Low Polydispersity Index Values Research Articles

Well‐defined structures and nanoscale morphology for all‐conjugated BCPs

A series of conjugated donor–acceptor (D–A) block copolymers (BCPs) were synthesised using a one-pot Stille coupling polycondensation reaction. This involved reaction between a series of mono-bromo-functionalised Poly3-hexylthiophene (P3HT) polymers (P3HT-Br, Mn: 17, 21 and 43 kg/mol) and [N, N ′-bis (2-decyl-tetradecyl)-1,7-dibromo-3,4,9,10-perylene diimide (PBI) and [2,5-bis(trimethylstannyl)-thiophene] (T) monomers. Purification using preparative gel permeation chromatography (GPC) removed any excess P3HT and resulted in BCPs with low polydispersity index values. The P3HT-b-PBIT BCPs were characterised using 1 H-NMR and Fourier-transform infrared spectroscopy. When compared to a P3HT/PBIT polymer blend, the D–A BCP films exhibited a remarkably fine structure with a nanoscale morphology. These results indicated that these D–A BCPs have the potential for use as nanostructured active layers in polymer solar cells.

Towards the production of monodisperse gelatin nanoparticles by modified one step desolvation technique

The aim of the present study was to prepare gelatin nanoparticles (GNPs) using modified one step desolvation method to obtain small, uniformly sized, and spherical GNPs. The modifications involved the preparation of high molecular weight gelatin (HMWG) by fractionation of gelatin. HMWG was freeze-dried to be used in a specified concentration for preparation of GNPs with controllable properties. Furthermore, HMWG was cationized by dissolving it in acidified deionized water at pH value less than its isoelectric point. Factorial design analysis was utilized to investigate the effect of different preparation variables (viz. HMWG concentration, pH and ratio of HMWG solution volume to non-solvent volume) on particle size, polydispersity index (PDI), zeta potential and yield of GNPs. Results revealed the formation of monodisperse GNPs with small particle size, low PDI values (< 0.2) and high yield. FT-IR spectroscopy and differential scanning calorimetry studies revealed that the conformational structure of HMWG chains was altered within GNPs matrices. The suggested modifications introduced on the one-step desolvation method enable to prepare successfully monodispersed GNPs with narrow size distribution and high particle yield.

Developing curcumin nanoemulsions by high-intensity methods: Impact of ultrasonication and microfluidization parameters

Curcumin nanoemulsions were produced by ultrasonication and microfluidization, two of the most used emulsification methods. The impact of the processing and formulation parameters on the mean droplet size, polydispersity index (PI), and zeta potential of the emulsions was evaluated. Curcumin was dissolved in diverse types of oil (e.g., medium chain triglycerides (MCT), grapeseed, or olive oil). Two ultrasonic processors (130 W & 750 W) were operated at different amplitudes (40% and 90%) for 1800 s. The droplet size and PI of the emulsions decreased with increases in time, amplitude, and power delivered by ultrasonication. The grapeseed and olive oils induced recrystallization of curcumin under the ultrasonication condition tested. Similar nanoemulsions with low PI values were produced with an amplitude of 90% and sonication of 1800 s (130 W & 750 W processors). Microfluidization decreased the droplet size with increasing the pressure and number of passes. However, over-processing of the samples was induced at 140 MPa and many passes for oil volume fractions of 0.10 and 0.20. The MCT oil produced the emulsion with the smallest droplet size. High negative zeta potential values were observed in all samples. Ultrasonication produced nanoemulsions with smaller droplet size and monomodal distribution than microfluidization.

Synthesis of PAN with adjustable molecular weight and low polydispersity index (PDI) value via reverse atom transfer radical polymerization

ABSTRACTThe reverse atom transfer radical polymerization (RATRP) of acrylonitrile (AN) was carried out in N, N-dimethylformamide (DMF) with AIBN as initiator, FeCl3•6H2O/triphenylphosphine (PPh3) and FeCl3•6H2O/pentamethyldle-thylenetrlamlne (PMDETA) as catalytic systems, respectively. Effect of reaction time and initiator concentration on polymerization rate, molecular weight and molecular weight distribution were investigated in detail. The Fourier transform infrared spectrometer (FTIR) and 1H nuclear magnetic resonance spectroscopy (1HNMR) were employed to analyze the chain end of the PAN. Gel permeation chromatography (GPC) was applied to measure the molecular weight and polydispersity index (PDI) of PAN. The polymerization demonstrated a typical pseudo first-order kinetics characteristics as evidenced by the number-average molecular weights (Mn) increasing linearly with monomer conversion; the Mn decreasing with the increasing of the initiator concentration. Meanwhile, the low PDI value (<1.2) indicated the controllability of polymerization.

