scholarly journals Crystallization of Poly(ethylene)s with Regular Phosphoester Defects Studied at the Air–Water Interface

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2408
Author(s):  
Nazmul Hasan ◽  
Karsten Busse ◽  
Tobias Haider ◽  
Frederik R. Wurm ◽  
Jörg Kressler
Keyword(s):  
Surface Pressure ◽  
Repeat Unit ◽  
Isothermal Condition ◽  
Chloroform Solution ◽  
Epifluorescence Microscopy ◽  
Polymer Backbone ◽  
Lb Films ◽  
Polar Groups ◽  
Poly Ethylene ◽  
Crystalline Domains

Poly(ethylene) (PE) is a commonly used semi-crystalline polymer which, due to the lack of polar groups in the repeating unit, is not able to form Langmuir or Langmuir–Blodgett (LB) films. This problem can be solved using PEs with hydrophilic groups arranged at regular distances within the polymer backbone. With acyclic diene metathesis (ADMET) polymerization, a tool for precise addition of polar groups after a certain interval of methylene sequence is available. In this study, we demonstrate the formation of Langmuir/LB films from two different PEs with regular phosphoester groups, acting as crystallization defects in the main chain. After spreading the polymers from chloroform solution on the water surface of a Langmuir trough and solvent evaporation, the surface pressure is recorded during compression under isothermal condition. These π-A isotherms, surface pressure π vs. mean area per repeat unit A, show a plateau zone at surface pressures of ~ (6 to 8) mN/m, attributed to the formation of crystalline domains of the PEs as confirmed by Brewster angle and epifluorescence microscopy. PE with ethoxy phosphoester defects (Ethoxy-PPE) forms circular shape domains, whereas Methyl-PPE-co-decadiene with methyl phosphoester defects and two different methylene sequences between the defects exhibits a film-like morphology. The domains/films are examined by atomic force microscopy after transferring them to a solid support. The thickness of the domains/films is found in the range from ~ (2.4 to 3.2) nm depending on the transfer pressure. A necessity of chain tilt in the crystalline domains is also confirmed. Grazing incidence X-ray scattering measurements in LB films show a single Bragg reflection at a scattering vector qxy position of ~ 15.1 nm−1 known from crystalline PE samples.

Investigating the Effect of Thermoelectric Processing on Ionic Aggregation in Thermoplastic Ionomers

2017 ◽  
Author(s):  
Prasant Vijayaraghavan ◽  
Vishnu-Baba Sundaresan
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Field ◽  
Thermal Studies ◽  
Effect Of Temperature ◽  
Self Healing ◽  
Polymer Backbone ◽  
Ionic Dissociation ◽  
Dissociation Temperature ◽  
Aggregate Morphology ◽  
Poly Ethylene

Ionomers are a class of polymers which contain a small fraction of charged groups in the polymer backbone. These ionic groups aggregate (termed ionic aggregates) to form temporary cross-links that break apart over the ionic dissociation temperature and re-aggregate on cooling, influencing the mechanical properties of these polymers. In addition to enhanced mechanical properties, some ionomers also exhibit self-healing behavior. The self-healing behavior is a consequence of weakly bonded ionic aggregates breaking apart and re-aggregating after puncture or a ballistic impact. The structure and properties of ionomers have been studied over the last several decades; however, there is a lack of understanding of the influence of an electrostatic field on ionic aggregate morphology. Characterizing the effect of temperature and electric field on the formation and structure of these ionic aggregates will lead to preparation of ionomers with enhanced structural properties. This work focuses on Surlyn 8940 which a poly-ethylene methacryclic acid co-polymer in which a fraction of the carboxylic acid is terminated by sodium. In this work, Surlyn is thermoelectrically processed over its ionic dissociation temperature in the presence of a strong electrostatic field. Thermal studies are performed on the ionomer to study the effect of the thermoelectric processing. It is shown that the application of a thermoelectric field leads to increase in the ionic aggregate order in these materials and reduction in crystal size distribution. Thermal Analysis is performed using a Differential Scanning Calorimeter and the resulting thermogram analysis shows that thermoelectric processing increases the peak temperature and onset temperature of melting by 4 C and 20 C respectively. The peak width at half maximum of the melting endotherm is reduced by 10 C due to thermoelectric processing. This serves as a measure of the increased crystallinity. A parametric study on the effect of field duration and field strength is also performed.

