Development of a thermosensitive grafted drug delivery system—synthesis and characterization of NIPAAm‐based grafts and hydrogel structure

A thermosensitive grafted hydrogel was investigated for heating‐activated drug release. The hydrogel was created by grafting oligomers of N‐isopropylacrylamide‐co‐acrylamide (AAm) to a poly(2‐hydroxyethyl methacrylate), or PHEMA, hydrogel. N‐Isopropylacrylamide‐co‐AAm oligomers were synthesized with a range of compositions to raise the lower critical solution temperature (LCST) above physiological temperature. PHEMA hydrogels with these thermosensitive grafts were synthesized by free‐radical solution polymerization, using an acrylated version of the oligomers. The oligomers were characterized for their molecular weight, LCSTs, and rate of response to a change in temperature. With the flexibility in tuning their properties by varying reaction parameters, these oligomers present possibilities in several fields, including drug delivery. The impact of cross‐linking agent type and the amount and presence of grafts on the polymer network structure was found by determining the hydrogel mesh sizes. PHEMA gels cross‐linked with methylenebisacrylamide had larger mesh sizes than those cross‐linked with ethylene glycol dimethacrylate. Increasing amounts of cross‐linking agent decreased mesh sizes. LCSTs exhibited by oligomers were slightly lower than those exhibited by polymer gels of the same composition. The grafting reaction was found to have only a slight impact on the hydrogel mesh size. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Yttrium barium copper oxide‐filled polystyrene as a dielectric material

Electrical impedance measurements are carried out on high temperature superconducting ceramic Yttrium Barium Copper Oxide (YBCO)–Polystyrene (PS) composite materials, in which superconducting particles are embedded in polystyrene matrix. The results of impedance versus frequency (100 Hz–13 MHz), phase angle versus temperature for volume percentage of superconductor (0–40%) are presented. No marked transition in phase angle is observed when the material goes through the superconducting transition temperature of the filler. The dielectric constant and losses increase with increasing YBCO content. However the increase in losses is modest and the excellent dielectric properties of the composites are not adversely affected. The system conforms to Clausius‐Mossotti equation. Dipole moment of YBCO particles and polarizability of the composites are calculated using the Clausius‐Mossotti approaches. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Prevailing Research Trends in Carbon Nanohorn and Polymer-based Hybrids

This review outlines research progress on carbon nanohorn (CNH) and polymer/CNH hybrids including structure, properties, application, and future stance. Carbon nanohorn is a type of nanocarbon existing as dahlia-like, bud-like, and seed-like structures. Most widely known form is single-walled carbon nanaohorn with diameter of ～5?nm and tube length ～50?nm. Polymers such as polystyrene, polyaniline, polythiophene, poly(vinylalcohol), poly(methylmethacrylate), poly(ethyleneglycol), polycaprolactone, polyimide, poly(2-aminopyridine), and nylon have been interacted with CNH using various techniques. Structural and physical properties of fine-tuned carbon nanohorn and polymer/CNH hybrids have been used for versatile applications such as dye-sensitized solar cell, supercapacitor, drug delivery, fuel cell, and sensors.     

Expanded Polystyrene Foam Formed from Polystyrene Beads Coated with a Nanocrystalline SiO2 Film and the Analysis of Its Moisture Adsorption and Resistance to Mechanical Stress

Conventional expanded polystyrene can absorb moisture, which significantly degrades its properties. In the present study, it was demonstrated that SiO₂ can be deposited on polystyrene beads before pre-expansion and molding steps. Under the applied test conditions, expanded polystyrene with nanocrystalline SiO₂ additives had approximately 10% lower moisture adsorption and an 8.4% better resistance to deformation. Expanded polystyrene analysis suggested that the observed improvements were caused by the hydrophobic nature of nanocrystalline SiO₂ and, even more importantly, because SiO₂ acted as an amalgamation catalyst and significantly increased adhesion between the expanded polystyrene beads during the expanded polystyrene molding process.     

