Isothermal and nonisothermal cold crystallization kinetics of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide)/functionalized eggshell powder composites

Functionalized eggshell powder (NES) with nucleating surface of calcium phenylphosphonic acid (PPCa) for poly(l-lactide) (PLLA) was compounded with PLLA via melt blending to improve the cold crystallization process of PLLA. The cold crystallization behavior of the PLLA/NES composites was studied by differential scanning calorimetry. The isothermal cold crystallization rates have been enhanced obviously in the PLLA/NES composites than in the neat PLLA, indicative of the excellent nucleating effects of NES on PLLA. For the nonisothermal cold crystallization, the overall crystallization rate of PLLA increased with both increasing NES loadings and heating rate. It was found that the Avrami equation and the combined Ozawa–Avrami model could describe the experiment data successfully.     

Novel terpolymers of poly(<Emphasis Type="Italic">p</Emphasis>-dioxanone-<Emphasis Type="Italic">co</Emphasis>-trimethylene carbonate-<Emphasis Type="Italic">co</Emphasis>-L-phenylalanine): Synthesis,characterization, thermal properties and copolymerization mechanism

In order to exploit the biological functions of materials, a series of new random terpolymers were synthesized by the ring-opening polymerization of p-dioxanone, trimethylene carbonate, and L-phenylalanine N-carboxyanhydride (L-Phe- NCA) in the presence of stannous octoate. The terpolymers were characterized by ¹H-NMR, ¹³C-NMR, FTIR, and gel permeation chromatography. The effects of the reactant ratio, catalyst dosage, reaction temperature and time on the copolymerization were investigated, and were found to regulate the composition of the terpolymer. Increases in the reaction temperature, polymerization time, L-Phe-NCA monomer amount, and catalyst content generated a product with a slightly decreased molecular weight. The crystallinity of the terpolymer was investigated by differential scanning calorimetry and polarized optical microscopy. A reasonable mechanism for the polymerization was proposed based on the obtained results.     

Biodegradable poly(butylene succinate-<Emphasis Type="Italic">co</Emphasis>-butylene dimerized fatty acid)s: Synthesis,crystallization, mechanical properties,and rheology

Poly(butylene succinate-co-butylene dimerized fatty acid) (P(BS-co-BDFA)) copolyesters were synthesized from succinic acid (SA) and dimerized fatty acid (DFA) with 1,4-butanediol (BDO) through a two-step process of esterification and polycondensation. The polyester compositions and physical properties of copolyesters were investigated by GPC, ¹H NMR and ¹³C NMR, DSC, WAXD, DMA, TGA, tensile and rheology test. The melting temperature (T_m), and crystallization temperature (T_c) decreased gradually as the content of DFA monomer increased. P(BS-co-BDFA) copolyesters showed the same crystal structure as the PBS homopolyester. Besides, TGA results indicated that P(BS-co-BDFA)s were of higher thermal stabilities. Moreover, it was found that the synthesized P(BS-co-BDFA)s showed the maximum elongation at break (591%) as the DFA contents were 10 mol%. Rheology analysis indicated that the viscoelastic behavior of the polyesters greatly depended on the molecular weight of polyesters.     

Synthesis and properties of organic-inorganic hybrid P(NIPAM-<Emphasis Type="Italic">co</Emphasis>-AM-<Emphasis Type="Italic">co</Emphasis>-TMSPMA) microgels

Utilizing the hydrolysis and condensation of the methoxysilyl moieties, organic-inorganic hybrid poly(N-isopropylacrylamide-co-acrylamide-co-3-(trimethoxysilyl)propylmethacrylate) P(NIPAM-co-AM-co-TMSPMA) microgels were prepared via two different methods. The first method was that the microgels were post-fabricated from the crosslinkable linear P(NIPAM-co-AM-co-TMSPMA) terpolymer aqueous solutions above the lower critical solution temperature (LCST) of the terpolymer. For the second method, the microgels were directly synthesized by conventional surfactant free emulsion copolymerization of NIPAM, AM, and TMSPMA. The hydrodynamic diameter and stability of the resultant P(NIPAM-co-AM-co-TMSPMA) microgels strongly depend on the pH and temperature of the microgel aqueous solution. The hydrodynamic diameters of the microgels decreased with increasing the measuring temperature. The phase transition temperature of the microgels was found to be around 34°C, which was independent of the initial terpolymer concentration and shifted to lower temperature with increasing the preparation temperature. Increasing the initial amount of AM will enhance the instability of the microgels at high pH values. Moreover, the P(NIPAM-co-AM-co-TMSPMA) microgels obtained from the linear terpolymer had more homogeneous microstructures as compared with the corresponding NIPAM/AM/TMSPMA microgels prepared by one step emulsion copolymerization as revealed by light scattering measurements.     

