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.     

Secondary self-assembly behaviors of PEO-<Emphasis Type="Italic">b</Emphasis>-P<Emphasis Type="Italic">t</Emphasis>BA-<Emphasis Type="Italic">b</Emphasis>-PS triblock terpolymers in solution

A series of PEO₄₅-b-PtBA₅₃-b-PS _x (x = 42, 84, 165) triblock terpolymers were synthesized by the atom transfer radical polymerization and characterized by size exclusion chromatography and ¹H NMR. Their self-assemblies were conducted by a two-step hierarchical self-assembly method and a one-step dialysis method and the self-assembly behaviors were investigated. The morphologies, sizes, and size distributions of micelles produced by the self-assembly were determined by transmission electron microscopy and dynamic light scattering. The secondary self-assembled structure of PEO₄₅-b-PtBA₅₃-b-PS _x obtained by the two-step hierarchical self-assembly could be controlled by tuning the length of PS block, the core forming block. The micelles were uniform with diameters of 20–25 nm and their size distributions, except for that of PEO₄₅-b-PtBA₅₃-b-PS₁₆₅, were narrow with particle size distribution indexes ranging from 0.014 to 0.246. The one-step dialysis of the triblock terpolymers produced vesicular micelles with distinct vesicle walls that exhibited similar thicknesses. The vesicles did not show significant aggregation. The size distribution of PEO₄₅-b-PtBA₅₃-b-PS₄₂ vesicle was the narrowest with a particle size distribution index value of 0.135. The PEO₄₅-b-PtBA₅₃-b-PS₁₆₅ vesicles tended to overlap with each other.     

Synthesis of amphiphilic diblock copolymers poly[2-(<Emphasis Type="Italic">N</Emphasis>, <Emphasis Type="Italic">N</Emphasis>-dimethylamino)ethyl methacrylate]-<Emphasis Type="Italic">b</Emphasis>-poly(stearyl methacrylate) and their self-assembly in mixed solvent

Amphiphilic diblock copolymers consisting of 2-(N, N-dimethylamino)ethyl methacrylate (DMAEMA, abbreviated as DMA) and stearyl methacrylate (SMA) with different degrees of polymerization and compositions were prepared by reversible addition–fragmentation chain transfer (RAFT) copolymerization. The composition and chemical structures of (co)polymers were confirmed by the measurements of ¹H NMR spectroscopy and gel permeation chromatography (GPC). The self-aggregating structures of amphiphilic diblock copolymers with the concentration of 0.1~0.3 wt.% in THF/water mixed solvent was investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). It was found that both the morphologies and aggregating particle size resulted from the amphiphilic diblock copolymers depended on the variation of pH values, the lengths of the hydrophobic PSMA chains, and the weight ratio of THF/water mixed solvent.     

Synthesis and characterization of thermoresponsive poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-co-<Emphasis Type="Italic">N</Emphasis>-hydroxymethylacrylamide-co-2-hydroxyethyl methacrylate) hydrogels

Thermoresponsive hydrogels based on N-isopropylacrylamide, N-hydroxymethylacrylamide, and 2-hydroxyethyl methacrylate, poly(NIPAM–co-NHMAAm–co-HEMA), have been synthesized and their swelling—deswelling behavior studied as a function of NIPAM concentration, NIPAM/NHMAAm and NIPAM/HEMA mole ratio, and total monomer concentration. Copolymers varying in composition have been obtained by redox copolymerization of these three monomers. Temperature has been changed in the ranges from 4 to 70 °C at fixed pH and total ionic strength. Equilibrium swelling ratio, dynamic swelling ratio, and dynamic deswelling ratio were evaluated for all hydrogel systems. The equilibrium swelling ratios of the copolymeric gels decrease with increasing NHMAAm and HEMA content. The formation of the intermolecular hydrogen bonding between hydroxyl and amido groups decreases the hydrophilic group numbers of the gel and the affinity of the gel towards water decreases. The copolymer gels also showed rapid volume transitions with time. The time required for equilibrium shrinking increased with increasing NHMAAm and HEMA content in the gel.     

