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.     

Novel amphiphilic temperature responsive graft copolymers PCL-<Emphasis Type="Italic">g</Emphasis>-P(MEO<Subscript>2</Subscript>MA-<Emphasis Type="Italic">co</Emphasis>-OEGMA) via a combination of ROP and ATRP: synthesis,characterization, and sol-gel transition

A series of well-defined novel amphiphilic temperature-responsive graft copolymers containing PCL analogues P(αClεCL-co-εCL) as the hydrophobic backbone, and the hydrophilic side-chain PEG analogues P(MEO₂MA-co-OEGMA), designated as P(αClεCL-co-εCL)-g-P(MEO₂MA-co-OEGMA) have been prepared via a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The composition and structure of these copolymers were characterized by ¹H NMR and GPC analyses. The self-assembly behaviors of these amphiphilic graft copolymers were investigated by UV transmittance, a fluorescence probe method, dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. The results showed that the graft copolymers exhibited the good solubility in water, and was given the low critical temperature (LCST) at 35(±1) °C, which closed to human physiological temperature. The critical micelle concentrations (CMC) of P(αClεCL-co-εCL)-g-P(MEO₂MA-co-OEGMA) in aqueous solution were investigated to be 2.0 × 10^?3, 9.1 × 10^?4 and 1.5 × 10^?3 mg·mL^?1, respectively. The copolymer could self-assemble into sphere-like aggregates in aqueous solution with diverse sizes when changing the environmental temperature. The vial inversion test demonstrated that the graft copolymers could trigger the sol-gel transition which also depended on the temperature.     

Synthesis and characterization of maleylated cellulose-<Emphasis Type="Italic">g</Emphasis>-polyacrylamide hydrogel using TiO<Subscript>2</Subscript> nanoparticles under sunlight

Graft polymerization onto the cellulose is one way to produce semisynthetic copolymers and semiconductors were hardly used as initiators. Maleylated cellulose (MC) with different degree of carboxyl groups was synthesized and degree of carboxyl groups was determined using titration method. Then the graft copolymers of acrylamide (AM) on MC were synthesized by titanium dioxide semiconductor photoinitiator in aqueous suspension under sunlight. The effect of different parameters, such as the degree of carboxyl groups, degassing of atmosphere, reactor type, light source, MC/AM ratio, and initiator concentration, was evaluated in the synthesis of graft copolymers. MC with a high degree of carboxyl groups about 2.8 mmol g^?1 was selected for graft photopolymerization. Maximum monomer conversion (55%) for Maleylated cellulose-g-polyacrylamide (MC-g-PAM) was achieved with 0.5 mg TiO₂, MC/AM = 0.056, argon atmosphere, sunlight source, and double quartz tube reactor. The maximum amount of equilibrium swelling (41 g g^?1) was achieved for MC-g-PAM with 34% monomer conversion. The resulting graft copolymers were characterized by FT-IR, SEM, and TGA. Synthesis of MC-g-PAM using TiO₂ nanoparticles (NPs) as the initiator was done successfully that shows the TiO₂ NPs are useable in graft polymerization of acrylamide monomers onto the MC under sunlight.     

Synthesis and properties of amphiphilic thermo-sensitive block copolymers

Octadecyl acrylate (ODA) as hydrophobic monomer and N-isopropylacryamide (NIPAAm) as hydrophilic monomer were chosen to synthetize the thermo-sensitive block copolymers PODA_x-PNIPAAm_y-PODA_x (BAB-type) via reversible-addition-fragmentation chain transfer (RAFT) polymerization, the block copolymers could self-assemble to flower-like micelles in aqueous solution with hydrophobic PODA as the inner core and stabilized by hydrophilic PNIPAAm as the outer shell. The characterizations of the micelles such as surfactivity, thermo-sensitivity, micelle hydrodynamic radius (R _h ) and polydispersity index (PdI) were demonstrated by surface tension technique, UV-Vis, and dynamic light scattering (DLS) measurements, respectively. The longer the hydrophilic chain was, the higher the critical micellization concentration (CMC) would be, and the higher content of the PODA was, the lower the lower critical solution temperature (LCST) would be. The average R _h remained at about 100 nm below LCST, but decreased sharply to about 42 nm and kept constant when reaching and above LCST, which meant the non-aggregation of BAB type block copolymers. The micelle was homogeneous with the small PdI within the range of research. B_0.5mA_24mB_0.5m had the largest capacity to encapsulate lipophilic Sudan Red IV model drugs and the drug loading efficiency was 9.76%.     

