Scaling Theory for End-Functionalized Polymers Confined Between Two Surfaces

2000 ◽  
Vol 629 ◽  
Author(s):  
Dmitri V. Kuznetsov ◽  
Anna C. Balazs
Keyword(s):  
Adsorption Energy ◽  
Volume Fraction ◽  
Scaling Theory ◽  
Functionalized Polymers ◽  
Equilibrium Behavior ◽  
Planar Surfaces ◽  
End Groups ◽  
Chain Lengths ◽  
End Group ◽  
Infinite Planar

ABSTRACTUsing scaling theory, we determine the equilibrium behavior of a melt of functionalized and non-functionalized polymers confined between two infinite, planar surfaces, which model clay sheets. The functionalized chains contain two end-groups (one at each chain-end) that are highly attracted to the surfaces. Through these calculations, we delineate the conditions for the formation of thermodynamically stable polymer/clay mixtures in terms of the end-group adsorption energy, volume fraction of the end-functionalized chains, and polymer chain lengths.

Macromolecular Engineering by Carbocationic Techniques: New Polymers That Contain Elastomeric Sequences

1983 ◽  
Vol 56 (3) ◽  
pp. 639-663 ◽  
Author(s):  
Joseph P. Kennedy
Keyword(s):  
Diblock Copolymers ◽  
Functionalized Polymers ◽  
Head Group ◽  
Key Concepts ◽  
Ultimate Properties ◽  
End Groups ◽  
Disturbed Systems ◽  
Dynamic Techniques ◽  
Continuous Feeding ◽  
End Group

Abstract The aim of this review was to outline some key concepts the macromolecular engineer can utilize in the task of assembling useful polymers. In addition to useful ultimate properties, convenient processing characteristics are also an important consideration. The way toward these objectives is by skillful combination of elementary events—by exploiting the mechanistic understanding of initiation, propagation, and termination processes. Tables V and VI summarize the processes surveyed and outlines the structures of macromolecules that can be synthesized by utilizing carbocationic macromolecular engineering. Table V summarizes the “Undisturbed” Systems i.e., systems in which only the monomer, initiator and coinitiator appear. Table VI shows the “Disturbed” Systems, i.e., systems in which, in addition to the three main species, others, such as proton traps or inifers, also appear. The Undisturbed Systems are further subdivided into Static and Dynamic (or Continuous) Techniques. Static methods use batch operations while dynamic techniques use continuous feeding of monomer(s). The flow of the examples from the top of Table V to the bottom of Table VI is by increasing complexities of the manipulations involved. Thus, the tables start with examples of materials whose synthesis requires only controlled initiation. In other words, controlled initiation alone will give rise to head-functionalized polymers (H = head group) or macromers or gTaft copolymers or bigrafts. for the materials in the second group of Table V, end-functionalized polymers (E = end group) or certain graft copolymers, only termination control is needed. Next, to prepare polymers whose head and end groups are tailor made, the macromolecular engineer has to combine controlled initiation plus termination. The same is true for grafts whose branches carry designed end groups. Combination of controlled termination plus initiation yields diblock copolymers.

Rotationsbarriere der Endgruppen bei Poly- methinoxonolen verschiedener Kettenlänge / Rotation Barrier of the End Groups of Polymethine Oxonols with Different Chain Lengths

1976 ◽  
Vol 31 (8) ◽  
pp. 1017-1018 ◽  
Author(s):  
H. Oehling ◽  
F. Baer
Keyword(s):  
Nmr Spectra ◽  
Rotation Barrier ◽  
Free Enthalpy ◽  
Temperature Dependent ◽  
Restricted Rotation ◽  
H Nmr ◽  
Enthalpy Of Activation ◽  
End Groups ◽  
Electron Contribution ◽  
Chain Lengths

Abstract Polymethine oxonols show temperature dependent 1H-NMR-spectra because of restricted rotation of the end groups. The dependence of the value of the corresponding free enthalpy of activation AGt on the length of the poly-methine chain can be explained by the change of the π-electron contribution to ⊿G≠.

scholarly journals Microbubbles Decorated with Dendronized Magnetic Nanoparticles for Biomedical Imaging. Effective Stabilization via Fluorous Interactions

2019 ◽  
Author(s):  
Da Shi ◽  
Justine Wallyn ◽  
Dinh-Vu Nguyen ◽  
Francis Perton ◽  
Delphine Felder-Flesch ◽  
...  
Keyword(s):  
Molar Ratio ◽  
Aqueous Dispersions ◽  
Force Microscopy ◽  
Atomic Force ◽  
Microscopy Investigation ◽  
End Groups ◽  
Mixed Films ◽  
Effective Stabilization ◽  
Effective Result ◽  
End Group

