Nanoporous Polycyanurates Created by Chemically-Induced Phase Separation: Structure-Property Relationships

2014 ◽  
Vol 341 (1) ◽  
pp. 57-66 ◽  
Author(s):  
Olga Grigoryeva ◽  
Alexander Fainleib ◽  
Kristina Gusakova ◽  
Olga Starostenko ◽  
Jean-Marc Saiter ◽  
...  
Keyword(s):  
Phase Separation ◽  
Structure Property ◽  
Structure Property Relationships ◽  
Chemically Induced

Elastomeric Polyether-Ester Block Copolymers. I. Structure-Property Relationships of Tetramethylene Terephthalate/Polyether Terephthalate Copolymers

1977 ◽  
Vol 50 (4) ◽  
pp. 688-703 ◽  
Author(s):  
J. R. Wolfe
Keyword(s):  
Phase Separation ◽  
Melting Point ◽  
Block Copolymers ◽  
Low Temperature ◽  
Chain Length ◽  
Chemical Structure ◽  
High Water ◽  
Structure Property ◽  
Tear Strength ◽  
Structure Property Relationships

Abstract The properties of elastomeric tetramethylene terephthalate/polyether terephthalate copolymers have been related to the chemical structure, chain length, and concentration in the copolymers of the PTMEG-, PEG-, and PPG-derived polyether units. Low-temperature properties and tear strength are dependent on all three polyether-related variables. Melting point, hardness, and stress at 100% elongation appear to be independent of polyether structure. Polyether glycols of low MW volatilize during copolymer preparation. High-MW polyethers tend to crystallize when present in the copolymers. Polyether glycols of intermediate MW (∼ 1000) yield copolymers with the best resistance to low-temperature stiffening. Copolymer synthesis is most difficult with PPG as the polyether glycol. Inherent viscosities are low, and phase separation occurs at lower polyether MW than with PTMEG or PEG. The PEG-based copolymers exhibit high water swell, particularly at intermediate and high PEG MW. The PTMEG-based copolymers are easiest to synthesize and exhibit the best overall combination of properties.

Summary

MRS Bulletin ◽  
1990 ◽  
Vol 15 (12) ◽  
pp. 44-46
Keyword(s):  
Phase Separation ◽  
Future Research ◽  
Initial Structure ◽  
Structure Property ◽  
Structure Property Relationships ◽  
Substantial Progress ◽  
Solvent Systems ◽  
Commercial Applications ◽  
Scientific Accomplishment ◽  
Made In

The development of LDMMs is a significant scientific accomplishment. This article provided an overview of the synthesis, structural characterization, and properties of these materials. Hopefully, the reader gained an appreciation for (1) the diverse morphologies of these materials, (2) their unique structure-property relationships, and (3) the difficulty in simultaneously achieving low densities with small cell sizes. This section will briefly discuss the future development of these materials and their potential commercial applications.Although substantial progress has been made in the scientific understanding of the formation of LDMMs, many important questions remain. As mentioned earlier, LDMMs rarely display an ideal spinodal morphology even though many of these structures have been established by phase-separation of polymer/solvent systems. Such morphologies appear to coarsen after the initial structure is established. The question arises — on what length scales is phase-separation taking place and how does its temporal evolution affect LDMM structure? In aerogel processing, polymerlike gels are formed, but certain sol-gels do not behave in accordance with theories on the swelling of conventional polymer gels. Why is this, and what is the effect on the final aerogel morphology? These and other questions can only be answered with a better understanding of gel structures and the dynamics of their formation. This is an important area for future research because the information gained can be used to tailor LDMMs for specific applications.

scholarly journals Hyperbranched Silicone MDTQ Tack Promoters

Molecules ◽  
2019 ◽  
Vol 24 (22) ◽  
pp. 4133 ◽  
Author(s):  
Sijia Zheng ◽  
Shuai Liang ◽  
Yang Chen ◽  
Michael A. Brook
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Complex Mixtures ◽  
Low Molecular Weight ◽  
Structure Property ◽  
Chain Entanglement ◽  
Silicone Gel ◽  
Structure Property Relationships ◽  
Branch Density