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.     

Effect of different structured POSS/GMA-containing copolymers on the morphology of porous coating by breath-figures method

Polyhedral oligomeric silsesquioxane (POSS) and glycidyl methacrylate (GMA) are used to synthesize linear L-(PGMA-b-MA-POSS), dicephalous D-(PGMA-b-MA-POSS)₂, and four-armed T-(PGMA-b-MA-POSS)₄ through atom transfer radical polymerization (ATRP). These different structured POSS/GMA-containing copolymers are applied to build the porous films through breath-figures (BF) method. L-(PGMA-b-MA-POSS) is easy to form the ordered porous BF film, and T-(PGMA-b-MA-POSS)₄ tends to form well-distributed BF film due to its high segment density which is beneficial to stabilize water drop. It is proven that solvent has a great effect on the morphologies of BF film. The perfect BF film is developed in the relatively wet atmosphere as 5–8 μm diameter of pores casted in THF and 2–4 μm diameter of pores casted in CH₂Cl₂ with regular morphology. The developed BF film has superior stability than the film developed in natural conditions due to the shorter stable balancing time. Therefore, it is believed that the obtained porous films show great potential in coating application.     

The role of molecular structure on impact resistance and bending strength of photocured urethane-dimethacrylate polymer networks

The objective of this study was to investigate the influence of molecular structure on impact resistance (a _n) and bending strength (σ) of photocured urethane-dimethacrylate polymer networks. Urethane-dimethacrylate (UDMA) monomers were synthesized through reaction of oligoethylene glycol monomethacrylate (OEGMMA) with diisocyanate (DI). OEGMMA varied within the length of the oligooxyethylene chain, which consisted of one to four oxyethylene units. DI varied in chemical character: aliphatic, cycloaliphatic or aromatic. The molecular structure of UDMA polymers was characterized by X-ray powder diffraction, which allowed the calculation of the d-spacing (d) and dimensions of microgel agglomerates (D). The measurements of the polymerization shrinkage were used for the determination of the degree of conversion (DC), whereas the concentration of double bonds was used as a measure of the crosslink density (q). It was found that all structural parameters depend on the UDMA chemical structure. The increasing length of the oligooxyethylene chains caused the decrease in d and q, in contrast to the increase in D and DC. The DI chemical character caused the increase in the DC and q accordingly: symmetrical cycloaliphatic or aromatic < asymmetrical cycloaliphatic and aromatic < substituted aliphatic < linear aliphatic. The compact packing and high DC in polymers derived from aliphatic DIs gave rise to the decrease in d and the increase in D. The non-planar conformation of cycloaliphatic DIs emerged in high d as well as D. The planar conformation of aromatic DIs resulted in the decrease in d as well as D. The study indicated that mechanical behavior of UDMA polymer networks can be explained in terms of the structural parameters. DC and q appeared to be the main factors determining both mechanical properties of poly(UDMA)s. The a _n was also shown to be affected by d. Particularly high linear correlations were found on a semi-logarithmic scale for the DC and d with a _n. a _n increased as the DC increased, whereas d decreased.     

Polycarboxylate superplasticizers of acrylic acid–isobutylene polyethylene glycol copolymers: monomer reactivity ratios,copolymerization behavior and performance

