Technique to Measure Adhesive Forces Between Electrospun Nanofibers

AbstractDue to the difficulty in handling nanofibers, little is reported and understood on the dry adhesion between electrospun nanofibers. In this study, we develop a technique to measure the dry adhesive forces between electrospun nanofibers. Of critical importance is the ability to mimic naturally occurring dry adhesion such as that between gecko's and spider's foot hairs and untreated surfaces. The adhesion test was performed on two poly(e-caprolactone) electrospun ultrafine fibers using a nanoforce tensile tester. It was found that the adhesive force per unit area increased with decreasing fiber diameter. The degree of crystallinity, order parameters of macromolecules in the amorphous region and crystallite orientation of the spun fibers were determined by the differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). The high measured adhesion between single PCL fibers in comparison to other reported values was attributed to crystal orientation due to electrospinning and the increase of adhesive force per unit area with decreasing fiber diameter.

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Formulation, Characterization and In vitro Cytotoxicity of 5-Fluorouracil Loaded Polymeric Electrospun Nanofibers for the Treatment of Skin Cancer

Recent Patents on Nanotechnology ◽

10.2174/1872210513666190314095643 ◽

2019 ◽

Vol 13 (2) ◽

pp. 114-128 ◽

Cited By ~ 2

Author(s):

Gayatri Patel ◽

Bindu K.N. Yadav

Keyword(s):

Skin Cancer ◽

Basal Cell Carcinoma ◽

Cell Viability ◽

Cell Carcinoma ◽

Basal Cell ◽

Fiber Diameter ◽

Electrospun Nanofibers ◽

In Vitro Cytotoxicity ◽

Fractional Factorial

Background: The purpose of this study was to formulate, characterize and conduct in vitro cytotoxicity of 5-fluorouracil loaded polymeric electrospun nanofibers for the treatment of skin cancer. The patents on electrospun nanofibers (US9393216B2), (US14146252), (WO2015003155A1) etc. helped in the selection of polymers and method for the preparation of nanofibers. Methods: In the present study, the fabrication of nanofibers was done using a blend of chitosan with polyvinyl alcohol and processed using the electrospinning technique. 5-fluorouracil with known chemotherapeutic potential in the treatment of skin cancer was used as a drug carrier. 24-1 fractional factorial screening design was employed to study the effect of independent variables like the concentration of the polymeric solution, applied voltage (kV), distance (cm), flow rate (ml / hr) on dependent variables like % entrapment efficiency and fiber diameter. Results: Scanning electron microscopy was used to characterize fiber diameter and morphology. Results showed that the fiber diameter of all batches was found in the range of 100-200 nm. The optimized batch results showed the fiber diameter of 162.7 nm with uniform fibers. The tensile strength obtained was 190±37 Mpa. Further in vitro and ex vivo drug release profile suggested a controlled release mechanism for an extended period of 24 hr. The 5-fluorouracil loaded electrospun nanofibers were found to decrease cell viability up to ≥50% over 24 hr, with the number of cells dropping by ~ 10% over 48 hr. As the cell viability was affected by the release of 5-fluorouracil, we believe that electrospun nanofibers are a promising drug delivery system for the treatment of Basal Cell Carcinoma (BCC) skin cancer. Conclusion: These results demonstrate the possibility of delivering 5-Fluorouracil loaded electrospun nanofiber to skin with enhanced encapsulation efficiency indicating the effectiveness of the formulation for the treatment of basal cell carcinoma type of skin cancer.

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PEG-POSS Star Molecules Blended in Polyurethane with Flexible Hard Segments: Morphology and Dynamics

Molecules ◽

10.3390/molecules26010099 ◽

2020 ◽

Vol 26 (1) ◽

pp. 99

Author(s):

Konstantinos N. Raftopoulos ◽

Edyta Hebda ◽

Anna Grzybowska ◽

Panagiotis A. Klonos ◽

Apostolos Kyritsis ◽

...

