Papers by Keyword: Phase Separation

Abstract: Co-Pоly (Urethane-Imide) s (CPUI) based on pоly (diethyleneglycol) adipate diol, tolylenediisocyanate, multinucleate dianhydrides and diamines were synthesized. The films and moldings from CPUI were processed and their mechanical characteristics were evaluated. Distinctions of specifications of the films formed from polymer solutions and the moldings formed from melt polymers are indicated when using the same starting CPUI. It appears that films and moldings possess typical properties of elastomers. The reprocessing of studied copolymers by using the injection molding method allows to assign CPUI to the thermoplastic elastomers or so-called thermoelastoplasts.

Abstract: Shape memory polyurethane (SMPU) is a very versatile material that has a broad array of applications. The selection of soft segments and hard segments play critical roles in determining the structure-property behaviors of SMPU. This research was conducted to evaluate the role of distinct types of diisocyanate on the final properties of polyurethane (PU). Palm kernel oil polyol (PKO) based PU were produced by using two-step bulk polymerization method with variations of diisocyanates. Isophorone diisocyanate (IPDI), 4,4-methylenebis (cyclohexyl isocyanate) (HMDI) and hexamethylene diisocyanate (HDI) were used in the preparation of PU and the soft segment crystallinity, thermal and shape memory properties of the PU were evaluated. Based on the analyses, it was found that different types of diisocyanate and combination of diisocyanates had huge impact on the properties of the synthesized PU. The Fourier transformation infrared (FTIR) analysis revealed that IPDI based PU achieved the highest hydrogen bonding index value which promoted the phase separation. This is in accordance with differential scanning calorimetric (DSC) and x-ray diffraction (XRD) analysis which showed that IPDI based PU exhibited crystalline soft phase, hence resulted in an excellent shape fixity behavior. On the other hand, HDI and HMDI based polyurethane prepared showed absence of crystalline soft phase based on the DSC thermogram and XRD diffractogram. These results suggest the phase mixing phenomenon between soft and hard segments which contributed to low shape memory behavior of the resulting polyurethane.

Abstract: The quaternary phase bioactive glasses (SiO₂-CaO-Na₂O-P₂O₅) were synthesized by the sol-gel process. Pluronic P123, using surfactant as structure-directing agents as well as phase separation inducers. The obtained bioactive glasses were characterized regarding morphology by using the scanning electron microscopy (SEM). Polymer colloidal crystals (CCTs) as the template component yielded either three-dimensionally ordered macroporous (3DOM) structure or hollow spheres shaped bioactive glass. The other type of morphology generation is related to the polymerization-induced phase separation (PIPS) in the gelation process. The heterogeneous precursor i.e. silica-rich regions caused the microspheres and solvent-rich areas produced micrometer-scale void space in bicontinuos structure. While the lower pH of starting precursor in 45S4P showed stronger precursor-template interactions than the 53S4P by generating the completely hollow spheres structure.

Abstract: Various polyurethane-based shape memory polymer was synthesized using polycaprolactone (PCL) as soft segment and, hexamethylene diisocyanate (HMDI) and isophorone diisocyanate (IPDI) as the hard segments. Palm kernel oil-based polyol was used to replace part of the petroleum-based polyol due to the increasing demand on renewable resources as a result of environmental awareness. The synthesis has been carried out using two step polymerization method. The effects of varying the molar ratio of IPDI/HMDI on material properties such as crystallinity, transition temperature, morphology, shape memory effect and tensile strength were investigated by using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), shape memory test and tensile test. A high IPDI content in SMPU results in better shape memory effect, whereas increasing HMDI content leads to a better chain flexibility. In this work, the incorporation of IPDI contributes to the formation of phase separation which enhance the formation of crystalline soft segment structure while the incorporation of HMDI as isocyanate tend to promote phase mixing which enhance the chain flexibility of the SMPU backbone.

Abstract: Poly (diethylene glycol) adipate diol, tolylene-2,4-diisocyanate, 1,3-bis (3',4-dicarboxylphenoxy) benzene and 1,4-bis (4'-aminophenoxy) biphenyl were used as monomers to form statistical copoly (urethane-imide) s with variable content of imide blocks (from 37 to 65% (wt)). The copolymers imide blocks on the T_g and T_m values relative content increasing effect was traced, which is associated with the phase separation of hard imide and flexible polyester blocks in the systems studied.