Preparation,characterization and morphological study of poly(<Emphasis Type="Italic">m</Emphasis>-toluidine-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">m</Emphasis>-aminoacetophenone) conductive copolymer

A new series of copolymers of poly(m-toluidine-co-m-aminoacetophenone) were synthesized by the chemical oxidative method in acid medium. The copolymers were characterized by UV–Vis and FTIR spectroscopy. X-ray diffraction analysis revealed the partial crystalline nature of copolymer. The morphological study by SEM analysis indicated that the surface of the copolymer had the granular structure of agglomerated morphology with average particle size of 200 nm. The conductivity of the copolymers ranged from 2 × 10^–4 to 3.3 × 10^–8 S/cm and the conductivity decreased with the increase of comonomer concentration. The resultant copolymers showed an enhanced solubility and an improved processability when compared with pure polyaniline.     

Molecular properties of the copolymers of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride and maleic acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.     

In situ oxidative copolymerization and characterization of new poly(benzidine-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">o</Emphasis>-phenylenediamine)/kaolinite microcomposites

Copolymers of benzidine and o-phenylenediamine/kaolinite clay composites with different percentages of kaolinite clay particles were synthesized via in situ oxidative copolymerization. The spectral characteristics upon incorporation of o-phenylenediamine units into the polybenzidine backbone in presence of kaolinite clay were investigated by means of UV–Vis and FTIR spectroscopy. The copolymer in the absence and in the presence of kaolinite clay was studied by thermal gravimetric analysis under non-oxidative conditions. The morphology of the copolymer kaolinite composites system was investigated by the scanning electron microscopy.     

Solvent dependent swelling behaviour of poly(<Emphasis Type="Italic">N</Emphasis>-vinylcaprolactam) and poly(<Emphasis Type="Italic">N</Emphasis>-vinylcaprolactam-<Emphasis Type="Italic">co</Emphasis>-itaconic acid) gels and determination of solubility parameters

Swelling behaviour of poly(N-vinylcaprolactam) (PVC) and poly(N-vinylcaprolactam-co-itaconic acid) (P(VC-co-IA)) gels was investigated in different solvents (water, ethanol, methanol, isopropyl alcohol (IPA), chloroform, toluene, acetone) and in binary solvent mixtures (ethanol/chloroform, ethanol/methanol, IPA/chloroform, ethanol/water, IPA/water). Gels were synthesised in ethanol by the free radical cross-linking polymerisation method at 60°C for 24 h in the presence of azo-bis(isobutyronitrile) and allyl methacrylate as the initiator and cross-linker, respectively. And also, ethanol/distilled water mixture (?_r = 4:1) was used as the synthesis medium to determine its effect on the swelling of gels. It was found that the presence of water in the synthesis medium significantly affected the equilibrium swelling value (ESV) and the swelling tendency of gels both in solvents and in solvent mixtures. All gels synthesised in ethanol showed the highest swelling in chloroform. The gels synthesised in the ethanol/water mixture displayed different swelling behaviour. In this case, while chloroform was still valid for maximum swelling of PVC, P(VC-co-IA) had the highest swelling in methanol. Solubility parameters of gels were predicted by the van Krevelen-Hoftyzer (VKH) and Hoy methods (group contribution methods) and theoretical calculations verified the experimental swelling order.     

The influence of the synthesis pressure on the chromatographic properties of poly(divinylbenzene-<Emphasis Type="Italic">co</Emphasis>-ethylvinylbenzene-<Emphasis Type="Italic">co</Emphasis>-2-hydroxyethyl methacrylate) monolithic columns

Monolithic columns based on copolymer of divinylbenzene (DVB), ethylvinylbenzene (EVB), and 2-hydroxyethyl methacrylate (HEMA) were prepared and applied to the separation of low-molecular-weight aromatic compounds. The monoliths were synthesized via thermally initiated free-radical polymerization in confines of stainless steel tubes with dimensions of 100 × 4.3 mm. In order to compensate for the polymer shrinkage during the synthesis and prevent the monolith from detachment from the column wall, the polymerization was conducted under nitrogen pressure. The excess pressure was varied from 0 bar to 9 bar. The synthesis under pressure was shown to improve the peak shapes and column efficiency in comparison with the synthesis in the closed tube. The optimum pressure for poly(DVB-co-EVB-co-HEMA) monoliths was found to be 3 bar. The efficiency of the column obtained at 3 bar is 13 500 TP/m for propylbenzene (k′ = 6) and 38 300 TP/m for uracil (k′ = 0).     

