Aliphatic polycarbonate-based polyurethane elastomers and nanocomposites. I. The influence of hard-segment content and macrodiol-constitution on bottom-up self-assembly

2012 ◽  
Vol 126 (3) ◽  
pp. 1016-1030 ◽  
Author(s):  
Milena Špírková ◽  
Rafał Poręba ◽  
Jelena Pavličević ◽  
Libor Kobera ◽  
Josef Baldrian ◽  
...  
Keyword(s):  
Self Assembly ◽  
Hard Segment ◽  
Polyurethane Elastomers ◽  
Bottom Up ◽  
Hard Segment Content ◽  
Aliphatic Polycarbonate

Synthesis of Polyurethane Elastomers by One-shot Technique and Study of Different Polyol Types and Hard Segment Content After Exposure to γ-Irradiation

2018 ◽  
Vol 12 (4) ◽  
pp. 705-715
Author(s):  
H. M. Abd El-Raheem ◽  
Y. K. Abdel-Monem ◽  
I. M. El-Sherbiny ◽  
K. Lotfy ◽  
M. M. Basuni ◽  
...  
Keyword(s):  
Hard Segment ◽  
Γ Irradiation ◽  
Polyurethane Elastomers ◽  
Hard Segment Content

scholarly journals Modification of epoxy resins with thermoplastic segmented polycarbonate-based polyurethanes

2014 ◽  
Vol 68 (6) ◽  
pp. 755-765 ◽  
Author(s):  
Jelena Pavlicevic ◽  
Mirjana Jovicic ◽  
Vesna Simendic ◽  
Oskar Bera ◽  
Radmila Radicevic ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Epoxy Resin ◽  
Hard Segment ◽  
Crosslinking Agent ◽  
Polyurethane Elastomers ◽  
Hard Segment Content ◽  
Weight Content ◽  
Epoxy Curing ◽  
Hard Segments ◽  
Modified Epoxy

In this work, epoxy hybrid materials were synthesized by addition of thermoplastic segmented aliphatic polyurethanes with good elastic properties. The modified epoxy samples were obtained by curing of previously homogenized mixture of prepared polyurethane melts, epoxy resin and crosslinking agent Jeffamine D-2000. The influence of different weight content of polyurethanes (5, 10 and 15 wt. % compared to pure epoxy resin) as well the influence of different hard segments of elastomers (20, 25 and 30 wt. %) on the curing of modified epoxy systems was studied. The curing was followed by differential scanning calorimetry (DSC), in dynamic regime from 30 to 300?C, at three heating rates (5, 10 and 20?C/min). With the increase of hard segments content of polyurethanes added in higher concentration (10 and 15 wt. %) into epoxy matrix, the temperature of maximum ratio of curing was shifted to lower values (from 205 to 179?C). Obtained DSC data were analyzed using two integral methods (Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose) and one differential kinetic model (Friedman). The significant differences were observed in the second part of the epoxy curing (for the reaction degrees higher than 60 %), where the values of activation energies remarkably increase. The addition of polyurethane elastomers retarded the curing process due to decreased mobility of reactant molecules caused by higher viscosity of reaction mixture. By detailed analysis of determined kinetic parameters, it is concluded that the influence of slow diffusion is more pronounced in the presence of thermoplastic polycarbonate-based polyurethanes, which confirmed their effect on the mechanism of epoxy curing. The highest tensile strength and hardness showed the DGEBA modified with the polyurethane with highest hard segment content. Increasing the hard segment content of polyurethane and its concentration in matrix, the tensile strength of modified epoxy was increased. The elongation at break of modified epoxy samples was significantly improved by addition of polycarbonate-based polyurethanes with low hard segment content, due to higher content of flexible soft segment chains.

Investigating the Properties and Structure of Polyurethane Elastomers with Monoethylene Glycol Chain Extender

2020 ◽  
Vol 986 ◽  
pp. 18-23
Author(s):  
Patcharapon Somdee ◽  
Timea Lassu-Kuknyo ◽  
Csaba Konya ◽  
Tamás Szabó ◽  
Kálmán Marossy
Keyword(s):  
Hard Segment ◽  
Chain Extender ◽  
Polypropylene Glycol ◽  
Polyurethane Elastomers ◽  
Elongation At Break ◽  
Peak Intensity ◽  
Hard Segment Content ◽  
Polymeric Chains ◽  
Monoethylene Glycol ◽  
Hardness Values