Abstract: Abstract. The in situ forming gel (ISG) has been developed as a controlled drug delivery system to prolong drug release. This study aims to prepare ISG system based on gamboge resin (GB) as matrix former. The various amounts of GB dissolving in dimethyl sulfoxide (DMSO) and N-methyl pyrrolidone (NMP) were used to obtain the ISG systems and evaluated for their pH, viscosity, injectability and matrix forming. The antimicrobial activities against three strains of Staphylococcus aureus including the Methicilin Resistant S. aureus (MRSA) and Porphyromonas gingivalis were conducted. GB ISG systems exhibited good injectability with low viscosity. GB in DMSO showed a faster transformation to solid matrix compared to that in NMP. The gambogic acid (GA) content in crude GB was 33.70 ± 0.13%. The sustainable GA release from GB ISG could be attained. Thus, GB ISG exhibits the potential application as a drug delivery system for active compounds and is enable for using as a therapeutic dosage form owing to its antimicrobial activity.

Abstract: Stress-strain responses and microstructure of multi-phase CoCrCuMnNi and CoCrMnFeCu alloys in which Fe or Ni was replaced by Cu from Cantor alloy were studied. The deformation mechanisms of CoCrCuMnNi and CoCrMnFeCu were observed to be influenced by the presence of brittle sigma phase and the separated Cu-rich and the matrix phase. CoCrCuMnNi exhibited the relatively lower strength and excellent deformability, while CrMnFeCoCu alloy exhibited higher strength and lower ductility. The higher strength and the lower ductility of CoCrCuMnNi is associated with the presence more frequent and coarser sigma phase than those in CoCrCuMnNi.

Abstract: For revealing internal atomic processes in bimetallic nanoparticles, individual hemispherical Ag-Cu alloy particles were grown by direct current (DC) magnetron sputtering. Phase separation of particles was found to be size- and composition-dependent. Particles smaller than 5 nm in diameter remained as a solid solution of the components for all tested compositions (15-80 at.% Ag). At 15 and 30 at.% Ag compositions phase separation was observed only for particles above 5 nm in diameter. Computer simulations by Stochastic Kinetic Mean Field model reproduced the size-dependence of the decomposition and the internal structure of two-phase particles. Theoretical explanation is given for the composition dependence of the phase separation tendency.

Abstract: Fluorinated urethane-acrylic monomer (FUA) was synthesized using toluene diisocyanate (TDI), 1H, 1H, 2H, 2H-Perfluorooctanol(FOH) as well as hydroxyethyl methacrylate(HEMA), and then applied to prepare waterborne fluorinated polyurethane-acrylate (FPUA) via emulsion polymerization. The effect of FUA content on surface properties of latex films was evaluated by means of nuclear magnetic resonance (¹H NMR), atomic force microscope (AFM) and water contact angle test. It is shown that FUA monomer content is related to phase separation of the film surface and water contact angle. As FUA content was increased from 0 wt% to 11.8 wt%, water contact angle was increased from 84° to 104.5°. Further increase of FUA has little influence on surface hydrophobicity but obvious effect on surface phase separation, and the reason which led to this phenomenon is described.

Abstract: The present study focuses on characterization the physical properties of liposome formulation which was dispersed in HPMC matrix and lyophilized in the presence of disaccharides. The lyophilized formulations featured cationic dimethyldioctadecylammonium (DDA) to produce dry solid and overcome limitations in terms of detrimental phase separation in phospholipid membranes during production process. Disaccharides, such as sucrose and lactose, have been reported to protect phospholipid membranes during drying, while HPMC was used as dispersed matrix to inhibit recrystallization of disaccharide. Their physical properties were characterized including their morphology using scanning electron microscopy (SEM), crystallinity using x-ray diffractometry (XRD), and solid phase separation using differential scanning calorimetry (DSC). On the basis of these evaluations it was found that the presence of sucrose and HPMC in the formulation showed a miscible mixture and relatively less crystalline-forming properties compared to those using lactose, thus potentially construct a stable dried liposomal formulation. The present study reveals prospective advantages of using combination of sucrose and HPMC in development of dried–DDA liposomal formulation.