Keyword(s):

Glass Transition ◽

Star Polymer ◽

Polymerization Process ◽

Degree Of Crystallinity ◽

Dielectric Relaxation Spectroscopy ◽

Scanning Calorimetry ◽

Similar System ◽

Soft Phase ◽

Hard Segments ◽

Star Molecules

A star polymer with a polyhedral oligomeric silsesquioxanne (POSS) core and poly(ethylene glycol) (PEG) vertex groups is incorporated in a polyurethane with flexible hard segments in-situ during the polymerization process. The blends are studied in terms of morphology, molecular dynamics, and charge mobility. The methods utilized for this purpose are scanning electron and atomic force microscopies (SEM, AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and to a larger extent dielectric relaxation spectroscopy (DRS). It is found that POSS reduces the degree of crystallinity of the hard segments. Contrary to what was observed in a similar system with POSS pendent along the main chain, soft phase calorimetric glass transition temperature drops as a result of plasticization, and homogenization of the soft phase by the star molecules. The dynamic glass transition though, remains practically unaffected, and a hypothesis is formed to resolve the discrepancy, based on the assumption of different thermal and dielectric responses of slow and fast modes of the system. A relaxation α′, slower than the bulky segmental α and common in polyurethanes, appears here too. A detailed analysis of dielectric spectra provides some evidence that this relaxation has cooperative character. An additional relaxation g, which is not commonly observed, accompanies the Maxwell Wagner Sillars interfacial polarization process, and has dynamics similar to it. POSS is found to introduce conductivity and possibly alter its mechanism. The study points out that different architectures of incorporation of POSS in polyurethane affect its physical properties by different mechanisms.

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Crystallization Behavior and Mechanical Properties of Poly(ε-caprolactone) Reinforced with Barium Sulfate Submicron Particles

Materials ◽

10.3390/ma14092368 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2368

Author(s):

Hegoi Amestoy ◽

Paul Diego ◽

Emilio Meaurio ◽

Jone Muñoz ◽

Jose-Ramon Sarasua

Keyword(s):

Barium Sulfate ◽

Thermal Studies ◽

Polarized Light ◽

Optical Microscope ◽

Submicron Particles ◽

Degree Of Crystallinity ◽

Scanning Calorimetry ◽

Nucleation Effect ◽

Crystal Fraction ◽

Light Optical Microscope

Poly(ε-caprolactone) (PCL) was mixed with submicron particles of barium sulfate to obtain biodegradable radiopaque composites. X-ray images comparing with aluminum samples show that 15 wt.% barium sulfate (BaSO4) is sufficient to present radiopacity. Thermal studies by differential scanning calorimetry (DSC) show a statistically significant increase in PCL degree of crystallinity from 46% to 52% for 25 wt.% BaSO4. Non-isothermal crystallization tests were performed at different cooling rates to evaluate crystallization kinetics. The nucleation effect of BaSO4 was found to change the morphology and quantity of the primary crystals of PCL, which was also corroborated by the use of a polarized light optical microscope (PLOM). These results fit well with Avrami–Ozawa–Jeziorny model and show a secondary crystallization that contributes to an increase in crystal fraction with internal structure reorganization. The addition of barium sulfate particles in composite formulations with PCL improves stiffness but not strength for all compositions due to possible cavitation effects induced by debonding of reinforcement interphase.

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Structural and thermal properties of the amaranth starch granule obtained by high-impact wet milling

International Journal of Food Engineering ◽

10.1515/ijfe-2020-0024 ◽

2020 ◽

Vol 0 (0) ◽

Author(s):

Diego Fernando Roa Acosta ◽

José Fernando Solanilla Duque ◽

Lina Marcela Agudelo Laverde ◽

Héctor Samuel Villada Castillo ◽

Marcela Patricia Tolaba

Keyword(s):

