Polymer Nano Research Articles

Fabrication of Microfiber Patterns with Ivy Shoot-Like Geometries Using Improved Electrospinning.

Fibers and fibrous structures are used extensively in various fields due to their many advantages. Microfibers, as well as nanofibers, are considered to be some of the most valuable forms of advanced materials. Accordingly, various methods for fabricating microfibers have been developed. Electrospinning is a useful fabrication method for continuous polymeric nano- and microfibers with attractive merits. However, this technique has limitations in its ability to control the geometry of fibrous structures. Herein, advanced electrospinning with direct-writing functionality was used to fabricate microfiber patterns with ivy shoot-like geometries after experimentally investigating the effects of the process conditions on the fiber formation. The surface properties of the fibers were also modified by introducing nanoscale pores through the use of higher levels of humidity during the fabrication process.

Analysis of strength and response of polymer nano thin film interfaces applying nanoindentation and nanoscratch techniques

Polymer and hydrogel thin films on a compliant substrate are gaining significant attention these days in the fields of soft electronics, digital display, biomedical devices and sensors to name a few. The functional characteristics of these thin films depend on the performance of its interface with the substrate. The interface response is a non-linear function of surface energy and stiffness of a substrate beside other factors. The deviation of thin film properties under confinement from its bulk counterparts and its ultra-low physical dimension makes characterization of an interface extremely challenging. Probing and shearing of these interfaces with appropriate load value and up to the critical load rate can provide insight into the integrity of these interfaces under different service conditions. We have studied the response of PMMA thin film (150 nm) on a softer epoxy substrate and a stiffer glass substrate of increasing interfacial strength applying nanoindentation (NI) and nanoscratching. Pile up behaviour of the film material at confined state, the critical load at the interface proximity and the plastic work done during indentation as determined in this work can be successfully applied to characterize interface behaviours. These parameters also help in developing interface models and build qualitative correlations between thermodynamic work of adhesion and true mechanical work of adhesion at the interface. We hypothesize that the elasto-plastic region around load tip plays a significant role in determining pile up above film surface. We have discussed the possible molecular mechanisms in this region under stress leading to pile up.

Solution-Blown Core-Shell Self-Healing Nano- and Microfibers.

Self-healing microfibers with core-shell geometry were studied. A commercial binary epoxy was encased in solution-blown polymer nano-/microfibers in the 0.2-2.6 μm diameter range. The core-shell microfibers were formed by coaxial nozzles, which encapsulated the epoxy resin and its hardener in separate cores. Solution blowing, the fiber-forming process used in this work, was at least 30 times faster than the electrospinning method used previously and has already been scaled up to the industrial level. These core-shell microfibers show self-healing capability, in which epoxy and hardener are released from the cores of damaged fibers, resulting in polymerization. The epoxy used had a higher strength and shorter solidification time than poly(dimethylsiloxane) (PDMS) used previously. Also, the larger fiber diameters in the present study facilitated faster release of the epoxy resin and its hardener from the fiber cores, shortening the solidification time in comparison to the previous studies. Blister tests were conducted, which measured the adhesion energy of microfiber mats to substrates and the cohesion energy between layers of microfiber mats before and after fatigue damage followed by self-healing.

Synthesis, kinetic study, and applications of polyethyleneimine supported nano zirconium chromate in oxidation of furfuryl alcohol to corresponding carbonyl compound

The efficiency of highly branched polyethyleneimine has been investigated as a support for nano zirconium chromate and subsequent use as a heterogeneous oxidant for selective oxidation of furfuryl alcohol to furfural. These were synthesized using polyethyleneimine to produce a polymer coordinated nano zirconium, a noble and straightforward method for screening high catalytically active polymer nano composites. The one-step systematic derivatization of the polyethyleneimine scaffold led structurally correlated to the stabilization of zirconium nanoparticles and catalysis. Analysis of this polymeric reagent identified the zirconium chromate nano composite that was able to be effective to oxidation reaction in tetrahydrofuran under mild conditions due to the surface area of the nano zirconium chromate per unit volume. Capacity of the reagent and fixation of nano zirconium chromate is confirmed by ICP and atomic absorption technique. Morphology of this nano composite is investigated by SEM and TEM. The kinetic of oxidation of furfuryl alcohol, over heterogeneous catalyst, nano zirconium chromate in THF, were investigated. Power-law rate model was applied to describe the experimental results and obtain the orders of the reaction with respect to furfuryl alcohol, catalyst, and furfural, which were found to be 0.989, 0.991, and −0.68, respectively, with the activation energy of 76.78 kJ/mol.

