Hsin-Jiant Liu

Effect of soft segment on degradation kinetics in polyethylene glycol/poly(l-lactide) block copolymers

SummaryThe hydrolytic degradation of polyethylene glycol(PEG)/poly (L-lactide)(PLLA) copolymers with various PEG wt% contents at 37°C and pH=7 was studied by differential scanning calorimetry(DSC) and gel permeation chromatography(GPC). The effect of PEG contents in PEG/PLLA copolymers on the crystalline morphology and hydrolytic degradation rate was investigated. Due to the hydrophilic PEG segments in PEG/PLLA copolymers, the exothermic recrystallization and the shoulder portion of melting endotherm appear immediately following the hydrolysis of copolymers. Moreover, after a period of hydrolysis of 100 h. the molecular weight distribution turn to a bimodal shape from a unimodal in the original, and the polydispersity becomes greater with a value from 1.5 up to 5, which are not observed for PLLA homopolymer. The rate constants of hydrolysis for the first-order auto-catalytic kinetics, increase with the PEG content over 0 to 18.3 wt%, ranging from 1 to 6x10-4hr-1.

Synthesis and surface activity of polyethylene glycol–maleic anhydride–polydimethylsiloxane polyester surfactants

Abstract A novel series of water-soluble polyethylene glycol (PEG)–silicone polyester surfactants has been prepared by the polymerization of PEG, maleic anhydride, polydimethylsiloxane and fumaric acid. The unique structural features of these surfactants have been confirmed by FTIR, proton nuclear magnetic resonance and elemental analysis. Also, the influences of the PEG segment lengths of PEG–silicone polyesters on the surface tension, wetting power and dispersant properties were investigated. The experimental results indicated that the solution that contained the PEG–silicone polyester surfactants exhibits excellent surface active properties.

Solute diffusion through degradable semicrystalline polyethylene glycol/poly(l-lactide) copolymers

SummaryThe diffusion of C.I. direct orange 34(MW=299) and benzoic acid(MW=122) through degraded semicrystalline polyethylene glycol(PEG)/poly(L-lactide)(PLLA) block copolymers with various PEG contents and PEG segment lengths at 37°C was studied by UV-visible spectroscopy, differential scanning calorimetry(DSC), wide angle X-ray diffractometer (WAXS) and scanning electron microscopy(SEM). The influences of the PEG contents, PEG segment lengths and hydrolytic degradation of PEG/PLLA copolymers on the solute diffusion coefficient and mode for transport were investigated. It is concluded that the diffusion rate increases with the increase of PEG contents and PEG segment lengths in PEG/PLLA copolymers. This is understandable that the increase of PEG content and PEG segment length both make the degree of crystallinity decrease. The steady state of mass flux could not be reached at the diffusion times up to 1000 h, because the copolymers underwent hydrolysis reaction during this period. Furthermore, it is understood that the characteristic time of diffusion as defined by the square of film thickness at an instant of time over the diffusion coefficient of solute through polymer decreases with the increasing diffusion time.

Crystallization and Thermal Properties of PLLA–PEG 600/Clay Nanocomposites

This study explored the crystallization and thermal properties of copolymers of polylactic acid–polyethylene glycol (Mn: 600) (PLLA–PEG 600 copolymer) nanocomposites with added montmorillonite (clay). The d-spacing of the hydrophilic montmorillonite was increased by using a quaternary ammonium salt. The salt was used to modify montmorillonite via ion exchange. The modified montmorillonite was then evenly dispersed in the matrix of the PLLA–PEG 600 copolymer to synthesize the nanoscale polymer via solution casting method. Thermogravimetric analysis and differential scanning calorimetry were used to measure the thermal properties of the PLLA–PEG 600 copolymers with various proportions of added clay. Wide-angle X-ray diffraction was used to identify the crystal structure and lattice displacements of PLLA–PEG 600 copolymer and the copolymer with added clay. Using polarized optical microscopy and transmission electron microscopy, the crystal growth and size of PLLA–PEG 600 copolymer with various proportions of added clay, as well as the dispersion of the clay, were observed. Adding clay to PLLA–PEG 600 copolymer improved its thermal properties and crystallinity without changing its original crystal structure. GRAPHICAL ABSTRACT

Preparation and Drug Release of Aspirin-Loaded PLGA-PEG-PLGA/Montmorillonite Microparticles