Thermal Properties ◽

Structural Changes ◽

Starch Granule ◽

Amorphous Region ◽

Extraction Yield ◽

High Impact ◽

Degree Of Crystallinity ◽

Wet Milling ◽

Starch Structure ◽

Structure Changes

AbstractIn this study, amaranth starch was extracted by high-impact wet milling and its structural and thermal properties and the effect of NaOH and SDS concentrations on extraction yield were evaluated. The best condition was 55 g of starch/100 g of amaranth, with a decrease from 2.5 to 3.5 kJ/g using different milling energies. The decrease in the protein content of the starch granule is due to an effect of the interaction between surfactant and alkali, preventing the destruction of granules. All starches presented a degree of crystallinity between 21 and 28%. The internal structural changes of the starch granule were monitored by attenuated total reflectance - Fourier-transform infrared (ATR-FTIR) in the region of 990 to 1060 cm−1. Spectra showed significant differences between the peaks at 1032 and 1005 cm−1, corresponding to the crystalline/amorphous region of the starch structure. Changes in viscosity profiles were observed between 0.302 and 1.163 Pa s.

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Optimization of Electrospun Poly(caprolactone) Fiber Diameter for Vascular Scaffolds to Maximize Smooth Muscle Cell Infiltration and Phenotype Modulation

Polymers ◽

10.3390/polym11040643 ◽

2019 ◽

Vol 11 (4) ◽

pp. 643 ◽

Cited By ~ 9

Author(s):

Dae Geun Han ◽

Chi Bum Ahn ◽

Ji-Hyun Lee ◽

Yongsung Hwang ◽

Joo Hyun Kim ◽

...

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cell ◽

Muscle Cell ◽

Fiber Diameter ◽

Electrospun Fiber ◽

Electrospun Nanofibers ◽

Macrophage Infiltration ◽

Vsmc Proliferation ◽

Vascular Scaffolds ◽

Poly Caprolactone

Due to the morphological resemblance between the electrospun nanofibers and extracellular matrix (ECM), electrospun fibers have been widely used to fabricate scaffolds for tissue regeneration. Relationships between scaffold morphologies and cells are cell type dependent. In this study, we sought to determine an optimum electrospun fiber diameter for human vascular smooth muscle cell (VSMC) regeneration in vascular scaffolds. Scaffolds were produced using poly(caprolactone) (PCL) electrospun fiber diameters of 0.5, 0.7, 1, 2, 2.5, 5, 7 or 10 μm, and VSMC survivals, proliferations, infiltrations, and phenotypes were recorded after culturing cells on these scaffolds for one, four, seven, or 10 days. VSMC phenotypes and macrophage infiltrations into scaffolds were evaluated by implanting scaffolds subcutaneously in a mouse for seven, 14, or 28 days. We found that human VSMC survival was not dependent on the electrospun fiber diameter. In summary, increasing fiber diameter reduced VSMC proliferation, increased VSMC infiltration and increased macrophage infiltration and activation. Our results indicate that electrospun PCL fiber diameters of 7 or 10 µm are optimum in terms of VSMC infiltration and macrophage infiltration and activation, albeit at the expense of VSMC proliferation.

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Preparation and Characterization of Talc Filled Thermoplastic Polyurethane/Polypropylene Blends

Journal of Polymers ◽

10.1155/2014/289283 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 7

Author(s):

Emi Govorčin Bajsić ◽

Vesna Rek ◽

Ivana Ćosić

Keyword(s):

Thermal Properties ◽

Thermoplastic Polyurethane ◽

Mechanical Analysis ◽

Degree Of Crystallinity ◽

Scanning Calorimetry ◽

Polypropylene Blends ◽

Pp Blends ◽

The Degree Of Crystallinity ◽

Better Than

The effect of the addition of talc on the morphology and thermal properties of blends of thermoplastic polyurethane (TPU) and polypropylene (PP) was investigated. The blends of TPU and PP are incompatible because of large differences in polarities between the nonpolar crystalline PP and polar TPU and high interfacial tensions. The interaction between TPU and PP can be improved by using talc as reinforcing filler. The morphology was observed by means of scanning electron microscopy (SEM). The thermal properties of the neat polymers and unfilled and talc filled TPU/PP blends were studied by using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The addition of talc in TPU/PP blends improved miscibility in all investigated TPU/T/PP blends. The DSC results for talc filled TPU/PP blends show that the degree of crystallinity increased, which is due to the nucleating effect induced by talc particles. The reason for the increased storage modulus of blends with the incorporation of talc is due to the improved interface between polymers and filler. According to TGA results, the addition of talc enhanced thermal stability. The homogeneity of the talc filled TPU/PP blends is better than unfilled TPU/PP blends.

