Heat capacities of solid copoly(amino acid)s

Recently heat capacities C_p of poly(amino acid)s of all naturally occurring amino acids have been determined. In a second step the heat capacities of four copoly(amino acid) s are studied in this research. Poly(L -lysine · HBr-alanine), poly(L -Lysine · HBr-phenylalanine), poly(sodium-L -glutamate-tyrosine), and poly(L -proline-glycine-proline) heat capacities are measured by differential scanning calorimetry in the temperature range 230–390 K. This is followed by an analysis using approximate group vibrations and fitting the C_p contributions of the skeletal vibrations of the corresponding homopolymers to a two-parameter Tarasov function. Good agreement is found between experiment and calculation. Predictions of heat capacities based on homopoly(amino acid)s are thus expected to be possible for all polypeptides, and enthalpies, entropies, and Gibbs functions for the solid state can be derived.     

Heat capacities of aqueous solutions of amino acid and dipeptide derivatives of fullerene

The concentration dependences of heat capacities of aqueous solutions of several amino acid and peptide derivatives of fullerene were measured by scanning differential calorimetry at 298 K. The heat capacities for the arginine, alanylalanine, and glycylvaline derivatives dissolved in water depend slightly on concentration. The concentration dependences of the heat capacities of aqueous solutions of the serine and alanine derivatives display extrema. The calculated contributions of hydration to the heat capacities of the dissolved fullerene derivatives have both positive and negative signs. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2202–2204, November, 1998.     

Microbial production of natural poly amino acid

Three kinds of poly amino acids, poly-γ-glutamic acid, poly(ε-L-lysine) and multi-L-arginyl-poly (L-aspartic acid) can be synthesized by enzymatic process independently from ribosomal protein biosynthesis pathways in microorganism. These biosynthesized polymers have attracted more and more attentions because of their unique properties and various applications. In this review, the current knowledge on the biosynthesis, biodegradations and applications of these three poly amino acids are summarized.     

Molecular modeling of polymers. 10. Characterization of conformational transitions of poly(acrylic acid) and poly(methacrylic acid) using dyad structures

The conformational profiles of nearest side-chain neighbors, methylene-dyad structures, of poly(acrylic acid), PAA, and poly(methacrylic acid), PMA, were determined as a function of tacticity, extent of ionization, and presence of counterion. The dominant backbone conformer states are quite similar for both isotactic and syndiotactic diads in a common charge state. Thus, the overall dimensional properties of isotactic syndiotactic and atactic chains of PAA or PMA, based upon dyad interactions, are predicted to be alike for a given charge state. Significant deviations from precise t, g⁺, and g^? states are found for the dyad minimum energy conformations. The rod-to-coil and coil-to-rod transitions observed in PAA and PMA, respectively, as a function of increasing counterion concentration can be explained, to a large extent, by the conformational profiles of the corresponding dyad model structures. © 1994 John Wiley & Sons, Inc.     

Asymmetric induction by helical poly(amino acid)s in cyanosilylation of aldehydes

It was first demonstrated that helical poly(amino acid)s have an ability to induce enantioselectivity in the cyanosilylation of aldehydes. The helicity of poly(amino acid)s and the N-terminal amino group were essential for the enantioinduction of the reaction.     

Miscibility of poly(ϵ-caprolactone) and of poly(styrene-co-acrylonitrile) with poly(styrene-co-acrylic acid)

The miscibility of poly (?-caprolactone) (PCL) with poly (styrene-co-acrylic acid) (SAA) and of poly (styrene-co-acrylonitrile) (SAN) with SAA was examined as a function of the comonomer composition in the copolymers. For PCL/SAA blends it was found that PCL is miscible with SAA within a specific range of copolymer compositions. Segmental interaction energy densities were evaluated by analysis of the equilibrium melting point depression and application of a binary interaction model. The results suggest that the intramolecular repulsion in SAA copolymer plays an important role in inducing the miscibility. Additionally, the critical AA content in SAA for the blend to be homogeneous was predicted by correlating the segmental interaction energy densities with the binary interaction model. For SAN/SAA blends, it was also found that SAA is miscible with SAN within a specific range of copolymer compositions. From the binary interaction model, segmental interaction energy denisties between different monomer units were estimated from the miscibility map and were found to be positive for all pairs, indicating that the miscibility of the blends is due to the strong repulsion in the SAA copolymers.     

