scholarly journals Polymers with pendant ferrocenes

2016 ◽  
Vol 45 (19) ◽  
pp. 5216-5231 ◽  
Author(s):  
Rudolf Pietschnig
Keyword(s):  
Polymer Chains ◽  
Smart Polymer ◽  
The Difference

Charges make the difference in the arrangement of smart polymer chains and networks.

Chemical Stress Relaxation of NR Networks Prepared in the Swollen State

1986 ◽  
Vol 59 (4) ◽  
pp. 541-550 ◽  
Author(s):  
Kyung-Do Suh ◽  
Hidetoshi Oikawa ◽  
Kenkichi Murakami
Keyword(s):  
Stress Relaxation ◽  
Network Structure ◽  
Three Dimensional ◽  
Polymer Chains ◽  
Chemical Stress ◽  
Network Chain ◽  
Crosslinking Process ◽  
Dimensional Network ◽  
Chemical Relaxation ◽  
The Difference

Abstract From the experimental results of the present investigation, it is apparent that two kinds of networks which have a different three-dimensional network structure give quite different behavior of chemical stress relaxation, even if both networks have the same network chain density. The difference in three-dimensional network structure for the two kinds of rubber arises from the degree of entanglement, which changes with the concentration of the polymer chains prior to the crosslinking process. The direct cause of chemical relaxation is due to the scission of network chains by degradation, whereas the total relaxation is caused by the change of geometrical conformation of network chains. This then casts doubt on the basic concept of chemorheology which is represented by Equation 2.

scholarly journals Isotypic one-dimensional coordination polymers:catena-poly[[dichloridocadmium]-μ-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylato-κ2N5:N6] andcatena-poly[[dichloridomercury(II)]-μ-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylato-κ2N5:N6]

2016 ◽  
Vol 72 (8) ◽  
pp. 1214-1218 ◽  
Author(s):  
Montserrat Alfonso ◽  
Helen Stoeckli-Evans
Keyword(s):  
Hydrogen Bonds ◽  
Metal Ions ◽  
Coordination Polymers ◽  
Rotation Axis ◽  
Dimethyl Ester ◽  
Polymer Chains ◽  
Coordination Geometry ◽  
One Dimensional ◽  
The Difference ◽  
Title One

The isotypic title one-dimensional coordination polymers, [CdCl2(C18H14N4O4)]n, (I), and [HgCl2(C18H14N4O4)]n, (II), are, respectively, the cadmium(II) and mercury(II) complexes of the dimethyl ester of 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylic acid. In both compounds, the metal ions are located on a twofold rotation axis and a second such axis bisects the Car—Carbonds of the pyrazine ring. The metal ions are bridged by binding to the N atoms of the two pyridine rings and have anMN2Cl2bisphenoidal coordination geometry. The metal–Npyrazinedistances are much longer than the metal–Npyridinedistances; the difference is 0.389 (2) Å for the Cd—N bonds but only 0.286 (5) Å for the Hg—N bond lengths. In the crystals of both compounds, the polymer chains are linkedviapairs of C—H...Cl hydrogen bonds, forming corrugated slabs parallel to theacplane.

cAMP sensitive nanochannels driven by conformational transition of a tripeptide-based smart polymer

2020 ◽  
Vol 56 (23) ◽  
pp. 3425-3428
Author(s):  
Shengyan Ji ◽  
Yuting Xiong ◽  
Wenqi Lu ◽  
Minmin Li ◽  
Xue Wang ◽  
...  
Keyword(s):  
Conformational Transition ◽  
Polymer Chains ◽  
Smart Polymer ◽  
Coil Transition ◽  
Opening And Closing

The opening and closing of nanochannels are precisely manipulated by cAMP through globule to coil transition of smart polymer chains.

