Thermally Induced Phase Separation Technique Research Articles

Effect of conductive polyaniline on the cationic and anionic dye adsorption properties of amphoteric alginate/chitosan composite foams

Doped polyaniline is a widely used conductive material and could be used for adsorption based on the electrostatic neutralization effect through the protonation of the imine group. However, the adsorption effect and mechanism towards cationic and anionic pollutants are not clear. Herein, the conductive sulfonic acid doped polyaniline was introduced into alginate/chitosan amphoteric composite foams prepared with a thermal induced phase separation technique. The composite foams were characterized in terms of scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electrochemical impedance. The composite foam exhibited rich pores and fibrous matrix due to the unique ternary solvent system. The polyaniline was well-distributed and enhanced the cationic dye adsorption ability, contrary to that of anionic dye. Compared with pure alginate/chitosan composite foam, the adsorption capacity of methylene blue was increased by 91.1%, and that of acid blue-113 was reduced by 49.2%. The adsorption rate of the two dyes was both increased. Polyaniline addition enhances the ionic mobility rate and accelerates the movement of dye molecules. Moreover, the composite foams exhibited excellent selective adsorption capacity and reusability. The study indicates that the conductive polymer could find its share in developing high-performance adsorbents.

PLA aerogel as a universal support for the typical organic phase change energy storage materials

We first prepared Polylactic acid (PLA) aerogels with high porosity based on a facile and efficient thermal induced phase separation technique. In view of the excellent internal nano structure of PLA aerogel, high porosity and suitable interfacial affinity, it was selected as a support material to encapsulate four common organic phase change materials (PCMs), thereby preparing anti-leakage, shape-stable and sustainable PCMs with ultra-high latent heat (178.9–224.9 J g−1). PLA aerogel encapsulated PCMs perform high enthalpy efficiency (>92 %), which may benefit from the highly internal compatible nanostructure of PLA. Thermally conductive fillers (Boron nitride and Graphene nanoplatelet) were introduced to improve thermal conductivity. An important factor of PLA aerogel as a universal encapsulation matrix is analyzed based on the solubility parameters and Flory-Huggins parameters. The application cases of smart container and thermal regulation in confined spaces further prove the practical application value in the thermal regulation and energy saving area.

Azithromycin-carrying and microtubule-orientated biomimetic poly (lactic-co-glycolic acid) scaffolds for eyelid reconstruction.

Tarsal plate repair is the major challenge of eyelid reconstruction for the oculoplastic surgeon. The ideal synthetic tarsal plate substitute should imitate the microstructure and mechanical strength of the natural eyelid. The aim of this work was to develop a novel bionic substitute for eyelid reconstruction. Three types of poly(lactic-co-glycolic acid) (PLGA) scaffolds (random, oriented, and azithromycin-loaded oriented scaffolds) were prepared using an improved thermal-induced phase separation technique. The microstructure of the scaffolds was examined by scanning electron microscopy. In vitro cytotoxicity was assessed using scaffold extracts. Fibroblast and primary rat meibomian gland epithelial cells (rMGCs) were cultured within the scaffolds, and their behavior was observed using fluorescence staining. Three types of PLGA scaffolds were implanted into rabbit eyelid defect in vivo to evaluate their inductive tissue repair function. We successfully fabricated three types of PLGA scaffolds with varying pore architectures, and the axially aligned scaffold demonstrated interconnected and vertically parallel channels. In vitro cytotoxicity tests using scaffold extracts revealed no apparent cytotoxicity. Fluorescence staining showed that both Fibroblast and rMGCs could adhere well onto the pore walls, with fibroblast elongating along the axially aligned porous structure. At 8 weeks post-implantation, all scaffolds were well integrated by fibrovascular tissue. The axially aligned scaffold groups exhibited faster degradation compared to the random scaffold group, with smaller fragments surrounded by mature collagen fibers. The study found that the axially aligned scaffolds could well support and guide cellular activities in vitro and in vivo. Moreover, the axially aligned scaffold group showed a faster degradation rate with a matched integration rate compared to the random scaffold group. The findings suggest that the oriented scaffold is a promising alternative for eyelid tarsal plate substitutes.