Synthesis,characterisation, and electrical properties of novel nanostructured conducting poly(aniline-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">m</Emphasis>-chloroaniline) with incorporated silver particles

Novel copolymers of poly(aniline-co-m-chloroaniline)-doped dodecylbenzenesulphonic acid (DBSA) with embedded silver nanoparticles were synthesised using the in situ chemical oxidative method. The structural properties of the copolymers were characterised using the UV-VIS and FTIR spectroscopic methods. The crystalline nature of the copolymer was demonstrated by way of the X-ray diffraction (XRD) pattern. Scanning electron microscopy (SEM) revealed the presence of particle agglomerates measuring 50 nm to 100 nm on the surface of the nanocomposites. The electrical conductivity of the copolymer was dependent on the monomer composition and was found to be in the range of 10^?2 S cm^?1 to 10^?6 S cm^?1 with an increasing chloroaniline content and exhibiting improved solubility.     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Preparation and polymerization mechanism of dihydroxy-capped PCL,poly(CL-<Emphasis Type="Italic">b</Emphasis>-PEG-<Emphasis Type="Italic">b</Emphasis>-CL) and poly(DTC-<Emphasis Type="Italic">b</Emphasis>-CL-<Emphasis Type="Italic">b</Emphasis>-DTC)

The ring opening polymerization of ε-caprolactone (CL) was initiated by glycol and yttrium tri(2,6-di-tert-butyl-4-methylphenolate)s (Y(OAr)₃), preparing dihydroxy-capped poly (ε-caprolactone) (PCL) with controllable molecular weight. ¹H NMR and SEC analyses indicate that two kinds of active species and corresponding PCL with different structures exist in the system. Increasing the ratio of glycol to Y(OAr)₃ benefits the formation of monofunctional active species. However, poly(ethylene glycol) (PEG)/Y(OAr)₃ system only contains sole bifunctional active species to synthesize copolymer of CL with PEG (poly(CL-b-PEG-b-CL)). Dihydroxycapped PCL as macroinitiator can further initiate the polymerization of 2,2-dimethyltrimethylene carbonate (DTC). Thus, triblock copolymer of CL with DTC (poly(DTC-b-CL-b-DTC)) has been prepared.     

Mono-<Emphasis Type="Italic">meso</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylporphyrin

Summary. Treatment of meso-tetra(tert-butyl)porphyrin with sulfuric acid/n-butanol affords a mixture of porphyrin and mono-tert-butylporphyrin in relatively high yield.     

Film Composites of polyimide with polyaniline and poly(aniline-<Emphasis Type="Italic">co</Emphasis>-anthranilic acid)

New two-component composite polymer films are prepared and studied in terms of thermal stability and stress-strain properties. The matrix component of the composite is polyimide based on 3,3′,4,4′-(1,3-diphenoxybenzene)tetracarboxylic dianhydride and 4,4′-bis(4″-aminophenoxy)diphenyl sulfone. Another component is polyaniline or the copolymer poly(aniline-co-2-aminobenzoic acid). Composite films are cast from mixed solutions of individual polymers in N-methyl-2-pyrrolidone. Interpolymer interactions in polyimide composites with polyaniline or the copolymer of aniline and 2-aminobenzoic acid are investigated via viscometry and IR spectroscopy. The thermal treatment of composite films with poly(aniline-co-2-aminobenzoic acid) results in decarboxylation of the copolymer and formation of polyimide-polyaniline composite films. The morphology, microphase structure, and porosity of the composite films are different from those of the films cast from solutions of polyimide-polyaniline mixtures.     

Thermal analysis characterization of PAAm-<Emphasis Type="Italic">co</Emphasis>-MC hydrogels

This paper reports the thermal characterization of polyacrylamide-co-methylcellulose hydrogels and the constituent monomers (acrylamide and methylcellulose). Polymeric materials can be used to produce hydrogels, which can be natural, synthetic, or a mixture. The hydrogels described here were obtained by free radical polymerization, in the presence of N,N′-methylene-bis-acrylamide as a cross-linker agent. Four acrylamide concentrations were used for the synthesis of hydrogels: 3.6, 7.2, 14.7, and 21.7% (w/v). The materials so obtained were analyzed by TG, DTG, DSC, and FT-IR. The TG curves of acrylamide and methylcellulose showed three mass loss events. In DSC curves, the acrylamide exhibited one melting peak at 84.5 °C, and methylcellulose indicated one exothermic event. Nevertheless, acrylamide was considered more stable than methylcellulose. The TG curves of the hydrogels exhibited three mass loss events, and on the DSC curves, three endothermic events were observed. It was verified that the different acrylamide proportions influenced the thermic behavior of hydrogels, and that the authors considered the 7.2% hydrogel a promising drug carrier system. The absorption bands were well defined, confirming the presence of the functional groups in the samples.     

