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Polymers, Volume 7, Issue 6 (June 2015) – 10 articles , Pages 985-1191

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1786 KiB  
Article
Size-Controlled Nanomicelles of Poly(lactic acid)–Poly(ethylene glycol) Copolymers with a Multiblock Configuration
by Shota Somekawa, Kazunari Masutani, Yu-I Hsu, Atsushi Mahara, Yoshiharu Kimura and Tetsuji Yamaoka
Polymers 2015, 7(6), 1177-1191; https://doi.org/10.3390/polym7061177 - 23 Jun 2015
Cited by 9 | Viewed by 7019
Abstract
The ability to control the micelle size of poly(lactic acid) and poly(ethylene glycol) (PLA–PEG) block copolymers is important for controlling their circulation in blood cell recognition, drug release and therapeutic effects. We successfully controlled the micelle size by changing the block number of [...] Read more.
The ability to control the micelle size of poly(lactic acid) and poly(ethylene glycol) (PLA–PEG) block copolymers is important for controlling their circulation in blood cell recognition, drug release and therapeutic effects. We successfully controlled the micelle size by changing the block number of copolymers (multiblock index). PLA–PEG multiblock copolymers with multiblock indexes ranging from 1.35 to 2.78 were synthesized by direct polycondensation with tin chloride/p-toluenesulfonic acid binary catalysts, using PEG with a molecular weight (Mw) of 3200 Da. The Mw of PLA–PEG copolymers increased with an increase in the multiblock index, while micelle size, measured by dynamic light scattering, decreased greatly from 349 to 28 nm. In addition, the X-ray diffraction peak of the PLA crystal disappeared when the multiblock index was increased. These results indicate that a multiblock structure is useful for controlling micelle size without changing the PLA/PEG composition or PEG molecular weight, which strongly influences other micelle features. Full article
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3024 KiB  
Article
A Novel Melt-Dispersion Technique for Simplistic Preparation of Chlorpromazine-Loaded Polycaprolactone Nanocapsules
by Thiresen Govender, Yahya E. Choonara, Pradeep Kumar, Lisa C. Du Toit, Girish Modi, Dinesh Naidoo and Viness Pillay
Polymers 2015, 7(6), 1145-1176; https://doi.org/10.3390/polym7061145 - 19 Jun 2015
Cited by 16 | Viewed by 7342
Abstract
The aim of this study was to design, synthesize and optimize chlorpromazine hydrochloride (CPZ)-loaded, poly-ε-caprolactone (PCL) based nanocapsules, intended for site specific delivery to the frontal lobe, using a novel melt-dispersion technique that is non-arduous, inexpensive and devoid of any hazardous organic solvents. [...] Read more.
The aim of this study was to design, synthesize and optimize chlorpromazine hydrochloride (CPZ)-loaded, poly-ε-caprolactone (PCL) based nanocapsules, intended for site specific delivery to the frontal lobe, using a novel melt-dispersion technique that is non-arduous, inexpensive and devoid of any hazardous organic solvents. Experimental trials using a central composite design were performed on 13 statistically derived formulations of various combinations of PCL (1000–3000 mg) and Polysorbate 80 (2%–5% v/v) on the physicochemical and physicomechanical properties and interactive effects on PCL nanocapsule formulation. Differential scanning calorimetry (DSC), Temperature modulated differential scanning calorimetry (TMDSC) and Fourier transform infrared spectroscopy (FTIR) revealed that there was no thermodegardation of the constituents utilized in the melt dispersion technique. Nanocapsule yields achieved were very high however entrapment of CPZ proved to be relatively low due to the highly hydrophilic nature of CPZ and the processing of the nanocapsules post synthesis. Nanocapsule sizes were in the nanotherapeutic range and varied from 132.7 ± 6.8 nm to 566.6 ± 5.5 nm. Zeta potential ranged