The effect of monoethylene glycol (mEG) acting as chain extender in polypropylene glycol (PPG-4000) and 4,4ʹ-diphenylmethane diisocyanate (MDI) reaction was investigated. Polyurethane elastomers (PUR) were changed from flexible to rigid materials by varying the mEG content. Results show that Shore A and D hardness values trend to increase with increasing mEG content. It appears that increasing the chain extender content increases the hard segment content in the polyurethane structure. Moreover, increasing the mEG content increases Young’s modulus and the tensile strength of PUR, while elongation at break decreases. The chemical structure of the hard segment of PUR was characterized by Infrared (IR) spectroscopy. IR spectra exhibited the bands typical for PUR consisting of –NH, CH2– and C=O groups. The spectra reveal a few interactions between the polymeric chains that appear to be responsible for the shift of transmittance peak and decrease of some peak intensity. This may be due to the hard segment aggregating more to form domains in the PUR when mEG content was increased.

scholarly journals The influence of bentonite and montmorillonite addition on thermal decomposition of novel polyurethane/organoclay nanocomposites

2013 ◽  
Vol 32 (1) ◽  
pp. 319 ◽  
Author(s):  
Jelena Pavličević ◽  
Milena Špírková ◽  
Oskar Bera ◽  
Mirjana Jovičić ◽  
Katalin Mészáros Szécsényi ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Hard Segment ◽  
Reaction Order ◽  
Hexamethylene Diisocyanate ◽  
Scanning Calorimetry ◽  
Degradation Kinetic ◽  
Polyurethane Elastomers ◽  
Hard Segment Content ◽  
Butane Diol ◽  
Thermal Stability Of

Polycarbonate-based polyurethane (PC-PUs) hybrid materials were obtained by the addition oforganically modified bentonite and montmorillonite (1 w/w %). PC-PUs and their nanocomposites wereprepared using prepolymerization with two polycarbonate diols (both of Mr ca 1000) differing in chainconstitution, hexamethylene-diisocyanate and 1,4-butane diol (chain extender) as starting components. All samples contained the same hard-segment content (30 w/w %). Thermogravimetry coupled with differential scanning calorimetry (TG-DSC) was performed to obtain information about the organoclays addition on the thermal stability of the prepared polyurethane elastomers. The effect of bentonite and montmorillonite nanofillers on the decomposition pattern has been evaluated. By deconvolution of derivative thermogravimetric (DTG) curves, it has been found that the thermal decomposition of polyurethane samples takes place in three overlapping processes. Degradation kinetic parameters (activation energy and reaction order) were calculated on the basis of thermal data obtained at only one heating rate.

A Bottom-Up Approach to Solution-Processed, Atomically Precise Graphitic Cylinders on Surfaces

2018 ◽  
Author(s):  
Erik Leonhardt ◽  
Jeff M. Van Raden ◽  
David Miller ◽  
Lev N. Zakharov ◽  
Benjamin Aleman ◽  
...  
Keyword(s):  
Self Assembly ◽  
Carbon Nanostructures ◽  
Carbon Nanomaterials ◽  
Circle Packing ◽  
Pyrolytic Graphite ◽  
Building Blocks ◽  
Bottom Up ◽  
Casting Technique ◽  
New Class ◽  
Solution Casting Technique

Extended carbon nanostructures, such as carbon nanotubes (CNTs), exhibit remarkable properties but are difficult to synthesize uniformly. Herein, we present a new class of carbon nanomaterials constructed via the bottom-up self-assembly of cylindrical, atomically-precise small molecules. Guided by supramolecular design principles and circle packing theory, we have designed and synthesized a fluorinated nanohoop that, in the solid-state, self-assembles into nanotube-like arrays with channel diameters of precisely 1.63 nm. A mild solution-casting technique is then used to construct vertical “forests” of these arrays on a highly-ordered pyrolytic graphite (HOPG) surface through epitaxial growth. Furthermore, we show that a basic property of nanohoops, fluorescence, is readily transferred to the bulk phase, implying that the properties of these materials can be directly altered via precise functionalization of their nanohoop building blocks. The strategy presented is expected to have broader applications in the development of new graphitic nanomaterials with π-rich cavities reminiscent of CNTs.