氨基酸酯-烷基醚混合取代聚膦腈的合成与表征

聚膦腈高聚物,因其良好的生物相容性而用作生物医用材料。若在其侧链引入对热(如烷氧基醚)或对pH值敏感和可生物降解的基团(如氨基酸酯),则可得到具有环境敏感性和可生物降解性能的高聚物,这些高聚物可望作为药物载体,用于药物的控制释放。     

Synthesis and characterization of thianthrene-containing poly(benzoxazole)s

New thioether- and thianthrene-containing poly(benzoxazole)s (PBOs) were synthesized from 4,4′-thiobis[3-chlorobenzoic acid] and thianthrene-2,7- and -2,8-dicarbonyl chlorides with commercially available bis-o-aminophenols. Polymers were prepared via solution polycondensation in poly(phosphoric acid) at 90–200°C. Transparent PBO films were cast directly from polymerization mixtures or m-cresol. The films were flexible and tough. Non-fluorinated PBOs were soluble only in strong acids and AlCl₃/NO₂R systems by forming complexes with the benzoxazole heterocycle Glass transition temperatures ranged from 298–450°C, and thermogravimetric analysis showed good thermal stabilities in both air and nitrogen atmospheres. © 1995 John Wiley & Sons, Inc.     

Depurination of synthetic poly(inosinic acid) analogues

A poly(inosinic acid) analogue, poly{[1′-(β-hypoxanthine-9-yl)-5′-deoxy-D -erythro-pent-4′-enofuranose]-alt-[maleic acid]} (4), was synthesized by the alternating copolymerization of nucleoside derivative 1 with maleic anhydride and subsequent hydrolysis. N-Glycosidic bonds of the polymer were spontaneously hydrolyzed to liberate hypoxanthine from the polymer backbone in a buffer solution (pH 7.4) at room temperature. The depurination rate constant of the polymer at pH 7.4 and 37°C was measured to be 1.9 × 10⁻⁶ sec⁻¹, which was 10⁵-fold higher than that (3 × 10⁻¹¹ sec⁻¹) of the depurination of DNA that occurred in the biological systems. The increase in the depurination rate was attributable to the high potential energy of the polymer caused by the crowded environment around the bases, so that the polymer was more susceptible to the hydrolysis. Since natural nucleic acids often have compact structures with the crowded environment around the bases by the intricate chain folding, the depurination may also be accelerated in a similar manner in the biological system. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3361–3365, 1999     

Heat capacities and thermodynamic properties of chrysanthemic acid

The heat capacities of chrysanthemic acid in the temperature range from 80 to 400 K were measured with a precise automatic adiabatic calorimeter. The chrysanthemic acid sample was prepared with the purity of 0.9855 mole fraction. A solid-liquid fusion phase transition was observed in the experimental temperature range. The melting point, T _m, enthalpy and entropy of fusion, Δ_fus H _m, Δ_fus S _m, were determined to be 390.741±0.002 K, 14.51±0.13 kJ mol^-1, 37.13±0.34 J mol^-1 K^-1, respectively. The thermodynamic functions of chrysanthemic acid, H _(T)-H_(298.15), S _(T)-S_(298.15) and G _(T)-G ₍₂₉₈.₁₅₎ were reported with a temperature interval of 5 K. The TG analysis under the heating rate of 10 K min^-1 confirmed that the thermal decomposition of the sample starts at ca. 410 K and terminates at ca. 471 K. The maximum decomposition rate was obtained at 466 K. The purity of the sample was determined by a fractional melting method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Heat capacity of poly(trimethylene terephthalate)