from 15.1 ± 0.65 mV to 28.8 ± 0.84 mV revealing capsules that were of incipient to moderate stability. Transmission electron microscopy revealed nanocapsules that were spherical shape, well individualized with a moderate degree of flocculation. In vitro CPZ release was biphasic for all formulations with an initial burst release followed by pseudo-steady controlled release over 30 days. The cytotoxicity of the optimized nanocapsule system on a PC12 neuronal cell line proved to be minimal. Following incorporation of the optimized nanocapsules within a polymeric membrane, in vivo implantation of the device in a New Zealand Albino rabbit model proved the efficacy of the system in achieving prolonged more targeted CPZ levels to the brain. Extensive in vitro testing and optimization and preclinical evaluation supports the application for the use and feasibility of the CPZ-loaded, PCL based nanocapsules for the long-term management of certain psychotropic disorders where the benefits of nanotechnology can be exploited. Full article
(This article belongs to the Special Issue Polymers and Polymeric Nanoparticles for Therapy and Imaging)
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2409 KiB  
Article
Flavonoids as Natural Stabilizers and Color Indicators of Ageing for Polymeric Materials
by Anna Masek
Polymers 2015, 7(6), 1125-1144; https://doi.org/10.3390/polym7061125 - 18 Jun 2015
Cited by 33 | Viewed by 9689
Abstract
Few changes have occurred in the use of various stabilizers over recent years. In the current literature, phosphate derivatives are used as anti-ageing additives in polymers, and the most popular of these are sterically hindering cyclic amines. However, most of these compounds are [...] Read more.
Few changes have occurred in the use of various stabilizers over recent years. In the current literature, phosphate derivatives are used as anti-ageing additives in polymers, and the most popular of these are sterically hindering cyclic amines. However, most of these compounds are carcinogenic. Synthetic phenols have been increasingly used as antioxidants in food and in polymers. Ecological standards encourage the elimination of harmful additives in polymeric products that come in contact with food or with the human body. This article presents application of flavonoid (silymarin/flavonoligand) for polymer stabilization and use of natural phytocompounds such as color indicators of polymers ageing time. In this research, I propose two ways of application: traditional, during processing; and the new one, by using impregnation method. Based on the change of deformation energy (ageing coefficient K), FTIR, oxidative induction time (OIT) evaluated by differential scanning calorimetry (OIT), thermogravimetry analysis (TG), spectrophotometric color measurements in terms of CIE-Lab color space values, I confirmed the high antioxidant activity of flavonoids in EPM. They provide coloration of the polymeric materials that changes cyclically as a function of aging time. Additionally, the use of phytocompounds in polymers provides similar stabilizing effect to those of synthetic antioxidants. Full article
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1391 KiB  
Article
Effect of Plasticizer Type and Concentration on Tensile, Thermal and Barrier Properties of Biodegradable Films Based on Sugar Palm (Arenga pinnata) Starch
by Muhammed L. Sanyang, Salit M. Sapuan, Mohammad Jawaid, Mohamad R. Ishak and Japar Sahari
Polymers 2015, 7(6), 1106-1124; https://doi.org/10.3390/polym7061106 - 18 Jun 2015
Cited by 358 | Viewed by 19858
Abstract
The use of starch based films as a potential alternative choice to petroleum derived plastics is imperative for environmental waste management. This study presents a new biopolymer (sugar palm starch) for the preparation of biodegradable packaging films using a solution casting technique. The [...] Read more.