Influence of bio-based chitosan on properties of 5-nitrosalicylaldehyde-anilinenanocomposites

The biopolymeric nano composites between the crosslinks of 5nitrosalicylaldehyde- aniline composite material with chitosan a biopolymer were prepared in the form of nano thin sheets. The effect of antimicrobial activities were studied. Solution of nanoparticles was found stable in the dilute form and was characterized by UV-Visible absorption spectrum,FESEM-EDX, and XRD techniques. UV-Visible absorption spectrum has 220nm peak and has an optical band gap of 1.37 ev which provides primary information about the synthesis of core-shell and elongated nanoparticles. The phase analysis was carried out using X-ray diffraction and the result confirmed that the nano composite were single-phase. The morphological investigations by field emission scanning electron microscope (FESEM-EDX) revealed that the nano composite was mono- dispersed in a large quantity. The bio polymeri c nano composite was spherical and rod shaped respectively. The molecular mechanism of the biological properties such as antimicrobial and antioxidant has been updated .The results showed that the new bio polymeric nano composite exhibited promising antioxidant and antimicrobial activities.

Synthesis and Characterization of Polymeric Nanoparticles and Capsules as Payload for Anticancer Drugs and Nanomedicines

Novel and bio-compatible polymeric nano scale cuboid particles and spherical nanoporous capsules have been developed by the synthesis of AB-type block copolymer from L-Alanine (L-Ala) and polycaprolactone (PCL). The morphology of (L-Ala)-b-(PCL) particles depends on dispersion solvents. Block copolymer (BCP) gives spherical nanoporous capsules upon dispersion in ethanol and cuboid particles in water. Herein, we have engineered nano (∼200 nm) scale polymer (cubic and spherical shaped) capsules for enhanced anticancer drug (Imatinib-ITM) loading and controlled and sustained release for therapeutics in cancer therapy. Synthesis of BCP followed without using any surfactants and precursors. The formation of cubic and spherical polymeric capsules is associated with the self-assembly of (L-Ala)-b-(PCL) due to presence of active functional groups. Spherical nanoporous capsules have been used to develop nanoformulations to kill the cancerous (K562-leukemia blood cancer) cells. These nanoformulations played a key and potential role to load nanomedicine to check the cancer cell inhibition and rupture upon incubation for 24 h in CO2 incubator.

In vitro evaluation of substance-P conjugated nanofibers for potential wound dressing material

In vitro evaluation of substance-P conjugated nanofibers for potential wound dressing material

Polymers in Drug Delivery

Polymers are being used extensively in drug delivery due to their surface and bulk properties. They are being used in drug formulations and in drug delivery devices. These drug delivery devices may be in the form of implants for controlled drug delivery. Polymers used in colloidal drug carrier systems, consisting of small particles, show great advantage in drug delivery systems because of optimized drug loading and releasing property. Polymeric nano particulate systems are available in wide variety and have established chemistry. Non toxic, biodegradable and biocompatible polymers are available. Some nano particulate polymeric systems possess ability to cross blood brain barrier. They offer protection against chemical degradation. Smart polymers are responsive to atmospheric stimulus like change in temperature; pressure, pH etc. thus are extremely beneficial for targeted drug delivery. Some polymeric systems conjugated with antibodies/specific biomarkers help in detecting molecular targets specifically in cancers. Surface coating with thiolated PEG, Silica-PEG improves water solubility and photo stability. Surface modification of drug carriers e.g. attachment with PEG or dextran to the lipid bilayer increases their blood circulation time. Polymer drug conjugates such as Zoladex, Lupron Depot, On Caspar PEG intron are used in treatment of prostate cancer and lymphoblastic leukemia. Polymeric Drug Delivery systems are being utilized for controlled drug delivery assuring patient compliance.

