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Ahmed J.,Polymer Source Inc. | Auras R.,Michigan State University
LWT - Food Science and Technology | Year: 2011

A comparative rheological and thermal study was carried out between acid hydrolyzed and unhydrolyzed (control) lentil starch dispersions (25-33.3 g starch per 100 g water) as function of temperature. After acid hydrolysis, the peak gelatinization temperature (Tp) shifted to higher temperature than the corresponding starch without hydrolysis whereas the gelatinization enthalpy remained unaffected by hydrolysis. The starch gelatinization kinetics was evaluated by a non-isothermal technique as function of elastic modulus (G′) and G′ vs. time (t) data up to the gelatinization peak value was considered for rate estimation. A 2nd-order reaction kinetics described well the starch gelatinization process and the process activation energy was ranged between 241 and 434 kJ/mol. Acid hydrolysis strongly affected the rheological properties by lowering gel strength compared to unhydrolyzed starch. The creep analysis further revealed that starch gel was significantly affected by hydrolysis and exhibited less resistant to the stress. A 4-parameters Burgers model well-described creep curves and supported oscillatory rheological data. © 2010 Elsevier Ltd.

Khanna K.,McGill University | Varshney S.,Polymer Source Inc. | Kakkar A.,McGill University
Polymer Chemistry | Year: 2010

Miktoarm polymers are a relatively new and unique class of macromolecules, and constitute a topical area of research due to their intriguing properties which can be tailored by varying their polymer arms. Much emphasis has been placed in the recent past in developing synthetic methodologies to these star polymers, and examining their self-assembly in solution. This review summarizes the progress made in the area of miktoarm star polymers in terms of their synthesis, behavior in solution, and applications. The different synthetic strategies to construct a variety of miktoarm star polymers are described, and each methodology strikes a balance between ease of synthesis and control over the final architecture. The self-assembly of miktoarm polymers in solution is then elaborated, which is frequently studied as a function of either arm-length (an intrinsic property of the star) or the application of an external stimulus (pH, temperature, etc.). This is followed by an overview of the applications of these stars in areas including drug delivery. © 2010 The Royal Society of Chemistry.

Chen X.,University of Montréal | Perepichka I.I.,University of Montréal | Perepichka I.I.,Polymer Source Inc. | Bazuin C.G.,University of Montréal
ACS Applied Materials and Interfaces | Year: 2014

A new nanometallic pattern, characterized by randomly disposed double or twin one-dimensional stripes and that adds to the nanotechnology toolbox, has been obtained from a unique template possessing the nanostrand morphology. This morphology had previously been shown to form in Langmuir-Blodgett films made from a polystyrene-poly(4-vinylpyridine) (PS-P4VP) diblock copolymer blended with 3-n-pentadecylphenol (PDP). The nanostrand backbone is composed of PS, and it is bordered along both sides by a P4VP monolayer, visualized for the first time by high resolution atomic force microscopy. The exposed P4VP alongside the nanostrands serves as sites for depositing compounds attracted selectively to P4VP. Here, both gold ions (HAuCl4·3H2O) and gold nanoparticles (AuNP, 12 nm in diameter, stabilized with sodium citrate) were complexed to the P4VP. Plasma treatment of the gold ions led to double stripes of monolayer metallic gold. To obtain dense deposition of AuNP in double rows, it was necessary to acidify the AuNP aqueous solution (pH 5.2 here). The achievement of the metallic double-stripe patterns also confirms the composition of the nanostrand morphology, which up to now had been deduced indirectly. The double-stripe pattern has possible applications for plasmonic lasers, energy transport, and biosensors. © 2014 American Chemical Society.

Khanna K.,McGill University | Varshney S.,Polymer Source Inc. | Kakkar A.,McGill University
Macromolecules | Year: 2010

The design and synthesis of a well-defined molecular building block with three orthogonal functionalities which facilitate the construction of ABC-type miktoarm star polymers via a combination of sequential CuI-catalyzed cycloaddition of an azide to an alkyne ("click") followed by ring-opening polymerization are reported. Using this simple and highly versatile methodology, a variety of miktoarm star polymers were prepared which consisted of hydrophilic poly(ethylene glycol) and hydrophobic polystyrene and poly(ε-caprolactone) arms. Their self-assembly in an aqueous medium was examined using dynamic light scattering and transmission electron microscopy. These ABC miktoarm polymers were found to self-assemble into spherical micelles whose core size and hydrodynamic diameter were found to be inversely proportional to the size of the PEG arm. The potential of encapsulating small molecules into these micelles was explored using Disperse Red 1 dye. An enhancement in the loading capacity of the micelles was observed with an increase in the length of the hydrophobic arm. © 2010 American Chemical Society.

