Bioengineering functional copolymers: synthesis and characterization of poly(<Emphasis Type="Italic">N</Emphasis>-isopropyl acrylamide-<Emphasis Type="Italic">co</Emphasis>-3,4-2H-dihydropyran)s

Novel bioengineering copolymers were synthesized by radical copolymerization of N-isopropylacrylamide (NIPA) and 3,4-2H-dihydropyran (DHP) with 2,2′-azobisisobutyronitrile as an initiator in acetone solution at 70 °C under nitrogen atmosphere. Structure, tacticity and compositons of the copolymers prepared in a wide range of monomer feed were confirmed by FTIR, ¹H{¹³C} NMR-DEPT and elemental analyses. The monomer reactivity ratios (r ₁ and r ₂) were detected using known two methods: r ₁ (NIPA)?=?1.25 and r ₂?=?0.035 (DHP), and r ₁ (NIPA) ?=?0.97 and r ₂?=?0.022 (DHP) by Kelen-Tüdös and Jaacks methods, respectively. It was demonstrated that the studied monomer pair has a tendency to form H-bonding beween amide/ether groups through ?NH...O< complexation which played an important role in the stereoselective chain growth, and significant decrease of allyl degradative chain transfer reactions. This phenomenon is also confirmed by the observed relatively high molecular weights of copolymers (M _v ). The synthesized water-soluble stimuli-responsive poly(NIPA-co-DHP)s exhibit thermal stability, higher glass-transition temperature, polyelectrolyte, pH- and temperature-sensitive behavior and can be attributed to the class of bioengineering functional copolymers useful for various bio- and gene-engineering, and drug delivery applications.     

Optimization of controlled ring-opening polymerization of <Emphasis Type="SmallCaps">l</Emphasis>-lactide to hydroxyl terminated polylactides using zinc acetate catalyst

Hydroxyl terminated polylactide polymers with number of average molecular weights (M _n ) varying from 1625 to 3459 g mol^?1 were synthesized by ring opening bulk polymerization of lactide in the presence of zinc acetate being a potent catalyst. The use of 1,4 butanediol (BDO) initiator leads to hydroxyl terminated polylactides, thus excellent precursors for shape-memory biodegradable polyurethanes. Different reaction conditions employed for the synthesis of hydroxyl terminated polylactide polymers via activated monomer mechanism may result in differences in M _n , percentage mass conversion and percentage degree of crystallinity (%χ _c ) of the product. Influence of process parameters, i.e. catalyst concentration, initiator concentration, reaction temperature and time on characteristics of hydroxyl terminated polylactides was studied. These polymers were characterized by Nuclear Magnetic Resonance (¹H-NMR) spectroscopy, Fourier transforms infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and X-ray diffraction (XRD) techniques. FTIR and ¹H-NMR confirmed the formation of hydroxyl terminated polylactides. M _n was determined by ¹H-NMR, GPC and end group analysis. %χ _c was calculated from XRD spectra. Maximum mass conversion, M _n and %χ _c were observed at 5 mol% SnOct₂ and 5 mol% BDO concentration. At optimum temperature of 145 °C, these characteristics improved linearly with polymerization time up to 6 h and declined thereafter.     

Sol-Gel Synthesis,Thermal Behavior of Nanopowders and Chemical Stability of La<Subscript>1 – <Emphasis Type="Italic">x</Emphasis></Subscript>Ho<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript> Ceramic Matrices

Nanosized powders of orthophosphates in the LaPO₄–HoPO₄–H₂O system have been synthesized to determine the mutual solubility of LaPO₄ · nH₂O and HoPO₄ · nH₂O initial components and to obtain ceramic matrices by sintering them. Formation of hexagonal, monoclinic or tetragonal solid solutions was revealed, and their limits and thermal stability were determined. A series of limited hexagonal LaPO₄ · nH₂O-based solid solutions was observed within the 0 ≤ x ≤ 0.6 concentration range up to 600°C. Further they transformed to monoclinic LaPO₄-based form within the 0 ≤ x ≤ 0.3 concentration range. Solubility of LaPO₄ · nH₂O and LaPO₄ in tetragonal HoPO₄(· nH₂O) is lower (≤10 mol %). Specific surface area of La_1–xHo_xPO₄ · nH₂O powders was in the range of 90.5–165.0 m²/g depending on x. Leaching rate of La³⁺ and Ho³⁺ from La_1–xHo_xPO₄ matrices in nitric acid solution (pH 1–2) was determined to be 10^–5–10^–2 g/(cm² day) for both ions.     