New flavonoid-<Emphasis Type="Italic">C</Emphasis>-glycosides from <Emphasis Type="Italic">Triticum aestivum</Emphasis>

Two new flavonoid-C-glycosides named triticuside A (1a) and triticuside B (1b) were isolated from bran of Triticum aestivum L. The structures of the two new compounds were elucidated by spectral techniques including ¹H NMR, ¹³C NMR as well as HSQC, HMBC, and COSY. Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 135–137, March–April, 2008.     

Hydrogels of starch-g-(<Emphasis Type="Italic">tert</Emphasis>-butylacrylate) and starch-g-(<Emphasis Type="Italic">n</Emphasis>-butylacrylate) copolymers

The synthesis, characterization, and hydrogel properties of starch-g-(tert-butylacrylate) and starch-g-(n-butylacrylate) copolymers were studied. The optimum conditions for the grafting process of tert-butylacrylate into 1.0 g of starch were as follows: [tert-butylacrylate] = 0.04 mol/L, [CAN] = 9.0 × 10⁻⁴ mol/L, temperature = 20 °C in 100 mL solution, whereas the results using n-butylacrylate monomer were as follows: [n-butylacrylate] = 0.04 mol/L, [CAN] = 4.0 × 10⁻³ mol/L, temperature = 30 °C in 100 mL solution. The grafting evidences of monomers into starch were done through TG and its derivative DTG for thermal changes and mass losses, scanning electron microscope (SEM) for morphological changes, powder X-ray for crystallinity measurements and FTIR for functional group changes. Acid hydrolysis method was used efficiently to allow the calculations of the viscosity average molecular weight (M _v) of the grafted chains on starch and consequently the real percent of grafting efficiency (i.e. %GY). The capability of starch-g-(n-BAC) hydrogel to absorb water were found 10 times more than starch-g-(tert-BAC) hydrogel, which were clarified through the X-ray and SEM results.     

Molecular orientation and optical anisotropy in drawn films of cellulose diacetate-<Emphasis Type="Italic">graft</Emphasis>-PLLA: comparative investigation with poly(vinyl acetate-<Emphasis Type="Italic">co</Emphasis>-vinyl alcohol)-<Emphasis Type="Italic">graft</Emphasis>-PLLA

Cellulose diacetate-graft-poly(L-lactide) (CDA-g-PLLA) and poly(vinyl acetate-co-vinyl alcohol)-graft-PLLA (P(VAc-co-VOH)-g-PLLA) were synthesized over a range of compositions, by ring-opening copolymerization of L-lactide at the original hydroxyl positions of the respective trunk polymers, CDA (acetyl DS = 2.15) and P(VAc-co-VOH)-g-PLLA (VAc = 64.2 mol%). All the products of both graft copolymer series were non-crystallizable and their solution-cast films showed no domain segregation of the two components that constituted the trunk and side-chains. A comparative study on the molecular orientation and optical anisotropy induced by uniaxial stretching of film samples was undertaken for the two copolymer series with various side-chain lengths. Overall behaviour of the orientation was estimated from the statistical second (<cos² ω>) and fourth (<cos⁴ ω>) moments obtained by a fluorescence polarization method using a rod-like probe of ~2.5 nm. Upon stretching, any film of both series imparted a positive orientation function, i.e., f = (3 <cos² ω> − 1)/2 > 0, which increased with the extent of deformation. The degree of molecular orientation was higher in the CDA-graft series with a semi-rigid trunk, and, in both series, it declined monotonically with increasing content of the PLLA side-chain. With regard to the optical anisotropy, CDA-g-PLLA films always exhibited a positive birefringence (Δn > 0) upon stretching, while drawn films of P(VAc-co-VOH)-g-PLLA displayed a negative one. This contrast in polarity reflects a difference in the intrinsic birefringence between the two trunk polymers. Of interest was the finding of a discontinuous change in Δn value with copolymer composition (PLLA content) for the respective graft series, when compared at a given stage of elongation of the films. Discussion took into consideration the locally different orientation manners of the attached PLLA chain segments.     

Conformations and properties of <Emphasis Type="Italic">O</Emphasis>-Alkyl-<Emphasis Type="Italic">S</Emphasis>-(2-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH₃P(O)(OR)(SCH₂CH₂NR ₂ ^′ ), where (I) R = i-C₄H₉, R′ = C₂H₅ and (II) R = C₂H₅, R′ = i-C₃H₇, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.