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Montreal, Canada

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. Source

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. Source

Chen X.,University of Montreal | Perepichka I.I.,University of Montreal | Perepichka I.I.,Polymer Source Inc. | Bazuin C.G.,University of Montreal
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. Source

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. Source

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. Source

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