Acrylic acid–isobutylene polyethylene glycol (AA-TPEG) copolymers are typical of polycarboxylate superplasticizers (PCEs). AA-TPEG copolymers are prepared via free-radical polymerization with potassium persulfate as the initiator. The obtained copolymers were characterized by gel permeation chromatography (GPC) and infrared spectra (FTIR). The GPC method can break through the former limitations of the instruments and receive instantaneous unreacted and instantaneous monomer concentrations and not the initial monomer feeds. Since TPEG monomer is highly bulky, the common calculation methods for determining monomer reactivity ratios in copolymerization based on terminal copolymerization equation are not suitable. However, this study created non-linear least squares curve fitting of terminal copolymerization equation (NLLSQ-T) and penultimate copolymerization equation (NLLSQ-P) methods, which used Python’s NumPy, SciPy, and SymPy libraries to generate code and did numerical computations, bringing greater accuracy of monomer reactivity ratios. The monomer reactivity ratios were calculated with Fineman–Ross, Kelen–Tüdös, YBR, NLLSQ-T, and NLLSQ-P methods and found to be r _AA = 10.888, r′ _AA = 1.131, r _TPEG = 0.012, and r′ _TPEG = 0.042 for AA-TPEG copolymers. Moreover, this study also explored specific copolymerization behavior of similar structure of copolymers with steric hindrance under penultimate copolymerization equation, such as dependence of the mole fractions in the copolymer on the mole fractions of unreacted monomers in solution, variation of copolymer compositions with conversion and sequence length distribution. The fluidity and flow loss of pastes containing PCEs were investigated, and the appropriate PCEs dosages resulted in a better workability of cement pastes.     

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 Characterization of pH-Responsive Organic–Inorganic Hybrid Material with Excellent Catalytic Activity

Poly(N-isopropylmethacrylamide-co-methacrylic acid) [p(NipAam-Mac)] microgels were synthesized and used as microreactors to fabricate silver nanoparticles. Pure and hybrid microgels were characterized using Ultraviolet–Visible (UV/Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy and transmission electron microscopy (TEM). Catalytic activity of hybrid microgels and mechanism of catalysis by this system was explored using different reaction conditions. At the same temperature, apparent rate constant (k_app) was found to be varied from 0.0414 to 0.7852 min^?1 by increasing the concentration of NaBH₄ from 2.49 to 22.41 mM at constant concentration of substrate and catalyst. However upon extra increase in concentration of NaBH₄ from 22.41 to 37.35 mM reduced the value of k_app to 0.2178 min^?1. Likewise, the value of k_app was found to be increased from 0.1242 to 0.5495 min^?1 with increasing the concentration of 4-nitrophenol [Para-nitrophenol (p-Np)] from 0.063 to 0.079 mM keeping other parameters constant. Further increase in concentration of p-Np caused decline in the value of k_app. Kinetic data reveals that catalytic reduction of p-Np obeys Langmuir–Hinshelwood mechanism and p-Np is converted to p-Ap on the surface of the silver nanoparticles passing through various reaction intermediates.     

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.     

Combined extracts of <Emphasis Type="Italic">Garcinia mangostana</Emphasis> fruit rind and <Emphasis Type="Italic">Cinnamomum tamala</Emphasis> leaf supplementation enhances muscle strength and endurance in resistance trained males

Background

A proprietary composition GMCT contains extracts of two popular Asian herbs viz., Garcinia mangostana (GM) fruit rind and Cinnamomum tamala (CT) leaf. We systematically evaluated physical performance and muscle strength enhancing ability of GMCT in a preclinical mouse model followed by a 42-days double-blind placebo controlled human trial in resistance trained adult males.

Methods

Four groups of Swiss albino mice (20–30 g body weight) (n?=?6) were fed a standard laboratory diet and given Carboxymethylcellulose sodium (CMC), 150 mg/kg GMCT (GMCT-150), 300 mg/kg GMCT (GMCT-300) or 50 mg/kg Oxymetholone (OXY) via oral gavage for 21 days. On day 22, the animals’ physical performance and muscle strength were assessed in a forced swimming test (FST) and forelimb grip strength experiment, respectively.In the human trial, thirty-eight resistance-trained young adults (mean age 26.32?±?4.39 years, body weight 67.79?±?12.84 kg, BMI 22.92?±?3.54 kg/m²) completed the trial. The participants received either GMCT (n?=?19; 800 mg daily) or matched placebo (n?=?19) for 42 days. As primary variables, 1-RM bench press, 1-RM leg press, and leg extension repetitions were measured at baseline and on days 14, 28 and 42 of the intervention. Anthropometric parameters and serum markers such as free testosterone, insulin-like growth factor 1 (IGF-1), insulin and lactate were also measured before and after the intervention.

