Effect Of Polymer Characteristics Research Articles

液晶性高分子の構造と物性にみる高分子性と液晶性の影響

液晶性高分子の構造と物性にみる高分子性と液晶性の影響

Adsorption of hybrid polyacrylamides on anisotropic kaolinite surfaces: Effect of polymer characteristics and solution properties

Abstract Adsorption kinetics of organic-inorganic (hybrid) Al(OH) 3 -polyacrylamide (Al-PAM) with different molecular weights (for organic characteristics) and contents of aluminum hydroxide nanoparticles (for inorganic characteristics) on kaolinite basal planes was studied using a versatile quartz crystal microbalance with dissipation (QCM-D). The flocculation dynamics of kaolinite by Al-PAMs was assessed by measuring the initial settling rate of flocculated kaolinite particles and the turbidity of the supernatant after settling of flocculated solids. The areal mass (mg/m 2 ) of Al-PAMs adsorbed on tetrahedral silica and octahedral alumina basal planes of kaolinite increased with increasing molecular weight of the polymer. Increasing the content of Aluminum hydroxide nanoparticle in Al-PAM has resulted in an increase of the amount of the polymer adsorbed on silica basal planes while opposite trend was found on alumina basal planes. Results obtained from the adsorption kinetics study of Al-PAM 6R ( M w = 2.2 million Dalton, 0.11 wt% Aluminum) on silica basal planes revealed that the early stage of adsorption is diffusion-controlled. Thus, initially the adsorption rate increased with increasing temperature while the maximum coverage decreased. Moreover, the adsorption of Al-PAMs on silica basal planes was shown to decrease significantly in plant recycle (process) water compared to deionized water. Al-PAMs of higher molecular weight and/or high content of inorganic Al (OH) 3 nanoparticles were found to be more effective in flocculating kaolinite as indicated by the faster settling rates and clearer supernatant.

Effect of Polymer Characteristics on Particle Formation and Growth in Batch Emulsion Polymerization

This article is an extensive investigation on particle coagulation growth in emulsion polymerization proposed by our team (Colloid and Polymer Science, 2013, 291, 2385–2398). Monodispersed, large-scale, high-solid content poly (butyl acrylate) latex was obtained by varying the reaction procedures in previous studies. However, the present method, which could be used in other monomer systems such as styrene, methyl methacrylate, or the copolymerization of different monomers, has not been reported to date. In this article, the particle formation and growth behaviors of different monomer compositions were investigated in regard to the range of application and to clarify the effect of monomer characteristics on particle coagulation. Experimental results indicated that polymer characters such as hydrophilicity play an important role in particle coagulation, which was increased with increasing monomer hydrophilicity. Moreover, particle coagulation could improve reaction system stability and enhance the likelihood of obtaining a high solid content. The optimal systems for styrene, methyl methacrylate, and butyl acrylate were 40, 50, and 60 wt%, respectively, due to variation in monomer hydrophilicity.

Effect of Polymer Characteristics on the Thermal Stability of Retinol Encapsulated in Aliphatic Polyester Nanoparticles

The present study investigates how the thermal stability of retinol (vitamin A) encapsulated in polyester nanoparticles is influenced by the types of polyester used for the nanoparticles. A variety of polyester-retinol nanoparticles were prepared with various polyesters like: poly(ethylene adipate), PEA; poly(butylene adipate), PBA; poly(hexamethylene adipate), PHMA; and three polycaprolactones, PCL, of different molecular weights (<TEX>$M_n$</TEX> ~10, 40, and 80K). The chemical stability of retinol in these nanoparticles, monitored in an aqueous solution at <TEX>$25^{\circ}C$</TEX> and <TEX>$40^{\circ}C$</TEX> for 4 weeks, was high in the following order of the nanoparticles prepared with PHMA > PCL 40K > PCL 10K > PCL 80K > PBA~PEA at <TEX>$25^{\circ}C$</TEX> and PCL 10K > PCL 40K > PHMA > PCL 80K > PEA > PBA at <TEX>$40^{\circ}C$</TEX>. More importantly, this study has also found that the thermal stability of the retinol in the nanoparticles was closely connected with the melting temperatures of polyesters and polyester nanoparticles. The results were further discussed with possible factors - such as sample preparation condition (or history) and miscibility between the polyesters and retinol - affecting <TEX>$T_m$</TEX> of the polyesters and the nanoparticles.

Modelling PCC flocculation by bridging mechanism using population balances: Effect of polymer characteristics on flocculation

A population balance model for flocculation of PCC particles with polyelectrolytes of very high molecular weight, medium charge density and different degree of branching is presented. The model considers simultaneously aggregation, breakage and flocs restructuring to describe the PCC flocculation by bridging mechanism. The maximum collision efficiency factor, a parameter related with the fragmentation rate and a time constant for flocs restructuring have been taken as fitting parameters. These fitting parameters are optimized to get the best fit between experimental data obtained by LDS in a previous study and the modelled results. The optimized parameters were correlated with flocculant concentration, flocs structure and polymer branching. The correlations obtained show well the effects of flocculant concentration, flocs structure and polymer structure on the flocculation kinetics and flocs restructuring which are translated in the model parameters. Moreover, the flocs break up due to polymer degradation was introduced in the model by decreasing, with time, the maximum collision efficiency factor. It was shown that this effect can be neglected since the improvement in the results is too small relatively to the high increase of the computational time required to perform the simulation.