Low molecular weight, highly crosslinked silicone resins are widely used as reinforcing agents for highly transparent elastomers and adhesion/tack promoters in gels. The resins are complex mixtures and their structure / property relationships are ill defined. We report the synthesis of a library of 2, 3 and 4-fold hyperbranched polymeric oils that are comprised of linear, lightly branched or highly branched dendronic structures. Rheological examination of the fluids and tack measurements of gels filled with 10, 25 or 50% dendronic oils were made. Viscosity of the hyperbranched oils themselves was related to molecular weight, but more significantly to branch density. The properties are driven by chain entanglement. When cured into a silicone gel, less densely branched materials were more effective in improving tack than either linear oils or Me3SiO-rich, very highly branched oils of comparable molecular weight, because the latter oils underwent phase separation.

scholarly journals Chemically Induced Splay Nematic Phase with Micron Scale Periodicity

2019 ◽  
Author(s):  
Perri Connor ◽  
Richard Mandle
Keyword(s):  
Nematic Phase ◽  
Orientational Order ◽  
Periodic Variation ◽  
Structure Property ◽  
X Ray ◽  
Structure Property Relationships ◽  
X Ray Scattering ◽  
Chemically Induced ◽  
Crystal Phases ◽  
Optical Textures

<p>Nematic liquid crystals lack positional order of their constituent molecules, which share an average orientational order only. Modulated nematic liquid crystal phases also lack positional order, but possess a periodic variation in this direction of average orientation. In the recently discovered splay nematic (N<sub>S</sub>) phase the average orientational order is augmented with a periodic splay deformation of orientation perpendicular to the director. In this communication we report the first example of a splay nematic phase which is chemically induced by mixing two materials, neither of which exhibit the N<sub>S</sub>­ phase. The splay-nematic phase is identified based on its optical textures, X-ray scattering patterns, and small enthalpy of the associated phase transition. We measure the splay periodicity optically, finding it to be ~ 9 μm. This unexpected generation of the splay-nematic phase through binary mixtures offers a new route to materials which exhibit this phase which complements ongoing studies into structure-property relationships and could accelerate the development of technologies utilising this remarkable polar nematic variant.</p>

scholarly journals Chemically Induced Splay Nematic Phase with Micron Scale Periodicity

2019 ◽  
Author(s):  
Perri Connor ◽  
Richard Mandle
Keyword(s):  
Nematic Phase ◽  
Orientational Order ◽  
Periodic Variation ◽  
Structure Property ◽  
X Ray ◽  
Structure Property Relationships ◽  
X Ray Scattering ◽  
Chemically Induced ◽  
Crystal Phases ◽  
Optical Textures

<p>Nematic liquid crystals lack positional order of their constituent molecules, which share an average orientational order only. Modulated nematic liquid crystal phases also lack positional order, but possess a periodic variation in this direction of average orientation. In the recently discovered splay nematic (N<sub>S</sub>) phase the average orientational order is augmented with a periodic splay deformation of orientation perpendicular to the director. In this communication we report the first example of a splay nematic phase which is chemically induced by mixing two materials, neither of which exhibit the N<sub>S</sub>­ phase. The splay-nematic phase is identified based on its optical textures, X-ray scattering patterns, and small enthalpy of the associated phase transition. We measure the splay periodicity optically, finding it to be ~ 9 μm. This unexpected generation of the splay-nematic phase through binary mixtures offers a new route to materials which exhibit this phase which complements ongoing studies into structure-property relationships and could accelerate the development of technologies utilising this remarkable polar nematic variant.</p>

Structure-property relationships of PE/PP sandwiched films

1987 ◽  
Vol 45 ◽  
pp. 454-455
Author(s):  
J. Petermann ◽  
G. Broza ◽  
U. Rieck ◽  
A. Jaballah ◽  
A. Kawaguchi
Keyword(s):  
Mechanical Tests ◽  
Polymer Materials ◽  
Ionic Crystals ◽  
Structure Property ◽  
Polymer Systems ◽  
Structure Property Relationships ◽  
Oriented Films ◽  
Materials Used ◽  
Polymer Laminates ◽  
Heated Glass