Results

GMCT-300 mice showed significant improvement in swimming time (GMCT: 395.3?±?81.70 s vs. CMC: 271.6?±?56.86 s; p?=?0.0166), distance (GMCT: 341.22?±?65.88 m vs. CMC: 260.84?±?49.15 m; p?=?0.0461) and grip strength (GMCT: 43.92?±?6.97 N vs. CMC: 35.0?±?6.92 N; p?=?0.0490), compared with the CMC group.At the end of the 42-day human trial, the per protocol analyses reveal that mean changes from baseline 1-RM bench press (GMCT: 23.47?±?10.07 kg vs. PL: 3.42?±?2.06 kg; p?<?0.0001), leg press (GMCT: 29.32?±?16.17 kg vs. PL: 5.21?±?1.72 kg; p?<?0.0001), number of leg extension repetitions (GMCT: 6.58?±?2.57 vs. PL: 2.05?±?1.22; p?<?0.0001) in GMCT group were significantly improved, compared with placebo. Intergroup difference analyses show that the changes from baseline left arm (GMCT: 1.09?±?0.36 cm vs. PL: 0.68?±?0.42 cm; p?=?0.0023), right arm (GMCT: 1.50?±?0.44 cm vs. PL: 1.11?±?0.43 cm; p?=?0.0088) circumference and lean mass (GMCT: 2.29?±?2.09 kg vs. PL: 0.52?±?2.58 kg; p?=?0.0404) in GMCT group were also significantly improved, compared with placebo. In comparison to placebo, GMCT supplementation did not improve free testosterone, IGF-1, insulin or lactate levels. Parameters of clinical biochemistry, hematology, urine and vital signs of the participants were within the normal range.

Conclusion

GMCT supplementation is effective in increasing muscle strength, muscle size and, total lean mass, as well as endurance performance.Trial Registration.Clinical Trial Registry of India (CTRI/2015/01/005374), Registered on Jan 07, 2015; CTRI Website URL - http://ctri.nic.in

     

Paramagnetic Quantum Dots as Multimodal Probes for Potential Applications in Nervous System Imaging

An axonal tracer that can be detected by both magnetic resonance imaging (MRI) and fluorescence is of great interest for studying nerve regeneration, particularly for spinal cord injury repairs. In this study, we develop a new type of multifunctional nanoparticle that combines three different functionalities of paramagnetism, fluorescence, and axonal tracing into one nanomaterial. We demonstrate that the new synthesized quantum dot nanoparticles have good biocompatibilities and can be readily taken up by cells. In addition, the quantum dots show excellent longitudinal and transverse relaxivities (i.e. r ₁ ?=?11.22?±?0.10 mM^?1 s^?1 and r ₂ ?=?24.50?±?0.51 mM^?1 s^?1) at 1.5 T, MRI contrast properties better than those of Magnevist®, a commercially available MRI contrast agent. The UV–vis absorbance spectra of all the pQDs-BDA samples indicate that these tracers are stable at different temperatures. Taken together, this new nanomaterial demonstrates good performances for both optical and MR imaging modalities, suggesting its promising potential applications in non-invasive imaging, particularly as a novel multimodal axonal tracer for nervous system imaging.     

Synthesis and Characterization of Novel Aryl Alkyl Sulfonates Based on Nonylphenol

A series of nonylphenol-substituted alkyl sulfonates (C _x NPAS, x = 8, 10, 12, 14, 16) with two hydrocarbon chains and two different hydrophilic groups has been synthesized from α-olefins and nonylphenol. The respective products have a “pseudo-gemini” surfactant structure. The structures of the C _x NPAS have been characterized by IR, UV, ¹H nuclear magnetic resonance, electrospray ionization mass spectrometry, and elemental analysis. The effects of carbon chain length of the obtained surfactants on properties such as the critical micelle concentrations (CMC) in aqueous solutions, surface tension at the CMC (γ _CMC), and efficiency of adsorption at the water/air interface (pC ₂₀) have been determined. The γ _CMC of the surfactants first decreased and then increased with increasing length of the carbon chain x, and reached a minimum of 29.25 mN/m at x = 10, which is much lower than that of α-olefin sulfonate (AOS) (33.52 mN/m). The CMC decreased and pC ₂₀ increased with increasing x. The introduction of the hydroxyl group is responsible for multiple molecular conformations at the water/air interface and leads to a greater molecular area A _min and smaller Γ_max than those of AOS.     

