Polydispersity Values Research Articles

Combining Photodynamic Therapy and Chemotherapy: Improving Breast Cancer Treatment with Nanotechnology.

Nanomedical approaches are the major transforming factor in cancer therapies. Based on important previous works in the field of drug delivery nanomaterials, recent years have brought a broad array of new and improved intelligent nanoscale platforms that are suited to deliver drugs. In this context, the purpose of this study was to investigate the action of different nanoemulsions designed to encapsulate chloroaluminum phthalocyanine, a hydrophobic photosensitizer used in photodynamic therapy, and doxorubicin, a well-known chemotherapeutic agent used to treat aggressive breast cancer cells. The mean nanostructured system size ranged from 170.8 to 181.0 nm, and the nanoemulsions presented spherical morphology. All formulations exhibited negative zeta potential values (-68.7 to -75.0 mV) and suitable polydispersity values (0.20 to 0.28), explaining their colloidal stability up to three months. Murine breast cancer cells (4T1) were incubated with nanoemulsions for three hours at various concentrations and were subjected to cell viability tests to find the concentration dependence profile. Thereafter, the in vitro phototoxic effect was evaluated in the presence of the visible laser light irradiation. Less than 10% of 4T1 viable cells were observed when photodynamic therapy and chemotherapy were combined at a 1.0 J · cm-2 laser light dose with 1.0 μM phthalocyanine and 0.5 μM doxorubicin. The cell death assay and cell cycle arrest analysis confirmed the therapy efficiency demonstrating an increase in the apoptosis rate and in the cell cycle arrest on G2. Additionally, 15 genes related to apoptosis and 25 target genes of anti-cancer drugs were overexpressed. Four genes related to apoptosis and four target genes of anti-cancer drugs were downregulated in 4T1 cells after treatment with nanoemulsion with phthalocyanine and doxorubicin associated with photodynamic therapy. Thus, the nanoemulsions loaded with phthalocyanine and doxorubicin presented appropriate physical stability, improved photophysical properties, and remarkable activity in vitro to be considered as promising formulations for photodynamic therapy and chemotherapeutic use in breast cancer treatment.

Phase Equilibria of Polydisperse Square-Well Chain Fluid Confined in Random Porous Media: TPT of Wertheim and Scaled Particle Theory.

Extension of Wertheim's thermodynamic perturbation theory and its combination with scaled particle theory is proposed and applied to study the liquid-gas phase behavior of polydisperse hard-sphere square-well chain fluid confined in the random porous media. Thermodynamic properties of the reference system, represented by the hard-sphere square-well fluid in the matrix, are calculated using corresponding extension of the second-order Barker-Henderson perturbation theory. We study effects of polydispersity and confinement on the phase behavior of the system. While polydispersity causes increase of the region of phase coexistence due to the critical temperature increase, confinement decreases the values of both critical temperature and critical density making the region of phase coexistence smaller. This effect is enhanced with the increase of the size ratio of the fluid and matrix particles. The increase of the average chain length at fixed values of polydispersity and matrix density shifts the critical point to a higher temperature and a slightly lower density.

Chemical composition, total phenolic content, antioxidant and antinutritional characterisation of exudate gums

Abstract Present study was conducted to determine the chemical composition, antioxidant potential and antinutritional factors in some plant gums that have been commercially used as additives in different food formulations. For this purpose, exudate gums were chosen which included commercially used acacia and karaya gum. The properties were compared with an underutilised gum exuded from apricot tree, called apricot gum. Monosaccharide composition and linkages in gum polysaccharides were studied using Electron spray ionization-mass spectrometry coupled with time-of-flight analyser (ESI-MS-TOF). The assay involves ionization of gum polysaccharides by passing their organic solution into electric field and converting them into a mist of charged droplets that are further analysed and detected using Time-of-flight mass spectrometry. Relative array of peaks elucidated the presence of glucosyl, galactosyl and a small proportion of uronic acid units in all gums. Spectral fragmentation distribution was bimodal with polydispersity values greater than or equal to two (Mw/Mn ≥ 2). In all the antioxidant assays, methanol and ethanol were separately used for extraction. Total phenolic content, ferrous ion chelating ability and reducing power of the gums varied from 0.44 to 1.25 mg GAE/g, 11.80–60.42% and 0.12–0.23 AAE/g, respectively. The DPPH radical scavenging ability (12.03–27.23%) and bile acid binding activity (40.98–46.60%) of the gums was also high. Presence of tannins (0.20–0.73 TAE/g), phytic acid (0.03–0.60 mg/g) and haemagglutinins (0.006–0.11 HU/mg protein) was observed at a very small concentration. On the other hand, the antinutritional factors like terpenoids, saponins and alkaloids were found completely absent.