Supramolecular Architectures in Three Metal(II) Coordination Polymers with 2,5-Dichloroterephthalate and Flexible Bis(Benzimidazole) Ligands

Three supramolecular coordination polymers, namely [Ni(L1)(DCTP)(H₂O)] _n (1), [Cu(L2)(DCTP)] _n (2), [Co(L3)(DCTP)] _n (3) (L1?=?1,5-bis(5,6-dimethylbenzimidazole)pentane, L2?=?1,4-bis(5,6-dimethylbenzimidazole)butane, L3?=?1,4-bis(benzimidazole)-2-butylene) have been hydrothermally synthesized and characterized by single crystal X-ray structure determination, FT-IR, elemental analysis, X-ray powder diffraction (XPD), and thermogravimetric analysis (TGA). CP 1 exhibits 2D 6³ honeycombed network structure, which is further extended into a 3D Moganite (mog) supramolecular framework by classical O–H?O hydrogen-bonding interaction. CPs 2 –3 present 2D (4,4) layers, and 3D supramolecular frameworks that are formed by π–π stacking interactions. Furthermore, the catalytic activities of CPs 1–3 for the degradation of methyl orange in a Fenton-like process has been investigated, and CPs 1–3 show strong photoluminescence properties at room temperature in solid state.     

Partition of <Emphasis Type="Italic">n</Emphasis>-Butanol Among Phases and Solubilization Ability of Winsor type III Microemulsions

The partition of n-butanol in Winsor type III (W-III) microemulsions was investigated in this work. Three kinds of anionic surfactants (sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (DSS), and sodium dodecyl benzene sulfonate (SDBS)) and two kinds of anionic/cationic surfactant mixtures (SDS/octadecyl trimethyl ammonium chloride (OTAC) mixtures and DSS/OTAC mixtures) were studied. Internal standard gas chromatography was employed in n-butanol content analysis. The results showed that no water exists in the excess oil (EO) phase and no oil exists in the excess water (EW) phase. For the W-III microemulsions obtained by salinity scanning, relatively constant n-butanol content in the EO (11–12 v%) and EW (1–4 v%) was found under different salinities. Accurate measurement of n-butanol content in each phase is important for those systems having low solubilization ability. For the W-III microemulsions prepared using SDS/OTAC surfactant mixture, the percentage of n-butanol distributed into the interfacial layer decreased while the fraction of n-butanol in the interfacial layer first increased sharply and then tended to be stable with the addition of n-butanol. For the different optimum W-III microemulsion systems tested, most of the surfactant-to-alcohol molar ratio data are near 1:3, but obvious deviation could be observed for some data. On the basis of the accurate measurement of n-butanol content in the EO and EW phases, the standard free energy, ΔG _o→in ^* (T = 298.15 K) of n-butanol transferring from the EO phase to the interfacial region was calculated. The results show negative ΔG _o→in ^* values. For microemulsions with the same components, n-butanol content is an important factor influencing the ΔG _o→in ^* value, and a high absolute value of ΔG _o→in ^* leads to high solubilization ability.     

Synthesis and thermal properties of novel microencapsulated phase-change materials with binary cores and epoxy polymer shells

A series of novel epoxy polymer shell microcapsules with n-tetradecane and dimethylbenzene as binary core materials are successfully synthesized via interfacial polymerization. Dimethylbenzene is used as the solvent for epoxy and n-tetradecane. The chemical structure, surface morphology, and thermal properties of the microencapsulated phase-change materials (micro-PCMs) are characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscope. Results show that the micro-PCMs have relatively spherical profiles and smooth surfaces with diameters ranging from 10 to 70 μm. The epoxy shell successfully encapsulates the binary core. Phase-change enthalpy and binary core content in the micro-PCMs increase with the increasing mass ratio of the binary core to the epoxy resin. The micro-PCMs degrade in two steps, and the resulting microcapsules exhibit good thermal stabilities. The degradation temperature decreases, as the core-to-shell mass ratio increases.     