The use of starch based films as a potential alternative choice to petroleum derived plastics is imperative for environmental waste management. This study presents a new biopolymer (sugar palm starch) for the preparation of biodegradable packaging films using a solution casting technique. The effect of different plasticizer types (glycerol (G), sorbitol (S) and glycerol-sorbitol (GS) combination) with varying concentrations (0, 15, 30 and 45, w/w%) on the tensile, thermal and barrier properties of sugar palm starch (SPS) films was evaluated. Regardless of plasticizer types, the tensile strength of plasticized SPS films decreased, whereas their elongation at break (E%) increased as the plasticizer concentrations were raised. However, the E% for G and GS-plasticized films significantly decreased at a higher plasticizer concentration (45% w/w) due to the anti-plasticization effect of plasticizers. Change in plasticizer concentration showed an insignificant effect on the thermal properties of S-plasticized films. The glass transition temperature of SPS films slightly decreased as the plasticizer concentration increased from 15% to 45%. The plasticized films exhibited increased water vapor permeability values from 4.855 × 10−10 to 8.70 × 10−10 g·m−1·s−1·Pa−1, irrespective of plasticizer types. Overall, the current study manifested that plasticized sugar palm starch can be regarded as a promising biopolymer for biodegradable films. Full article
(This article belongs to the Collection Polysaccharides)
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2125 KiB  
Article
Dual Cross-Linked Carboxymethyl Sago Pulp-Gelatine Complex Coacervates for Sustained Drug Delivery
by Saravanan Muniyandy, Thenapakiam Sathasivam, Anand Kumar Veeramachineni and Pushpamalar Janarthanan
Polymers 2015, 7(6), 1088-1105; https://doi.org/10.3390/polym7061088 - 15 Jun 2015
Cited by 16 | Viewed by 7714
Abstract
In the present work, we report for the first time the complex coacervation of carboxymethyl sago pulp (CMSP) with gelatine for sustained drug delivery. Toluene saturated with glutaraldehyde and aqueous aluminum chloride was employed as cross-linkers. Measurements of zeta potential confirm neutralization of [...] Read more.
In the present work, we report for the first time the complex coacervation of carboxymethyl sago pulp (CMSP) with gelatine for sustained drug delivery. Toluene saturated with glutaraldehyde and aqueous aluminum chloride was employed as cross-linkers. Measurements of zeta potential confirm neutralization of two oppositely charged colloids due to complexation, which was further supported by infrared spectroscopy. The coacervates encapsulated a model drug ibuprofen and formed microcapsules with a loading of 29%–56% w/w and an entrapment efficiency of 85%–93% w/w. Fresh coacervates loaded with drug had an average diameter of 10.8 ± 1.93 µm (n = 3 ± s.d.). The coacervates could encapsulate only the micronized form of ibuprofen in the absence of surfactant. Analysis through an optical microscope evidenced the encapsulation of the drug in wet spherical coacervates. Scanning electron microscopy revealed the non-spherical geometry and surface roughness of dried drug-loaded microcapsules. X-ray diffraction, differential scanning calorimetry and thermal analysis confirmed intact and crystalline ibuprofen in the coacervates. Gas chromatography indicated the absence of residual glutaraldehyde in the microcapsules. Dual cross-linked microcapsules exhibited a slower release than mono-cross-linked microcapsules and could sustain the drug release over the period of 6 h following Fickian diffusion. Full article
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1055 KiB  
Article
Perfluoro-p-xylene as a New Unique Monomer for Highly Stable Arylene Main-Chain Ionomers Applicable to Low-T and High-T Fuel Cell Membranes
by Imre Hajdok, Vladimir Atanasov and Jochen Kerres
Polymers 2015, 7(6), 1066-1087; https://doi.org/10.3390/polym7061066 - 15 Jun 2015
Cited by 3 | Viewed by 7241
Abstract
In this study, we present the synthesis and the characterization of novel functionalized arylene main-chain ionomers based on perfluoro-p-xylene (PFX). The polymers were prepared by polycondensation of PFX and 4,4'-dihydroxybiphenyl or bisphenol 2,2-bis(4-hydroxyphenyl)-hexafluoropropane (bisphenol AF). After polymerization, the PFX unit was still able [...] Read more.