A polymerization method was used to synthesize biodegradable poly(lactide-co-glycolide)/poly(ethyleneglycol)/poly(lactide-co-glycolide) (PLGA-PEG-PLGA) copolymers. These copolymers were then used to prepare microparticles for encapsulating drug (aspirin). The results of X-ray diffraction (XRD) analysis showed that the montmorillonite (MMT) can be converted into organic montmorillonite (o-MMT). Subsequently, the emulsion solvent evaporation method was used to separately prepare aspirin-loaded PLGA-PEG-PLGA and aspirin-loaded PLGA-PEG-PLGA/o-MMT microparticles. The results of scanning electron microscopy (SEM) showed that microparticle formation was related to the polyvinyl alcohol (PVA) concentration and the proportion of o-MMT. In addition, the ultraviolet-visible (UV-Vis) spectroscopy was conducted to determine the release rate of these microparticles. GRAPHICAL ABSTRACT

Utilization of dried activated sludge for the removal of basic dye from aqueous solution

AbstractTextile dye wastewater can easily lead to environmental pollution issues because of its toxicity and difficult treatment. If the waste sludge produced from sewage treatment plant is used as an adsorbent to treat textile dye wastewater, waste recycling can be achieved. This study investigated the use of dried activated sludge (DAS) for the removal of Basic Red 29 dye from aqueous solution and used granular-activated carbon to compare differences in adsorption capacity. Influence on adsorption capacity of various factors, such as adsorbent properties, initial dye concentration and dye solution temperature, were investigated on the original dye solution. Kinetic data followed well both pseudo-first-order model and pseudo-second-order model. Equilibrium data fitted well with the Langmuir isotherm model. The monolayer adsorption capacity was found as 224.72 mg g−1 at 30°C. Thermodynamic studies indicated that adsorption process was exothermic in nature and the adsorption heat was −17.70 kJ mol−1. The F...

Polyethylene Glycol/Polydimethylsiloxane Polyester Products as Leveling Agents in Nylon Dyeing

A novel series of water-soluble PEG-silicone polyesters surfactants is prepared by polymerization of polyethylene glycol (PEG), maleic anhydride (MA), polydimethylsilox ane, and fumaric acid (FA). The unique structural features of these surfactants are confirmed by FTIR, 1H-NMR, and elemental analysis. The presence of these surfactants retards the rate of nylon dyeing with acid dyes, which, along with the low-foaming property of these novel PEG-silicone polyesters, makes it possible for these surfactants to be used as leveling agents for modem nylon dyeing with acid dyes.

Preparation and dispersion properties of water-soluble polyethylene glycol-dimethyl 5-sulfoisophthalate sodium salt polyester surfactants

Abstract The reaction of polyethylene glycol (PEG, number-average molecular weights Mn=400–2000) and dimethyl 5-sulfoisophthalate sodium salt (SIPM) produced a series of water-soluble polymeric surfactants. The structure of these surfactants was confirmed by IR, 1H-NMR and elemental analysis. These polymeric surfactants have been found to exhibit excellent pH buffer capacity and dispersant properties in disperse dye system. The experimental results indicated that these surfactants could retard the rate of polyester dyeing with disperse dyes and may be used as leveling agents.

Preparation and Photocatalytic Properties of PEG-Silicone Polyesters/Titanium Dioxide Nanotube Composites

This study uses a series of hydrophilic PEG-silicone polyester and titanium dioxide nanotubes to prepare high-performance titanium dioxide nanotube (TNT) composites. The decomposition of these titanium dioxide nanotube composites for the methylene blue is investigated by using UV-Vis spectroscopy. These changes in structure have been observed by FTIR and Raman analysis at 365 nm UV irradiation. The surface microstructures of composites were characterized with scanning electron microscopy (SEM). It was found that titanium dioxide nanotube composites possessed excellent solubility and dispersion effects. This makes fixation of photocatalysts possible and retards oxidation of organic materials in the PEG-silicone polyesters. GRAPHICAL ABSTRACT

Crystallization Behavior of Nanocomposites Synthesized from the Poly (L-lactide)-poly (Propylene Glycol) and Organoclay

This study explored the thermal behavior of PLLA–PPG nanocomposite with added organoclay. The modified clay was evenly dispersed into the matrix of LPG1000 to synthesize the nanoscale polymer. Thermogravimetric analysis and differential scanning calorimetry were used to measure the thermal properties of the PLLA–PPG copolymers. Wide-angle X-ray diffraction was used to identify the crystal structure of PLLA–PPG copolymer. The crystal growth of PLLA–PPG copolymer with various proportions of added clay was observed by using polarized optical microscopy and transmission electron microscopy. The results show that adding clay could enhance the thermal stability of LPG1000 and significantly change its crystal property. GRAPHICAL ABSTRACT