Soliman G.M.,McGill University | Sharma R.,McGill University | Choi A.O.,McGill University | Varshney S.K.,Polymer Source Inc. | And 3 more authors.
Biomaterials | Year: 2010

We report a nanocarrier based on A2B type miktoarm polymers (A=polyethylene glycol (PEG); B=polycaprolactone (PCL)) for nimodipine (NIM), a hydrophobic drug with very poor aqueous solubility that is commonly prescribed for the prevention and treatment of delayed ischemic neurological disorders. The A2B star polymers were constructed on a core with orthogonal functionalities that facilitated the performance of " click" chemistry followed by ring-opening polymerization. These star polymers assemble into spherical micelles into which NIM can be easily loaded by the co-solvent evaporation method. The micelles obtained from the star polymer PEG7752-PCL5800 showed NIM encapsulation efficiency of up to 78wt% at a feed weight ratio of 5.0%. The loading efficiency of the micelles was dependent on the length of the PCL arm in the A2B miktoarm polymers. Aqueous solubility of NIM was increased by ∼200 fold via micellar encapsulation. The in vitro release of NIM from the micelles was found to occur at a much slower rate than from its solution. Lipopolysaccharide induced nitric oxide production in N9 microglia cells was reduced in the presence of micelle-encapsulated NIM, as well as in the presence of micelles alone. The treatment of microglia with micelle-encapsulated NIM reduced the release of TNF-α, a pro-inflammatory cytokine. These results suggest that NIM-loaded miktoarm micelles could be useful in the treatment of neuroinflammation. © 2010 Elsevier Ltd.

Ahmed J.,Polymer Source Inc. | Varshney S.K.,Polymer Source Inc. | Auras R.,Michigan State University | Hwang S.W.,Michigan State University | Hwang S.W.,Korea Institute of Industrial Technology
Journal of Food Science | Year: 2010

The melt rheology and thermal properties of polylactide (PLA)-based nanocomposite films that were prepared by solvent casting method with L-PLA, polyethylene glycol (PEG), and montmorillonite clay were studied. The neat PLA showed predominantly solid-like behavior (G' > G") and the complex viscosity (η*) decreased systematically as the temperature increased from 184 to 196 °C. The elastic modulus (G') of PLA/clay blend showed a significant improvement in the magnitude in the melt, while clay concentration was at 6% wt or higher. At similar condition, PEG dramatically reduced dynamic modulii and complex viscosity of PLA/PEG blend as function of concentration. A nanocomposite blend of PLA/PEG/clay (74/20/6) when compared to the neat polymer and PLA/PEG blend exhibited intermediate values of elastic modulus (G') and complex viscosity (η) with excellent flexibility. Thermal analysis of different clay loading blends indicated that the melting temperature (Tm) and glass transition temperature (Tg) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the Tg and the Tm of the blends (PLA/PEG and PLA/PEG/clay) significantly, however, crystallinity increased in the similar condition. The transmission electron microscopy (TEM) image of nanocomposite films indicated good compatibility between PLA and PEG, whereas clay was not thoroughly distributed in the PLA matrix and remained as clusters. The percent crystallinity obtained by X-ray was significantly higher than that of differential scanning calorimeter (DSC) data for PLA. © 2010 Institute of Food Technologists®.

Ahmed J.,Polymer Source Inc. | Varshney S.K.,Polymer Source Inc. | Auras R.,Michigan State University
Journal of Food Science | Year: 2010