Supported Cu0 nanoparticles catalyst for controlled radical polymerization reaction and block-copolymer synthesis

The synthesis of Cu0 nanoparticles on different supports and their activity in controlled living radical polymerization processes is presented. The type of support influences the final size of the copper nanoparticles as well as their adhesion to the support. These aspects have a direct influence on the characteristics of the polymers obtained. The best results were obtained for SiO2 particles, which afforded a good molecular weight distribution (Mw/Mn = 1.25). The activity, recovery and recycling of the catalyst was explored for ultrafast polymerization reaction of butyl acrylate. Further, the terminal bromine reactivity was used for the synthesis of a block poly(n butyl acrylate-block-styrene). The influence of ligand type on the control of the reaction was studied. Also, a straightforward polymerization procedure without any ligand afforded a polydispersity value of 1.38.

Formulation, Characterization and Stability Assessment of a Food-Derived Tripeptide, Leucine-Lysine-Proline Loaded Chitosan Nanoparticles.

The chicken- or fish-derived tripeptide, leucine-lysine-proline (LKP), inhibits the angiotensin converting enzyme and may be used as an alternative treatment for prehypertension. However, it has low permeation across the small intestine. The formulation of LKP into a nanoparticle (NP) has the potential to address this issue. LKP-loaded NPs were produced using an ionotropic gelation technique, using chitosan (CL113). Following optimization of unloaded NPs, a mixture amount design was constructed using variable concentration of CL113 and tripolyphosphate at a fixed LKP concentration. Resultant particle sizes ranged from 120 to 271 nm, zeta potential values from 29 to 37 mV, and polydispersity values from 0.3 to 0.6. A ratio of 6:1 (CL113:TPP) produced the best encapsulation of approximately 65%. Accelerated studies of the loaded NPs indicated stability under normal storage conditions (room temperature). Cytotoxicity assessment showed no significant loss of cell viability and in vitro release studies indicated an initial burst followed by a slower and sustained release.

The effect of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry instrumentation parameters on the matrix-assisted laser desorption/ionization simulated size exclusion chromatography number-mass, average-weight and polydispersity values of dextran against corresponding values obtained by size exclusion chromatography.

The matrix-assisted laser desorption/ionization simulated size exclusion chromatography (SECPC) average-number mass, weight average and polydispersity of dextran 1000 were determined by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry. The instrument parameters were varied and the SECPC value determined via the Bruker XMASS software was compared to the value obtained from aqueous-phase size exclusion chromatography. The aqueous-phase size exclusion chromatography values for average-number mass, weight average and polydispersity were 1223 Da, 1500 Da and 1.23 (1010 Da, 1270 Da and 1.26 from manufacturer), whereas the SECPC value varied on the instrumental parameters. The factors that had the greatest effect on the average-number mass, weight average and polydispersity were: (most effect on SECPC value) laser attenuation > matrix-analyte molar concentration > matrix-analyte molar ratios > delay extraction time > solvent-system composition > detector delay (least effect on SECPC value). The oligosaccharide signal distribution as a function of laser attenuation indicate that two distinct regions exist in dextran 1000, where one corresponds to the higher mass oligosaccharides (hexasaccharide or greater), while another region corresponds to lower oligosaccharides (tetra-saccharide). This distribution depends upon the crystallization of the biopolymer and the efficiency of desorption/ionization, which yields the SECPC value. There was broad agreement between the SECPC values and size exclusion chromatography values for dextran, although the polydispersity indicated by SECPC was less than size exclusion chromatography (1.10 vs. 1.26). It can be shown that for narrow polydisperse biopolymers the instrumental conditions are less critical in the determination of average-number mass, weight average and polydispersity, although the SECPC Mn, and weight average values are often higher than the corresponding values obtained by aqueous-phase size exclusion chromatography.