Synthesis of oxo derivatives of <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">p</Emphasis>-tolysulfonyl)hexahydrocycloalka[<Emphasis Type="Italic">b</Emphasis>]indoles

Hydroxymercuration-demercuration of N-p-tolysulfonyl-4,4a,9,9a-tetrahydro-3H-carbazoles and N-p-tolyl(or methyl)sulfonyl-1,3a,4,8b-tetrahydrocyclopenta[b]indoles leads to the formation of the corresponding N-p-tolylsulfonyl-2,3,4,4a,9,9a-hexahydro-1H-carbazol-2-ols and N-p-tolyl(or methyl)sulfonyl-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indol-2-ols. The latter are oxidized to 2-oxo derivatives with potassium dichromate. The oxidation of 2-methoxy-8-methyl-N-p-tolylsulfonyl-2,3,4,4a,9,9a-hexahydro-1H-carbazol-1-ol under analogous conditions gives 2-methoxy-8-methyl-N-p-tolysulfonyl-2,3,4,4a,9,9a-hexahydro-1H-carbazol-1-one.     

Magnolol entrapped ultra-fine fibrous mats electrospun from poly(ethylene glycol)-<Emphasis Type="Italic">b</Emphasis>-poly(L-lactide) and <Emphasis Type="Italic">in vitro</Emphasis> release

Ultra-fine fibrous mats with magnolol entrapped have been prepared by electrospinning biodegradable copolymer poly(ethylene glycol) blocked poly(L-lactide). Drug entrapment was perfect which was confirmed by scanning electron microscopy and differential scanning calorimetry. According to in vitro drug release investigation by high performance liquid chromatography, it was found that fibers with 10%, 20% and 30% drug entrapped respect to polymer (mass ratio) presented dramatically different drug release behavior and degradation behavior under the effect of proteinase K. The reason may be that fibers with 10% drug entrapped was more easily affected by enzyme while, to some degree, magnolol in fibers with 20% and 30% entrapped prevented polymer from being degraded by enzyme.     

Effect of Halogen Chain End Fidelity on the Synthesis of Poly(methyl methacrylate-<Emphasis Type="Italic">b</Emphasis>-styrene) by ATRP

Poly(methyl methacrylate-b-styrene) (PMMA-b-PS) block copolymers are synthesized by two consecutive ATRPs and fractionated into four fractions. The halogen chain end fidelity (CEF) in PMMA-b-PS is quantified based on the analysis of each fraction. Compared to ethyl 2-phenyl-2-bromoacetate/CuBr/2,2′-bipyridine (EPBA/CuBr/bpy) and CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine (CuBr/PMDETA) catalysts, PMMA-b-PS synthesized using p-toluenesulfonyl chloride/CuCl/bpy (TsCl/CuCl/bpy) and CuCl/PMDETA catalysts has a higher halogen CEF and a better control on molecular weight.     

Synthesis of (<Emphasis Type="Italic">E</Emphasis>)-<Emphasis Type="Italic">N</Emphasis>-(3-alkoxy-4-acyloxyphenylmethylene)-<Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">e</Emphasis>-cyclohexyl)amines

Previously unknown E isomers of azomethines (Schiff bases) were synthesized from vanillal and vanillin esters by their reaction with cyclohexylamine.     

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.     

RAFT polymerization of linear ABC triblock copolymer P<Emphasis Type="Italic">t</Emphasis>BA-<Emphasis Type="Italic">b</Emphasis>-PS-<Emphasis Type="Italic">b</Emphasis>-P2VP and regulation of its hierarchical self-assembly structure in solution

Linear ABC triblock copolymer PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ was successfully synthesized by RAFT polymerization. Block copolymer micelles were prepared by the two-step hierarchical self-assembly process. Size exclusion chromatography and ¹H NMR were used to characterize the structure of samples. Morphologies and size of micelles were determined by transmission electron microscope. The results showed that the densely dispersed spherical micelles of PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ were obtained in the first step of the hierarchical self-assembly process. In the second step, core-compartmentalized micelle strings with different lengths and distribution densities were obtained when the primary self-assembled solution was dialyzed in distilled water with pH ≈ 3. When distilled water with pH ≈ 3 was added drop-wise to this solution, uniformly dispersed spherical core-compartmentalized micelles of PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ were prepared. Thus, hierarchical self-assembly structure of linear ABC triblock copolymer was obtained successfully and the preparation of uniformly dispersed spherical micelles of triblock copolymers was realized simply by changing the secondary self-assembly methods.     