Automatic pore size measurements from scanning electron microscopy images of porous scaffolds

Pore sizes and distribution are amongst the main morphological characteristics of porous scaffolds which indicate the suitability of scaffolds for many biological applications. Scaffolds usually have complex structures and are designed to have a specific range of pore sizes appropriate for target cells. Pore sizes are commonly estimated manually or based on semi-automatic techniques requiring high level of human intervention. Such methods are time consuming and subject to error, mainly due to lack of consistency in the process and subjective nature of the results following operator involvement. In this work, we present a novel image processing method for the measurement pore size distribution (the main morphological characteristics of scaffolds) independent from their complexity. We use thresholding, based on the histogram analysis, to segment pore areas from scaffold, followed by morphological filters to separate pores from each other. This algorithm provides robust detection and measurement of pore sizes and the distribution. The performance of the algorithm is assessed using standard calibration kit which is used for calibration of Scanning Electron Microscopy (SEM) imaging systems. The results showed consistent output with 1.3% average error as compared against their true size.The algorithm was applied to 3D Apatite-Wollastonite scaffolds manufactured using the Thermally Induced Phase Separation technique. The results were robust and consistent with visual evaluation of SEM images. The algorithm also provides the morphology of each pore and, subsequently, offering further comprehension of the influence of microstructures across a range of fields, such as tissue engineering processes.

Interconnected porous nanofibrous gelatin scaffolds prepared via a combined thermally induced phase separation/particulate leaching method

To mimic the fibrous architecture of collagen, the nanofibrous gelatin scaffolds are fabricated employing a thermally induced phase separation (TIPS) technique. The influences of processing parameters, including polymer concentration and solvent mixture composition on the scaffold microstructure are investigated. However, using the TIPS technique, a limited pore size range is generally obtained. To yield the well-interconnected macroporous structures with equiaxed pores and nanofibrous architectures, the TIPS technique is combined with particulate leaching. The macroporous structure of produced scaffolds duplicates the predefined three-dimensional template structure. The homogenous macrostructure with well-interconnected equiaxed pores and no particular orientation is created. Modulating the size and shape of microspheres has precise control over porosity, pore size, and interconnection of the matrix. Because of the well-interconnected macroporous nanofibrous structure, the useful applications of these scaffolds in the tissue engineering field are expected.

A tailored polylactic acid/polycaprolactone biodegradable and bioactive 3D porous scaffold containing gelatin nanofibers and Taurine for bone regeneration

The focus of the current study was to develop a functional and bioactive scaffold through the combination of 3D polylactic acid (PLA)/polycaprolactone (PCL) with gelatin nanofibers (GNFs) and Taurine (Tau) for bone defect regeneration. GNFs were fabricated via electrospinning dispersed in PLA/PCL polymer solution, Tau with different concentrations was added, and the polymer solution converted into a 3D and porous scaffold via the thermally-induced phase separation technique. The characterization results showed that the scaffolds have interconnected pores with the porosity of up to 90%. Moreover, Tau increased the wettability and weight loss rate, while compromised the compressive strengths. The scaffolds were hemo- and cytocompatible and supported cell viability and proliferation. The in vivo studies showed that the defects treated with scaffolds filled with new bone. The computed tomography (CT) imaging and histopathological observation revealed that the PLA/PCL/Gel/Tau 10% provided the highest new bone formation, angiogenesis, and woven bone among the treatment groups. Our finding illustrated that the fabricated scaffold was able to regenerate bone within the defect and can be considered as the effective scaffold for bone tissue engineering application.