Crystallinity of large single crystals of FAU-type zeolites with a wide range of Si/Al ratios

Large colorless single crystals of FAU-type zeolites were synthesized from gels with the composition xSiO₂ : 2.0NaAlO₂ : 7.5NaOH : 454H₂O : 5.0TEA, where x = 2.0–6.0. FAU-type zeolite with Si/Al = 1.26(4) was nearly pure and the maximum size of the single crystals was ca. 150 μm. In case of FAU-type zeolites with Si/Al = 1.54(5), the maximum size of single crystals was ca. 200 μm and the ratio of FAU/impurity was 0.07. The framework Si/Al ratio of the as-synthesized FAU-type zeolite tended to increase with the Si/Al ratio of gel composition. All of the large single crystals had good crystallinities for single-crystal X-ray diffraction, leading to enough numbers of significant reflections which have strong intensity. The structure of a single crystal of dehydrated zeolite Na-X (Si/Al = 1.41(4)) with composition |Na₈₀|[Si₁₁₂Al₈₀O₃₈₄]-FAU per unit cell was determined by X-ray diffraction methods in the cubic space group \( Fd \bar{3} m; \) a = 24.9434(6) Å at 294 K. The structure was refined by using all intensities to the final error indices (using only the 771 reflections for which F _o > 4σ(F _o)), R ₁ = 0.048 (based on F) and R ₂ = 0.188 (based on F ²). In the crystallographic studies, the Si/Al ratio of the synthetic FAU-type zeolite is 1.41(4) which is quite consistent with the SEM–EDS analysis.     

Preparation of high surface area mesoporous nickel oxides and catalytic oxidation of toluene and formaldehyde

Mesoporous nickel oxide (NiO) nanoparticles were synthesized by the thermal decomposition reaction of Ni(NO₃)₂·9H₂O using oxalic acid dihydrate as the mesoporous template reagent. The pore structure of nanocrystals could be controlled by the precursor to oxalic acid dihydrate molar ratio, thermal decomposition temperature and thermal decomposition time. The structural characteristic and textural properties of resultant nickel oxide nanocrytals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N₂ adsorption–desorption isotherm and temperature programmed reduction. The results showed that the most excellently mesoporous nickel oxide particles (m-Ni-1-4) with developed wormlike pores were prepared under the conditions of the mixed equimolar precursor and oxalic acid and calcined for 4 h at 400 °C. The specific surface area and pore volume of m-Ni-1-4 are 236 m² g^?1 and 0.42 cm³ g^?1, respectively. Over m-Ni-1-4 at space velocity = 20,000 mL g^?1 h^?1, the conversions of toluene and formaldehyde achieved 90 % at 242 and 160 °C, respectively. It is concluded that the reactant thermal decomposition with oxalic acid assist is a key step to improve the mesoporous quality of the nickel oxide materials, the developed mesoporous architecture, high surface area, low temperature reducibility and coexistence of multiple oxidation state nickel species for the excellent catalytic performance of m-Ni-1-4.     

Complex-radical copolymerization of <Emphasis Type="Italic">N-</Emphasis>vinyl pyrrolidone with isostructural analogs of maleic anhydride

Radical copolymerizations of N-vinyl-2-pyrrolidone (VP) with isostructural analogs of maleic anhydride (MA), such as citraconic anhydride (CA) and N-substituted maleimides [maleimide (MI), N-ethylmaleimide (EMI) and N-phenylmaleimide (PhMI)] were studied. Compositions of copolymers synthesized in a wide range of monomer feed ratios were determined by alkali titration (for anhydride copolymers), FTIR and ¹H NMR spectroscopy using 1495 and 630 cm^-1 (for VP-MI), 1289 and 1225 cm^-1 (for VP-EMI) and 1050 and 3067 cm^-1 (for VP-PhMI) analytical bands and integral areas of CH₂ (pyrrolidone ring) and CH (MI), CH₃ (EMI) and CH= (benzene ring in PhMI) groups, respectively. Electron-donor VP monomer was found to have substantially different reactivities in the radical copolymerization with MA, CA and N-substituted (H, C₂H₅ and phenyl) malemides as electron-acceptor comonomers. Effects of H-bonding and N→O=C coordination on the monomer reactivity ratios were evaluated. Tendency to alternation of the monomer pairs increases in the order of VP–MA > VP–CA > VP-MI > VP-PhMI > VP-EMI. Structure-thermal property-relationship for the synthesized copolymers was also studied.     