Preparation of tailor‐made polystyrene nanocomposite with mixed clay‐anchored and free chains via atom transfer radical polymerization

Tailor‐made polystyrene nanocomposite with mixed free and clay‐attached polystyrene chains was synthesized using atom transfer radical polymerization. Vinylbenzyl trimethylammonium chloride having a double bond, which could be incorporated into polystyrene chains by a grafting through process, was used as a nanoclay modifier. Conversion and molecular weight evaluation was carried out using gas chromatography and gel permeation chromatography, respectively. The thermogravimetric analysis results confirmed the elevated thermal stability of the nanocomposites in comparison with the neat polystyrene sample. Additionally, the T_g increases by clay loading was confirmed by differential scanning calorimetry (DSC). The difference in the degradation temperature of C? Br bond in attached and free polystyrene chains was well revealed in DSC thermograms. Finally, a lower clay loading resulted in an exfoliated structure as proved by X‐ray diffraction and transmission electron microscopy results. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Methylamino‐group‐modified hypercrosslinked polystyrene resin for the removal of phenol from aqueous solution

Chemical modification was performed for macroporous crosslinked chloromethylated polystyrene. The obtained HJ‐K01 resin was used to remove phenol from aqueous solution, and its adsorption behaviors for phenol were compared with commercial Amberlite XAD‐4. The results indicate that methylamino groups were successfully uploaded onto the surface of the HJ‐K01 resin and the adsorption capacity of phenol onto the HJ‐K01 resin was much larger than that onto XAD‐4. Furthermore, the original phenol solution was suitable for the adsorption, the adsorption isotherms could be fitted by the Freundlich model, and its kinetic curves could be characterized by a pseudo‐second‐order rate equation. The fixed‐bed column adsorption demonstrated that the HJ‐K01 resin was an excellent resin for the removal of phenol. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of cation‐exchange membrane based on sulfonated sty/HEA/LMA terpolymer

A cation‐exchange membrane based on a styrene/hydroxyethyl acrylate/lauryl methacrylate (Sty/HEA/LMA) terpolymer was prepared via a postsulfonation reaction for various sulfonation times. Sulfonic groups were introduced into the membrane structure with sulfuric acid as the sulfonating agent and silver sulfate as an initiator in a nitrogen atmosphere. Sulfonated Sty/HEA/LMA terpolymer membranes were characterized by Fourier transform infrared (FTIR) spectrometry and nuclear magnetic resonance as well as by determining the degree of sulfonation (DS), ion‐exchange capacity (IEC), water uptake (WU), and electrical property of the membranes. The presence of sulfonic groups in the sulfonated Sty/HEA/LMA terpolymer was confirmed by FTIR, and the resulting membrane showed an IEC of 1.29 meq/g and an electrical resistance of 0.1 Ω cm². The WU of the prepared membranes increased with the DS at the reaction time. The surface morphology obtained by atomic force microscopy clearly showed an increase of roughness with reaction time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Sensing behaviors of polymer/carbon nanotubes composites prepared in reversed microemulsion polymerization

Polystyrene/carbon nanotubes composites were readily prepared by reversed microemulsion polymerization. Compared with the composites prepared by solution mixing, the uniform dispersion of carbon nanotubes in polymer matrix could be obtained more easily and the thermal and electrical properties of the as‐prepared composites were also enhanced. The as‐prepared composites were deposited onto a microelectrode array to fabricate a vapor sensor. The response for different organic vapors was evaluated by monitoring the change in the resistance of the composites upon exposure to various gases. The change in resistance was of the order of about 10³ for the composites prepared by reversed microemulsion polymerization. The chemical sensors based on the composites prepared by reversed microemulsion polymerization presented excellent reproducibility and reversibility in response. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

聚苯乙烯注塑成型制品双折射行为模拟分析

建立了模拟聚合物注塑成型过程中流动应力的数学模型.利用Leonov黏弹性模型对聚苯乙烯熔体在非等温幂率稳态剪切流下的流动行为进行模拟分析.并研究了聚苯乙烯在注塑成型填充过程中,由于流动而产生的剪切和拉伸作用以及模腔内聚合物熔体的温度变化对制品双折射行为的影响,得到了与实验相符的结果,证明了本研究中模拟方法的可行性.