Effect of Polymer Chains on Heat Transfer on Nanofins

2008 ◽  
Author(s):  
Navdeep Singh ◽  
Debjyoti Banerjee
Keyword(s):  
Carbon Nanotube ◽  
Polymer Chains ◽  
Interfacial Thermal Resistance ◽  
Working Fluid ◽  
Base Temperature ◽  
Equilibration Time ◽  
Interfacial Resistance ◽  
Dynamic Simulations ◽  
The Matrix ◽  
The Difference

Recent experimental results show that precipitation of nanoparticles on heater surfaces can result in heat flux enhancements observed in nanofluids. These precipitated nanoparticles can potentially act as nano-fins. Hence, in this study molecular dynamic simulations are performed to study the interfacial thermal resistance between a nanofin and a working fluid. A (5, 5) carbon nanotube (CNT) of diameter 6.78 Å and various lengths are immersed in various fluids in these analyses. For this simulation the total numbers of the fluid molecules, and the breath and the height of the cell are kept constant. So due to the different densities of the matrix, the length of the cell as well as the length of the nanotube is different for each matrix. In these simulations, the nanotube is placed at the centre of the cell and the fluid molecules surround the nanotube. Periodic boundary conditions are applied in all the directions. So the system under consideration is array of long nanotubes aligned in the horizontal direction. Simulation procedure consists of first minimizing the system. During the minimization the system is allowed to relax. During the simulations, nanotube and water molecules are allowed to move but the cell size remains constant. After minimization, NVT process is performed for 10ps to scale the velocities so that the average temperature of the cell is 300K. After the ensemble is equilibrated to the base temperature of 300K, the temperature of the nanotube is raised to 750K, by scaling the velocities of the carbon atoms. In the next step the system is allowed to relax under constant energy. This is done by performing the NVE equilibration for 10ps. The difference in the temperature of the carbon nanotube and the fluid is then calculated and plotted against the equilibration time. For the CNT-fluid system, the temperature decreases exponentially with time as predicted by various researchers in the literature. From the graphs the interfacial resistance for 1-Hexene, 1,7-Dodecene and 1,7,13-Octadecene is estimated and the effect of polymer chains is investigated.

Sequence Distribution of Polyisoprenes

1976 ◽  
Vol 49 (5) ◽  
pp. 1259-1268 ◽  
Author(s):  
Y. Tanaka ◽  
H. Sato
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Polymer Chains ◽  
Absolute Amount ◽  
Mechanical And Thermal Properties ◽  
13C Nmr Spectra ◽  
Pyrolysis Gas ◽  
Sequence Distribution ◽  
The Difference ◽  
Isomeric Structures

Abstract Isoprene can be polymerized into four types of isomeric structures; cis-1,4, trans-1,4, 3,4, and 1,2, depending on catalysts and polymerization conditions. So far, the difference of mechanical and thermal properties among polyisoprenes has been discussed chiefly on the basis of amounts of these isomeric structures. However, it is quite reasonable to expect that the polymer properties are affected not only by the composition of isomeric structures but also by the distribution of isomeric structures, the arrangement of head and tail linkages, and the degree of branching. This idea was adopted by Hackathorn and Brock as an explanation of the poor crystallizability of lithium polyisoprene; i.e. head-to-head and/or tail-to-tail linkages of 1,4- and 3,4-units prevented the crystallization of the polymer. Pyrolysis-gas chromatography has been applied to the investigation of the sequence distribution of 1,4- and 3,4-units in polyisoprenes. This method is based on the structural relationship between the isoprene dimers and the diad sequences of 1,4- and 3,4-units. However, it is difficult to discuss the slight differences in the yield of each dimer because the absolute amount of the dimers is small (∼30%) compared to the isoprene monomer (∼65%). Ozonolysis has been used to measure the amount of head-to-head, head-to-tail, and tail-to-tail linkages of the 1,4-unit in polyisoprenes. This method, however, is limited to the detection of these linkages of 1,4-units. In a previous paper, we have investigated 13C NMR spectra of chicle and cis-trans isomerized polyisoprenes and determined the sequence distribution of cis-1,4- and trans- 1,4-units in these polymers. We have also studied 13C NMR spectra of hydrogenated polyisoprenes prepared with n-BuLi-Et2O catalysts and found that 1,4- and 3,4-units were distributed randomly along the polymer chains regardless of the amounts of 3,4-units. In the present investigation we prepared various types of polyisoprenes and discussed the distribution of 1,4-and 3,4-units, arrangements of head and tail linkages, the branches of polymer chains, and the tacticity of polyads of 3,4-unit by the use of 13C NMR spectra of hydrogenated polyisoprenes.