Formulation and In-vitro Characterization of Self Nano-emulsifying Drug Delivery System (SNEDDS) for enhanced Solubility of Candesartan Cilexetil

Candesartan cilexetil is the prodrug of candesartan, a selective angiotensin II receptor antagonist, used in the management of hypertension and heart failure. It is characterized by poor aqueous solubility resulting in low bioavailability. Self-nanoemulsifying drug delivery systems (SNEDDS) loaded with candesartan cilexetil were successfully developed to overcome such obstacles. Preliminary screening was carried out to select proper oil, surfactant and co-surfactant combination for successful SNEDDS formulation. Ternary and pseudo ternary diagrams were constructed to optimize the system. Capryol 90® as an oil showed high emulsification ability. The nature of obtained dispersions was found to be nanoemulsions. Six formulations were visually inspected and evaluated for stability, robustness to dilution, effect of drug loading on the nano-emulsion boundary, viscosity, content uniformity, their mean droplet size, polydispersity index (PDI), zeta potential in addition to in vitro drug release study. Three formulations showed a very short emulsification time of less than 3minutes. The emulsification efficiency was significantly superior at pH6.8. All selected formulations showed mean droplet size (124.25 to 460.15nm), very low PDI values (0.311–0.562) and zeta potential (30.5–44.45 mV). Formulation F16 (10% w/w Capryol 90®, 30% w/w Tween80, 60% w/w Transcutol®) was selected for further characterization. Droplet size of F16 showed robustness to different dilution folds with different media. These results indicate that, SNEDDS could be promising delivery systems with a rapid onset of action and prolonged therapeutic effect of candesartan cilexetil.

Production of dry-state ketoprofen-encapsulated PMMA NPs by coupling micromixer-assisted nanoprecipitation and spray drying

We present a two-step process to produce dry-state Ketoprofen-loaded poly(methyl methacrylate) nanoparticles (NPs) with controllable size and tunable drug release profile. A colloidal suspension of drug-loaded nanoparticles was first obtained from a nanoprecipitation process and then transferred into a commercial spray dryer. Three micromixers of different designs and mixing principles (molecular diffusion and impact mixing) were tested. After the first step, highly monomodal NPs in the size range 100 to 210 nm were obtained as seen by the low polydispersity index value (ca. PDI ∼ 0.2) returned by a dynamic light scattering detector. Physicochemical properties, encapsulation efficiency/ratio and drug release kinetics of NPs before and after drying were determined. For similar operating conditions, the best micromixer tested (impact mixing) allowed concluding that the NPs size was not significantly affected by the spray drying while encapsulation parameters and drug release rate were slightly decreased compared to the non spray-dried NPs. A sustained drug release was observed over 6 h and the drug release rate (up to 70%) was found to vary with the size of the NPs which in turn was a function of the flow rate ratio between the polymer solution and the non-solvent solution.

Ring opening polymerization and copolymerization of L‐lactide and ɛ‐caprolactone by bis‐ligated magnesium complexes

ABSTRACTSeven magnesium complexes (1–7) were synthesized by reaction of new (L 3‐H–L 5‐H) and previously reported ketoimine pro‐ligands with dibutyl magnesium and were isolated in 59–70% yields. Complexes 1–7 were characterized fully and consisted of bis‐ligated homoleptic ketoiminates coordinated in distorted octahedral geometry around the magnesium centers. The complexes were investigated for their ability to initiate the ring opening polymerization (ROP) of l‐lactide (L‐LA) to poly‐lactic acid (PLA) and ɛ‐caprolactone (ɛCL) to poly‐caprolactone in the presence of 4‐fluorophenol co‐catalyst. For L‐LA polymerization, complexes containing ligand electron‐donating groups (1–5) achieved &gt;90% conversion in 2 h at 100 °C, while the presence of CF3 groups in 6 and 7 slowed or resulted in no PLA detected. With ɛCL, ROP initiated with 1–7 resulted in lower percentage conversion with similar electronic effects. Moderate molecular weight PLA polymeric material (14.3–21.3 kDa) with low polydispersity index values (1.23–1.56) was obtained, and ROP appeared to be living in nature. Copolymerization of L‐LA and ɛCL yielded block copolymers only from the sequential polymerization of ɛCL followed by L‐LA and not the reverse sequence of monomers or the simultaneous presence of both monomers. Polymers and copolymers were characterized with NMR, gel permeation chromatography, and differential scanning calorimetry. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 48–59