Dendrons fitted with three oligoethylene glycol (OEG) chains, one of which carrying a fluorinated or hydrogenated end group, and bearing a bisphosphonate polar head (C n X2 n +1OEG8Den, X = F or H; n= 2 or 4) were synthesized and grafted on the surface of iron oxide nanoparticles (IONPs) for microbubble-mediated imaging and therapeutic purposes. The size and stability of the dendronized IONPs (IONP@C n X2 n +1OEG8Den) in aqueous dispersions were monitored by dynamic light scattering. Investigation of the spontaneous adsorption of IONP@C n X2 n +1OEG8Den at the interface between air - or air saturated with perfluorohexane - and an aqueous phase establishes that exposure to the fluorocarbon gas markedly increases the rate of adsorption of the dendronized IONPs to the gas/water interface and decreases the equilibrium interfacial tension. This suggests that fluorous interactions are at play between the supernatant fluorocarbon gas and the fluorinated end groups of the dendrons. Furthermore, small, stable perfluorohexane-stabilized microbubbles (MBs) with a dipalmitoylphosphatidylcholine (DPPC) shell that incorporates IONP@C n X2 n +1OEG8Den (DPPC/Fe molar ratio 28:1) were prepared and characterized using both optical microscopy and an acoustical method of size determination. The dendrons fitted with fluorinated end groups lead to smaller and more stable MBs than those fitted with hydrogenated groups. The most effective result is already obtained with C2F5, for which MBs, ~1.0mm in radius, reach a half-life of ~6.0 h. An atomic force microscopy investigation of spin-coated mixed films of DPPC/IONP@C2X5OEG8Den combinations (molar ratio 28:1) shows that the IONPs grafted with the fluorinated dendrons are located within the phospholipid film, while those grafted with the hydrocarbon dendrons are completely absent from the phospholipid film.

Scaling of Complex Conductivity for A Percolating Metal-Insulator Composite with Inter granular Tunneling Above and Below the Superconducting Transition

1995 ◽  
Vol 411 ◽  
Author(s):  
D. S. Mclachlan ◽  
A. B. Pakhomov ◽  
I. I. Oblachova ◽  
F. Brouers ◽  
A. Sarychev
Keyword(s):  
Volume Fraction ◽  
Frequency Dispersion ◽  
Scaling Theory ◽  
Complex Conductivity ◽  
Superconducting Transition ◽  
Percolation Transition ◽  
Metal Insulator ◽  
Metal Volume ◽  
Metal Volume Fraction ◽  
Composite Samples

ABSTRACTThe complex conductivity was measured on 3d granular NbC-KCI composite samples at varying metal volume fraction p, frequency ω and temperature above and below the superconductivity critical Tc. The observed frequency dispersion is anomalous in that it is not in accord with the scaling theory of percolation transition. The results are compared with a recently developed scaling theory, which takes both intercluster tunneling and intercluster capacitance into account. The experimental estimates for the new critical exponents are in reasonable agreement with the theory. The very low value of the crossover frequency can also be understood. We also present the data showing the dispersion of the complex conductivity well below the superconducting transition Tc of NbC.

Functionalized Polymers with Dimethylamine and Sulfozwitterionic End-Groups

1998 ◽  
pp. 96-120
Author(s):  
Nikos Hadjichristidis ◽  
Marinos Pitsikalis ◽  
Stergios Pispas
Keyword(s):  
Functionalized Polymers ◽  
End Groups

scholarly journals The nature of the 5'-linked 5' nucleotide sequence at the 5' end of rabbit globin messenger ribonucleic acid

1976 ◽  
Vol 155 (3) ◽  
pp. 637-644 ◽  
Author(s):  
J A Hunt ◽  
G N Oakes
Keyword(s):  
Messenger Rna ◽  
Periodate Oxidation ◽  
Hydroxyl Group ◽  
Globin Mrna ◽  
Pancreatic Ribonuclease ◽  
Phosphodiester Bond ◽  
Messenger Ribonucleic Acid ◽  
End Groups ◽  
A Charge ◽  
End Group