In this study, we present the synthesis and the characterization of novel functionalized arylene main-chain ionomers based on perfluoro-p-xylene (PFX). The polymers were prepared by polycondensation of PFX and 4,4'-dihydroxybiphenyl or bisphenol 2,2-bis(4-hydroxyphenyl)-hexafluoropropane (bisphenol AF). After polymerization, the PFX unit was still able to undergo nucleophilic aromatic substitution reaction, which was used to introduce phosphonic acid groups into the polymer via a reaction with tris(trimethylsilyl)phosphite. Furthermore, electrophilic sulfonation of these polymers was possible in the bisphenol unit when using H2SO4/SO3 as the sulfonation agent. The so-obtained water-soluble PFX-based polyelectrolytes showed excellent chemical stability and were blended with polybenzimidazoles. The blend membranes formed flexible and mechanically robust films with excellent chemical and thermal stabilities. Full article
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1698 KiB  
Article
Highly Sulfonated Diamine Synthesized Polyimides and Protic Ionic Liquid Composite Membranes Improve PEM Conductivity
by Bor-Kuan Chen, Tzi-Yi Wu, Jhong-Ming Wong, Yu-Ming Chang, Hsu-Feng Lee, Wen-Yao Huang and Antonia F. Chen
Polymers 2015, 7(6), 1046-1065; https://doi.org/10.3390/polym7061046 - 08 Jun 2015
Cited by 23 | Viewed by 7558
Abstract
A novel sulfonated diamine was synthesized from 1,4-bis(4-aminophenoxy) benzene [pBAB]. Sulfonated polyimides (SPIs) were synthesized from sulfonated pBAB, 1,4-bis(4-aminophenoxy-2-sulfonic acid) benzenesulfonic acid [pBABTS], various diamines and aromatic dianhydrides. Composite proton exchange membranes (PEMs) made of novel SPIs and [...] Read more.
A novel sulfonated diamine was synthesized from 1,4-bis(4-aminophenoxy) benzene [pBAB]. Sulfonated polyimides (SPIs) were synthesized from sulfonated pBAB, 1,4-bis(4-aminophenoxy-2-sulfonic acid) benzenesulfonic acid [pBABTS], various diamines and aromatic dianhydrides. Composite proton exchange membranes (PEMs) made of novel SPIs and a protic ionic liquid (PIL) 1-vinyl-3-H-imidazolium trifluoromethanesulfonate [VIm][OTf] showed substantially increased conductivity. We prepared an SPI/PIL composite PEM using pBABTS, 4,4′-(9-fluorenylidene) dianiline (9FDA) as diamine, 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA) as dianhydride and 40 wt % [VIm][OTf] with a high conductivity of 16 mS/cm at 120 °C and anhydrous condition. pBABTS offered better conductivity, since the chemical structure had more sulfonated groups that provide increased conductivity. The new composite membrane could be a promising anhydrous or low-humidity PEM for intermediate or high-temperature fuel cells. Full article
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6046 KiB  
Article
Interlaminar Fracture Toughness of CFRP Laminates Incorporating Multi-Walled Carbon Nanotubes
by Elisa Borowski, Eslam Soliman, Usama F. Kandil and Mahmoud Reda Taha
Polymers 2015, 7(6), 1020-1045; https://doi.org/10.3390/polym7061020 - 05 Jun 2015
Cited by 97 | Viewed by 11883
Abstract
Carbon fiber reinforced polymer (CFRP) laminates exhibit limited fracture toughness due to characteristic interlaminar fiber-matrix cracking and delamination. In this article, we demonstrate that the fracture toughness of CFRP laminates can be improved by the addition of multi-walled carbon nanotubes (MWCNTs). Experimental investigations [...] Read more.