Obtainment of the alumina polyamide-coated spherical particles

The indirect selective laser sintering (SLS) process consists of a powder-based additive manufacturing (AM) technique. Recently, an attempt was carried out using the indirect-SLS method on ceramics to obtain complex geometric parts without the need to fabricate tools or molds. In this context, the ceramic particles employed in indirect-SLS must be coated with a polymer layer and retain spherical format. Currently, several processes of encapsulation and balling up of ceramic particles are available, among which thermally induced phase separation (TIPS) is noteworthy. The present study describes the synthesis, via TIPS, of spherical micrometric alumina particles coated with polyamide 12 to be employed in indirect-SLS. Dimethyl sulfoxide (DMSO) was used as a solvent to obtain these particles. After encapsulation, the agglomerates were characterized according to granulometry, microstructure, thermal behavior, and flowability. The obtained results delineated the ideal conditions to synthesize agglomerates with adequate flowability, particle size profile, and similar thermal behavior to that verified for PA-12, a currently used material in SLS printing. Based on the results of the present study, it is possible to confirm the effectiveness of the TIPS technique in obtaining ceramic polymer-coated spherical particles that are suitable for use in AM processes via indirect-SLS.

The influence of hydroxyapatite content on properties of poly(L-lactide)/hydroxyapatite porous scaffolds obtained using thermal induced phase separation technique

In the research we obtained porous scaffolds based on poly(L-lactide) and synthetic hydroxyapatite (HA) using thermal induced phase separation technique (TIPS) supported by salt leaching process (SL). The obtained series of composite foams differ in hydroxyapatite content (10, 25, 50, 75, 90 wt% of the HA in PLLA/HA systems). The investigated scaffolds porosity ranged from 88 to 98%, density from 0.024 to 0.140 g/cm3. Water contact angle measurements indicated more hydrophilic scaffold surface with increasing hydroxyapatite content in the composites. Thermogravimetric analysis revealed higher thermal stability of all composites comparing to neat PLLA, indicated presence of ∼3 wt% residual sodium chloride in the scaffolds. Differential scanning calorimetry analysis showed nucleation effect of hydroxyapatite and higher crystallinity of PLLA in the composites as compared to the neat PLLA. The above tests were supplemented with compressive strength measurements, which showed an increase in the Young’s modulus and compressive stresses values parallelly with the increase of the filler content. Proliferation tests of MC3T3-E1 mouse calvaria pre-osteoblast cells indicated directly proportional relationship between hydroxyapatite content and cells proliferation rate.

Human nasoseptal chondrocytes maintain their differentiated phenotype on PLLA scaffolds produced by thermally induced phase separation and supplemented with bioactive glass 1393