Stability assessment of neonatal parenteral nutrition solutions with various amino acid concentrations

Objective To explore the influence of various concentrations of amino acid on the stability of neonatal parenteral nutrition solutions. Methods Five formulations were designed with 5 different amino acid concentrations containing the same components. The final amino acid concentrations of admixtures were 0%, 1%, 2%, 3%, and 3.5%, respectively. The appearance, pH, and osmolality were observed or measured after preparation (0 hour) and at 12, 24, 48 and 72 hours after preparation. The average size and the size distribution of the lipid globules were also evaluated by laser nanometer particle size analyzer. Results There was no observable alteration in color, phase separation, precipitate, and flocculation in any admixture at any of the observation time points. The mean pH values for all groups were between (5.49±0.01) to (6.19±0.01) within 72 hours. The mean osmolalities for all groups were between (774±3) to (1 106±13)mOsm/kg. The mean diameters of lipid globules for all groups were between (280.6±0.7)mm to (332.2±2.0)nm. The mean polydispersity for all groups were between (0.200±0.011) to (0.245±0.012). The enrichment of amino acid concentration was linked to lower pH (P=0.000), higher osmolality (P=0.000) and larger average lipid globules size (P=0.000). However, there was no distinct linear dependence between amino acid concentration and polydispersity value (P=0.628). Conclusion After 72 hours of storage at room temperature, the appearance, pH, osmolality, and the average lipid globules diameter of the parenteral nutrition solutions are within the safe range when the amino acid is not contained or the concentrations are no more than 3.5%. Key words: Amino acid; Fat emulsions, intravenous; Stability; Neonatal parenteral nutrition

One-step enzymatic synthesis of poly(p-dioxanone-co-butylene-co-succinate) copolyesters with well-defined structure and enhanced degradability

In this work, we present a mild one-step enzymatic-catalyzed copolymerization of diethyl succinate, 1,4-butanediol and p-dioxanone (PDO) to synthesize poly(p-dioxanone-co-butylene-co-succinate) copolyesters. Their chemical structure, triad distributions, and molecular weight of the copolyesters are characterized by 1H NMR, 13C NMR and GPC. All copolyesters have narrow molecular weight polydispersity (1.3–1.5) and higher molecular weight (Mw) values (23700–33200 g mol−1), which are well controlled by varying the amount of PDO units from 9 to 30 mol%. NMR, DSC, and XRD results show that copolyesters are semicrystalline random copolyesters and thermal properties depended on their composition. Furthermore, the degradation rate of the poly(p-dioxanone-co-butylene-co-succinate) are enhanced compared to PBS.

Magnetorheological properties of sodium sulphonate capped electrolytic iron based MR fluid: a comparison with CI based MR fluid

Magnetorheological fluids have numerous engineering applications due to their interesting field assisted rheological behavior. Most commonly used dispersed phase in MR fluids is carbonyl iron (CI). The relatively high cost of CI warrants the need to develop cheaper alternatives to CI, without compromising rheological properties. With the above goal in mind, we have synthesized sodium sulphonate capped electrolytic iron based MR fluid and studied their magnetorheological properties. The results are compared with that of CI based MR fluid. EI and CI particles of average particle size of ∼10 μm with fumed silica particles additives are used in the present study. The dynamic yield stress for EI and CI based MR fluid were found to vary with field strength with an exponent of roughly 1.2 and 1.24, respectively. The slightly lower static and dynamic yield stress values of EI based MR fluid is attributed to the lower magnetization and polydispersity values. The dynamic yield stress showed a decrease of 18.73% and 61.8% for field strengths of 177 mT and 531 mT, respectively as the temperature was increased from 293 to 323 K. The optorheological studies showed a peak in the loss moduli, close to the crossover point of the storage and loss moduli, due to freely moving large sized aggregates along the shear direction that are dislodged from the rheometer plates at higher strains. Our results suggests that EI based MR fluids have magnetorheological behavior comparable to that of CI based MR fluids. As EI is much cheaper than CI, our findings will have important commercial implications in producing cost effective EI based MR fluids.

Poly(2-hydroxyethyl methacrylate)-Based Amphiphilic Block Copolymers for High Water Flux Membranes and Ceramic Templates

Microphase separation drives the structure formation in block copolymers (BCP), and it is a promising and convenient way for the preparation of well-defined hierarchically structured materials. In this work, we focus on the synthesis of amphiphilic block copolymers, i.e., polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA), via sequential anionic polymerization. Molecular weights of the prepared BCPs were in the range of 103–308 kg mol–1 with low polydispersity values (Đ = 1.03–1.25) and a PHEMA content of 17–25 vol % as proven by size exclusion chromatography (SEC) and 1H NMR spectroscopy measurements. For the first time, the PS-b-PHEMA BCPs were subjected to the self-assembly and non-solvent-induced phase separation (SNIPS) process for the generation of integral asymmetric films on tailor-made porous paper substrates. After water immersion, the final BCP membranes reveal an isoporous open structure at the surface featuring adjustable pore diameters of 20–60 nm. It is demonstrated that a hig...