High performance nature of biodegradable polymeric nanocomposites for oil-well drilling fluids

Multi-walled carbon nanotube (MWCNT) and graphene nanoplatelet reinforced thermoplastic poly(lactic acid) (PLA) biodegradable nanocomposites were designed and prepared using solution casting techniques. The prepared biodegradable polymers are expected to provide an environmentally friendly alternative to petroleum-based polymers. Both nanocomposite systems exhibited better thermal stability and improved mechanical performance over the unreinforced polymer exhibiting excellent strength and degradability. The addition of graphene nanofiller in varied amounts was aimed to enhance the thermal and mechanical properties of the nanocomposites even further and incorporate the outstanding characteristics of graphene nanoplatelets into the nanocomposites. The polymeric nanocomposites showed also superior advantages for oil drilling relevances, automotive lubricating purposes, membrane technology and food packaging. Scanning electron microscopy images indicated a homogeneous dispersion of the nanofiller within the polymeric matrix at low filler loadings and a cluster formation at higher loadings that could be responsible for the polymeric matrix movement restrictions. The enthalpy of mixing (the polymer and the nanofiller) measured could explain the cause of the repulsive interactions between the nanoparticles and the polymeric chains, which created an additional excluded volume that the polymeric segments were restricted to occupy, thus forcing the conformational characteristics of the polymeric chains to deviate away from those of the bulk chains. The prepared polymeric nano composites (poly lactic acid carbon nano tube and poly lactic acid graphene nanoplatelets) were utilized in the formulation of oil-base mud as a viscosifier. The rheological, filtration properties and electrical stability of the oil based mud formulation with the new polymeric nanocomposite were studied and the result compared to the oil-based mud formulation with commercial viscosifier.

Designing π-Conjugated Polymeric Nano- and Microstructures via Light Induced Chemistry

We report the synthesis and characterization of a new class of photoreactive conjugated polymers (Mn= 9300 g mol–1, Đ = 1.24; Mn= 9100 g mol–1, Đ = 1.23; Mn= 8800 g mol–1, Đ = 1.24) consisting of functionalized polythiophene-containing photoresponsive groups, i.e. a polythiophene containing 4-hydroxy-2,5-dimethylbenzophenone (DMBP) (“photoenol”) and/or maleimide groups. We evidence the chemical versatility and platform character of the generated light reactive polythiophenes in a range of examples by creating variable polythiophene functional 2D and 3D structures and morphologies. Single-chain nanoparticles and polymeric networks are formed by cross-linking of DMBP and maleimide containing polythiophene via UV light irradiation by varying the polymer concentration. Maleimide-functionalized polythiophene is employed for spatially resolved functionalization of surfaces and the coating of preformed 3D polymeric microstructures via direct laser writing (DLW). The generated polythiophene functional materials a...

Tuning the Interfacial Thermal Conductance between Polystyrene and Sapphire by Controlling the Interfacial Adhesion.

In polymer-based electric microdevices, thermal transport across polymer/ceramic interface is essential for heat dissipation, which limits the improvement of the device performance and lifetime. In this work, four sets of polystyrene (PS) thin films/sapphire samples were prepared with different interface adhesion values, which was achieved by changing the rotation speeds in the spin-coating process. The interfacial thermal conductance (ITC) between the PS films and the sapphire were measured by time domain thermoreflectance method, and the interfacial adhesion between the PS films and the sapphire, as measured by a scratch tester, was found to increase with the rotation speed from 2000 to 8000 rpm. The ITC shows a similar dependence on the rotation speed, increasing up to a 3-fold from 7.0 ± 1.4 to 21.0 ± 4.2 MW/(m(2) K). This study demonstrates the role of spin-coating rotation speed in thermal transport across the polymer/ceramic interfaces, evoking a much simpler mechanical method for tuning this type of ITC. The findings of enhancement of the ITC of polymer/ceramic interface can shed some light on the thermal management and reliability of macro- and microelectronics, where polymeric and hybrid organic-inorganic nano films are employed.