Flexibility and Shape of Macromolecules

1963 ◽  
Vol 36 (2) ◽  
pp. 337-350 ◽  
Author(s):  
V. N. Tsvetkov
Keyword(s):  
Solid Phase ◽  
Surrounding Medium ◽  
Chain Structure ◽  
Polymer Chains ◽  
Relaxation Processes ◽  
Geometrical Shape ◽  
Intermolecular Reactions ◽  
The Difference ◽  
Intramolecular Forces

Abstract The main feature of high molecular weight substances is the great size, chain structure and flexibility of the molecules. Investigation of macromolecules flexibility must be regarded as one of the most important tasks in the investigation of the structure of polymers. In the present article we shall deal quite briefly with certain results achieved in this field, which seem to us to be of fundamental importance. The cause of the flexibility of polymeric chains is the existence of a certain freedom of rotation around the valency bonds of the atoms making up the molecule. Nevertheless, this rotation is always more or less hindered by forces which may be either intramolecular (between the atoms of one and the same chain), or else inter-molecular (between atoms of a given chain and their molecules of the surrounding medium). It is possible to a certain extent to separate the influence of these forces from each other, by studying and comparing the properties of macromolecules in solutions (using different solvents) and in the solid phase. Here, nevertheless, we must keep in mind the difference between thermodynamic (equilibrium) and kinetic (nonequilibrium) flexibility of the polymer chain. The deduction of equilibrium flexibility is made on the basis of investigation of configurations (the dimensions and geometrical shape) of macromolecules in solution in the statistically equilibrium state; and of the kinetic, on the basis of investagation of the rate of the processes which convert the macromolecules from one equilibrium configuration to another. The vast majority of experimental work dealing with the determination of kinetic flexibility has been carried out for polymers in bulk (mechanical and dielectric relaxation processes). In this case the influence of the intermolecular reactions is just as great as that of the intramolecular forces, and therefore it is very difficult to separate these two effects. Therefore at the present time we have at our disposal for the determination of equilibrium flexibility of polymer chains considerably more experimental and theoretical possibilities than is the case for kinetic flexibility.

cAMP-modulated biomimetic ionic nanochannels based on a smart polymer

2019 ◽  
Vol 7 (23) ◽  
pp. 3710-3715 ◽  
Author(s):  
Zhixiang Chen ◽  
Taolei Sun ◽  
Guangyan Qing
Keyword(s):  
Conformational Transition ◽  
Adenosine Monophosphate ◽  
Specific Adsorption ◽  
Polymer Chains ◽  
Smart Polymer

Dynamic gating behaviour of ionic nanochannel is precisely manipulated by cyclic 3′,5′-adenosine monophosphate (cAMP) by taking advantage of reversible conformational transition of the smart polymer chains in response to cAMP specific adsorption, which provides a new idea for developing smart nanochannels regulated by crucial signal-biomolecules.

Physical Adsorption of Polymers on Disordered Filler Surfaces

1995 ◽  
Vol 68 (1) ◽  
pp. 26-36 ◽  
Author(s):  
Gert Heinrich ◽  
Thomas A. Vilgis
Keyword(s):  
Carbon Black ◽  
Physical Adsorption ◽  
Polymer Networks ◽  
Particle Surface ◽  
Configurational Entropy ◽  
Polymer Chains ◽  
Filled Polymer ◽  
Fractal Surfaces ◽  
The Difference ◽  
Surface Dimension

Abstract The problem of polymer adsorption on carbon black surfaces is considered within the concept of disorder-induced localization of polymer chains on disordered or fractal surfaces. The model describes how physical adsorption properties are enhanced compared to the adsorption on a flat surface. The difference is based on the configurational entropy which is less restricted in the disordered case than in the flat case. In fact, the surface of the carbon black particles is disordered over certain length scales and several experimental techniques have shown that the particle surface is fractal. This fractal nature can be quantified by the surface spectral density and the noninteger fractal surface dimension. As a main consequence, the coupling between filler and polymer is caused by entanglements formed between tightly adsorbed bound rubber on the filler surface and the bulk rubber far removed from the surface. The corresponding density of couples is estimated for several filled polymer networks using tensile test results. The stress-strain relations used are based on a new rigorous molecular-statistical model of filled polymer networks with quenched topology that includes the entanglements within the mobile rubber phase (configurational tube-model).