LTCC 3D MICROMIXERS FOR NON-MISCIBLE FLUIDS MICROEMULSION GENERATION

Abstract The present work shows a ceramics microfluidic device for non-miscible fluids microemulsion generation using 3D serpentine micromixers. The technology used for device fabrication was Low Temperature Cofired Ceramics (LTCC) which allows us for complex, high temperature and pressure resistant 3D microfluidic devices. The proposed device aims to obtain microemulsion with controlled drop size, low dispersion index and high production volumes using Top-Down approach. Previous simulation work had showed 3D serpentine as one of the best structures for rapid mixing due the chaotic advection generated on every 90 deg direction change. This effect, when mixing two fluids as oil and water leads to streamlines pinching-off making possible drop generation. We have used this effect on our device. For the experimental section, it was fabricated a 3D serpentine mixer microfluidic device with working region suitable for variable total flow rate. For certain value of total flow rate, the microemulsion showed higher drop diameter and polydispersity values. In this region, no control could be done in order to obtain the same drop value with the same process parameters. Inside the working region drop diameter values repeatability was obtained. In this region our experimental results had showed a relation between drop diameter and total flow rate. As a total flow rate increase the drop diameter decrease due to a stronger chaotic advection effect. In the other hand, the polydispersity index also decreases. Microemulsions with average size lower than few micrometer or submicron were obtained. When compared with other reported devices, our device presented a production volume in the range of tens of ml/s for the same output microemulsion size.

Influence of anti-solvents on lignin fractionation of eucalyptus globulus via green solvent system pretreatment

Abstract This study focused on the anti-solvents precipitation process of lignin fractionation. Eucalyptus globulus wood was pretreated by ionic liquid–ethanol–water mixture before anti-solvents precipitation experiments. The influence of potential anti-solvents on lignin fractionation was extensively studied. Water, methanol, dichloromethane and iso-propanol were proven effective for lignin fractionation by the formation of precipitation. Lignin fractionation performance (yield and purity) was significantly affected by temperature and anti-solvents dosage. The purity of fractionated lignins increased with growing anti-solvents dosage and temperature. While the yield of fractionated lignins decreased as temperature rose. An increase in anti-solvents dosage could dramatically improve lignin yield. Lignin yield increased to a maximum value, but decreased when the anti-solvents dosage increased further. For different anti-solvents, the sequence on lignin yield was: iso-propanol > water > dichloromethane > methanol. While the sequence of anti-solvents on lignin purity displayed in reverse with lignin yield. Lignins fractionated by different anti-solvents were characterized by FT-IR and GPC. Results showed that the fractionated lignins were G–S type, of low molecular weight, with narrow distribution range (450–2250 g/mol) and extremely low polydispersity ( M w / M n ) value (1.12–1.13). These fractionated lignins could be promising materials for the production of high value chemical and fuels.

Characterizing the chemical and rheological properties of severely aged reclaimed asphalt pavement materials with high recycling rate

Frequent mill and overlay activities result in the production of a considerable amount of reclaimed asphalt pavement (RAP) materials. Many pavements that incorporated RAP exhibit a shorter service life than do those without RAP. One of the possible reasons is that certain RAP materials have already undergone multiple recycling processes during the past decade. This results in severe aging of the reclaimed asphalt binder (RAB). In this study, three severely aged RABs, two RAP blending scenarios, two virgin binders, and two commercial rejuvenators were used to investigate the feasibility of using severely aged binders for constructing pavements. The chemical and rheological properties of the rejuvenated severely aged binders were evaluated using high-performance gel permeation chromatography and a dynamic shear rheometer. The molecular size distributions of rejuvenated RABs revealed that the rejuvenators used in this study could rebalance the proportions of large, medium, and small molecular components among the rejuvenated RABs. However, the polydispersity values still enabled clearly distinguishing between virgin binders and rejuvenated RABs. Two performance parameters were used to evaluate the potential of age-induced damage as well as permanent rutting in the binders. A Glover–Rowe damage zone was evaluated, and it revealed promising results to distinguish among severely aged binders, virgin binders, and rejuvenated binders. Oscillation and multiple stress creep and recovery tests were performed to obtain rutting potential parameter G∗/sin(δ) and Jnr, respectively. The results indicated that all rejuvenated aged binders exhibited higher G∗/sin(δ) values and lower Jnr values compared with the control virgin binders.