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Post-Processing Time Dependence of Shrinkage and Mechanical Properties of Injection-Molded Polypropylene

Materials ◽

10.3390/ma14010022 ◽

2020 ◽

Vol 14 (1) ◽

pp. 22

Author(s):

Artur Kościuszko ◽

Dawid Marciniak ◽

Dariusz Sykutera

Keyword(s):

Mechanical Properties ◽

Impact Strength ◽

Injection Molding ◽

Accelerated Aging ◽

Mold Temperature ◽

Degree Of Crystallinity ◽

Injection Mold ◽

Secondary Crystallization ◽

Scanning Calorimetry ◽

Injection Molded

Dimensions of the injection-molded semi-crystalline materials (polymeric products) decrease with the time that elapses from their formation. The post-molding shrinkage is an effect of secondary crystallization; the increase in the degree of polymer crystallinity leads to an increase in stiffness and decrease in impact strength of the polymer material. The aim of this study was to assess the changes in the values of post-molding shrinkage of polypropylene produced by injection molding at two different temperatures of the mold (20 °C and 80 °C), and conditioned for 504 h at 23 °C. Subsequently, the samples were annealed for 24 h at 140 °C in order to conduct their accelerated aging. The results of shrinkage tests were related to the changes of mechanical properties that accompany the secondary crystallization. The degree of crystallinity of the conditioned samples was determined by means of density measurements and differential scanning calorimetry. It was found that the changes in the length of the moldings that took place after removal from the injection mold were accompanied by an increase of 20% in the modulus of elasticity, regardless of the conditions under which the samples were made. The differences in the shrinkage and mechanical properties of the samples resulting from mold temperature, as determined by tensile test, were removed by annealing. However, the samples made at two different injection mold temperature values still significantly differed in impact strength, the values of which were clearly higher for the annealed samples compared to the results determined for the samples immediately after the injection molding.

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Thermal Properties and Non-Isothermal Crystallization Kinetics of Poly (δ-Valerolactone) and Poly (δ-Valerolactone)/Titanium Dioxide Nanocomposites

Crystals ◽

10.3390/cryst8120452 ◽

2018 ◽

Vol 8 (12) ◽

pp. 452 ◽

Cited By ~ 3

Author(s):

Waseem Saeed ◽

Abdel-Basit Al-Odayni ◽

Abdulaziz Alghamdi ◽

Ali Alrahlah ◽

Taieb Aouak

Keyword(s):

Titanium Dioxide ◽

Crystallization Kinetics ◽

Isothermal Crystallization ◽

Three Dimensional ◽

Degree Of Crystallinity ◽

Simultaneous Occurrence ◽

Scanning Calorimetry ◽

Isothermal Crystallization Kinetics ◽

The Stability ◽

Kinetics Of

New poly (δ-valerolactone)/titanium dioxide (PDVL/TiO2) nanocomposites with different TiO2 nanoparticle loadings were prepared by the solvent-casting method and characterized by Fourier transform infra-red, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy, and thermogravimetry analyses. The results obtained reveal good dispersion of TiO2 nanoparticles in the polymer matrix and non-formation of new crystalline structures indicating the stability of the crystallinity of TiO2 in the composite. A significant increase in the degree of crystallinity was observed with increasing TiO2 content. The non-isothermal crystallization kinetics of the PDVL/TiO2 system indicate that the crystallization process involves the simultaneous occurrence of two- and three-dimensional spherulitic growths. The thermal degradation analysis of this nanocomposite reveals a significant improvement in the thermal stability with increasing TiO2 loading.