Poly(A)-containing messenger RNA isolated from rabbit reticulocytes as estimated by periodate oxidation and condensation with [3H]isoniazid has two oxidizable end groups per molecule of mol. wt. 220000. When the mRNA is subjected to stepwise degradation by beta-elimination, only one oxidizable end-group is found. This indicates that one of the 2′,3′ hydroxyl end-groups is linked through the normal 3′-5′ phosphodiester bond, but that the other is linked in such a way that after stepwise degradation no new 2′,3 hydroxyl group is revealed. This structure could be a 5′-linked 5′-phospho di- or tri-ester. On digestion with ribonuclease the isoniazid-labelled RNA produced oligonucleotide hydrazones consistent with a poly(A) sequence at the 3′ end plus fragments that are not found after stepwise degradation. These fragments have a charge of -6 and -8 from pancreatic ribonuclease or -7 from ribonuclease T1 digestion. These charges are changed to -3.4 and -4.1 after pancreatic ribonuclease, ribonuclease T2 and alkaline phosphatase digestion. methyl-3H-labelled-poly(A)-containing RNA isolated from late erythroid cells contain a methyl-labelled fragment resistant to endonuclease and phosphodiesterase II digestion. After digestion with phosphodiesterase I this fragment produces methyl-3 H-labelled nucleotides with the electrophoretic mobility of pm7G and pAm. It is concluded that globin mRNA has the 5′ sequences m7G(5′)ppp′AmpYpGp ... and m7G(5′)pppAmpApGpYp.

Synthesis and Mesomorphic Properties of New Liquid Crystalline Cyclohexyl-phenyl- and Dicyclohexyl-pyrimidines

1979 ◽  
Vol 34 (11) ◽  
pp. 1535-1541 ◽  
Author(s):  
Alois Villiger ◽  
Arthur Boiler ◽  
Martin Schadt
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Alkyl Chain ◽  
Viscosity Reduction ◽  
Refractive Indices ◽  
Thermal Compatibility ◽  
Chain Lengths ◽  
New Compounds ◽  
Mesomorphic Properties ◽  
End Group

Abstract Liquid Crystals, Cyclohexyl-phenyl-pyrimidines, Dicyclohexyl-pyrimidines The synthesis and mesomorphic properties of three new classes of cyano-substituted cyclohexyl-phenyl-and dicyclohexyl-pyrimidines are reported. The compounds are colourless, chemically and photochemically stable and have wide nematic mesophases. The thermal compatibility of the new compounds with other nematic liquid crystals is excellent. The large static positive dielectric anisotropics are shown to depend strongly on the position and number of hydrogenated rings as well as on the alkyl chain lengths within a homologous series. The reported bulk viscosities vary considerably among homologues. Hydrogenating the ring adjacent to the cyano end group causes η to increase, whereas a considerable viscosity reduction compared to nonhydrogenated homologues was found by hydrogenating the ring adjacent to the alkyl end group. The measured refractive indices of the new compounds are comparable to those of biphenyls.

Brillouin scattering and dielectric relaxation in PPG of different chain lengths and end groups

Polymer ◽  
1999 ◽  
Vol 40 (17) ◽  
pp. 4755-4761 ◽  
Author(s):  
D. Engberg ◽  
J. Schüller ◽  
B. Strube ◽  
A.P. Sokolov ◽  
L.M. Torell
Keyword(s):  
Dielectric Relaxation ◽  
Brillouin Scattering ◽  
End Groups ◽  
Chain Lengths

Spreading Characteristics of Molecularly Thin Lubricant on Surfaces With Groove-Shaped Textures: Effects of Molecular Weight and End-Group Functionality

2003 ◽  
Vol 125 (2) ◽  
pp. 350-357 ◽  
Author(s):  
Hedong Zhang ◽  
Yasunaga Mitsuya ◽  
Maiko Yamada
Keyword(s):  
Molecular Weight ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Ising Model ◽  
Monte Carlo Simulations ◽  
Simulation Method ◽  
Solid Surfaces ◽  
The Monte Carlo Method ◽  
End Groups ◽  
End Group

Effects of molecular weight and end-group functionality on spreading of molecularly thin perfluoropolyether (PFPE) film over solid surfaces with groove-shaped textures have been studied by experiments and Monte Carlo simulations. In the experiments, lubricant spreading on a surface with groove-shaped textures was measured by making use of the phenomenon in which diffracted light weakens in the lubricant-covered region. It is found that grooves serve to accelerate spreading and this effect increases for deeper grooves, and also the accelerating rate becomes larger for a lubricant having a larger molecular weight or functional end-groups. In the simulations, the Monte Carlo method based on the Ising model was extended to enable us to evaluate the effect of molecular weight on the spreading of non-functional lubricant inside a groove. The validity of the newly developed simulation method was well confirmed from the agreement between the simulation and experimental results.

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