Laser‐induced surface structures on gold‐coated polymers: Influence of morphology on surface‐enhanced Raman scattering enhancement

The fabrication of highly sensitive and reproducible substrates for Surface‐Enhanced Raman Scattering (SERS) remains a challenging scientific and technological issue. In this work, laser‐induced periodic surface structures are generated on poly(trimethylen terephthalate) films upon laser irradiation with the linearly polarized beams of a Nd:YAG laser (4th harmonic, 266 nm), an ArF excimer laser (193 nm), and a Titanium:sapphire laser (795 nm), resulting in periods close to the laser wavelength when irradiating at normal incidence, and larger periods for different angles of incidence. Additional irradiation with a circularly polarized beam at 266 nm produces superficial circular structures. The nanostructured polymers are coated with a nanoparticle assembled gold layer by pulsed laser deposition at 213 nm. The capabilities of these substrates for SERS are evaluated using benzenethiol as a test molecule and different degrees of Raman signal enhancement are observed depending on the nanostructure type. The highest enhancement factor is obtained by for nanostructured substrates with the highest values of period, depth, and roughness. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42770.     

Polypropylene random copolymer/MWCNT nanocomposites: Isothermal crystallization kinetics,structural, and morphological interpretations

This article describes the crystallization process of polypropylene random copolymer (PPCP) under isothermal conditions in presence of varying amounts of multiwalled carbon nanotubes (MWCNT) ranging from 0.5 to 4.0% w/w. Increase in the crystallization temperature under dynamic conditions confirmed the nucleating behavior of MWCNTs, which was also corroborated by crystallization studies under isothermal conditions. The crystallization kinetics was analyzed using Avrami equation and the parameters such as Avrami exponent, the equilibrium melting temperature and fold surface energy for the crystallization of PPCP chains in nanocomposites were obtained from the calorimetric data in order to determine the effect of MWCNTs on these parameters. Spherulitic growth of PPCP crystals was also investigated as a function of time and MWCNT content using hot stage polarizing microscope. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41734.     

Poly(ethylene oxide)‐g‐gellan polysaccharide nanocarriers for controlled gastrointestinal delivery of simvastatin

Herein, a novel gellan polysaccharide‐based amphiphilic copolymer was synthesized for the development of simvastatin‐loaded micellar nanoparticles. The nanoparticles were explored for their controlled drug release and improved pharmacodynamic potentials. The copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The onset of copolymer micellization was detected by fluorescence spectroscopy. Simvastatin was loaded into micellar particles by solvent evaporation method and the particles were then characterized by microscopic and light scattering techniques. The physical state of drug was studied by X‐ray diffraction analysis. Pharmacodynamic assessment of the micellar preparations was done on rabbit models. The copolymer formed micellar nanoparticles in water. Critical micellar concentration was 9.12mg/l. The micellar particles (426.8–912.6nm) entrapped a maximum of 18.86% drug. Higher negative zeta potential indicated physical stability of micellar systems. A simple diffusion mechanism was operative in the event of comparatively faster drug release in pH6.8 phosphate buffer solution. No significant drug‐copolymer interaction was traced by FTIR spectroscopy. The amorphization of drug into micellar particles reduced LDL‐cholesterol level by ～45% in hyperlipidemic rabbits and this was about 2.5 times higher than pure drug dispersion. Copolymer micellar nanoparticles of simvastatin could control cholesterol level in hyperlipidemic rabbits and thus had potential in drug delivery applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42399.     

壳聚糖季铵盐修饰的辅酶Q10纳米结构脂质载体的制备及表征

为了增强运载辅酶Q10的纳米结构脂质载体(CoQ10-NLC)的透皮效果,采用促渗剂——壳聚糖季铵盐(QCS)对CoQ10-NLC进行了表面修饰,并结合QCS分子链的自聚集行为,明确了壳聚糖季铵盐修饰的包载辅酶Q10的纳米脂质体(QCS-CoQ10-NLC)的形成机制,得到了粒径在500 nm左右的脂质载体。进一步通过体外透皮实验,考察了QCS-CoQ10-NLC的透皮吸收效果。结果显示,经质量分数0.5%的QCS修饰后,脂质载体可将CoQ10在皮肤中的渗透总量由1.36μg/cm~2显著增加至5.14μg/cm~2。     

Estimation of the mechanical properties of urea–formaldehyde microcapsules by compression tests and finite element analysis

Information on the mechanical properties of microcapsules is essential to understanding their performance during manufacturing, processing, and applications. The mechanical properties of urea–formaldehyde (UF) microcapsules filled with ethyl phenyl acetate (EPA) were determined by applying single‐microcapsule compression and a finite element model. Microcapsules were prepared by in situ polymerization, and the average wall thickness of microcapsules was 192 ± 12 nm as determined using scanning electron microscopy. The deformation behavior of the microcapsule was measured by a single‐microcapsule compression experiment between two parallel plates. The results show that both burst deformation and burst force were linearly related to microcapsule size. A model for an elastic shell filled with incompressible fluid was used to simulate compression of the microcapsule in ABAQUS. Dimensionless parameters were introduced to the model. The relationship between dimensionless force and dimensionless displacement depended on the ratio of wall thickness to diameter (ε). However, the relationship remained the same when ε was less than 1% and can be fitted well by the mathematical equation. An estimation of Young's modulus can be obtained from the compression data for the dimensionless deformation from 10% to 15%. The average Young's modulus of a UF/EPA microcapsule is estimated to be 2.12 ± 0.45 GPa. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43414.     