Producing a lycopene nanodispersion: The effects of emulsifiers

In the present work, the effect of the emulsifier type, namely Tween 80 (T80), lecithin, sodium caseinate and gum arabic, on the physicochemical properties of lycopene nanodispersions was investigated. A lycopene nanodispersion was produced by emulsification-evaporation method. The lycopene nanodispersion exhibited different physicochemical properties with different types of emulsifiers. The smallest particle size and the highest transmittance of lycopene nanodispersion were obtained by using Tween 80 followed by lecithin, sodium caseinate and gum arabic. The lycopene nanodispersion produced from lecithin was the most stable, exhibiting the lowest polydispersity (PDI) value, narrow and monomodal distribution and high zeta potential value. Sodium caseinate retained the highest lycopene concentration among all the emulsifier types. Transmission electron microscopy (TEM) micrographs revealed sphere-shaped lycopene droplets at different sizes depending on the types of emulsifier used. The results from this study provide useful information to produce desirable properties in lycopene nanodispersions for food applications.

Acidification treatment of lignin from sugarcane bagasse results in fractions of reduced polydispersity and high free-radical scavenging capacity

Lignin constitutes up to one-third of the material found in plant cell walls and is considered the second most abundant natural polymer in the world. Despite unique characteristics of lignin, it is mostly used for low-value commercial applications. In this study, lignin obtained after alkaline treatment of steam-exploded sugarcane bagasse was submitted to an acidification process. The soluble fractions produced at different pH values were comprehensively characterized and in vitro antioxidant capacity against reactive oxygen (ROO and H2O2) and nitrogen (ONOO−) species was evaluated. The soluble fraction obtained at pH 2 exhibited the highest scavenging capacities against all species tested (10.2±0.7mmol Trolox equivalent g−1 for ROO, IC30=14.9μgmL−1 for H2O2 and IC50=2.3μgmL−1 for ONOO−) and the lowest polydispersity value (1.2) compared to others fractions. According to the SAXS data, the soluble fractions obtained at pH 4 and pH 2 consisted of small nanometer-sized discs and low molecular weight polyphenolic clusters, while soluble fractions obtained at high pH predominated wide lignin nanoparticles and larger aggregates. Mass spectroscopy analysis revealed the presence of phenolic and non-phenolic compounds, well-known as efficient antioxidants, which were identified in all soluble fractions. Collectively, our results provided further demonstration that acidification treatment is a promising strategy to upgrade heterogeneous lignin-enriched stream from sugarcane bagasse, such as preparations with homogeneous compositions and high antioxidant activity.

Synthesis of unsaturated polyesters based on renewable monomers: Structure/properties relationship and crosslinking with 2-hydroxyethyl methacrylate

This work presents the preparation of unsaturated polyesters (UPs) with ‘high green content’ and their crosslinking reaction with 2-hydroxyethyl methacrylate (HEMA), to yield the unsaturated polyester resins (UPRs). The chemical structure analysis revealed the presence of mesaconate moieties in the UPs prepared with itaconic acid (IA) as the unsaturated diacid. These UPs were also characterized by high values of polydispersity (PDI), which is indicative of the presence of branched structures. The UPs have shown good thermal stability. The UPRs presented high gel content, which has shown to be dependent on the amount of HEMA in the formulation. The dynamic mechanical thermal analysis (DMTA) revealed the existence of two transitions, corresponding to the motion of different domains in the UPRs. The swelling tests revealed that the UPRs have a highly hydrophobic nature. The in vitro hydrolytic degradation tests showed that the UPRs are hardly degraded in a phosphate buffered saline solution (PBS), at pH=7.4 and 37°C.