Hierarchical scaffolds enhance osteogenic differentiation of human Wharton’s jelly derived stem cells

Hierarchical structures, constituted by polymeric nano and microfibers, have been considered promising scaffolds for tissue engineering strategies, mainly because they mimic, in some way, the complexity and nanoscale detail observed in real organs. The chondrogenic potential of these scaffolds has been previously demonstrated, but their osteogenic potential is not yet corroborated. In order to assess if a hierarchical structure, with nanoscale details incorporated, is an improved scaffold for bone tissue regeneration, we evaluate cell adhesion, proliferation, and osteogenic differentiation of human Wharton’s jelly derived stem cells (hWJSCs), seeded into hierarchical fibrous scaffolds. Biological data corroborates that hierarchical fibrous scaffolds show an enhanced cell entrapment when compared to rapid prototyped scaffolds without nanofibers. Furthermore, upregulation of bone specific genes and calcium phosphate deposition confirms the successful osteogenic differentiation of hWJSCs on these scaffolds. These results support our hypothesis that a scaffold with hierarchical structure, in conjugation with hWJSCs, represents a possible feasible strategy for bone tissue engineering applications.

Anomalous Viscosity Reduction and Hydrodynamic Interactions of Polymeric Nanocolloids in Polymers

One of the central dogmas of fluid physics is the no-slip boundary condition, whose validity has come under scrutiny, especially in the fields of micro and nanofluidics. Although various studies show the violation of the no-slip condition its effect on flow of colloidal particles in viscous media has been rarely explored. Here we report unusually large reduction of effective viscosity experienced by polymeric nano colloids moving through a highly viscous and confined polymer, well above its glass transition temperature. The extent of reduction in effective interface viscosity increases with decreasing temperature and polymer film thickness. Concomitant with the reduction in effective viscosity we also observe apparent divergence of the wave vector dependent hydrodynamic interaction function of these colloids with an anomalous power law exponent of similar to 2 at the lowest temperatures and film thickness studied. Such strong hydrodynamic interactions are not expected for polymeric colloidal motion in polymer melts. We suggest hydrodynamics, especially slip present at the colloid-polymer interface which determines the observed reduction in interface viscosity and presence of strong hydrodynamic interactions.

Synthesis, characterization and ultrasonic study of aqueous suspensions containing polymeric nano particles of poly (L-lactide)

Aqueous suspensions containing polymeric nano particles (PNPs) of Poly (L-lactide) are prepared by interfacial deposition in two different mixed solvents (dichloromethane+n-hexane and dichloromethane+chloroform) and in the presence of stabilizers. The PNPs are characterized by FT-IR spectra, DSC and XRD measurements. The particle size is determined by TEM analysis and dynamic light scattering method. The influence of solvent on the size, shape and physicochemical properties such as crystalline nature, degree of dispersion, melting temperature, and stability of the suspensions is investigated. The size of PNPs is correlated with ultrasonic velocity and degree of dispersion with absorption coefficient. Experimental density and ultrasonic velocity values are compared with those calculated using theoretical Urick, Kuster–Toksöz and Urick–Ament models.

Targeted multidrug-resistance reversal in tumor based on PEG-PLL-PLGA polymer nano drug delivery system

The study investigated the reversal of multidrug resistance (MDR) and the biodistribution of nanoparticles (NPs) that target leukemia cells in a nude mice model via a surface-bound transferrin (Tf). The cytotoxic cargo of daunorubicin (DNR) and tetrandrine (Tet) was protected in the NPs by an outer coat composed of polyethylene glycol (PEG)-poly-l-lysine (PLL)-poly(lactic-co-glycolic acid) (PLGA) NPs. Injection of DNR-Tet-Tf-PEG-PLL-PLGA NPs into nude mice bearing MDR leukemia cell K562/A02 xenografts was shown to inhibit tumor growth, and contemporaneous immunohistochemical analysis of tumor tissue showed the targeted NPs induced apoptosis in tumor cells. Targeted tumor cells exhibited a marked increase in Tf receptor expression, with noticeable decreases in P-glycoprotein, MDR protein, and nuclear factor κB, as assessed by quantitative real-time polymerase chain reaction and Western blot analysis. Moreover, the concentration of DNR was shown to increase in plasma, tumor tissue, and major organs. Flow cytometry analysis with a near-infrared fluorescent (NIRF) dye, NIR797, was used to study the effectiveness of Tf as a targeting group for leukemia cells, a finding that was supported by NIRF imaging in tumor-bearing nude mice. In summary, our studies show that DNR-Tet-Tf-PEG-PLL-PLGA NPs provide a specific and effective means to target cytotoxic drugs to MDR tumor cells.