New functional copolymers of <Emphasis Type="Italic">N</Emphasis>-acryloyl-<Emphasis Type="Italic">N</Emphasis>′-methyl piperazine and 2-hydroxyethyl methacrylate: synthesis,determination of reactivity ratios and swelling characteristics of gels

Copolymers of N-acryloyl-N′-methylpiperazine (AcrNMP) and 2-hydroxyethyl methacrylate (HEMA) were synthesized by free radical solution polymerization in dioxane at 70 ± 1 °C, using 2,2′-azobisisobutyronitrile (AIBN) as initiator. The copolymer compositions were analyzed by the methods of FTIR spectroscopy and elemental analysis. Both the method of analysis yielded results that agreed reasonably well. The monomer reactivity ratios of the copolymerization were determined by the linearization methods of Finemann–Ross (FR) and Kelen–Tüdös (KT). The reactivity parameter results derived using FTIR analysis showed that the copolymerization yielded mainly alternating structure with reactivity ratios, r ₁(AcrNMP) = 0.263 ± 0.011 and r ₂(HEMA) = 0.615 ± 0.097 by F–R method and r ₁ = 0.227 ± 0.074 and r ₂ = 0.53 ± 0.15 by KT method. Microstructure data calculated by the method of Igarashi also supports the alternating structure (tendency) of the copolymer. Crosslinked polymer gels of this system exhibited remarkably high swelling of more than 500% in water at ambient temperature.     

Copolymerization of alkyl acrylates with triallyl cyanurate: Kelen-Tüdös method applied for determining copolymerization reactivity ratios

The copolymerization of methyl acrylate (MA), ethyl acrylate (EA), straight-chain butyl acrylate (n-BA) and styrene (S) with triallyl cyanurate (TAC) has been studied in bulk at 343±1 K using benzoyl peroxide as initiator. The reactivity ratios of the monomers are determined by the Fineman-Ross (F-R) method and compared to those determined by the Kelen-Tüdös (K-T) method.     

Synthesis of all-acrylic graft copolymers by grafting-through strategy in emulsion

In this paper, PnBA-g-PMMA brush-like and centipede multigraft copolymers were synthesized via DPE seeded emulsion polymerization and miniemulsion polymerization. PMMA macromonomers with single tail and double tails were prepared by DPE-technique in emulsion and Steglich esterification. Then PnBA-g-PMMA multigraft copolymers were obtained by miniemulsion copolymerization. The molecular weight and polydispersity indices of PMMA macromonomers and graft copolymers were characterized by GPC. The structural characteristics, weight content of PMMA and the number of grafting sites in brush-like and centipede multigraft copolymers were determined by ¹H NMR. The thermal performance of graft copolymers were analyzed by DSC and TGA. AFM confirmed microphase separation between PnBA block and PMMA block.     

Synthesis,Characterization and Surface Properties of Amidosulfobetaine Surfactants Bearing Odd-Number Hydrophobic Tail

Three amidosulfobetaine surfactants were synthesized namely: 3-(N-pentadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2a); 3-(N-heptadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2b), and 3-(N-nonadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2c). These surfactants were prepared by direct amidation of commercially available fatty acids with 3-(dimethylamino)-1-propylamine and subsequent reaction with 1,3-propanesultone to obtain quaternary ammonium salts. The synthesized surfactants were characterized by IR, NMR and mass spectrometry. Thermogravimetric analysis (TGA) results showed that the synthesized surfactants have excellent thermal stability with no major thermal degradation below 300 °C. The critical micelle concentration (CMC) values of the surfactants 2a and 2b were found to be 2.2 × 10^?4 and 1.04 × 10^?4 mol/L, and the corresponding surface tension (γ_CMC) values were 33.14 and 34.89 mN m^?1, respectively. The surfactants exhibit excellent surface properties, which are comparable with conventional surfactants. The intrinsic viscosity of surfactant (2b) was studied at various temperatures and concentrations of multi-component brine solution. The plot of natural logarithm of relative viscosity versus surfactant concentration obtained from Higiro et al. model best fit the surfactant behavior. Due to good salt resistance, excellent surface properties and thermal stability, the synthesized surfactant has potential to be used in various oil field applications such as enhanced oil recovery, fracturing, acid diversion, and well stimulation.     