The heat capacity of poly(trimethylene terephthalate) (PTT) has been measured using adiabatic calorimetry, standard differential scanning calorimetry (DSC), and temperature-modulated differential scanning calorimetry (TMDSC). The heat capacities of the solid and liquid states of semicrystalline PTT are reported from 5 to 570 K. The semicrystalline PTT has a glass transition temperature of 331 K. Between 340 and 480 K, PTT can show exothermic ordering depending on the prior degree of crystallization. The melting endotherm of semicrystalline samples occurs between 480 and 505 K, with a typical onset temperature of 489 K (216°C). The heat of fusion of the semicrystalline samples is about 15 kJ mol⁻¹. For 100% crystalline PTT the heat of fusion is estimated to be 30 ± 2 kJ mol⁻¹. The heat capacity of solid PTT is linked to an approximate group vibrational spectrum and the Tarasov equation is used to estimate the heat capacity contribution due to skeletal vibrations (θ₁ = 550.5 K and θ₂ = θ₃ = 51 K, N_skeletal = 19). The calculated and experimental heat capacities agree to better than ±3% between 5 and 300 K. The experimental heat capacities of liquid PTT can be expressed by: $ C^L_p(exp) $ = 211.6 + 0.434 T J K⁻¹ mol⁻¹ and compare to ±0.5% with estimates from the ATHAS data bank using contributions of other polymers with the same constituent groups. The glass transition temperature of the completely amorphous polymer is estimated to be 310–315 K with a ΔC_p of about 94 J K⁻¹ mol⁻¹. Knowing C_p of the solid, liquid, and the transition parameters, the thermodynamic functions enthalpy, entropy, and Gibbs function were obtained. With these data one can compute for semicrystalline samples crystallinity changes with temperature, mobile amorphous fractions, and resolve the question of rigid-amorphous fractions.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2499–2511, 1998     

Osmotic deswelling of weakly charged poly(acrylic acid) solutions and gels

The osmotic pressure of weakly charged aqueous poly(acrylic acid) (PAA) solutions and the swelling pressure PAA gels were studied by osmotic deswelling at different degrees of ionization (α). In solution, the osmotic pressure was found to scale linearly with concentration, whereas the scaling power of the swelling pressure of gels was higher (1.66). The effect of the ionization degree on the osmotic coefficient in PAA solutions was in agreement with the theory of Borue and Erukhimovich [Macromolecules, 21 , 3240 (1988)]. Ionization increases the swelling capacity of the PAA gels until a plateau is reached at about 35% neutralization. The concentration at equilibrium swelling scales as C_e ～ α^?0.6. The contribution of the network to the gel swelling pressure is evaluated by subtracting the osmotic pressure of the polymer solution at the same concentration and degree of ionization. In swollen gels the extended network opposes swelling. As the gel is osmotically deswelled, a state of zero network pressure exists at a certain concentration, below which the network elasticity favors swelling. The crossover concentration shifts to lower values as the degrees of ionization increases. © 1995 John Wiley & Sons, Inc.     

Structures of poly(p-hydroxybenzoic acid) (PHBA) at ambient temperature

The molecular structure of poly (p-hydroxybenzoic acid) (C₆H₄COO)_x at ambient temperature was determined by x-ray powder diffraction analysis. The diffraction pattern is explained as a mixture of two orthorhombic phases having the same space group Pbc2₁ with four C₆H₄COO chemical repeats in the unit cell and the following cell parameters: a = 7.42 Å, b = 5.70 Å, and c = 12.45 Å for phase I (ρ_calc = 1.51 g cm^?3); and a = 3.83 Å, b = 11.16 Å, and c = 12.56 Å for phase II (ρ_calc = 1.48 g cm^?3). The chain conformation is the same in both phases, involving two benzoyl rings staggered by ca. 120° along the chain. Disorder has been considered in the packing of phase I by giving equal occupancy to the two molecules oriented up or down along the c chain axis. ©1995 John Wiley & Sons, Inc.     