Formulation of chloroaluminum phthalocyanine incorporated into PS-b-PAA diblock copolymer nanomicelles

Chloroaluminum phthalocyanine (ClAlPc) is considered to be an important photosensitizer compound, and it has been extensively explored in photodynamic therapy (PDT) against several types of cancer cell lines. However, ClAlPc is known to be a highly hydrophobic compound. Thus, it requires physical association with a drug delivery system for clinical use. In this study, distinct formulations of PS70.5-b-PAA13 diblock copolymer nanostructures containing ClAlPc were studied. Results found in this study showed that the ClAlPc/PS70.5-b-PAA13 diblock composite presented micellar morphology and a size of 200 nm while dispersed in aqueous media. Additionally, zeta potential studies revealed that such formulations presented colloidal stability with low polydispersity index (PDI) values (0.121). The encapsulation efficiency of ClAlPc by such copolymer micelles, made through spectroscopic measures, was higher than 95% while at the phthalocyanine concentration range from 9.0 to 70 μmol L−1. Spectroscopic studies also showed that the existence of monomeric ClAlPc in such nanostructured micelles is closely dependent on the PS concentration. Low PS concentration resulted in monomeric ClAlPc, as observed from the correspondent absorption and emission spectra of freshly-prepared composite. However, even after 15 days of storage and at low PS concentration, the ClAlPc can self-aggregate within the polymer-micellar nanoenvironment (as observed through spectroscopic studies). Photophysical properties of ClAlPc incorporated in the PS-b-PAA copolymer system revealed promising values of oxygen singlet generation (ΦΔ1O2 = 0.3). Skin permeation studies performed by photoacoustic spectroscopy showed that the ClAlPc/PS-b-PAA nanosystem permeates and reaches the superficial dermis layer. In vitro tests, using Caco-2 cell-lines incubated with ClAlPc/PS-b-PAA formulations at different phthalocyanine concentrations, showed cellular damage after 30 min under light radiation (663 nm with LED, fluence of 1.62 μJ cm−2). The IC50 obtained for the system containing ClAlPc/PS-b-PAA was 1.74 · 10−7 mol L−1. Furthermore, no cytotoxicity effect was observed during cell growth tests performed using both ClAlPc/PS-b-PAA composite and pristine PS-b-PAA nanomicelles in the absence of light irradiation. These findings suggested that the PS-b-PAA diblock copolymer produced a promising nanostructured system suitable for the incorporation of the hydrophobic ClAlPc photosensitizer and for subsequent use in the PDT field.

Preparation, characterization, and antibacterial activity of diclofenac-loaded chitosan nanoparticles

Emerging antibiotic resistance necessitates the development of new therapeutic approaches. Many studies have reported the antimicrobial activity of diclofenac sodium (DIC) and chitosan nanoparticles (CNPs). Hence, this study aimed to prepare non-antibiotic DIC-loaded CNPs (DIC.CNPs) and characterize their in vitro antibacterial activity. DIC.CNPs were prepared from low and high molecular weight (LMW and HMW, respectively) chitosan using an ionic gelation method. Prepared NPs were characterized, and their antibacterial activity against gram-positive Staphylococcus aureus and Bacillus subtilis was evaluated using the agar diffusion and broth dilution methods. The particle size, polydispersity index (PDI), and encapsulation efficiency of the formulated DIC.CNPs increased with increasing MW of chitosan. The prepared NPs showed a narrow size distribution with low PDI values (0.18 and 0.24) and encapsulation efficiency (29.3% and 31.1%) for LMW.DIC.CNPs and HMW.DIC.CNPs, respectively. The in vitro release profile of DIC from the DIC.CNPs was biphasic with a burst release followed by slow release and was influenced by the MW of chitosan. DIC.CNPs exhibited significantly higher antibacterial activity against S. aureus (minimum inhibitory concentration [MIC90] LMW.DIC.CNPs = 35 µg/mL and MIC90 HMW.DIC.CNPs = 18 µg/mL) and B. subtilis (MIC90 LMW.DIC.CNPs = 17.5 µg/mL and MIC90 HMW.DIC.CNPs = 9 µg/mL) than DIC alone did (MIC90 DIC = 250 and 50 µg/mL against S. aureus and B. subtilis, respectively). The antibacterial activity was influenced by pH and the MW of chitosan. Collectively, these results may suggest the potential usefulness of DIC.CNPs as non-antibiotic antibacterial agent necessitating further future studies to asses the stability of DIC.CNPs prepared.