Synthesis and characterization of MC nylon/modified yttrium hydroxide nanocomposites

In this article, monomer casting (MC) nylon is synthesized. MC nylon could replace nonferrous metals in certain applications, including gears, wheels, and other moving parts. However, compared with metals, MC nylon products have poor strength and stiffness, and crack easily, especially at low temperatures. In addition, the dimensional stability of MC nylon is poor, especially in the large casting nylon products, causing significant internal stresses due to shrinkage. Thus, MC nylon cracks easily when cast and molded. The yttrium hydroxide particles are modified by stearic acid and dispersed in the caprolactam. The polymerization time is short due to fast anionic polymerization. Copolymerization with different ratios of yttrium hydroxide particles can be used to prepare the copolymer. The effects of different amounts of yttrium hydroxide on the performance of the monomer casting nylon are studied. The products are characterized using X‐ray diffraction, impact, and tensile testing. When the percentage of modified yttrium hydroxide is 0.3 wt %, the composite exhibits the maximum impact strength, thus the 0.3 wt % of modified yttrium hydroxide is the suitable percentage to enhance the impact strength of MC nylon. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43356.     

Latex‐templated biomineralization of silica nanoparticles with porous shell and their application for drug delivery

A latex‐templating method for synthesizing the core‐shell silica nanoparticles (NPs) with porous shell was developed via biomineralization in the presence of poly[2‐(methacryloyloxy)ethyl] trimethylammonium chloride (pDMC)‐modified polystyrene latex. Calcination of the as‐obtained SiO₂ NPs led to the removal of the latex core and consequently to hollow silica NPs with porous shell. In particularly, the microstructure and thickness of silica shell could be controlled by simply changing the reaction parameters of silicification. Furthermore, facile encapsulation of a drug molecules and its sustained release were demonstrated. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44200.     

Low‐cost,environmentally friendly route to produce glass fiber‐reinforced polymer composites with microfibrillated cellulose interphase

In this article, an easy, effective, and eco‐friendly method to improve the mechanical performance of glass fiber‐reinforced polymer composites is proposed, which involves the coating of unsized glass fiber fabric layers by simple immersion in an aqueous suspension containing sugarcane bagasse microfibrillated cellulose (MFC), followed by vacuum‐assisted liquid resin infusion as the processing method. From atomic force microscopy, a 250 nm MFC‐rich interphase was found, revealing its ability to build micro‐ and nanobridges acting as bulk epoxy matrix and GF linker. The interlaminar shear strength, quasi‐static tensile, and flexural tests, as well as the morphological and fractographic inspection of test coupons containing the secondary substructure, broadly supported the assumption of the efficient role on the interfacial level of this nano reinforcement by enhancing the load transference and distribution from the polymer matrix to the main reinforcing fiber system compared to baseline unsized fiber‐reinforced epoxy laminates. This finding permits this class of composite materials to be considered as having great potential to achieve products with excellent performance/cost ratios. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44183.     

Morphology‐dependent electrocatalytic activity of nanostructured Pt/C particles from hybrid aerosol–colloid process

An optimum nanostructure and pore size of catalyst supports is very important in achieving high catalytic performances. In this instance, we evaluated the effects of various carbon nanostructures on the catalytic performances of carbon‐supported platinum (Pt/C) electrocatalysts experimentally and numerically. The Pt/C catalysts were prepared using a hybrid method involving the preparation of dense, hollow, and porous nanostructured carbon particle via aerosol spray pyrolysis followed by microwave‐assisted Pt deposition. Electrochemical characterization of the catalysts showed that the porous Pt/C catalyst gave the best performance; its electrochemical surface area was much higher, more than twice than those of hollow or dense Pt/C. The effects of pore size on electrocatalysis were also studied. The results showed the importance of a balance between mesopores and macropores for effective catalysis with a high charge transfer rate. A fluid flow model showed that good oxygen transport contributed to the catalytic activity. © 2015 American Institute of Chemical Engineers AIChE J, 62: 440–450, 2016     

POSS‐based fluorinated azobenzene‐containing polymers: Photo‐responsive behavior and evaluation of water repellency

The photoresponsive polyhedral oligomeric silsesquioxanes (POSS) based fluorinated azobenzene‐containing polymers were prepared and characterized by NMR, FT‐IR, GPC, XRD, TG and UV–Vis spectra. The thermal property of the polymers was improved by the introduction of POSS cage. The trans‐cis photoisomerization of the polymers in solution was similar to that of the fluorinated azobenzene monomer and in accordance with the first‐order reaction kinetics equation within the first 250 seconds UV irradiation. The cotton fabrics coated with the polymers showed excellent water repellency and possessed switchable wettability under UV irradiation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43540.