ABSTRACTDamage of hyaline cartilage such as nasoseptal cartilage requires proper reconstruction, which remains challenging due to its low intrinsic repair capacity. Implantation of autologous chondrocytes in combination with a biomimetic biomaterial represents a promising strategy to support cartilage repair. Despite so far mostly tested for bone tissue engineering, bioactive glass (BG) could exert stimulatory effects on chondrogenesis.The aim of this work was to produce and characterize composite porous poly(L-lactide) (PLLA)/1393BG scaffolds via thermally induced phase separation (TIPS) technique and assess their effects on chondrogenesis of nasoseptal chondrocytes.The PLLA scaffolds without or with 1, 2.5, 5% BG1393 were prepared via TIPS technique starting from a ternary solution (polymer/solvent/non-solvent) in a single step. Scaffolds were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetric analysis (DSC). Human nasoseptal chondrocytes were seeded on the scaffolds with 1 and 2.5% BG for 7 and 14 days and cell survival, attachment, morphology and expression of SOX9 and cartilage-specific extracellular cartilage matrix (ECM) components were monitored.The majority of chondrocytes survived on all PLLA scaffolds functionalized with BG for the whole culture period. Also inner parts of the scaffold were colonized by chondrocytes synthesizing an ECM which contained glycosaminoglycans. Type II collagen and aggrecan gene expression increased significantly in 1% BG scaffolds during the culture. Chondrocyte protein expression for cartilage ECM proteins indicated that the chondrocytes maintained their differentiated phenotype in the scaffolds.BG could serve as a cytocompatible basis for future scaffold composites for osteochondral cartilage defect repair.Abbreviations: AB: alcian blue ACAN: gene coding for aggrecan; BG: Bioactive glass; 2D: two-dimensional; 3D: three-dimensional; COL2A1: gene coding for type II collagen; DAPI: 4ʹ,6-diamidino-2-phenylindole; DMEM: Dulbecco’s Modified Eagle’s Medium; DMMB: dimethylmethylene blue; DSC: Differential scanning calorimetric analysis; ECM: extracellular matrix; EDTA: ethylenediaminetetraacetic acid; EtBr: ethidium bromide; FCS: fetal calf serum; FDA: fluorescein diacetate; GAG: glycosaminoglycans; HDPE: high density polyethylene; HE: hematoxylin and eosin staining; HCA: hydoxylapatite; PBE: phosphate buffered EDTA100 mM Na2HPO4 and 5 mM EDTA, pH8; PBS: phosphate buffered saline; PFA: paraformaldehyde; PG: proteoglycans; PI: propidium iodide; PLLA: Poly-L-Lactic Acid Scaffold; RT: room temperature; SD: standard deviation; SEM: scanning electron microscopy; sGAG: sulfated glycosaminoglycans; SOX9/Sox9: SRY (sex-determining region Y)-box 9 protein; TBS: TRIS buffered saline; TIPS: Thermally Induced Phase Separation; XRD: X-ray diffraction analysis

Effect of vascular endothelial growth factor 165-loaded porous poly (ε-caprolactone) scaffolds on the osteogenic differentiation of adipose-derived stem cells

To explore the effect of vascular endothelial growth factor 165 (VEGF 165)-loaded porous poly (ε-caprolactone) (PCL) scaffolds on the osteogenic differentiation of adipose-derived stem cells (ADSCs). The VEGF 165-loaded porous PCL scaffolds (written, Sf-g/VEGF) were fabricated through a combination of solvent casting/salt leaching and a thermal-induced phase separation technique and then observed under scanning electron microscope (SEM). The release kinetics was determined by ELISA kit. The ADSCs were isolated from inguinal fat pads of 15 Sprague Dawley rats and cultured. The passage 3-4 ADSCs were seeded into the scaffolds, and then cultured in vitro for 7 days. The passage 3-4 ADSCs were seeded into the porous PCL scaffolds (written, Sf-g) as control. The alizarin red S (ARS) staining, ARS activity assay, and real-time quantitative PCR (RT-PCR) were performed to measure the osteogenic differentiation of ADSCs in vitro. Six Sprague Dawley rats were recruited to prepare the bilateral calvarial bone defects models ( n=12). The 12 calvarial bone defects were randomly divided into 3 group ( n=4). The defects of negative control group were not treated; the defects of Sf-g group and Sf-g/VEGF group were repaired with ADSCs-Sf-g scaffold complex and ADSCs-Sf-g scaffold complex, respectively. At 8 weeks after transplantation, the Micro-CT and HE staining were conducted to evaluate the osteogenic effects in vivo. The morphology of the Sf-g/VEGF scaffolds were porous and well-connected, and the cumulative release rate was approximately 80% in 120 hours. The ARS staining showed that the ARS activity of Sf-g/VEGF group were stronger than that of Sf-g group ( t=10.761, P=0.000). The mRNA expressions of osteogenic specific markers [special AT-rich sequence protein 2 (Satb2), alkaline phosphatase (ALP), osteocalcin (OCN), and osteopontin (OPN)] were significantly higher in Sf-g/VEGF group than in Sf-g group ( P<0.05). The results of Micro-CT and HE staining also confirmed the promotion effect of Sf-g/VEGF scaffolds. All defects of 2 groups were partially repaired by new bone tissue, especially in Sf-g/VEGF group. The volume and area of new bone tissue were significantly higher in Sf-g/VEGF group than in Sf-g group ( P<0.05). The VEGF 165-loaded scaffolds can significantly improve the osteogenic differentiation of ADSCs both in vitro and in vivo.