Oriented overgrowth of polymer materials onto ionic crystals is well known and recently it was demonstrated that this epitaxial crystallisation can also occur in polymer/polymer systems, under certain conditions. The morphologies and the resulting physical properties of such systems will be presented, especially the influence of epitaxial interfaces on the adhesion of polymer laminates and the mechanical properties of epitaxially crystallized sandwiched layers.Materials used were polyethylene, PE, Lupolen 6021 DX (HDPE) and 1810 D (LDPE) from BASF AG; polypropylene, PP, (PPN) provided by Höchst AG and polybutene-1, PB-1, Vestolen BT from Chemische Werke Hüls. Thin oriented films were prepared according to the method of Petermann and Gohil, by winding up two different polymer films from two separately heated glass-plates simultaneously with the help of a motor driven cylinder. One double layer was used for TEM investigations, while about 1000 sandwiched layers were taken for mechanical tests.

Approaches for TEM imaging of cavitation in toughened nylon

1989 ◽  
Vol 47 ◽  
pp. 352-353
Author(s):  
Barbara A. Wood
Keyword(s):  
Morphological Characteristics ◽  
Structure Property ◽  
Polymer Systems ◽  
Selective Staining ◽  
Structure Property Relationships ◽  
Rubber Toughened ◽  
Shear Yield ◽  
Controversial Topic ◽  
Selection Of ◽  
Diamond Knife

A controversial topic in the study of structure-property relationships of toughened polymer systems is the internal cavitation of toughener particles resulting from damage on impact or tensile deformation.Detailed observations of the influence of morphological characteristics such as particle size distribution on deformation mechanisms such as shear yield and cavitation could provide valuable guidance for selection of processing conditions, but TEM observation of damaged zones presents some experimental difficulties.Previously published TEM images of impact fractured toughened nylon show holes but contrast between matrix and toughener is lacking; other systems investigated have clearly shown cavitated impact modifier particles. In rubber toughened nylon, the physical characteristics of cavitated material differ from undamaged material to the extent that sectioning of heavily damaged regions by cryoultramicrotomy with a diamond knife results in sections of greater than optimum thickness (Figure 1). The detailed morphology is obscured despite selective staining of the rubber phase using the ruthenium trichloride route to ruthenium tetroxide.

Catalyst Halogenation Enables Rapid and Efficient Polymerizations with Visible to Near-Infrared Light

2020 ◽  
Author(s):  
Alex Stafford ◽  
Dowon Ahn ◽  
Emily Raulerson ◽  
Kun-You Chung ◽  
Kaihong Sun ◽  
...  
Keyword(s):  
Near Infrared ◽  
Transient Absorption ◽  
Reaction Times ◽  
Infrared Light ◽  
Structure Property ◽  
Light Emitting ◽  
Structure Property Relationships ◽  
Nir Light ◽  
Light Intensities ◽  
Emission Quenching

Driving rapid polymerizations with visible to near-infrared (NIR) light will enable nascent technologies in the emerging fields of bio- and composite-printing. However, current photopolymerization strategies are limited by long reaction times, high light intensities, and/or large catalyst loadings. Improving efficiency remains elusive without a comprehensive, mechanistic evaluation of photocatalysis to better understand how composition relates to polymerization metrics. With this objective in mind, a series of methine- and aza-bridged boron dipyrromethene (BODIPY) derivatives were synthesized and systematically characterized to elucidate key structure-property relationships that facilitate efficient photopolymerization driven by visible to NIR light. For both BODIPY scaffolds, halogenation was shown as a general method to increase polymerization rate, quantitatively characterized using a custom real-time infrared spectroscopy setup. Furthermore, a combination of steady-state emission quenching experiments, electronic structure calculations, and ultrafast transient absorption revealed that efficient intersystem crossing to the lowest excited triplet state upon halogenation was a key mechanistic step to achieving rapid photopolymerization reactions. Unprecedented polymerization rates were achieved with extremely low light intensities (< 1 mW/cm<sup>2</sup>) and catalyst loadings (< 50 μM), exemplified by reaction completion within 60 seconds of irradiation using green, red, and NIR light-emitting diodes.

Sign in / Sign up

Export Citation Format

Share Document