Raspberry-like and other hexagonal close-packed morphologies of P(St-MMA-AA) particles obtained from different emulsifiers for photonic applications.

A facile one-pot synthesis of Poly(Styrene-methyl-methacrylate-acrylic acid) P(St-MMA-AA) terpolymers by soap seeded emulsion polymerization was examined. Raspberry-like and hexagonal close-packed morphologies were conveniently obtained using Cetyltrimethylammonium bromide (CTAB), Sodium dodecyl sulphate (SDS) and Gum arabic (GA) emulsifiers. The resultant colloidal latex samples were used to fabricate coloured tunable photonic crystals via vertical deposition process. The results showed that the emulsifiers used effectively reduced the polydispersity index (PDI) and zeta potential of the terpolymer samples (Ter-PSDS, Ter-PGA and Ter-PCTAB 0.021, 0.097 and 0.076; –36.20, –35.60 and –32.80, respectively). Thus, the interfacial tension between particles that promote the formation of the stable nanosized photonic crystals is also reduced. The low PDI values are clear indication of monodispersity of the terpolymer samples. Varying the choice of emulsifiers also resulted in changes in the particles sizes as well as the resultant morphologies. The particles diameters of 117.15, 209.20 and 315.00 nm were obtained for Ter-PSDS, Ter-PGA and Ter-PCTAB, respectively. The results showed that Ter-PSDS was the most stable of all terpolymers examined. The fabricated photonic crystals were observed to reflect different wavelengths (Iridescent colours) as the observation angles changed. This could be due to the bandgap resulting from the different morphologies associated with the different emulsifiers. The variation in the colour reflectance with change in the observation angle confirms the photonic potential of the synthesized P(St-MMA-AA) crystals.

Size-controlled fabrication of zein nano/microparticles by modified anti-solvent precipitation with/without sodium caseinate.

Zein-based nano/microparticles have been demonstrated to be promising carrier systems for both the food industry and biomedical applications. However, the fabrication of size-controlled zein particles has been a challenging issue. In this study, a modified anti-solvent precipitation method was developed, and the effects of various factors, such as mixing method, solvent/anti-solvent ratio, temperature, zein concentrations and the presence of sodium caseinate (SC) on properties of zein particles were investigated. Evidence is presented that, among the previously mentioned factors, the mixing method, especially mixing rate, could be used as an effective parameter to control the size of zein particles without changing other parameters. Moreover, through fine-tuning the mixing rate together with zein concentration, particles with sizes ranging from nanometers to micrometers and low polydispersity index values could be easily obtained. Based on the size-controlled fabrication method, SC-coated zein nanoparticles could also be obtained in a size-controlled manner by incubation of the coating material with the already-formed zein particles. The resultant nanoparticles showed better performance in both drug loading and controlled release, compared with zein/SC hybrid nanoparticles fabricated by adding aqueous ethanol solution to SC solution. The possible mechanisms of the nanoprecipitation process and self-assembly formation of these nanoparticles are discussed.