scholarly journals Interaction of poly(ethylene-glycols) with air-water interfaces and lipid monolayers: investigations on surface pressure and surface potential

1995 ◽  
Vol 69 (4) ◽  
pp. 1372-1381 ◽  
Author(s):  
M. Winterhalter ◽  
H. Bürner ◽  
S. Marzinka ◽  
R. Benz ◽  
J.J. Kasianowicz
Keyword(s):  
Surface Potential ◽  
Surface Pressure ◽  
Lipid Monolayers ◽  
Ethylene Glycols ◽  
Poly Ethylene

Surface Modification of PEOT/PBT Membrane with Silk Fibroin Anchoring and its Potential Application in Artificial Salivary Gland Construct

2012 ◽  
Vol 538-541 ◽  
pp. 52-59
Author(s):  
Jie Zhu ◽  
Ming Shi Li ◽  
Li Qun Wang ◽  
Xiao Lin Zhu
Keyword(s):  
Salivary Gland ◽  
Silk Fibroin ◽  
Potential Application ◽  
Contact Angles ◽  
Water Contact ◽  
Polar Groups ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Surface Modified

We reported the preparation of surface modified poly (ethylene oxide terephthalate) - poly (butylene terephthalate) membrane by the method of silk fibroin anchoring, namely SF/(PEOT/PBT). Its surface properties were characterized by contact angles and XPS and the biocompatibility of the composite membrane was further evaluated by human salivary epithelial cells (HSG cells) growth in vitro. Results revealed that SF/(PEOT/PBT) possessed the low water contact angle (48.0±3.0°) and immobilized a great amount of fibroin (fibroin surface coverage: 26.39 wt%), which attributed to the formation of polar groups such as hydrosulfide group, sulfonic group, carboxyl and carbonyl ones in the process of SO2 plasma treatment. HSG cells growth in vitro indicated that the silk fibroin anchoring could significantly enhance the biocompatibility of PEOT/PBT membrane, which suggested the potential application of fibroin anchoring PEOT/PBT for clinical HSG cells transplantation in the artificial salivary gland construct.

Accelerated Heat-Aging Studies on Fluorosilicone Rubber

1975 ◽  
Vol 48 (5) ◽  
pp. 944-952 ◽  
Author(s):  
S. H. Kalfayan ◽  
R. H. Silver ◽  
A. A. Mazzeo
Keyword(s):  
Weight Loss ◽  
Stress Relaxation ◽  
Repeat Unit ◽  
Accelerated Aging ◽  
Basic Mechanism ◽  
Inert Atmosphere ◽  
Polymer Backbone ◽  
Aging Studies ◽  
Relaxation Measurements ◽  
Fluorosilicone Rubber

Abstract The accelerated aging of a vulcanizate of fluorosilicone rubber was studied by four methods: infrared spectroscopy, GPC, weight loss, and stress relaxation, with the object of gathering information pertinent to understanding the basic mechanism of its aging. No changes were observed in infrared spectra of the rubber aged in air up to 315°C although severe degradation took place, as evidenced by high weight loss and drastic change in the physical condition of the test samples. It was concluded that although the polymer degrades, there is no change detectable within the precision of the analytical methods in the structure of the repeat unit of the elastomer. The gel-permeation chromatogram of unheated rubber showed peaks at MW 450 000 (95%) and 630 (5%). The low-molecular-weight component is very likely the cyclic tetramer of λ,λ′,λ″-trifluoropropylmethylsiloxane, the principal monomer of the FVMQ used. Heat aging increased the concentration of the 630 MW component, but rate studies were prevented by complications resulting from solvent-induced rubber degradation. Rapid decrease in the MW of FVMQ, as found by GPC, indicated random scission in the polymer backbone, as opposed to ordered unzipping of the repeat unit. The same conclusion was reached from the effects of crosslink density on stress relaxation. Activation energies obtained from weight-loss measurements (104 kJ/mol) were lower than those obtained from stress-relaxation measurements, (150–155 kJ/mol), suggesting that the processes being measured in each case may not be the same. Chemical stress relaxation takes place more rapidly in the presence of air than in an inert atmosphere, and intermittent stress-relaxation measurements indicate that crosslinks form during thermal aging in air, their rate first increasing and then decreasing.