Biomimetic design and fabrication of multilayered osteochondral scaffolds by low-temperature deposition manufacturing and thermal-induced phase-separation techniques

Integrative osteochondral repair is a useful strategy for cartilage-defect repair. To mimic the microenvironment, it is necessary that scaffolds effectively mimic the extracellular matrix of natural cartilage and subchondral bone. In this study, biomimetic osteochondral scaffolds containing an oriented cartilage layer, a compact layer, and a three-dimensional (3D)-printed core-sheath structured-bone layer were developed. The oriented cartilage layer was designed to mimic the structural and material characteristics of native cartilage tissue and was fabricated with cartilage matrix-chitosan materials, using thermal-induced phase-separation technology. The 3D-printed core-sheath structured-bone layer was fabricated with poly(L-lactide-co-glycolide)/β-tricalcium phosphate-collagen materials by low-temperature deposition technology, using a specially designed core-sheath nozzle, and was designed to mimic the mechanical characteristics of subchondral bone and improve scaffold hydrophilicity. The compact layer was designed to mimic the calcified-layer structure of natural cartilage to ensure the presence of different suitable microenvironments for the regeneration of bone and cartilage. A dissolving-bonding process was developed to effectively combine the three parts together, after which the bone and cartilage scaffolds exhibited good mechanical properties and hydrophilicity. Additionally, goat autologous bone mesenchymal stem cells (BMSCs) were isolated and then seeded into the bone and cartilage layers, respectively, and following a 1 week culture in vitro, the BMSC-scaffold constructs were implanted into a goat articular-defect model. Our results indicated that the scaffolds exhibited good biocompatibility, and 24 weeks after implantation, the femoral condyle surface was relatively flat and consisted of a large quantity of hyaloid cartilage. Furthermore, histological staining revealed regenerated trabecular bone formed in the subchondral bone-defect area. These results provided a new method to fabricate biomimetic osteochondral scaffolds and demonstrated their effectiveness for future clinical applications in cartilage-defect repair.

A Versatile Technique to Produce Porous Polymeric Scaffolds: The Thermally Induced Phase Separation (TIPS) Method

Among the various scaffold fabrication techniques, thermally induced phase separation (TIPS) is one of the most versatile methods to produce porous polymeric scaffold and it has been largely used for its capability to produce highly porous and interconnected scaffolds. The scaffold architecture can be closely controlled by varying the process parameters, including polymer type and concentration, solvent/non-solvent ratio and thermal history. TIPS technique has been widely employed, also, to produce scaffolds with a hierarchical pore structure and composite polymeric matrix/inorganic filler foams.

Removal of Cadmium from Industrial Wastewater Using Water-Soluble Polymer via Hollow Fiber Membranes

The removal of toxic and polluting metal ions from industrial effluents, water supplies, as well as mine waters is an important challenge to avoid one of the major causes of water and soil pollution. To enable further processing and achieve recovery of metals, separation should be selective. One separation technique, which can meet this requirement, is polymer-enhanced ultra filtration (PEUF). Ultra filtration membranes would only retain macromolecular solutes. PEUF uses water-soluble polymeric agents to complex easily interesting metallic ions and give them a macromolecular size. Binding of metal ions to water soluble polymers enables us to separate them from solution and retain them when they are pumped through an ultra filtration membrane. In the present work Polyetherimide (PEI) is used as water soluble polymer for removal of cadmium ions from waste water via hollow fiber membrane contactor module. Polyvinylidene fluoride (PVDF) hollow fiber membrane contactor is used for this purpose. The PVDF fiber was custom made using thermal induced phase separation techniques. Experimental observations reveal that when PEI concentration increases the percentage removal of Cd (II) also increases. The molecular weight of PEI has positive impact on Cd (II) retention. The pH value of feed has effect on Cd (II) withholding. The percentage of removal increases with solution pH value. Recycling either retentate; the part of a solution that does not cross the membrane; or permeate have no effect on removal. Increase of mixing time before operation increases metal ions removal rate