Effects of ionization on the phase behavior of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-co-acrylic acid) and poly(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diethylacrylamide-co-acrylic acid) in water

Phase transitions of poly(N-isopropylacrylamide-co-acrylic acid) (PiPA-AA) and poly(N,N- diethylacrylamide-co-acrylic acid) (PdEA-AA) in water have been investigated by means of turbidimetry, Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The phase transition temperatures (T_p) of these copolymers increase with the degree of ionization () of the acrylic acid (AA) units, which in turn is dependent on the pH of the solutions. Apparent values of pK_a for the AA units, determined from the pH dependencies of T_p, are 4.7 and 5.4 for PiPA-AA and PdEA-AA, respectively. Differences between T_p for PiPA-AA and T_p for PiPA homopolymer (T_p) are +1.5 and –0.2 °C/mol% of AA at =1 and 0, respectively. The values of T_p for PdEA-AA are +2.6 (ionic) and –0.5 (nonionic)°C/mol%, indicating that the incorporated AA units have a larger effect on PdEA than on PiPA. DSC measurements performed with each of these copolymers at different pH values show a linear relationship between T_p and the enthalpy of transition (H). IR measurements of PiPA-AA show that the profiles of IR bands from both iPA and AA units exhibit critical changes at T_p of the copolymer. Heating the solution above T_p leads to shifts of the amide II, C–H stretch, and C–H bend bands from the iPA units toward lower wavenumbers, as well as a shift of the amide I band from the iPA units toward higher wavenumbers. A decrease in the intensity of the symmetric C=O stretch IR band from carboxylate anions (1560 cm^–1), and an increase in the intensity of the C=O stretch band from COOH groups (1705 cm^–1) suggest that a partial protonation of the carboxylate groups (COO^–+H⁺COOH) takes place upon the phase transition.     

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.     

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.     

<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.     

An efficient <Emphasis Type="Italic">Mannich</Emphasis>-type synthesis of <Emphasis Type="Italic">bis</Emphasis>(pyrido[2,1-<Emphasis Type="Italic">b</Emphasis>][1,3,5]thiadiazin-7-yl)-methanes

Morpholinium 3-cyano-4-methyl-6-oxo-1,6-dihydropyridine-2-thiolate upon treatment with primary amines and a formaldehyde excess under mild conditions produces bis(pyrido[2,1-b][1,3,5]thiadiazin-7-yl)methane derivatives in good yields (67–87%). Correspondence: Victor V. Dotsenko, State Enterprise “Luganskstandartmetrology”, 91021 Lugansk, Ukraine.     

Cytotoxicity of poly(<Emphasis Type="Italic">p</Emphasis>-phenylenediamine)

Although poly(p-phenylenediamine) is an electric non-conductor, it exhibits, analogously to conducting polymers, redox activity and could, therefore, find applications in biomedicine. In the current work, the cytotoxicity of poly(p-phenylenediamine) polymer powder produced by the chemical oxidation of p-phenylenediamine with ammonium peroxydisulfate in acidic aqueous media has been studied. Primary mouse embryonic fibroblasts were used for this purpose. Interestingly, the standard methods for the determination of polymer cytotoxicity based on international standard EN ISO 10993-5 could not be applied. The reason was the interaction of polymer extracts with MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. On the basis of the evaluation of flow cytometry and micrographs taken by fluorescence microscopy on cells treated with extracts of poly(p-phenylenediamine), it can be concluded that the powder polymer possesses severe cytotoxicity. The results suggest that practical application of the polymer within biomedicine is, at the current state of knowledge, difficult, and modification of the preparation techniques and/or subsequent purification of poly(p-phenylenediamine) is needed.     

Electrosynthesis of poly(<Emphasis Type="Italic">p</Emphasis>-phenylene) and poly(<Emphasis Type="Italic">p</Emphasis>-phenylene/pyrrole) films under controlled humidity

Poly(p-phenylene/pyrrole) (PPP-PPY) films were electrochemically synthesised on transparent indium-tin-oxide-covered glass (ITO) electrodes. The presence of two monomers, p-phenylene and pyrrole, in the polymerisation medium facilitated the synthesis process, yielding electroactive, uniform and stable films. In order to obtain materials with improved quality, PPP, PPY and PPP-PPY films were prepared in a mild, dry atmosphere. The morphological, electrochemical and optical properties were compared for different films obtained by varying the number of cycles with and without controlling humidity.     

Recyclization of 1,3-dialkyl-6-nitro-1<Emphasis Type="Italic">H</Emphasis>-imidazo[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridine-2,5(3<Emphasis Type="Italic">H</Emphasis>,4<Emphasis Type="Italic">H</Emphasis>)-diones into imidazole derivatives

Treatment of 5-amino-1,3-dialkyl-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones with sodium nitrite in aqueous HCl gave 1,3-dialkyl-1H-imidazo[4,5-b]pyridine-2,5(3H,4H)-diones which were nitrated with potassium nitrate in sulfuric acid to 6-nitro derivatives, and the latter underwent recyclization into 4-amino-1,3-dialkyl-5-(1H-pyrazol-5-yl)-2,3-dihydro-1H-imidazol-2-ones by the action of hydrazine hydrate.     

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.