Carbon fiber reinforced polymer (CFRP) laminates exhibit limited fracture toughness due to characteristic interlaminar fiber-matrix cracking and delamination. In this article, we demonstrate that the fracture toughness of CFRP laminates can be improved by the addition of multi-walled carbon nanotubes (MWCNTs). Experimental investigations and numerical modeling were performed to determine the effects of using MWCNTs in CFRP laminates. The CFRP specimens were produced using an epoxy nanocomposite matrix reinforced with carboxyl functionalized multi-walled carbon nanotubes (COOH–MWCNTs). Four MWCNTs contents of 0.0%, 0.5%, 1.0%, and 1.5% per weight of the epoxy resin/hardener mixture were examined. Double cantilever beam (DCB) tests were performed to determine the mode I interlaminar fracture toughness of the unidirectional CFRP composites. This composite material property was quantified using the critical energy release rate, GIC. The experimental results show a 25%, 20%, and 17% increase in the maximum interlaminar fracture toughness of the CFRP composites with the addition of 0.5, 1.0, and 1.5 wt% MWCNTs, respectively. Microstructural investigations using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) verify that chemical reactions took place between the COOH–MWCNTs and the epoxy resin, supporting the improvements experimentally observed in the interlaminar fracture toughness of the CFRP specimens containing MWCNTs. Finite element (FE) simulations show good agreement with the experimental results and confirm the significant effect of MWCNTs on the interlaminar fracture toughness of CFRP. Full article
(This article belongs to the Collection Fiber-Reinforced Polymer Composites in Structural Engineering)
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1377 KiB  
Article
Photochemical Stability and Photostabilizing Efficiency of Poly(methyl methacrylate) Based on 2-(6-Methoxynaphthalen-2-yl)propanoate Metal Ion Complexes
by Emad Yousif, Gamal A. El-Hiti, Raghad Haddad and Asim A. Balakit
Polymers 2015, 7(6), 1005-1019; https://doi.org/10.3390/polym7061005 - 03 Jun 2015
Cited by 41 | Viewed by 7983
Abstract
The photostabilization of poly(methyl methacrylate) (PMMA) films having 2-(6-methoxynaphthalen-2-yl)propanoate and Sn(II), Ni(II), Zn(II) and Cu(II) complexes was investigated. The production of PMMA films containing such complexes (0.5% by weight) was carried out by the casting method using chloroform. The photostabilization activities of the [...] Read more.
The photostabilization of poly(methyl methacrylate) (PMMA) films having 2-(6-methoxynaphthalen-2-yl)propanoate and Sn(II), Ni(II), Zn(II) and Cu(II) complexes was investigated. The production of PMMA films containing such complexes (0.5% by weight) was carried out by the casting method using chloroform. The photostabilization activities of the compounds were determined by monitoring the hydroxyl index with irradiation time. The quantum yield of the chain scission (Φcs) for the complexes in PMMA films and the changes in the viscosity average molecular weight of PMMA with irradiation time were evaluated. The rate of photostabilization for PMMA in the presence of the additives was found to follow the order NiL2 > CuL2 > ZnL2 > SnL2 (L, ligand). Depending on the structure of the additive, such as a peroxide decomposer, UV absorption or a radical scavenger for the photostabilizer, several mechanisms are suggested. Full article
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5045 KiB  
Article
Warpage Analysis of Electroplated Cu Films on Fiber-Reinforced Polymer Packaging Substrates
by Cheolgyu Kim, Tae-Ik Lee, Min Sung Kim and Taek-Soo Kim
Polymers 2015, 7(6), 985-1004; https://doi.org/10.3390/polym7060985 - 03 Jun 2015
Cited by 25 | Viewed by 14381
Abstract
This paper presents a warpage analysis method that predicts the warpage behavior of electroplated Cu films on glass fiber-reinforced polymer (GFRP) packaging substrates. The analysis method is performed using the following sequence: fabricate specimens for scanning 3D contours, transform 3D data into curvatures, [...] Read more.
This paper presents a warpage analysis method that predicts the warpage behavior of electroplated Cu films on glass fiber-reinforced polymer (GFRP) packaging substrates. The analysis method is performed using the following sequence: fabricate specimens for scanning 3D contours, transform 3D data into curvatures, compute the built-in stress of the film using a stress-curvature analytic model, and verify it through comparisons of the finite element method (FEM) simulations with the measured data. The curvature is used to describe the deflection and warpage modes and orientations of the specimen. Two primary factors that affect the warpage behavior of the electroplated Cu film on FRP substrate specimens are investigated. The first factor is the built-in stress in a Cu film that explains the room temperature warpage of the specimen under no thermal process. The second factor is the misfit of the coefficient of thermal expansion (CTE) between the Cu and FRP layer, which is a dominant factor during the temperature change. The calculated residual stress, and predicted curvatures using FEM simulation throughout the reflow process temperature range between 25 and 180 °C are proven to be accurate by the comparison of the FEM simulations and experiment measurements. Full article
(This article belongs to the Special Issue Packaging Films)
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