Polylactide (DL)/polyethylene glycol/silicate nanocomposite blended biodegradable films have been prepared by solvent casting method. Rheological and thermal properties were investigated for both neat amorphous polylactide (PLA-DL form) and blend of montmorillonite (clay) and poly (ethylene glycol) (PEG). Melt rheology of the PLA individually and blends (PLA/clay; PLA/PEG; PLA/PEG/clay) were performed by small amplitude oscillation shear (SAOS) measurement. Individually, PLA showed an improvement in the viscoelastic properties in the temperature range from 180 to 190 °C. Incorporation of nanoclay (3% to 9% wt) was attributed by significant improvements in the elastic modulus (G′) of PLA/clay blend due to intercalation at higher temperature. Both dynamic modulii of PLA/PEG blend were significantly reduced with addition of 10% PEG. Rheometric measurement could not be conducted while PLA/PEG blends containing 25% PEG. A blend of PLA/PEG/clay (68/23/9) showed liquid-like properties with excellent flexibility. Thermal analysis of different clay loading films indicated that the glass transition temperatures (Tg) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the Tg of the blend (PLA/PEG and PLA/PEG/clay) significantly. Both rheological and thermal analysis data supported plasticization and flexibility of the blended films. It is also interesting to study competition between PLA and PEG for the intercalation into the interlayer spacing of the clay. This study indicates that PLA/montmorillonite blend could serve as effective nano-composite for packaging and other applications. © 2010 Institute of Food Technologists®.

Ahmed J.,Kuwait Institute for Scientific Research | Varshney S.K.,Polymer Source Inc. | Janvier F.,IRSST
Journal of Thermal Analysis and Calorimetry | Year: 2014

Poly(l-lactide) (PLLA) and Poly(d-lactide) (PDLA) blended films (PLLA/PDLA) were prepared (5/95; 25/75; 50/50, and 75/25) by solvent casting method. Blend of PLLA and PDLA of medium molecular mass led to the formation of stereocomplex which was evidenced by differential scanning calorimetry, rheological measurement and Fourier transform infrared spectroscopy. The stereocomplex had a higher melting temperature (T m) (more than 50 C) and crystallized at higher temperature (T c) (more than 25 C) from the melt compared to neat PLLA and PDLA. The T m and T c gradually decreased with increasing the number of thermal scans. The enthalpy of fusion (δHm) for stereocomplex crystallites in 50/50 blend films was the highest than that of homo-crystallites. Rheological measurement at a temperature of 180-195 C revealed that the neat PLA was predominantly liquid-like behavior (G″ > G′) which transformed to extreme solid-like behavior by incorporation of PDLA into PLLA. Among blends, 50/50 PDLA/PLLA showed the maximum mechanical strength (G′) followed by 25/75, 75/25, and 5/95 blends. The significant increase in mechanical strength is believed to be attributed by stereocomplex formation by blends. Thermal and rheological data supported higher mechanical strength and an increase in melting and crystallization temperature adequately. © 2013 Akadémiai Kiadó, Budapest, Hungary.

Ahmed J.,Polymer Source Inc. | Varshney S.K.,Polymer Source Inc.
International Journal of Food Properties | Year: 2011

Polylactide (PLA), a biodegradable aliphatic polyester, has been studied extensively for its wide applications in various fields from food packaging to interior materials for automobiles. One of PLA's advantages is that the raw material, lactic acid can be derived from renewable resources, which makes PLA very attractive for the packaging and considered as green packaging. Although, the cost of PLA is relatively higher compared to petroleum based packaging materials and it is predicted that the price will go down after commercial success of the process. This paper presents a review on polylactide with focus on its chemistry, synthesis, properties, and applications. Plasticization effect on PLA, sorption isotherm and mechanical properties of PLA based packaging materials have been discussed. PLA/layered organo nanocomposites exhibit significant improvement in mechanical, thermal, optical, and physicochemical properties over pure PLA. This review includes brief overview of PLA based nanocomposite, their mechanical properties, potential as packaging materials for industrial usage and their environmental implications. Copyright © Taylor & Francis Group, LLC.

Cajot S.,University of Liège | Van Butsele K.,University of Liège | Paillard A.,University of Angers | Passirani C.,University of Angers | And 4 more authors.
Acta Biomaterialia | Year: 2012

The use of hybrid pH-sensitive micelles based mainly on the (PEO) 129(P2VP)43(PCL)17 ABC miktoarm star copolymer as potential triggered drug delivery systems was investigated. Co-micellization of this star copolymer with a second copolymer labeled by a targeting ligand, i.e. biotin, on the pH sensitive block (poly-2-vinylpyridine) is considered here in order to impart possible active targeting of the tumor cells. Two architectures were studied for these labeled copolymers, i.e. a miktoarm star or a linear ABC terpolymer, and the respective hybrid micelles are compared in terms of cytotoxicity (cells viability) and cellular uptake (using fluorescent dye loaded micelles). Finally, the triggered drug release in the cytosol of tumor cells was investigated by studying, on the one hand, the lysosomal integrity after internalization and, on the other hand, the release profile in function of the pH. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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