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Characterization of bi-layered magnetic nanoparticles synthesized via two-step surface-initiated ring-opening polymerization

Pure and Applied Chemistry ◽

10.1515/pac-2015-0607 ◽

2015 ◽

Vol 87 (11-12) ◽

pp. 1085-1097 ◽

Cited By ~ 2

Author(s):

Li Wang ◽

Stefan Baudis ◽

Karl Kratz ◽

Andreas Lendlein

Keyword(s):

Magnetic Nanoparticles ◽

Ring Opening ◽

Average Molecular Weight ◽

Polymer Networks ◽

Gel Permeation Chromatography ◽

Degree Of Crystallinity ◽

Scanning Calorimetry ◽

H Nmr ◽

Transmission Electron

AbstractA versatile strategy to integrate multiple functions in a polymer based material is the formation of polymer networks with defined nanostructures. Here, we present synthesis and comprehensive characterization of covalently surface functionalized magnetic nanoparticles (MNPs) comprising a bi-layer oligomeric shell, using Sn(Oct)2 as catalyst for a two-step functionalization. These hydroxy-terminated precursors for degradable magneto- and thermo-sensitive polymer networks were prepared via two subsequent surface-initiated ring-opening polymerizations (ROPs) with ω-pentadecalactone and ε-caprolactone. A two-step mass loss obtained in thermogravimetric analysis and two distinct melting transitions around 50 and 85°C observed in differential scanning calorimetry experiments, which are attributed to the melting of OPDL and OCL crystallites, confirmed a successful preparation of the modified MNPs. The oligomeric coating of the nanoparticles could be visualized by transmission electron microscopy. The investigation of degrafted oligomeric coatings by gel permeation chromatography and 1H-NMR spectroscopy showed an increase in number average molecular weight as well as the presence of signals related to both of oligo(ω-pentadecalactone) (OPDL) and oligo(ε-caprolactone) (OCL) after the second ROP. A more detailed analysis of the NMR results revealed that only a few ω-pentadecalactone repeating units are present in the degrafted oligomeric bi-layers, whereby a considerable degree of transesterification could be observed when OPDL was polymerized in the 2nd ROP step. These findings are supported by a low degree of crystallinity for OPDL in the degrafted oligomeric bi-layers obtained in wide angle X-ray scattering experiments. Based on these findings it can be concluded that Sn(Oct)2 was suitable as catalyst for the preparation of nanosized bi-layered coated MNP precursors by a two-step ROP.

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Impact of environmental agents on non-woven polylactide/natural rubber agrofiber

E3S Web of Conferences ◽

10.1051/e3sconf/202128507034 ◽

2021 ◽

Vol 285 ◽

pp. 07034

Author(s):

Yulia Tertyshnaya ◽

Maksim Zakharov ◽

Alina Ivanitskikh ◽

Anatoliy Popov

Keyword(s):

Natural Rubber ◽

Uv Irradiation ◽

Thermal Characteristics ◽

Degree Of Crystallinity ◽

Distilled Water ◽

Fibrous Materials ◽

Scanning Calorimetry ◽

Melting Temperatures ◽

Environmental Agents ◽

The Degree Of Crystallinity

In the work an eco-friendly non-woven fiber made of polylactide and natural rubber with a rubber content from 0 to 15 wt.% was obtained by electrospinning. The influence of distilled water and UV irradiation on the agrofibers has been investigated. The water sorption test showed that the addition of natural rubber into the polylactide matrix does not significantly affect the degree of water absorption of the fibrous materials, which is in the range of 49-50.6%. Thermal characteristics after 180 days of degradation in distilled water at 22±2 oC and UV irradiation at a wavelength of 365 nm during 100 hours were determined using the differential scanning calorimetry. Changes in the values for glass transition and melting temperatures, and the degree of crystallinity were determined.

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