Use of polydispersity index as control parameter to study melting/freezing of Lennard-Jones system: Comparison among predictions of bifurcation theory with Lindemann criterion, inherent structure analysis and Hansen-Verlet rule

Using polydispersity index as an additional order parameter we investigate freezing/melting transition of Lennard-Jones polydisperse systems (with Gaussian polydispersity in size), especially to gain insight into the origin of the terminal polydispersity. The average inherent structure (IS) energy and root mean square displacement (RMSD) of the solid before melting both exhibit quite similar polydispersity dependence including a discontinuity at solid-liquid transition point. Lindemann ratio, obtained from RMSD, is found to be dependent on temperature. At a given number density, there exists a value of polydispersity index (δ P) above which no crystalline solid is stable. This transition value of polydispersity(termed as transition polydispersity, δ P ) is found to depend strongly on temperature, a feature missed in hard sphere model systems. Additionally, for a particular temperature when number density is increased, δ P shifts to higher values. This temperature and number density dependent value of δ P saturates surprisingly to a value which is found to be nearly the same for all temperatures, known as terminal polydispersity (δ TP). This value (δ TP∼ 0.11) is in excellent agreement with the experimental value of 0.12, but differs from hard sphere transition where this limiting value is only 0.048. Terminal polydispersity (δ TP) thus has a quasiuniversal character. Interestingly, the bifurcation diagram obtained from non-linear integral equation theories of freezing seems to provide an explanation of the existence of unique terminal polydispersity in polydisperse systems. Global bond orientational order parameter is calculated to obtain further insights into mechanism for melting.

Use of High-Performance Size-Exclusion Chromatography for Characterization of Amylose Isolated from Diverse Botanical Sources

Amyloses were isolated from diverse botanical sources (apple, mango, maize, and potato), and they were studied in their molecular characteristics (amylose content, molar mass, and molecular weight) using high-performance size-exclusion chromatography as a repetitive and faster protocol. The amylose purity ranged between 85.6–92.6 %, in agreement with the λmax values (601–610 nm), showing that some impurities with molecules of higher molar mass (amylopectin) were present. The standard curve of pullulan showed a high regression coefficient (0.998) inside of the limits of molar mass of amylose. Chromatograms of amylose showed the presence of components of high molar mass with a principal peak that corresponds to amylose. Molar mass of amylose ranged between 1.2 and 8.5 × 105 g/mol with polydispersity values between 1.3–4.1, indicating a narrow range of molar mass distribution of the amyloses analyzed. The high-performance size-exclusion chromatography coupled with a refractive index methodology used in this study may be considered simple and rapid for molecular studies of amylose.

Nanoemulsion: for improved oral delivery of repaglinide

Repaglinide (RPG) is a fast-acting prandial glucose regulator. It acts by stimulating insulin release from pancreatic β-cells. Recurrent dosing of RPG before each meal is burdensome remedy. Hence the plan of the present study was to evaluate nanoemulsion as a hopeful carrier for RPG for persistent hypoglycemic effect. The drug was incorporated into oil phase of nanoemulsion to give improved biopharmaceutical properties as compared to the lipid-based systems. Pseudo ternary phase diagrams were prepared by aqueous titration method. Formulations were selected at a difference of 5% w/w of oil from the o/w nanoemulsion region of phase diagrams. The optimized nanoemulsion formulation constituted sefsol-218 (5% v/v) as an oil phase, 30% v/v of Tween-80 and transcutol as a surfactant and co-surfactant to restrain nanodroplet size and low viscosity and distilled water (65%). In vitro dissolution studies showed higher drug release (98.22%), finest droplet size (76.23 nm), slightest polydispersity value (0.183), least viscosity (21.45 cps) and immeasurable dilution capability from the nanoemulsion as compared with existing oral tablet formulation. The optimized RPG nanoemulsion formulation showed better hypoglycemic effect in comparison to tablet formulation in experimental diabetic rats. No significant variations were also observed in the optimized formulation when subjected to accelerated stability study at different temperature and relative humidity over a period of 3 months.

RAFT Polymerization of N-[3-(Trimethoxysilyl)-propyl]acrylamide and Its Versatile Use in Silica Hybrid Materials.

Reversible addition-fragmentation chain transfer (RAFT) polymerization and characterization of an alkoxysilane acrylamide monomer using a trithiocarbonate chain transfer agent are described. Poly(N-[3-(trimethoxysilyl)propyl]acrylamide) (PTMSPAA) homopolymers are obtained with good control over the polymerization. A linear increase in the molecular weight is observed whereas the polydispersity values do not exceed 1.2 regardless of the monomer conversion. Moreover, PTMSPAA is used as a macro-RAFT agent to polymerize N-isopropylacrylamide (NIPAM). By varying the degree of polymerization of NIPAM within the block copolymer, different sizes of thermoresponsive particles are obtained. These particles are stabilized by the condensation of the alkoxysilane moieties of the polymers. Furthermore, a co-network of silica and PTMSPAA is prepared using the sol-gel process. After drying, transparent mesoporous hybrids are obtained with a surface area of up to 400 m(2) g(-1).