The Effect of Different Grades of PLGA on Characteristics of Microspheres Encapsulated with Cyclosporine A

The aim of this study was to evaluate the effect of different grades of poly D, L lactide-co-glycolide (PLGA) on the properties of microspheres encapsulated with Cyclosporine A (CyA). Microspheres were prepared by solvent evaporation method using three grades of PLGA. Various characteristics of microspheres such as morphology, size distribution, encapsulation efficiency and release profile were evaluated. Complementary studies were also carried out by Infrared (IR) spectroscopy and Differential scanning calorimetry (DSC) to evaluate possible drug-polymer interactions. Scanning electron microscopy (SEM) studies showed microspheres as spherical particles with CyA deposited as islands on the surface of spheres. Particle size range was 1-25 microm for microspheres made of PLGA (50:50) which showed the minimum size. Encapsulation efficiency was found to vary from 75% to 92% in various formulations. The profile of release was biphasic, showing an initial rapid phase followed by a continuous and slower rate thereafter. Microspheres made of grades 50:50 and 85:15 showed the highest and lowest amount of drug release, respectively. IR spectra for drug, polymer and microspheres did not indicate any chemical interaction between the components of microsphere and DSC thermograms revealed that CyA was present in its amorphous state within microspheres. In conclusion, the effect of polymer characteristics should be considered in microsphere formulations. In this study, suitable microspheres especially with PLGA (50:50) were prepared which allow the controlled release of CyA over a prolonged period of time.

Segment-sphere size ratio influence on the stability of a polymer-colloid mixture.

The influence of the sphere to segment size ratio on the effective depletion layer thickness around a sphere and the resulting phase behaviour of a colloid-polymer mixture is considered. An analytical expression for the excluded volume between an ideal freely jointed chain and a sphere [L. Lue, J. Colloid Interface Sci. 202, 558 (1998)] allows the effect of polymer characteristics (chain length, segment/sphere size ratio) on the depletion interaction in polymer-colloid mixtures to be calculated. For both small and intermediate polymer-to-colloid size ratios the respectively gas-solid and gas-liquid coexistence curves shift to larger polymer coil volume fractions as the relative segment size increases. It is further demonstrated that the conditions for optimal (protein) crystallization are affected when the segment to sphere size is altered.

Biodegrable controlled release tablets: III. Effect of polymer characteristics on drug release from heterogeneous poly(lactide-co-glycolide) matrices

Spray dried poly(lactide-co-glycolide) powders were used to prepare phenobarbitone matrix tablets. The release of phenobarbitone was significantly sustained, indicating the suitability of using poly(lactide-co-glycolide) matrix tablets for long-term controlled drug delivery. Drug release profiles consisted of three regions: there were an initial region of relatively high release rate (burst effect), followed by an extended region of lower and essentially constant release rate from approx. 20 to 80% of drug release. This steady state release region was followed by a final one in which the rate of drug release fell off as exhaustion of the drug in the matrix approached. A composite mechanism of drug release is proposed involving diffusion of the drug through water-filled pores in the matrix and drug diffusion through the swollen polymer. The rate of drug release increased with an increase in the glycolide content of the polymers. Decreasing the polymer molecular weight caused initially an increase but later a decrease in the release rate. These results are discussed in terms of degradation, water uptake and swelling of the polymers upon immersion in aqueous media.

Positive Deep-UV Resist Based on Silylated Polyhydroxystyrene.

A chemically amplified, positive-working resist system based on silylated Polyhydroxystyrene has shown its potential ability for application to the quarter micron lithography. The present paper describes the recent improvement on resist performance achieved through studies on effects of polymer characteristics and process conditions. Especially reported is the methods for avoiding the T-shaped pattern profile which is often observed for many chemically amplified, positive- working resist systems.Although the development is still on the way, the silylated polyhydroxystyrene resist shows excellent properties on resolution capability, sensitivity and process latitude.

Photo-oxidative degradation of polyethylene: Effect of polymer characteristics on chemical changes and mechanical properties. Part 1—Quenched polyethylene

Photo-oxidative degradation of quenched samples of linear low density (LLD), medium density (MD) and two kinds of high density (HD) polyethylene (PE) films was studied using a medium-pressure mercury lamp. Greater amounts of crosslinking and build up of oxidation products were noticed in LLDPE than the other samples. The primary products of interaction between dienes and oxygen are considered to participate in the initiation of the photo-oxidation reactions. Using the FT-IR difference spectrum technique, the amount of branch concentration in the photo-irradiated PE samples was determined. Oxidation damage at the boundary region between crystalline and amorphous phases is considered to be important in determining the embrittlement time.