Supramolecular Aggregation of Tetrameric and Homododecameric Water Clusters in a 1D Cobalt(II) Coordination Polymer Containing 1,2,4,5-Benzenetetracarboxylate

A ternary mixed ligand Co(II) coordination polymer, namely, {[Co(L)(btec)_0.5(H₂O)]·3H₂O} _n , (L?=?1,4-bis(thiabendazole)butane, H₄btec?=?1,2,4,5-benzenetetracarboxylic acid) has been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. The coordination polymer features a 1D wave-like chain, which is further extended into a 3D supramolecular framework via O–H?O hydrogen bonding interactions. It is noteworthy, the chair-shaped homododecamers and quasirectangle teteramers assemble with the 1D loose-string-like water-btec^4? chain into a unusual boxing-glove-like 2D water layer. Hirshfeld surface analysis and fingerprint plots show that the coordination polymer is stabilized by O–H?O, π?π, O–H?π, and H?H intermolecular interactions. Furthermore, thermal behaviors, luminescence and catalytic properties of the coordination polymer for degradation of methyl orange in a Fenton-like process have been investigated.     

A Comprehensive Study on the Synthesis and Micellization of Disymmetric Gemini Imidazolium Surfactants

Two groups of disymmetric Gemini imidazolium surfactants, [C₁₄C₄C _m im]Br₂ (m = 10, 12, 14) and [C _m C₄C _n im]Br₂ (m + n = 24, m = 12, 14, 16, 18) surfactants, were synthesized and their structures were confirmed by ¹H NMR and ESI–MS spectroscopy. Their adsorption at the air/water interface, thermodynamic parameters and aggregation behavior were explored by means of surface tension, electrical conductivity and steady-state fluorescence. A series of surface activity parameters, including cmc, γ _cmc, π _cmc, pC ₂₀, cmc/C ₂₀, Γ _max and A _min, were obtained from surface tension measurements. The results revealed that the overall hydrophobic chain length (N _c) for [C₁₄C₄C _m im]Br₂ and the disymmetry (m/n) for [C _m C₄C _n im]Br₂ had a significant effect on the surface activity. The cmc values decreased with an increase of N _c or m/n. The thermodynamic parameters of micellization (ΔG _m ^θ , ΔH _m ^θ , ΔS _m ^θ ) derived from the electrical conductivity indicated that the micellization process of [C₁₄C₄C _m im]Br₂ and [C _m C₄C _n im]Br₂ was entropy-driven at different temperatures, but the contribution of ΔH _m ^θ to ΔG _m ^θ was enhanced by increasing N _c or m/n. The micropolarity and micellar aggregation number (N _agg) were estimated by steady-state fluorescence measurements. The results showed that the surfactant with higher N _c or m/n can form larger micelles, due to a tighter micellar structure.     

Synthesis and Physicochemical Properties of Alanine-Based Surfactants

The synthesis of a homologous series of alanine-based surfactants, namely sodium salts of n-alkanesulfonamido-2-propanoic acids in which n-alkane is n-dodecane, n-tetradecane, n–hexadecane, and n-octadecane having the formula RSO₂NHCH (CH₃)COO^?Na⁺, is described. The starting materials used were a mixture of secondary positional isomers of n-alkanesulfonyl chlorides obtained by photosulfochlorination reaction using sulfuryl chloride and a catalyst. Surface properties of the aqueous solutions of the synthesized surfactants, including the critical micelle concentration and minimal surface tension δ_min, were determined using surface tension measurements at 25 °C. The surface excess Γ and minimum area per molecule (A _min) where calculated using the Gibbs equation. The foaming power was also determined by the Bartsh method, and the R ₅ parameter was calculated to estimate the stability of the foam formed. The results obtained were compared to those of a commercial surfactant, sodium dodecylsulfate, and a series of synthesized glycine-based surfactants. The results obtained clearly show that the alanine-based surfactants possess good surface properties. The investigations highlight the influence on the surface properties of the addition of a methyl group in the hydrophilic part.     