Role of surface capping on the cytotoxicity of silica nanoparticles in rat alveolar epithelial cells

The aim of the present work was to develop and evaluate the potential of nanostructured lipid carriers associated with caffeine extracted from Coffee Silverskin (NLC-CS), a food by-product, as a new possible topical therapy of cellulitis. Caffeine gain increasing research interest due to their cosmetic potential, particularly in gynoid lipodystrophy, commonly known as cellulite. NLC-CS were prepared via double emulsion technique using polysorbate 60 as surfactant and characterized for their morphology, particle size, zeta potential, association encapsulation and stability. The in vitro skin permeation studies were performed on Franz diffusion cells using pig skin ear as permeation membrane and the optimized formulation was compared with a hydroalcoholic solution of Coffee silverskin (CS) extract.NLC-CS were within the nanosized range (≈200 nm), with a low polydispersity index (<0.25) and zeta potential values around −30 Mv, presenting storage stability up to 180 days at 25 °C/65% relative humidity (RH) and 40 °C/75% RH. The association efficiency (AE) of caffeine was about 30% at production time and after storage period. Cryo-SEM images confirmed the spherical shape of NLC-CS.The in vitro skin permeation study demonstrated that NLC-CS had a similar skin permeation profile when compared to caffeine in CS extract.

Development and in vitro/in vivo performance of self-nanoemulsifying drug delivery systems loaded with candesartan cilexetil

Candesartan cilexetil is widely used in the management of hypertension and heart failure. The drug delivery encounters obstacles of poor aqueous solubility, efflux by intestinal P-glycoprotein and vulnerability to enzymatic degradation in small intestine. Self-nanoemulsifying drug delivery systems (SNEDDS) loaded with candesartan cilexetil were successfully developed to overcome such obstacles. Preliminary screening was carried out to select proper surfactant, co-surfactant and oil combination for successful SNEDDS formulation. All screened excipients were reported for their P-glycoprotein and cytochrome P450 3A4 (CYP3A4) modulation activity. Ternary and pseudo ternary diagrams were constructed to optimize the system. Peppermint oil and clove oil showed a high emulsification ability. The nature of obtained dispersions was identified to be nanoemulsions. Twenty-four formulations were evaluated for stability, robustness to dilution and self-emulsification efficiency. All formulations showed a very short emulsification time of <2min. The emulsification efficiency was significantly superior at pH6.8, at which the largest self-emulsifying region was also observed. Eight formulations were selected for further characterization according to cloud point measurement; mean droplet size, poly dispersity index (PDI) and zeta potential determination in addition to in vitro drug release study. All selected formulations showed very high cloud points (70–90°C), ultrafine mean droplet size (12±1.4 to 24.5±2.13nm), very low PDI values (0.015–0.1305) and almost a complete drug release after 12h. Formulation F15 (Peppermint oil 55% w/w: Cremophor RH40 25% w/w: Labrasol 20% w/w) was selected for further characterization. Its droplet size showed robustness to different dilution folds with different media and its TEM photograph showed spherical particles without any apparent aggregation even after 24h. Formulation F15 successfully controlled the systolic blood pressure of hypertensive rats for 24h with the maximum effect was observed after 2h. These results indicate that, SNEDDS could be promising delivery systems with a rapid onset of action and prolonged therapeutic effect of candesartan cilexetil.

Development and characterization of mucoadhesive buccal gels containing lipid nanoparticles of ibuprofen

The lipid nanoparticles, namely Nanostructured Lipid Carriers (NLC), as drug delivery systems have been investigated for several years.One of the delivery routes for which these carriers can be applied is buccal administration. However, the liquid dispersions of lipid nanoparticles can be rapidly removed from oral cavity by saliva. Thus, the development of a system that allows increased retention time on the mucosa is necessary. For this reason, the development of mucoadhesive preparations for buccal administration of lipid nanoparticles becomes important.Hydrogels prepared with mucoadhesive polymers (Carbopol® 980 and polycarbophil) constitute a promising option. The aim of this work was to develop mucoadhesive buccal hydrogels with NLC, using ibuprofen as a model drug.The obtained results showed that the developed NLC dispersions presented particles in the nanometric size range, with low polydispersity index values and efficient ability for the entrapment of the model drug. Moreover, the incorporation of NLC in hydrogels of mucoadhesive polymers resulted in preparations with desirable rheological features as well as texture (firmness and adhesiveness) and mucoadhesive properties, which could benefit the therapeutic efficacy, by increasing the residence time and easiness for topical application in the buccal mucosa. Additionally, the developed preparations exhibited sustained drug release as intended for these systems.

Preparation of Chitosan-Coated Nanostructured Lipid Carriers (CH-NLCs) to Control Iron Delivery and Their Potential Application to Food Beverage System.