Synthesis and Useful Reactions of Organosilicon Polymeric Precursors for Ceramics

1991 ◽  
Vol 249 ◽  
Author(s):  
Dietmar Seyferth ◽  
Carsten Strohmann ◽  
Henry J. Tracy ◽  
Jennifer L. Robison
Keyword(s):  
World War Ii ◽  
Repeat Unit ◽  
Organometallic Polymers ◽  
Inorganic Polymers ◽  
World War ◽  
Commercial Development ◽  
Polymer Backbone ◽  
Polymeric Systems ◽  
Macromolecular Systems ◽  
Long Time

Inorganic and organometallic polymers are macromolecular systems in which the polymer backbone contains elements other than the carbon, oxygen and nitrogen usually found in organic polymers [1]. To take as an example silicon-containing polymers, in the silicones the polymer backbone is composed of the Si-O repeat unit; in polysilazanes, of the Si-N unit; in polysilmethylenes, of the Si-C unit. In the polysilanes there are only silicon atoms in the polymer backbone. Many of the other metalloids and metals among the elements in the Periodic Table have been or, in principle, can be incorporated into polymeric systems, so it is clear that the field of inorganic and organometallic polymers is a very large one. Inorganic and organometallic polymers have been of interest to chemists for a long time. It was the commercial development of the silicones in the 1940's that gave this field of research its modem impetus [2]. Once it was appreciated how useful these versatile organosilicon polymers could be, chemists became interested in the possibility of developing other organometallic (and also inorganic) polymers, ones that might complement or even surpass the silicones as far as useful applications were concerned. Research on inorganic and organometallic polymers became very active in the 1950's and 1960's. Work in this area became an international effort, prompted by the need for new materials that would meet the exacting demands of the jet age that had effectively commenced around the end of World War II. Even greater demands, in terms of materials that would still be useful under extreme conditions, came with the space age.

Tracing the transport of organic colloids in porous media using tailored poly(ethylene glycol)

2021 ◽  
Author(s):  
Thomas Ritschel ◽  
Katharina Lehmann ◽  
Michaela Brunzel ◽  
Jürgen Vitz ◽  
Ivo Nischang ◽  
...  
Keyword(s):  
Porous Media ◽  
Ethylene Glycol ◽  
Water Solubility ◽  
Size Range ◽  
Large Fraction ◽  
Colloid Interface ◽  
Poly Ethylene Glycol ◽  
Polymer Backbone ◽  
Colloidal Transport ◽  
Poly Ethylene

<p>A large fraction of organic matter in natural aqueous soil solutions is given by molecules in sizes above one nanometer, which classifies them as colloids according to the IUPAC definition. Such colloids feature discernable mobility in soils and their transport is decisive for the cycling of carbon as well as the migration of nutrients or contaminants. Yet, their size-dependent hydrodynamics and functional diversity result in transport phenomena that are specific to colloids and, thus, largely differ from those observed for smaller substances. Still, tracers that appropriately represent small organic colloids are not available and the investigation of their transport in laboratory column experiments, in dependence of size and chemistry, remains difficult. To overcome this limitation, we tested if well-defined synthetic polymers in the colloidal size range are suitable as non-conventional tracers of colloidal transport. As polymer backbone, we selected poly(ethylene glycol) (PEG) due to its high water-solubility and established pathway of synthesis that permits tailoring of functional moieties to the fullest extent. An easy and sensitive detection in the aqueous phase became possible by using a fluorophore as starting group. After full characterization, we studied PEG adsorption to quartz, illite, goethite, and their mixtures in batch and column transport experiments. In numerical simulations, we successfully reconstructed and predicted PEG transport based on its physicochemical as well as hydrodynamic properties and, thus, show that PEG transport can be comprehensively and quantitatively studied. Considering also its low adverse effect on the environment, functional PEG therefore presents as promising candidate to be used as organic tracer, designable in the size range of natural organic (macro-)molecules (Ritschel et al., 2021).</p><p>References</p><p>Ritschel, T., Lehmann, K., Brunzel, M., Vitz, J., Nischang, I., Schubert, U., Totsche, K. U. (2021) <strong>Well-defined poly(ethylene glycol) polymers as non-conventional reactive tracers of colloidal transport in porous media</strong>.<em> J. Colloid Interface Sci.</em> 548, 592-601, doi: 10.1016/j.jcis.2020.09.056.</p>