Probing the Structural,Electronic, and Magnetic Properties of Ag<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>V (<Emphasis Type="Italic">n</Emphasis> = 1–12) Clusters

The structural, electronic, and magnetic properties of Ag _n V (n?=?1–12) clusters have been studied using density functional theory and CALYPSO structure searching method. Geometry optimizations manifest that a vanadium atom in low-energy Ag_nV clusters favors the most highly coordinated location. The substitution of one V atom for an Ag atom in Ag _n?+?1 (n ≥ 5) cluster modifies the lowest energy structure of the host cluster. The infrared spectra, Raman spectra, and photoelectron spectra of Ag _n V (n?=?1–12) clusters are simulated and can be used to determine the most stable structure in the future. The relative stability, dissociation channel, and chemical activity of the ground states are analyzed through atomic averaged binding energy, dissociation energy, and energy gap. It is found that V atom can improve the stability of the host cluster, Ag₂ excepted. The most possible dissociation channels are Ag _n V?=?Ag?+?Ag _n???1V for n?=?1 and 4–12 and Ag _n V?=?Ag₂?+?Ag _n???2V for n?=?2 and 3. The energy gap of Ag _n V cluster with odd n is much smaller than that of Ag _n?+?1 cluster. Analyses of magnetic property indicate that the total magnetic moment of Ag _n V cluster mostly comes from V atom and varies from 1 to 5 μ _B. The charge transfer between V and Ag atoms should be responsible for the change of magnetic moment.     

Crystal structure and thermal expansion of ammonium pentaborate NH<Subscript>4</Subscript>B<Subscript>5</Subscript>O<Subscript>8</Subscript>

Anhydrous ammonium pentaborate NH₄B₅O₈ has been synthesized by thermal dehydration of larderellite NH₄[B₅O₇(OH)₂] · H₂O at a temperature of 290°C for 7 h. The crystal structure has been determined from the X-ray powder diffraction data: a = 7.58667(5) Å, b = 12.00354(8) Å, c = 14.71199(8) Å, R _p = 6.23, R _wp = 7.98, R _B = 12.7, R _F = 8.95, and β-KB₅O₈ structure type. The double interpenetrating framework is formed by pentaborate groups, each consisting of a boron-oxygen tetrahedron and four triangles, in which all oxygen atoms are bridging. The thermal behavior of the NH₄B₅O₈ compound has been investigated using thermal X-ray diffraction. As for other pentaborates of this type, the thermal expansion of the NH₄B₅O₈ compound is anisotropic and reaches a maximum along the a axis. The thermal expansion coefficients are as follows: α _a = 39 × 10^?6, α _b = 6 × 10^?6, α _c = 20 × 10^?6, and α _V = 65 × 10^?6 °C^?1.     

Thermogravimetric characteristics of <Emphasis Type="Italic">α</Emphasis>-cellulose and decomposition kinetics in a micro-tubing reactor

The pyrolysis characteristics and kinetics of α-cellulose were investigated using thermogravimetric analyzer (TGA) and micro tubing reactor, respectively. Most of the α-cellulose decomposed between 250 and 400 °C at heating rate of 5–20 °C/min. The apparent activation energy was observed in the range of 263.02 kJ mol^?1 to 306.21 kJ mol^?1 at the conversion of 10-80%. The kinetic parameters were determined by nonlinear least-squares regression of the experimental data, assuming first-order kinetics. It was found from the kinetic rate constants that the predominant reaction pathway was A(α-cellulose) to B(bio-oil) rather than A(α-cellulose) to C(gas; C₁-C₄) and/or to B(bio-oil) to C(gas; C₁-C₄) at temperatures of 340-360 °C.     

