid repeat units. The dedoped form is in the emeral...

Porcine pancreatic lipase pre-incubated with phenyl methyl ketone in THF fails to recognize the ortho- and para-acetoxy functions with respect to the nuclear carbonyl group towards deacetylation reaction on 2,4-diacetoxyphenyl methyl ketones; this result is in conformity with our hypothesis on the mechanism of action of PPL in THF. Further, four racemic 2,4-diacetoxyphenyl alkyl ketones, the precursors for the synthesis of analogs of a potent antifungal coumarin, 7-acetoxy-4-(1-ethyl)pentyl-3-phenyl-2H-1-benzopyran-2-one, have been synthesized by Nencki's reaction between resorcinol and corresponding (±)-aliphatic acid, followed by acetylation of the resulting (±)-2,4-dihydroxyphenyl alkyl ketones. Porcine pancreatic lipase has been used successfully for regio- and enantioselective deacetylation of these diacetoxyphenyl alkyl ketones in tetrahydrofuran.

Surface relief gratings (SRG) on films of azobenzene–modified cellulose (azocellulose) with ultrahigh molecular weight were holographically recorded in a single step. Surface modulation depth of the SRGs increased with the degree of substitution (DS) of the azobenzene chromophores in the cellulose as well as with the grating spacing. Large surface modulations over 500 nm on all samples were obtained with a grating spacing of 4 μm. A linear increase of photoinduced birefringence with the azobenzene chromophore concentration in these photodynamic polymers was also observed. The maximum birefringence of 0.11 was achieved for an azocellulose polymer with a DS of 0.99. †Deceased.

Template guided enzymatic synthesis of conducting polyaniline (PANI) is a one-step reaction and more importantly, it is an environmentally friendly process. Understanding of the reaction and coupling mechanism at the molecular level is of paramount significance to improve its processability and conductivity. Solid-state NMR techniques are useful to investigate molecular structures of enzymatically synthesized polyaniline (PANI). The PANI sample in three different forms i.e., (a) as-synthesized, self-doped conducting form; (b) dedoped, base form and; (c) redoped, conducting form, are investigated by solid-state 13C and 15N CP/MAS NMR techniques. Solid-state NMR data analysis shows that the structural features of enzymatically synthesized PANI are similar to that of chemically synthesized PANI. The solid-state 13C CP/MAS NMR spectrum of the base form of PANI confirmed that benzenoid-quinoid repeating units are present in the backbone of the PANI polymer chain. The poly(vinylphosphonic acid) (PVP) template p...

A solution processible thiophene polymer with a hydrogen-bond-forming urethane group in the side chain, viz., poly[2-(3-thienyl)ethanol n-butoxycarbonylmethylurethane] (PURET), has been synthesized. The polymer is soluble in a wide variety of solvents such as chloroform, dimethylsulfoxide, N-methylpyrrolidone, and trifluoroacetic acid among others. Optical quality thick films are obtained by solution casting. The presence of extensive hydrogen bonding is established with the help of temperature-dependent infrared spectroscopy. NMR spectroscopic study indicates the presence of about 33% regio-isomeric defects in the polymer. The polymer forms yellow-colored solutions (λmax = 430 nm) in most of the organic solvents, while in trifluoroacetic acid the polymer is oxidized and exhibits an additional band with an absorption maximum at around 780 nm. The conductivity of the polymer is in the order of 1 S/cm.