Preparation and characterization of methoxy‐poly(ethylene glycol) side chain grafted onto chitosan as a wound dressing film

Chitosan has received extensive attention as a biomedical material; however, the poor solubility of chitosan is the major limiting factor in its utilization. In this study, chitosan‐based biomaterials with improved aqueous solubility were synthesized. Two molecular weights (750 Da and 2000 Da) of methoxypoly(ethylene glycol) (mPEG) were grafted onto chitosan (mPEG‐g‐chitosan) to form a ～100‐μm‐thick plastic film as a wound dressing. The chemical structures of the mPEG‐g‐chitosan copolymers were confirmed using Fourier transform infrared spectroscopy (FTIR), and the thermal properties were characterized using thermogravimetry analysis (TGA). Their microstructures were observed using scanning electron microscopy (SEM). The other properties were analyzed via the swelling ratio, tensile strength, elongation, and water vapor transmission rate (WVTR). Biocompatibility evaluations through biodegradability, cytotoxicity, and antimicrobial effect studies were also performed. The obtained mPEG‐g‐chitosan copolymers were soluble in slightly acidic aqueous solutions (pH～6.5) at a concentration of 10 wt %. The optimal mPEG‐g‐chitosan hydrogels had swelling ratios greater than 100% and WVTRs greater than 2000 g/m²/day. Their performance against Staphylococcus aureus will be subjected to further improvements with respect to medical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42340.     

Curing reaction of unsaturated polyester resin modified by dicyclopentadiene

The objective of this research is to prepare modified unsaturated polyester resin(UPR) with good processibility, dimension stability and mechanical properties. In this study, dicyclopentadiene (DCPD) is selected as a modifier and the effect of DCPD content on the curing behavior of the modified UPR is examined via Differential Scanning Calorimetry (DSC) and Rheometrics Dynamic Analysis (RDA) experiments. The results of ¹H NMR identification for the chemical structure of modified UPR show that the trans-structure of UPR decreases as the DCPD content increases. The curing time necessary to reach peak maximum in DSC during the curing reaction lengthens as the stereo obstacles formed by the binary rings increase.     

Fiber and film developments from immiscible blends of cellulose acetate propionate and poly(butylene terephthalate)

Binary blends of cellulose acetate propionate (CAP) and poly(butylene terephthalate) (PBT) in the composition range of 5–15 wt % for CAP were prepared in the form of films and fibers by compression molding and spinning, respectively. The presence of two invariant glass‐transition temperatures corresponding to the CAP and PBT components and viscosities lower than those of the neat PBT of the CAP–PBT blends implied that the CAP–PBT blends were immiscible. Moreover, the crystallinity of the PBT component was higher in the spun fibers than in the films; this was possibly due to the different cooling methods or the chain orientation in the spinning process. In the meantime, the CAP component could not undergo crystallization because of its rigid structure and alkyl substituents. For the CAP–PBT films, the amorphous CAP was present as dispersed particles in the PBT matrix; but it became rods in the spun fibers. In addition, the presence of the amorphous CAP resulted in a decrease in the tensile strength and an increase in the elongation at break for the CAP–PBT fibers. The CAP–PBT films and fibers could be applied in a wide range of applications requiring renewable properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45013.     

Preparation and enhanced mechanical properties of hydroxyapatite hybrid hydrogels via novel photocatalytic polymerization

Hydroxyapatite (HA) hybridized poly(N-isopropylacrylamide)-co-acrylic acid (PNIPAM-co-AAc) hydrogel on thermoplastic polyurethane (TPU) were successfully prepared via photocatalytic polymerization technique. Low temperature plasma processing of HMDSZ and O₂ plasma were deposition on substrate. The HA/hydrogel were stabilized by HA of which the wettability was modified by calcium nitrate and ammonium phosphate dibasic. The HA gradually increases with the increase of time cycles. The deposition of organic silicone group by the HMDSZ on the TPU substrate is hydrophobic surface. When deposition of O₂, the water contact angles (WCA) was changed to <10° and surface hydrophilicity. The materials were characterized by OM, SEM, FT-IR, XPS and XRD. The results showed that the NIPAM: AAc (1:1 mol) polymers possess macropores ranging from 2 to 20 μm, and their large numbers of carboxyl groups and hydroxyl groups result in a favorable adsorption capacity for HA. Swelling studies indicated that NIPAM: AAc (1:1 mol) was 446 ± 0.3%. This work provided a promising alternative method for the fabrication of polymer materials with tunable and interconnected pores structures for the HA.     

The Analysis of Photocuring Behavior of Polyester Acrylate by Means of Differential Photo Calorimeter (DPC) and Rigid-Body Pendulum Rheometer (RPT)

This study aims to understand the different photocuring behaviors of acrylated polyester by adding different photoinitiators and monomers. Differential photo calorimeter (DPC) is used to understand the exothermal effects during photocuring. The self-catalyst model of dynamic analysis software was then used to obtain the relationships between reaction speed, reaction extent, and rate of reaction. In addition, this study also tried to understand the formation of photocuring resin from the rigid-body pendulum rheometer (RPT) experiment. The results showed that the extent of reaction, conversion rate and speed varies directly with the concentration of the photoinitiator and monomer. The reaction level of propoxylated pentaerithritol triacrylate was higher than propoxylated neopentyl-glycol diacrylate. Moreover, the method using RPT shows better view of the molecule reaction status inside the photopolymer.     

Synthesis of Silicon Dioxide Optical Films Mixed with Acrylic Series Monomers by Sol-gel Process

In this study, silicon dioxide (SiO₂) particles are mixed with acrylic series monomers (methyl metacrylate (MMA) and 2-hydroxyethyl methacrylate (2-HEMA)) by sol-gel process to prepare inorganic-organic hybrid materials for the optical film. The other optical film has the same composition and process as the above but tri(ethylene glycol) dimethacrylate (TEGDMA) is added.

An infrared spectrometer, differential scanning calorimeter, thermo gravimetric analysis, ultraviolet-visible spectrophotometer, and spectroscopic-ellipsometer have been used to explore the effect on optical, hardness, and thermal properties of the two series of thin films. TEGDMA used as a bonding resin in this study showed that not only a better hardness and thermal properties, but also maintain good optical properties in the SiO₂ hybrid materials by sol-gel process.     

Preparation and properties of nadic‐end‐capped cyclotriphosphazene‐containing polyimide/carbon fiber composites

New novel fire‐resistant and heat‐resistant cyclotriphosphazene‐containing polyimide resins were prepared in situ by the polymerization of (p‐aminophenoxy)(phenoxy)cyclotriphosphazenes with 3,3′,4,4′‐benzophenonetetracarboxylic acid or 3,3′,4,4′‐diphenylsulfonetetracarboxylic acid and a crosslink agent, 5‐norbornene‐2,3‐dicarboxylic acid and were used as polymer matrix compositing with a woven carbon fiber to prepare nadic‐end‐capped cyclotriphosphazene‐containing polyimide/carbon fiber composites. The thermal stability, flame retardance, morphology of the surface fracture, and some physical properties of the composites were investigated by thermogravimetric analysis, scanning electron microscopy, and a material testing system, respectively. The composites had good thermal stability, flame retardance, and mechanical properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 810–818, 2003