A thermocouple method of following the non-stationary state of chemical reactions V. The evaluation of velocity coefficients for the propagation and termination reactions for the heterogeneous polymerization of acrylonitrile

1961 ◽  
Vol 260 (1301) ◽  
pp. 205-217 ◽  
Keyword(s):  
Stationary State ◽  
Bulk Polymerization ◽  
Polymer Chains ◽  
Polymerization Reaction ◽  
Kinetic Chain ◽  
A Value ◽  
Thermocouple Method ◽  
The Difference ◽  
Made In

An attempt has been made to evaluate the velocity coefficients for the propagation and termination reactions in the bulk polymerization of acrylonitrile using the thermocouple non-stationary-state method. The reaction has been studied at 25 °C, and 1. 1'-azo-bis- cyclo -hexane carbonitrile has been employed as a photosensitizer. In the very early stages of the reaction (< 0.1 % conversion) when there is very little dead polymer present, the intensity exponent is 0.5, which indicates that the termination reaction proceeds by the interaction of growing polymer chains. The values obtained for the propagation and termination velocity coefficients (namely, 52 and 5.0 × 10 6 1. mole -1 s- 1, respectively) are lower than those reported in the literature for the polymerization of acrylonitrile in dimethylformamide solution. The difference has been attributed to environmental factors. Measurements of rates and lifetimes of the kinetic chain have also been made in the region of 1 to 7% conversion. By means of a suitably designed dilatometer which could be centrifuged, the effects of polyacrylonitrile on the polymerization reaction was studied. It was shown that the presence of polymer produced an enormous increase in the lifetime of the kinetic chain, while the rate decreased a little probably due to the scattering of initiating irradiation by the precipitated polymer. The intensity exponent appeared to increase to a value of 0.7, but this may not have been a true effect, as errors in the determination of the rate may have arisen due to difficulties in maintaining adiabatic conditions throughout the non-stationary state. The results in general are in keeping with the occlusion theory suggested by previous workers to explain some peculiar characteristics of the bulk polymerization of acrylonitrile.

The Influence of Glass-Transition Temperatures of Poly (Ethylene Terephthalate) Films on the Fading Behavior of Fluorescent Brightening Agents

1977 ◽  
Vol 47 (5) ◽  
pp. 361-364 ◽  
Author(s):  
Keiko Suganuma
Keyword(s):  
Glass Transition ◽  
Physical State ◽  
Polymer Chains ◽  
Transition Temperatures ◽  
Segmental Mobility ◽  
Heat Setting ◽  
Glass Transition Temperatures ◽  
The Difference ◽  
Poly Ethylene ◽  
Pet Films

Studies have been made of the dependence of the fading behavior of dispersed-type fluorescent brightening agents in poly (ethylene tetrephthalate) (PET) films on the temperature at which the films have been heat-set and dyed. A measure of the variation in the fading behavior can be given by parameter A, defined as k2 (1st-order)ɛ/ k2' (2nd-order), as in Hida's equation. This constant decreases with increase in the temperatures of heat-setting and dyeing of PET films. And the rate of fading increases with increase in these temperatures. It is found that the physical state of adsorbed dye on PET films varies with these temperatures. The glass-transition temperatures Tg of heat-set PET films were measured. Tg decreases with increase in the heat-setting temperature. The values of parameter A are related to the difference between the dyeing temperature and Tg ( T — Tg), and so the physical state of adsorbed dye on PET films is considered to be governed by the segmental mobility of polymer chains during dyeing. The variation of the rate of fading and parameter A with the dyeing and heat-setting temperatures of PET films might be explained in terms of the additional free volume.

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