Nanostructured lipid carriers (NLCs) and chitosan-coated NLCs (CH-NLCs) were prepared by a combined double emulsion and melt dispersion method. The physicochemical properties of them were investigated to determine the optimum conditions. At 3% emulsifier concentration, the NLCs showed about 191.0 ± 4.1 nm mean particle size and low polydispersity index value compared to those observed under other conditions. The encapsulation efficiency of CH-NLCs was 83.9% which was about 10% higher than that of NLCs. In vitro release test showed that low release amount of iron from the NLCs (11%) and CH-NLCs (5%) in simulated gastric condition within 3 h, whereas the iron release amounts of the NLCs and CH-NLCs were high (over 77%) in simulated intestinal condition because both NLCs and CH-NLCs were totally destructed in the intestinal condition after 3 h. In the thiobarbituric acid test, the absorbance of milk-fortified NLC and CH-NLCs was lower than that of original milk. Based on these results, CH-NLCs showed great potential for iron fortification in milk.

Permeation of topically applied caffeine from a food by—product in cosmetic formulations: Is nanoscale in vitro approach an option?

The aim of the present work was to develop and evaluate the potential of nanostructured lipid carriers associated with caffeine extracted from Coffee Silverskin (NLC-CS), a food by-product, as a new possible topical therapy of cellulitis. Caffeine gain increasing research interest due to their cosmetic potential, particularly in gynoid lipodystrophy, commonly known as cellulite. NLC-CS were prepared via double emulsion technique using polysorbate 60 as surfactant and characterized for their morphology, particle size, zeta potential, association encapsulation and stability. The in vitro skin permeation studies were performed on Franz diffusion cells using pig skin ear as permeation membrane and the optimized formulation was compared with a hydroalcoholic solution of Coffee silverskin (CS) extract.NLC-CS were within the nanosized range (≈200nm), with a low polydispersity index (<0.25) and zeta potential values around −30Mv, presenting storage stability up to 180days at 25°C/65% relative humidity (RH) and 40°C/75% RH. The association efficiency (AE) of caffeine was about 30% at production time and after storage period. Cryo-SEM images confirmed the spherical shape of NLC-CS.The in vitro skin permeation study demonstrated that NLC-CS had a similar skin permeation profile when compared to caffeine in CS extract.

Synthesis of chemically amplified photoresist polymer containing four (Meth)acrylate monomers via RAFT polymerization and its application for KrF lithography

KrF photoresist polymers (PASTMs) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Four (meth)acrylates with lithographic functionalities including styrene (St), 4-acetoxystyrene (AST), 2-methyl-2-adamantyl methacrylate (MAMA), and tert-butyl acrylate(TBA) were used as monomer components and 2-methyl-2-[(dodecylsulfanylthiocarbonyl) sulfanyl]propanoic acid (MDFC) was used as RAFT agent, varying the RAFT content could modulate molecular weight. Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR) indicated that the synthesis was successful. Gel permeation chromatography (GPC) showed that the molecular weight decreased with the increased content of MDFC, and all the polymers possessed weight-average molecular weight below ten thousand and polydispersity less than 1.32. Thermogravimetric analysis (TGA) characterized the thermal properties, the results implied that initial thermal decomposition temperature reached 200 °C, which could satisfy the lithography process. Differential scanning calorimetry (DSC) showed that the Tg decreases with molecular weight. The RAFT polymerization kinetics plots demonstrated that the polymerization was first-order, the number-average molecular weights of the polymers with relatively low polydispersity index values increased with total monomer conversions indicating that the concentration of growing radicals was constant throughout the polymerization process. The narrow molecular weight distribution and composition uniformity of the polymers prepared by RAFT polymerization could be beneficial for lithography, after alcoholysis, lithography evaluation under KrF lithography showed that this homogeneous polymer photoresist exhibited better space and line (S/L) pattern with resolution of 0.18 μm according to the SEM image.