Bottom-up Evolution from Disks to High-Genus Polymersomes

2018 ◽  
Author(s):  
Claudia Contini ◽  
Russell Pearson ◽  
Linge Wang ◽  
Lea Messager ◽  
Jens Gaitzsch ◽  
...  
Keyword(s):  
Self Assembly ◽  
The Self ◽  
Amphiphilic Copolymers ◽  
Chain Entanglement ◽  
Bottom Up ◽  
New Approach ◽  
High Genus ◽  
Transmission Electron ◽  
Minimal Radius ◽  
Stop Flow

<div><div><div><p>We report the design of polymersomes using a bottom-up approach where the self-assembly of amphiphilic copolymers poly(2-(methacryloyloxy) ethyl phosphorylcholine)–poly(2-(diisopropylamino) ethyl methacrylate) (PMPC-PDPA) into membranes is tuned using pH and temperature. We study this process in detail using transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) spectroscopy, dynamic light scattering (DLS), and stop-flow ab- sorbance disclosing the molecular and supramolecular anatomy of each structure observed. We report a clear evolution from disk micelles to vesicle to high-genus vesicles where each passage is controlled by pH switch or temperature. We show that the process can be rationalised adapting membrane physics theories disclosing important scaling principles that allow the estimation of the vesiculation minimal radius as well as chain entanglement and coupling. This allows us to propose a new approach to generate nanoscale vesicles with genus from 0 to 70 which have been very elusive and difficult to control so far.</p></div></div></div>

Bottom-up Evolution from Disks to High-Genus Polymersomes

2018 ◽  
Author(s):  
Claudia Contini ◽  
Russell Pearson ◽  
Linge Wang ◽  
Lea Messager ◽  
Jens Gaitzsch ◽  
...  
Keyword(s):  
Self Assembly ◽  
The Self ◽  
Amphiphilic Copolymers ◽  
Chain Entanglement ◽  
Bottom Up ◽  
New Approach ◽  
High Genus ◽  
Transmission Electron ◽  
Minimal Radius ◽  
Stop Flow

<div><div><div><p>We report the design of polymersomes using a bottom-up approach where the self-assembly of amphiphilic copolymers poly(2-(methacryloyloxy) ethyl phosphorylcholine)–poly(2-(diisopropylamino) ethyl methacrylate) (PMPC-PDPA) into membranes is tuned using pH and temperature. We study this process in detail using transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) spectroscopy, dynamic light scattering (DLS), and stop-flow ab- sorbance disclosing the molecular and supramolecular anatomy of each structure observed. We report a clear evolution from disk micelles to vesicle to high-genus vesicles where each passage is controlled by pH switch or temperature. We show that the process can be rationalised adapting membrane physics theories disclosing important scaling principles that allow the estimation of the vesiculation minimal radius as well as chain entanglement and coupling. This allows us to propose a new approach to generate nanoscale vesicles with genus from 0 to 70 which have been very elusive and difficult to control so far.</p></div></div></div>

scholarly journals Nano- and Micropatterning on Optical Fibers by Bottom-Up Approach: The Importance of Being Ordered

2021 ◽  
Vol 11 (7) ◽  
pp. 3254
Author(s):  
Marco Pisco ◽  
Francesco Galeotti
Keyword(s):  
Optical Fiber ◽  
Optical Fibers ◽  
Self Assembly ◽  
Ordered Structures ◽  
Bottom Up ◽  
Photonic Structures ◽  
Fiber Technology ◽  
Optical Fiber Probes ◽  
Fiber Probes ◽  
Self Assembled

The realization of advanced optical fiber probes demands the integration of materials and structures on optical fibers with micro- and nanoscale definition. Although researchers often choose complex nanofabrication tools to implement their designs, the migration from proof-of-principle devices to mass production lab-on-fiber devices requires the development of sustainable and reliable technology for cost-effective production. To make it possible, continuous efforts are devoted to applying bottom-up nanofabrication based on self-assembly to decorate the optical fiber with highly ordered photonic structures. The main challenges still pertain to “order” attainment and the limited number of implementable geometries. In this review, we try to shed light on the importance of self-assembled ordered patterns for lab-on-fiber technology. After a brief presentation of the light manipulation possibilities concerned with ordered structures, and of the new prospects offered by aperiodically ordered structures, we briefly recall how the bottom-up approach can be applied to create ordered patterns on the optical fiber. Then, we present un-attempted methodologies, which can enlarge the set of achievable structures, and can potentially improve the yielding rate in finely ordered self-assembled optical fiber probes by eliminating undesired defects and increasing the order by post-processing treatments. Finally, we discuss the available tools to quantify the degree of order in the obtained photonic structures, by suggesting the use of key performance figures of merit in order to systematically evaluate to what extent the pattern is really “ordered”. We hope such a collection of articles and discussion herein could inspire new directions and hint at best practices to fully exploit the benefits inherent to self-organization phenomena leading to ordered systems.

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