Synthesis of polyimide and poly(imide-benzoxazole) in polyphosphoric acid

A polyimide made from 4,4′-diaminodiphenyl ether (ODA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) was synthesized in polyphosphoric acid. Although the polymerization proceeded heterogeneously, a polyimide with an inherent viscosity of 0.90 was obtained, and a tough and flexible film was made from this polyimide. This polymerization was a one-step reaction including polycondensation and imidization; this was also confirmed by a model reaction between aniline and phthalic anhydride. Utilizing this polymerization method, 3,3′-dihydroxy-4,4′-diaminobiphenyl and 2 mol of 4-aminobenzoic acid were reacted in PPA, then BPDA was reacted to obtain an alternate copolymer containing imide and oxazole rings. This reaction gave a homogeneous solution of the poly(imide-benzoxazole). © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(itaconate ester)s with etheric side chains

The synthesis and characterization of poly(itaconate ester)s with short poly(ethylene oxide) side chains have been studied. It was found that the monomer syntheses via esterification of itaconic acid resulted in incomplete esterification leaving up to 35 mol % monomers with carboxylic acid functionality. These acid groups were then incorporated into the polymers. This acid incorporation has not previously been reported, nor have the properties of the copolymers been studied. Techniques were developed to effectively remove the acid impurities to generate pure homopolymers. Titration and gas chromatographic techniques were developed to study the amount of acid impurity in the monomers, and titration was also used to characterize the polymers. Size exclusion chromatography and differential scanning calorimetry were used to study both the homopolymers and copolymers. It was found that the location and breadth of the glass transition is a function of acid content. Finally, isomerization of the itaconate monomers to the inactive mesaconate was also found to be a problem during the synthesis. Pure mesaconate and citraconate monomers were synthesized and characterized by ¹H-NMR. © 1993 John Wiley & Sons, Inc.     

Reaction of amino acid derivatives with C_(60)

Ammo acid derivatives react with C60 at 110-120℃to form adduct compounds.The products were isolated by column chromatography and were identified by FD-MS,UV-Vis,FT-IR and 13C NMR spectroscopies.     

Synthesis and characterization of poly(ether naphthalimide)s

A series of new poly(ether imide)s containing the naphthalimide moiety were prepared from bis(4-fluorobenzoyl)naphthalimides and several bisphenols by aromatic nucleophilic displacement polymerization. These polyimides had inherent viscosities in the range of 0.31–1.04 dL/g in chloroform and glass transition temperatures of 283.0–341.6°C by differential scanning calorimetry. The onset temperature for 5% weight loss for all the polymers was over 448°C, as assessed by thermogravimetry at a heating rate 10°C/min in nitrogen. In addition, these novel polyimides exhibited good solubility in organic solvents including N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, 1,1,2,2-tetrachloroethane and chloroform. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3227–3231, 1999     

Heat capacity and phonon dispersion in poly(L-methionine)

Poly(L -methionine) (PMet) is one of the two sulfur containing polyamino acids. Raman, FTIR spectra, and heat capacity measurements of PMet have been well interpreted through the normal mode analysis and the density of states derived therefrom. Earlier interpretation of heat capacity data is limited because it is based on the Tarasov model, wherein the concept of group frequency and skeletal similarity are used. A special feature of some dispersion curves is their tendency to bunch in the neighborhood of the helix angle. This has been attributed to the presence of strong intramolecular interactions. Repulsion between the dispersion curves is also observed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2281–2292, 1997     

Poly(arylene ether)s,poly(arylene thioether)s,and poly(arylene sulfone)s derived from a dihydroxy(imidoarylene) monomer

Novel poly(arylene ether)s, poly(arylene thioether)s, and poly(arylene sulfone)s were synthesized from the dihydroxy(imidoarylene) monomer 1 . The syntheses of poly(arylene ether)s were carried out in DMAc in the presence of anhydrous K₂CO₃ by a nucleophilic substitution reaction between the bisphenol and activated difluoro compounds. Poly(arylene thioether)s were synthesized according to the recently discovered one-pot polymerization reaction between a bis(N,N′-dimethyl-S-carbamate) and activated difluoro compounds in the presence of a mixture of Cs₂CO₃ and CaCO₃. The bis(N,N′-dimethyl-S-carbamate) 3 was synthesized by the thermal rearrangement reaction of bis(N,N′-dimethylthiocarbamate) 2 , which was synthesized from 1 by a phase-transfer catalyzed reaction. The poly(arylene thioether)s were further oxidized to form poly(arylene sulfone)s, which would be very difficult, if not impossible, to synthesize by other methods. All of the polymers described have extremely high T_gs and thermal stability as determined from DSC and TGA analysis. Poly(arylene sulfone)s have the highest T_gs and they are in the range of 298–361°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1201–1208, 1998