Cooperative Effects in Strained Polymeric Networks

1989 ◽  
Vol 177 ◽  
Author(s):  
B Deloche ◽  
P Sotta ◽  
J Herz
Keyword(s):  
Detailed Analysis ◽  
Polymer Network ◽  
Orientational Order ◽  
Uniaxial Stress ◽  
Experimental Fact ◽  
Cooperative Effects ◽  
Polymeric Networks ◽  
Orientational Interactions ◽  
Segmental Motions

ABSTRACTThe orientational order generated in a polymer network by an uniaxial stress is probed with NMR. The experiments are performed on an end-linked polydimethylsiloxane network. When a uniaxial force is applied a detailed analysis of the spectrum shows that the segmental motions become uniaxial around constraint direction. This experimental fact is explained by shortrange orientational interactions between chain segments.

Orientational order induced by a polymer network in the isotropic phase of liquid crystal

2020 ◽  
Vol 101 (5) ◽  
Author(s):  
V. Sergan ◽  
T. Sergan ◽  
I. Dozov ◽  
S. Joly ◽  
R. Voss
Keyword(s):  
Liquid Crystal ◽  
Polymer Network ◽  
Orientational Order ◽  
Isotropic Phase

A Novel Polymer Patterning Method based on Pattern Forming States of Liquid Crystals as Templates

2001 ◽  
Vol 709 ◽  
Author(s):  
Shin-Woong Kang ◽  
Samuel Sprunt ◽  
Liang-Chy Chien
Keyword(s):  
Liquid Crystals ◽  
Electric Field ◽  
Polymer Network ◽  
Orientational Order ◽  
Polymer Networks ◽  
Optical Cell ◽  
Uv Illumination ◽  
Patterning Technique ◽  
Pattern Forming ◽  
Third Dimension

ABSTRACTWe describe a new polymer patterning technique that produces controllable morphological and optical anisotropy in a polymer network. This technique is based on the use of pattern-forming states of nematic and cholesteric liquid crystals as templates for forming ordered polymer networks. One and two-dimensional optical patterns are induced by applying an electric field across a narrow gap of an electro-optical cell. These field-induced optical patterns are then stabilized by UV-induced polymerization of a typically 5 wt% reactive monomer in liquid crystal host. Depending on specific conditions (e.g., thickness to pitch ratio of a cholesteric, applied electric field, and wavelength of UV illumination), the polymer captures various degrees of the orientational order and spatial periodicity of the pattern-forming states of liquid crystals. The fidelity of the templating effect is explored using polarizing optical microscopy and SEM. We also describe the effect of UV wavelength on the network morphology and the morphological control over the”third” dimension (normal to the cell substrates).

scholarly journals Captured Orientational Order in Polymer Network Assemblies

1995 ◽  
Vol 5 (1) ◽  
pp. 8-11
Author(s):  
Gregory P. Crawford ◽  
William Doane ◽  
Slobodan Zumer
Keyword(s):  
Polymer Network ◽  
Orientational Order

2H NMR Study of Deformed Natural Rubber Networks

2008 ◽  
Vol 587-588 ◽  
pp. 687-691
Author(s):  
J. Alexandre ◽  
M.R. Marvão ◽  
G. Feio
Keyword(s):  
Natural Rubber ◽  
Molecular Model ◽  
Orientational Order ◽  
Uniaxial Stress ◽  
H Nmr ◽  
Uniaxial Elongation ◽  
Nmr Study ◽  
Link Density ◽  
Cross Link Density ◽  
Probe Head

The orientational order generated in a cross-linked elastomer by uniaxial stress is probed with deuterium NMR spectroscopy. Spectra of technical unfilled natural rubber (NR) vulcanisates (cis-1,4-polyisoprene), locally swelled with o-dichlorobenzene-d4, exhibits quadrupolar doublets under elongation, which have an explicit dependence on the extension ratio and cross-link density. A new mechanical device was designed to fit into an NMR probe-head to permit the elongation of the networks in the interior of the magnet without removal of the sample thus avoiding the effect of the relaxation of the network chains after each step of uniaxial elongation and the observation of always the same section of the stretched sample. A molecular model of rubber elasticity was applied to describe the behavior of rubber network in mechanical and NMR experiments.

