2 edition of Hydrogen bonding in polyurethanes and related model compounds. found in the catalog.
Hydrogen bonding in polyurethanes and related model compounds.
|The Physical Object|
|Number of Pages||85|
The temperature dependence of hydrogen bonding in 2,4-TDI and 2,6-TDI based polyurethanes was investigated using simple procedures to resolve hydrogen bonded and nonbonded NH and : Jiri Drobny. The calorimetrically determined energetics are interpreted in light of the crystal structures of the studied compounds. Our results indicate that the amide-amide and amide-hydroxyl hydrogen bonds both provide considerable enthalpic stability, but that the amide-amide hydrogen bond is about twice that of the by:
COVID Resources. Reliable information about the coronavirus (COVID) is available from the World Health Organization (current situation, international travel).Numerous and frequently-updated resource results are available from this ’s WebJunction has pulled together information and resources to assist library staff as they consider how to handle coronavirus. Figure A hydrogen bond in water occurs between the hydrogen atom of one water molecule and the lone pair of electrons on an oxygen atom of a neighboring water molecule. (CC BY-NC; CK) A hydrogen bond is an intermolecular attractive force in which a hydrogen atom that is covalently bonded to a small, highly electronegative atom is.
We describe the gelation of two-component immiscible blends consisting of a set of low molecular weight organogelators and a studied the blends of poly(ε-caprolactone) (PCL) and biscarbamates (model compounds for polyurethanes) with two hydrogen bonding motifs separated by a (CH 2) 6 spacer and symmetrically attached alkyl side chains.. Neither PCL nor the biscarbamates form gels Cited by: 4. Hydrogen bonding is a special case of permanent dipole-permanent dipole bonding. It is important to be clear that although it is called "hydrogen-bonding" it really is an intermolecular is alsovital that you refer to the hydrogen bonding as being between molecules and not within them. It exists where one of the most electronegative elements (fluorine, oxygen or nitrogen) is bonded to.
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Advanced quantum mechanical calculations within ab initio molecular orbital theory and density functional theory were performed using gaussian 98 programs in quantitative determination of hydrogen bond (H-bond) energies between various model compound pairs. Model compounds studied contained functional groups or segments that were similar to those in segmented polyurethanes and by: The distribution of hydrogen bonds in the polyurethane homopolymer was found to be quite similar to that found in an amorphous polyurethane studied previously in this laboratory.
However, upon annealing, some sort of ordered structure was detected by: Summarizing our current knowledge of the topic, this book describes the roles and effects of hydrogen bonding in polymer materials by reviewing the latest developments over recent years.
To this end, it discusses all relevant aspects from the fundamentals, via characterization, to properties and applications in various polymeric materials, including polymer blends, block Author: Shiao-Wei Kuo.
Summary This chapter contains sections titled: A Molecular Orbital Model of the Hydrogen Bond Electrostatic Interactions and the Hydrogen Bond The Electrostatic Model of the Hydrogen Bond. Hydrogen-bonding properties of hard-segment model compounds in polyurethane block copolymers | Macromolecules.
Hydrogen-bonding properties of hard-segment model compounds in polyurethane block copolymers. by: In model urethane compounds there are only two possibilities for intermolecular hydrogen bonding, which are either between the carbonyl oxygen and amide hydrogen (denoted as HB1), or between the carbamate oxygen and amide hydrogen (HB2) as shown in Cited by: Supported in part by the Army and Navy under Signal Corps Contract No.
DA‐36‐SC‐Cited by: With novel hydrogen bonding between two hard segments (NH⋯N) in N-methyldiethanolamine-extended polyurethane (NPU), the intensity of the NH⋯OC hydrogen bond between two hard segments increased. The influence of hydrogen bonding on the melting points and enthalpy of fusion values of urea and substituted ureas are given in Table 1.
As expected, there is a substantial difference between the melting points (T m) of hydrogen bonded compounds (U and DMU) and TMU, which cannot form hydrogen bonds internally in pure form. Similar behavior is Cited by: My holiday reading has been Derek Lowe’s excellent Chemistry Book setting out milestones in chemistry, organised by year.
An entry for entitled hydrogen bonding seemed worth exploring in more detail here. As with many historical concepts, it can often take a few years to coalesce into something we would readily recognise today, and hydrogen bonds are no s: 2.
Hydrogen Bonding covers the papers presented at the Symposium on Hydrogen Bonding, held at Ljubljana on July 29 to August 3, The book focuses on the developments, processes, approaches, methodologies, and reactions involved in hydrogen bonding. Hydrogen-Bonding Interactions in Hard Segments of Shape Memory Polyurethane: Toluene Diisocyanates and 1,6-Hexamethylene Diisocyanate.
A Theoretical and Comparative Study. The Journal of Physical Chemistry A(51), DOI: / by: Description Hydrogen Bonding covers the papers presented at the Symposium on Hydrogen Bonding, held at Ljubljana on July 29 to August 3, The book focuses on the developments, processes, approaches, methodologies, and reactions involved in hydrogen Edition: 1.
Four model compounds (Us, Uu, UEex, and UEin) and two polyurethanes (PU1 and PU2) were prepared to monitor the hydrogen-bond (H-bond) interactions of urethane−urethane and urethane−ester (including external and internal esters).Cited by: Four model compounds (Us, Uu, UEex, and UEin) and two polyurethanes (PU1 and PU2) were prepared to monitor the hydrogen-bond (H-bond) interactions of urethane−urethane and urethane−ester (including external and internal esters).
The results from differential scanning calorimetry (DSC) and X-ray diffraction suggested that the infrared absorption patterns in the −NH and −CO regions are Cited by: Hydrogen Bonding in Polymeric Materials, First.
Author(s): Shiao-Wei Kuo; this book describes the roles and effects of hydrogen bonding in polymer materials by reviewing the latest developments over recent years.
To this end, it discusses all relevant aspects from the fundamentals, via characterization, to properties and applications in. PUs have good abrasion properties and their resistance to crack propagation at tear test is high as well.
They can be used in a wide range of temperatures (−40 to 80°C) for a long time. Thermal stability of PU is strongly dependent on hydrogen bonding presence and the isocyanate type used.
Hydrogen bonding dissociates at around 80°C. An easy-to-read supplement to the often brief descriptions of hydrogen bonding found in most undergraduate chemistry and molecular biology textbooks, An Introduction to Hydrogen Bonding describes and discusses the current ideas concerning hydrogen bonding, ranging from the very strong to the very weak, with introductions to the experimental and Cited by: Hydrogen bonding.
WHAT IS A HYDROGEN BOND. A hydrogen bondexists when a hydrogen atom is bonded to two or more other atoms, a donor atom X and an acceptor atom Y. Since the hydrogen atom has only one orbital (1s) at sufficiently low energy, hydrogen bonds.
Hydrogen bonding rich polyurea/malonamide dendrons have been utilized as building blocks for the synthesis of novel SCDPUs.
The resulting microstructure of soft-rich domains reinforced by these. Hydrogen bonding in polymer blends is a topic of great interest to polymer scientists because such systems have many potential applications.
Introducing functional groups to one component to make Author: Shiao-Wei Kuo. A hydrogen bond results when this strong partial positive charge attracts a lone pair of electrons on another atom, which becomes the hydrogen bond acceptor. An electronegative atom such as fluorine, oxygen, or nitrogen is a hydrogen bond acceptor, regardless of whether it is bonded to a hydrogen atom or not.The chemistry of PUs involves reactions between organic isocyanates and polyols (i.e.
compounds containing active hydrogen) (Ionescu, ; Sonnenschein, ) in proper ratio in presence of.