Langmuir−Blodgett Films Formed by Continuously Varying Surface Pressure. Characterization by IR Spectroscopy and Epifluorescence Microscopy

Langmuir ◽  
2007 ◽  
Vol 23 (9) ◽  
pp. 4950-4958 ◽  
Author(s):  
Lin Wang ◽  
Antonio Cruz ◽  
Carol R. Flach ◽  
Jesús Pérez-Gil ◽  
Richard Mendelsohn
Keyword(s):  
Ir Spectroscopy ◽  
Surface Pressure ◽  
Epifluorescence Microscopy ◽  
Langmuir Blodgett ◽  
Langmuir Blodgett Films

scholarly journals The influence of poly(ethylene glycol) 6000 on spermine-induced aggregation of liposomes

1986 ◽  
Vol 236 (3) ◽  
pp. 651-655 ◽  
Author(s):  
B Tadolini ◽  
E Varani ◽  
L Cabrini
Keyword(s):  
Ethylene Glycol ◽  
Structural Modification ◽  
Poly Ethylene Glycol ◽  
Acidic Phospholipid ◽  
Hydration Force ◽  
Polar Groups ◽  
Water Of Hydration ◽  
Poly Ethylene ◽  
Induced Aggregation

Poly(ethylene glycol) 6000 affected the aggregation of mixed liposomes induced by spermine. It lowered the concentration of spermine causing 50% maximal aggregation, accelerated the rate and increased the extent of aggregation. The effect was inversely proportional to the density of the acidic phospholipid in the vesicles. These effects were not due either to poly(ethylene glycol) 6000-induced permanent structural modification of the liposome or increased binding of spermine to the vesicles. These findings are discussed in relation to a decreased hydration force caused by the ability of poly(ethylene glycol) 6000 to alter the water of hydration of the phospholipid polar groups in the liposome.

Microstructure of Thermally Crosslinkable Poly(Ethylene Terephthalate) (Pet-co-Xta) Benzocyclobutene Functionalized Copolymers

1996 ◽  
Vol 461 ◽  
Author(s):  
Brendan J. Foran ◽  
Elizabeth Pingel ◽  
Gary E. Spilman ◽  
Larry J. Markoski ◽  
Tao Jiang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Degree Of Crystallinity ◽  
Limiting Oxygen Index ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Poly Ethylene Terephthalate ◽  
Stable Flame ◽  
Poly Ethylene ◽  
Crystalline Domains ◽  
The Degree Of Crystallinity

ABSTRACTThe microstructure and thermal properties of copolymers of polyethylene terephthalate (PET) containing a crosslinkable terephthalic acid, 1,2-dihydrocyc Iobutabenzene 3,6 dicarboxylic acid (XTA) are reported. Wide angle x-ray scattering (WAXS) show that the addition of XTA does not alter the PET crystal structure in copolymers at low XTA contents. However, the degree of crystallinity drops for higher XTA levels. WAXS profiles show that PET-co-XTA 50% is amorphous, and that PEXTA homopolymer has a different crystal structure. Thermal data from DSC and TGA show that crosslinking of the benzocyclobutene groups (∼350°C) occurs at temperatures between melting (∼250°C) and degradation (∼400°C), making it possible to melt process the copolymers into fibers before the onset of crosslinking. Limiting oxygen index (LOI) measurements show that increased oxygen concentrations are required to sustain a stable flame in PET-co-XTA copolymers; whereas unmodified PET had an LOI value of -18%, the copolymers had LOI values near 32%. Further, while unmodified PET melts and drips as it burns, XTA copolymers formed a stable char that inhibiting flame propagation. An increased char was observed in optical micrographs for XTA containing polymers, and crystalline domains were observed near the burn surface in transmission electron micrographs.

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