Internal surface, orientational order, and distribution of a polymer network in a liquid crystal matrix

1995 ◽  
Vol 52 (2) ◽  
pp. R1273-R1276 ◽  
Author(s):  
G. P. Crawford ◽  
A. Scharkowski ◽  
Y. K. Fung ◽  
J. W. Doane ◽  
S. Zumer
Keyword(s):  
Liquid Crystal ◽  
Polymer Network ◽  
Orientational Order ◽  
Internal Surface ◽  
Crystal Matrix ◽  
Liquid Crystal Matrix

Monte Carlo Simulations of the Orientational Order in a Strained Polymer Network: Effect of Density

1995 ◽  
Vol 28 (21) ◽  
pp. 7208-7214 ◽  
Author(s):  
P. Sotta ◽  
P. G. Higgs ◽  
M. Depner ◽  
B. Deloche
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Polymer Network ◽  
Orientational Order ◽  
Network Effect

Method for Structural Characterization of High Polymeric Networks by an Osmotic Pressure Technique

1968 ◽  
Vol 41 (2) ◽  
pp. 432-436
Author(s):  
R. D. Seeley ◽  
P. B. Rand
Keyword(s):  
Molecular Weight ◽  
Osmotic Pressure ◽  
Polymer Network ◽  
Polymeric Materials ◽  
Polymer Systems ◽  
Polymeric Networks ◽  
A Value ◽  
Solvent Systems ◽  
Solute Component

Abstract An apparatus was designed to measure the osmotic pressure of solvent-polymer systems. The method is unique in that semirigid polymers may be incorporated as the solute component without specimen fissures occurring from excessive solvent dilative action. The advantages of this technique are: high polymeric materials both elastomeric and plastic can be structurally characterized by the same technique; the calculated effective molecular weight of the polymer network will reflect a value consistent with the polymer's performance characteristics; and the method is only restricted to lyophilic polymer—solvent systems.

scholarly journals Grafting versus Crosslinking of Silk Fibroin-g-PNIPAM via Tyrosine-NIPAM Bridges

Molecules ◽  
2019 ◽  
Vol 24 (22) ◽  
pp. 4096 ◽  
Author(s):  
Ionut-Cristian Radu ◽  
Iuliana-Elena Biru ◽  
Celina-Maria Damian ◽  
Andreea-Cristina Ion ◽  
Horia Iovu ◽  
...  
Keyword(s):  
Silk Fibroin ◽  
Photoelectron Spectroscopy ◽  
Polymer Network ◽  
Chemical Characterization ◽  
Redox System ◽  
Spatial Arrangement ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Polymeric Networks ◽  
Bombyx Mori Silk

This paper reports the synthesis and complex characterization of novel polymeric networks based on the crosslinking of Bombyx mori silk fibroin via poly(N-isopropylacrylamide) bridges generated by an ammonium cerium nitrate redox system. The research study gives an understanding of the polymerization mechanism in terms of the generation of radical sites, radical growth and termination reaction, as well as the involvement of modifications on silk fibroin structure and properties. The physico-chemical characterization was carried out by FTIR-ATR, X-ray photoelectron spectroscopy and RAMAN spectroscopy with unravelling the chemical modification. The structural characterization and spatial arrangement by secondary structure were carried out by X-ray diffraction and circular dichroism. The thermal behavior and thermal stability were evaluated by differential scanning calorimetry and thermogravimetric analysis. The novel complex polymer network is intended to be used in the field of smart drug delivery systems.

Freeze-etch TEM of aqueous polymer gel network morphology

1986 ◽  
Vol 44 ◽  
pp. 796-797
Author(s):  
J. A. N. Zasadzinski ◽  
R. K. Prud'homme
Keyword(s):  
Metal Ion ◽  
Polymer Network ◽  
Polymer Gels ◽  
Polymer Gel ◽  
Deformation History ◽  
Crosslinked Polymer ◽  
Aqueous Polymer ◽  
History Of ◽  
Gel Network ◽  
Network Morphology

The rheological and mechanical properties of crosslinked polymer gels arise from the structure of the gel network. In turn, the structure of the gel network results from: thermodynamically determined interactions between the polymer chain segments, the interactions of the crosslinking metal ion with the polymer, and the deformation history of the network. Interpretations of mechanical and rheological measurements on polymer gels invariably begin with a conceptual model of,the microstructure of the gel network derived from polymer kinetic theory. In the present work, we use freeze-etch replication TEM to image the polymer network morphology of titanium crosslinked hydroxypropyl guars in an attempt to directly relate macroscopic phenomena with network structure.

Prosodic Impairment Associated With Traumatic Brain Injury

2009 ◽  
Vol 19 (3) ◽  
pp. 97-102
Author(s):  
Billy Irwin
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Detailed Analysis ◽  
Acoustic Characteristics ◽  
Individual Variations

Abstract Purpose: This article discusses impaired prosody production subsequent to traumatic brain injury (TBI). Prosody may affect naturalness and intelligibility of speech significantly, often for the long term, and TBI may result in a variety of impairments. Method: Intonation, rate, and stress production are discussed in terms of the perceptual, physiological, and acoustic characteristics associated with TBI. Results and Conclusions: All aspects of prosodic production are susceptible to the effects of damage resulting from TBI. There are commonly associated prosodic impairments; however, individual variations in specific aspects of prosody require detailed analysis.

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