Magnetic Field-Induced Splitting of Optical Spectra in Silicon Nanotubes: Tight Binding Calculations

The splitting of band structure and absorption spectra, for silicon nanotubes (SiNTs) under axial magnetic field, are studied using the tight binding approximation. It is found that band splitting is approximately proportional to the magnitude of magnetic field as \(\frac {\Delta E}{E_{g}}=\nu _{ii} \frac {\Phi }{{\Phi }_{0}}\) where ν _{i i} is the splitting rate. For Si g-NTs, we calculated the splitting rate of the two first bands nearest to the Fermi level in the Γ point and found that it can be fitted with a two degree polynomial as \(\nu _{ii}={\sum }_{j=0}^{2}{a^{i}_{j}}x^{j}\) where \(x=\frac {1}{n^{2}}\) and for sufficiently large diameter Si g-NTs, the ν _{i i} can be fitted by a linear function. For semiconductor Si h-NTs the ν ₁₁ = 6 but ν ₂₂ and ν ₃₃ show radial dependence. Also we found that applying magnetic field leads to splitting for all peaks in the low energy ranges for all zigzag Si h-NTs and Si g-NTs. The first peak of group (I) of Si g-NTs does not show any splitting in the magnetic field and for all metallic Si h-NTs, the magnetic field leads to creating a peak in the energy range less than 0.2 eV where this peak arises from energy gap created around Fermi energy.     

Development of natural and synthetic polymer-based semi-interpenetrating polymer network for controlled drug delivery: optimization and in vitro evaluation studies

This research paper describes the development, optimization and in vitro characterization of chemically cross-linked pectin–polyvinyl alcohol-co-poly(2-Acrylamido-2-methylpropane sulfonic acid) semi-interpenetrating polymer network hydrogel [pectin–PVA-co-poly(AMPS) semi-IPN hydrogel] for controlled delivery of model drug tramadol HCl. Response surface methodology based on 3² factorial design was used for optimization and investigating the effect of independent factors: polymer-blend ratio (pectin:PVA = X ₁) and monomer (AMPS = X ₂) concentration on the dependent variables, swelling ratio (q _18th), percent drug release (R _18th, %), time required for 80 % drug release (t _{80 %}, h), drug encapsulation efficiency (DEE, %) and drug loaded contents (DLC, mg/g) in pectin-PVA-co-poly(AMPS) gels prepared by free radical polymerization. The optimized semi-IPN gel (FPP-10) showed controlled in vitro drug release (R _18th) of 56.34 % in 18 h, t _{80 %} of 30 h, and DEE of 23.40 %. These semi-IPN hydrogels were also characterized through SEM, FTIR, sol–gel analysis, swelling studies and drug release characteristics. Therefore, this newly synthesized polymeric network could be a potential polymeric system for controlled drug delivery of tramadol HCl for prolonged drug release.     

Influence of pressure on the refractive index and relative density of glasses in the CaO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

The pressure dependences of the refractive index for aluminosilicate glasses of the compositions 0.167CaO · 0.167Al₂O₃ · 0.666SiO₂ and 0.157CaO · 0.177Al₂O₃ · 0.666SiO₂ at pressures up to 6.0 GPa are determined using a polarizing interference microscope and an apparatus with diamond anvils. The compressibilities of the glasses are calculated from the measured refractive indices within the framework of the theory of photoelasticity. The structural-chemical parameters NBO/T (where NBO is the number of gram-ions of nonbridging oxygen atoms and T is the total number of gram-ions of network formers) are calculated for the glasses under investigation with allowance made for the formation of triclusters and highly coordinated aluminum.