Strength Improvement of a Functionally Graded and Layered Composite Membrane for Guided Bone Regeneration in Orthopedics

Fabrication of 3-layered composite membranes comprising of poly(lactic-co-glycolic) acid (PLGA)/nanoapatite (NAp)/lauric acid (LA)using thermally induced phase separation (TIPS) technique showed a significant increase in tensile strength from 1.54 to 2.27 MPawhen TIPS freezing temperature reduced from −18 to−25°C, respectively. Moreover, an increase in PLGA content at 20wt% in all layers of the membrane composition has increased the tensile strength to 2.45MPa at −25°C. A potential guided bone regeneration (GBR) barrier membrane with improved space-making properties (balanced stiffness and elasticity) is obtained by the utilization of TIPS technique and graded membrane compositions for orthopaedic applications.

A biomimetic 3D microtubule-orientated poly(lactide-co-glycolide) scaffold with interconnected pores for tissue engineering

An ideal tissue engineering scaffold should imitate physical and biochemical cues of natural extracellular matrix and have interconnected porous structures with high porosity to provide adequate space for cell seeding, growth and proliferation, as well as nutrient delivery and metabolized product elimination. In this study, we examined the feasibility of fabricating microtubule-orientated poly(lactide-co-glycolide) (PLGA) scaffolds with interconnected pores (denoted as MOIP-PLGA) by an improved thermal-induced phase separation technique. We successfully constructed MOIP-PLGA using 1,4-dioxane as the first solvent and benzene or water with lower freezing point as the second solvent. Especially, when water was used, the MOIP-PLGA had higher porosity and it could guide rabbit aortic smooth muscle cells (SMCs) to better grow along the microtubule direction of the scaffold. Comparing with microtubule-orientated scaffold without interconnected pores (denoted as MONIP-PLGA), the proliferation and viability of SMCs cultured on MOIP-PLGA were higher. Moreover, basic fibroblast growth factor could be effectively bound on MOIP-PLGA by a plasma treatment technique and the growth factor could be slowly released in vitro, maintaining bioactivity.

A novel bio-safe phase separation process for preparing open-pore biodegradable polycaprolactone microparticles

Open-pore biodegradable microparticles are object of considerable interest for biomedical applications, particularly as cell and drug delivery carriers in tissue engineering and health care treatments. Furthermore, the engineering of microparticles with well definite size distribution and pore architecture by bio-safe fabrication routes is crucial to avoid the use of toxic compounds potentially harmful to cells and biological tissues. To achieve this important issue, in the present study a straightforward and bio-safe approach for fabricating porous biodegradable microparticles with controlled morphological and structural features down to the nanometer scale is developed. In particular, ethyl lactate is used as a non-toxic solvent for polycaprolactone particles fabrication via a thermal induced phase separation technique. The used approach allows achieving open-pore particles with mean particle size in the 150–250μm range and a 3.5–7.9m2/g specific surface area. Finally, the combination of thermal induced phase separation and porogen leaching techniques is employed for the first time to obtain multi-scaled porous microparticles with large external and internal pore sizes and potential improved characteristics for cell culture and tissue engineering. Samples were characterized to assess their thermal properties, morphology and crystalline structure features and textural properties.