Tensile and Flexural Properties of Glass Fibre Reinforced Nano Polymer Composite Panels

This paper investigates the effect of nanoclay content on glass fibre reinforced polymer (GFRP) composites under tensile and flexural loading. Four different combinations of GFRP composite panels made of fiber glass/nanomodified polyester resin have been prepared by hand lay-up manufacturing technique (HL). Composite samples are tested for tensile and flexural properties. Scanning Electron Microscopy (SEM) has given morphological picture of the FRP fracture samples. The results showed that the tensile and flexural strength is greatly increased over the range of nanoclay loading by about 23% and 40% respectively.

Particle-based technologies for osteoarthritis detection and therapy.

Osteoarthritis (OA) is a disease characterized by degradation of joints with the development of painful osteophytes in the surrounding tissues. Currently, there are a limited number of treatments for this disease, and many of these only provide temporary, palliative relief. In this review, we discuss particle-based drug delivery systems that can provide targeted and sustained delivery of imaging and therapeutic agents to OA-affected sites. We focus on technologies such as polymeric micelles and nano-/microparticles, liposomes, and dendrimers for their potential treatment and/or diagnosis of OA. Several promising studies are highlighted, motivating the continued development of delivery technologies to improve treatments for OA.

Vinculin focal adhesion of osteoblast‐like cells on PEEK coated with ultra‐thin polymer nano films

ABSTRACTPEEK is the polymer of choice to replace metal encapsulants and other parts in active medical implants fixated into bone. The current challenge is to improve its biocompatibility with bone tissue to ultimately achieve osseointegration. PEEK sheets surfaces coated with plasma deposited nano thin polymer films using CH4, (CH4 + O2) and (CH4 + N2) gases. PEEK samples plasma treated with nonpolymerizing gases (O2) were also used for comparison. The adhesion performance of osteoblast like cells on the plasma‐treated PEEK surfaces and the presence of Vinculin in these cells were evaluated after long culturing period (12 days). X‐ray photoelectron spectroscopy and Auger spectroscopy were used to provide surface molecular information, surface hardness and molecular density. All plasma‐treated surfaces retained functionality after the sterilization process. PEEK surfaces with high number of oxygen functional groups and particularly oxygen rich thin polymer coating (plasma deposition using CH4+O2 gas mixture) resulted in strong cellular adhesion strength and large Vinculin amount. Further, osteoblast‐like cells responded better to surfaces with lower molecular density acting like another signal for cell adhesion. The osteoblast‐like cells response was weaker for surfaces with both thin films with nitrogen functional groups and nonfunctional (nonpolar) films. Furthermore, thin films rich in nitrogen functional groups repelled the cells, showed abnormal cells shape, smaller Vinculin amount and induced thicker cellular clusters with poor spread. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42181.

Residual layer-free Reverse Nanoimprint Lithography on silicon and metal-coated substrates

In this work we demonstrate that Reverse Nanoimprint Lithography is a feasible and flexible lithography technique applicable to the transfer of micro and nano polymer structures with no residual layer over areas of cm2 areas on silicon, metal and non-planar substrates. We used a flexible polydimethylsiloxane stamp with hydrophobic features. We present residual layer-free patterns imprinted using a commercial poly(methylmethacrylate) thermoplastic polymer over silicon, nickel and pre-patterned substrates. Our versatile patterning technology is adaptable to free form nano structuring and has coupling to adhesion technologies.

Improving the Dielectric Properties of High Density Polyethylene by Incorporating Clay-Nano Filler

Polymer Nano composites have been used for various important industrial applications. The preparation of high density polyethylene composed with Na-montmorillonite Nano filler using melt compounding method for different concentrations of clay-Nano filler of 0%, 2%, 6%, 10%, and 15% has been successfully done. The morphology of the obtained samples was optimized and characterized by scanning electron microscope showing the formation of the polymer Nano composites. The thermal stability and dielectric properties were measured for the prepared samples. Thermal gravimetric analysis results show that thermal stability in polymer Nano composites is more than that in the base polymer. It has been shown that the polymer Nano composites exhibit some very different dielectric characteristics when compared to the base polymer. The dielectric breakdown strength is enhanced by the addition of clay-Nano filler. The dielectric constant and dissipation factor have been studied in the frequency range 200 Hz to 2 MHz at room temperature indicating that enhancements have been occurred in dielectric constant and dissipation factor by the addition of clay-Nano filler in the polymer material when compared with the pure material.