Polystyrene-silica aerogel nanocomposites by in situ simultaneous reverse and normal initiation technique for ATRP

Hexamethyldisilazane (HMDS) was employed to surface modification of hydrophilic silica aerogel nanoparticles. Then, the resultant modified nanoparticles were used for in situ polymerization of styrene by simultaneous reverse and normal initiation technique for atom transfer radical polymerization (SR&NI ATRP) to synthesize tailor-made polystyrene nanocomposites. Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) were employed for demonstrating success surface modification of hydrophilic silica aerogel nanoparticles with HMDS. Nitrogen adsorption/desorption isotherm is applied to examine surface area and structural characteristics of the synthesized hydrophobic silica aerogel nanoparticles. Evaluation of size distribution and morphological studies were also performed by SEM and TEM. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography respectively. Addition of 3 wt% hydrophobic silica aerogel nanoparticles results in a decrease of conversion from 97 to 77%. Molecular weight of polystyrene chains decreases from 11095 to 8755 g.mol-1 by addition of 3 wt% hydrophobic silica aerogel nanoparticles; however, polydispersity index (PDI) values increases from 1.15 to 1.46. Appropriate agreement between theoretical and experimental molecular weight in combination with low PDI values demonstrate the living nature of the polymerization. Thermal stability of the neat polystyrene and its different nanocomposites are studied by TGA. Differential scanning calorimetry shows a decrease in glass transition temperature from 94.8 to 83.5 °C by adding 3 wt% of hydrophobic silica aerogel nanoparticles.

Thermosensitive copolymer synthesized by controlled living radical polymerization: Phase behavior of diblock copolymers of poly(N‐isopropyl acrylamide) families

ABSTRACTIn this study, we prepared a series of thermosensitive polymers with low polydispersity index (PDI) values by nitroxide‐mediated controlled radical polymerization (NMRP) with 2,2,6,6‐tetramethyl‐1‐piperdinyloxy nitroxide (TEMPO) as a stable nitroxide‐free radical. Poly(N‐isopropyl acrylamide) (PNIPAAm)‐block‐poly(N‐tert‐butyl acrylamide) (PNTBA) was successfully synthesized, first, through polymerization with N‐isopropyl acrylamide to obtain the reactive polymer PNIPAAm‐TEMPO and, second, through polymerization by the addition of N‐tert‐butyl acrylamide (NTBA). The added molar fraction of NTBA during the second polymerization was adjusted accordingly to obtain the final polymerization product, a thermosensitive polymer (PNIPAAm‐block‐PNTBA), which had a targeted lower critical solution temperature (LCST). The result shows that the synthesis method used in this study effectively controlled the formation of the polymer to obtain a low PDI. The thermosensitive block copolymer, PNIPAAm‐b‐PNTBA (molar ratio = 9:1), with LCSTs in the range 27.7–39.8°C, was obtained through controlled living radical polymerization with PNIPAAm–TEMPO. Specifically, the 5 wt % aqueous solution of PNIPAAm‐b‐PNTBA (molar ratio = 9:1) had an LCST of 37.4°C; this was close to body temperature, 37°C. The 5 wt % aqueous solution of PNIPAAm‐b‐PNTBA (molar ratio = 9:1) showed potential for use in biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43224.

Atorvastatin calcium loaded chitosan nanoparticles: in vitro evaluation and in vivo pharmacokinetic studies in rabbits

&lt;p&gt;In this study, we prepared atorvastatin calcium (AVST) loaded chitosan nanoparticles to improve the oral bioavailability of the drug. Nanoparticles were prepared by solvent evaporation technique and evaluated for its particle size, entrapment efficiency, zeta potential, &lt;italic&gt;in vitro&lt;/italic&gt; release and surface morphology by scanning electron microscopy (SEM). In addition, the pharmacokinetics of AVST from the optimized formulation (FT5) was compared with marketed immediate release formulation (Atorva&lt;sup&gt;(r))&lt;/sup&gt; in rabbits. Particle size of prepared nanoparticles was ranged between 179.3 ± 7.12 to 256.8 ± 8.24 nm with a low polydispersity index (PI) value. Zeta potential study showed that the particles are stable with positive values between 13.03 ± 0.32 to 46.90 ± 0.49 mV. FT-IR studies confirmed the absence of incompatibility of AVST with excipient used in the formulations. &lt;italic&gt;In vitro&lt;/italic&gt; release study showed that the drug release was sustained for 48 h. Results of pharmacokinetics study showed significant changes in the pharmacokinetic parameter (2.2 fold increase in AUC) of the optimized formulation as compared to marketed formulation (Atorva&lt;sup&gt;(r))&lt;/sup&gt;. Thus, the developed nanoparticles evidenced the improvement of oral bioavailability of AVST in rabbit model.&lt;/p&gt;