Synthesis and characterization of bio-based benzoxazine oligomer from cardanol for corrosion resistance application

The Mannich-like condensation of a cardanol, paraformaldehyde, and N,N′-bis(2-aminoethyl)ethane-1,2-diamine were carried out to synthesize the amine functional benzoxazine (Bnz) resin. The amine functionality of Bnz resin was evaluated by physiochemical methods, and the structure was characterized using Fourier transform infrared and ¹H-nuclear magnetic resonance spectroscopy. The added functionality into the Bnz resin backbone was utilized to modify the Bnz resin structure by glycidoxypropyltrimethoxysilane (GPTMS) in various proportions. The results revealed that the silane-modified Bnz coatings have improved mechanical, chemical, and solvent resistance properties as compared to the neat Bnz coating. The gel and water absorption of polyamide-cured coatings also has been evaluated. Furthermore, the cured films have been evaluated for glass transition temperature (T _g) and thermal resistance by differential scanning calorimetry and thermogravimetric analysis, respectively. The corrosion resistance properties were studied by salt spray and electrochemical analysis. It was observed that the highly crosslinked structure of the GPTMS-modified Bnz coatings enhanced the barrier protection to corrosive species.     

Parameters of luminescence and the local structure of Eu<Superscript>3+</Superscript> centers in fluorogermanate glasses

The influence of the chemical nature of the local environment of Eu³⁺ ions on the parameters of luminescence of these centers in glasses of the (BaGeO₃)_{1 ? x ? y} (Al₂O₃) _x (0.45CaF₂ · 0.55MgF₂) _y (x = 0.25, y = 0; x = 0.17, y = 0.17; x = 0.15, y = 0.22; x = 0.07, y = 37.00; x = 0, y = 0.45) system is investigated. The oxidation state of europium atoms and the degree of homogeneity of their local environment in the glasses are determined using ¹⁵¹Eu Mössbauer spectroscopy.     

Synthesis and Characterization of Stimuli-Responsive Poly(N-isopropylacrylamide-co-N-vinyl-2-pyrrolidone)

Radical copolymerization of N-isopropylacrylamide (NIPA) with N-vinyl-2-pyrrolidone (VP) were carried out with 2,2′-azobisisobutyronitrile (AIBN) as an intiator in N,N′-dimethylformamide solution at 65°C under nitrogen atmosphere. Compositon of the copolymers synthesized in a wide range of monomer feed ratios were determined by FTIR and ¹H (¹³C) NMR-DEPT-135 spectroscopy. The monomer reactivity ratios were determined by Fineman-Ross, Kelen-Tüdös and non-linear regression methods. It was observed that the studied monomer pair has some tendency to alternation in the chosen monomer feed ratios due to formation of intermolecular interaction through H-bonding and N → O = C coordination. The synthesized poly(NIPA-co-VP)s show temperature sensitivity (T _s), higher glass-transiton temperature (T _g ), thermal stability, polyelectrolyte and stimuli-responsive (temperature- and pH-sensitive) behavior and can be attributed to the class of bioengineering functional copolymers useful for application in various gene- and bioengineering processes, drug delivery systems and biomacromolecule conjugations.     

One Pot Synthesis and Properties of Cationic Surfactants: <Emphasis Type="Italic">n</Emphasis>-Alkyl-3-Methylpyridinium Bromide

Three new amphiphilic compounds i.e., n-decyl-3-methylpyridinium bromide (a), n-dodecyl-3-methylpyridinium bromide (b), and n-tetradecyl-3-methylpyridinium bromide (c), have been synthesized by condensation reaction and characterized by NMR (¹H, ¹³C) and FTIR spectroscopic techniques. The micellization behavior of the compounds has been studied in ethanol employing conductometry and UV/visible spectroscopy. The critical micellization concentration (CMC) values for compound a, b and c was found to be 0.31, 0.29 and 0.27 m mol L^?1, respectively. Effect of temperature on the CMC was checked in the range of 298-318 K. The thermodynamic parameters such as ΔG, ΔH and ΔS of the micellization process of these surfactants were computed. The negative values of ΔG and positive values of ΔH indicated the spontaneous and endothermic nature of the micellization process. Antimicrobial activities of these amphiphiles showed significant activity against different bacterial strains.