Preparation and performance of polymer electrolyte based on poly(vinylidene fluoride)/polysulfone blend membrane via thermally induced phase separation process for lithium ion battery

Poly(vinylidene fluoride)/polysulfone (PVDF/PSF) blend microporous matrix of polymer electrolyte for lithium ion battery is prepared via thermally induced phase separation (TIPS) technique. Because of only one parameter, i.e., the PSF/PVDF weight ratio, the membrane microstructure is conveniently controlled. The membrane formation mechanism of PVDF/PSF blend membranes is proposed with the assistance of a binary PSF/PVDF weight ratio-temperature phase diagram. In addition to studying the microstructure and mechanical properties of PVDF/PSF blend membrane, the relationship between properties of membrane, electrochemical performances of corresponding polymer electrolyte and membrane microstructure are also discussed in this paper. It is found that the addition of PSF not only increases ionic conductivity and electrochemical stable window of polymer electrolyte, but also markedly enhances charge–discharge performances of coin cell. The results reveal that PVDF/PSF blend microporous membranes prepared via TIPS technique can be used as polymer matrices of polymer electrolytes for lithium ion batteries.

Effects of processing parameters in thermally induced phase separation technique on porous architecture of scaffolds for bone tissue engineering

Tissue engineering makes use of 3D scaffolds to sustain three-dimensional growth of cells and guide new tissue formation. To meet the multiple requirements for regeneration of biological tissues and organs, a wide range of scaffold fabrication techniques have been developed, aiming to produce porous constructs with the desired pore size range and pore morphology. Among different scaffold fabrication techniques, thermally induced phase separation (TIPS) method has been widely used in recent years because of its potential to produce highly porous scaffolds with interconnected pore morphology. The scaffold architecture can be closely controlled by adjusting the process parameters, including polymer type and concentration, solvent composition, quenching temperature and time, coarsening process, and incorporation of inorganic particles. The objective of this review is to provide information pertaining to the effect of these parameters on the architecture and properties of the scaffolds fabricated by the TIPS technique.

Supported Liquid Membrane Extraction of Reactive Dye Using Fabricated Polypropylene Membrane

This study investigates the transport of dye ions across a supported liquid membrane (SLM) by using tridodecylamine as a carrier and sodium hydroxide (NaOH) as a stripping agent. A microporous polypropylene membrane was used as a membrane support and prepared by the thermal induced phase separation (TIPS) technique. Two different TIPS techniques were used when preparing membranes: solidification and without solidification with polymer concentrations varied at 10, 15 and 20%. The results revealed that both techniques produced membranes with similar morphologies, but different pore size structures. The membrane with 15% polymer concentration which was prepared by the solidification technique produced a microporous membrane with a symmetric structure, defined pore size and high stability, and thus is feasible as the support material. The fabricated membrane was tested and the results revealed that 100% of reactive dyes was succesfully removed with 58% recovery from an aqueous solution. The fabricated membrane also exhibited high stability up to 25.5 h of extraction, thereby demonstrating an improved method for the separation of reactive dyes using a SLM.

Thermal and morphological studies of liquid crystalline materials dispersed in a polymer matrix

Polymer dispersed liquid crystal (PDLC) films have been prepared by a combination of solvent-induced phase separation and thermal-induced phase separation techniques, for three mesogenic materials: 4-(undecyloxy) benzoic acid (UDBA), 4-(decyloxy) benzoic acid (DBA) and 4-(dodecyloxy) benzoic acid (DDBA) in poly(methyl methacrylate) (PMMA) as polymer matrix and tetrahydrofuran (THF) as common solvent. Differential scanning calorimetry and polarising optical microscopy are used for thermal and morphological investigations of prepared PDLCs, and findings are explained with the help of a suitable phase diagram. It is found that isotropic liquid–nematic transition temperature (TIN ) for these mesogens in the PMMA matrix decreases by about 2.8–5.6°C as compared with the pure mesogens. Methods based on the solubility parameter and the fraction of liquid crystal (LC) in LC-rich domains inside the PMMA matrix at different concentrations have been adopted to achieve an optimised condition for uniform dispersion of the film over a larger area. Remarkable changes in the droplet morphology of the mesogens confined in PMMA matrix as compared with their bulk counterparts have also been observed. Bipolar droplets and Maltese-type crosses are observed by POM for 75 and 30 wt% UDBA in the PMMA matrix.