Synthesis and reactions of uniform-size poly(dimethylsiloxanes) having carboxylic acid as a single end group and both end groups

1991 ◽  
Vol 24 (1) ◽  
pp. 122-125 ◽  
Author(s):  
Hideki Kazama ◽  
Yasuyuki Tezuka ◽  
Kiyokazu Imai
Keyword(s):  
Carboxylic Acid ◽  
Uniform Size ◽  
End Groups ◽  
End Group

Stabilization of perfluoropolyethers (PFPEs) with acyl fluoride and carboxylic acid end-groups by UV-irradiation

2019 ◽  
Vol 156 ◽  
pp. 44-49 ◽  
Author(s):  
Saurabh Saxena ◽  
Prateek Malik ◽  
Ajay K. Tyagi ◽  
Geetha Seshadri ◽  
Uttam Kumar Mandal
Keyword(s):  
Carboxylic Acid ◽  
Uv Irradiation ◽  
End Groups

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.

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.

Phase Behavior and Micellar Properties of Carboxylic Acid End Group Modified Pluronic Surfactants

Langmuir ◽  
2007 ◽  
Vol 23 (26) ◽  
pp. 12857-12863 ◽  
Author(s):  
Johan P. A. Custers ◽  
Leo J. P. van den Broeke ◽  
Jos T. F. Keurentjes
Keyword(s):  
Carboxylic Acid ◽  
Phase Behavior ◽  
Micellar Properties ◽  
End Group

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.

Hydrolytic degradation of poly(d,l-lactide) as a function of end group: Carboxylic acid vs. hydroxyl

Polymer ◽  
2006 ◽  
Vol 47 (6) ◽  
pp. 1960-1969 ◽  
Author(s):  
Jeffrey S. Wiggins ◽  
Mohammad K. Hassan ◽  
Kenneth A. Mauritz ◽  
Robson F. Storey
Keyword(s):  
Carboxylic Acid ◽  
Hydrolytic Degradation ◽  
End Group

Diversifying Polyhydroxyalkanoates – End-Group and Side-Chain Functionality

2017 ◽  
Vol 14 (6) ◽  
pp. 757-767 ◽  
Author(s):  
Michal Michalak ◽  
Iwona Kwiecien ◽  
Michal Kwiecien ◽  
Grazyna Adamus ◽  
Karin Odelius ◽  
...  
Keyword(s):  
Functional Groups ◽  
Polymer Chain ◽  
Ring Opening ◽  
Functional Group ◽  
Side Chain ◽  
Natural Origin ◽  
Polymer Formation ◽  
End Groups ◽  
Group Diversity ◽  
End Group

Background: Polyhydroxyalkanoates (PHAs) are a natural origin biodegradable polyesters consisted of various 3- and 4-hydroxyacid derived repeating units produced by microorganisms as energy storage. PHAs have been intensively studied due to their biodegradability and biocompatibility enabling their use both in packaging and agriculture as well as in medicine and pharmacy. PHAs obtained via biotechnological routes can possess various functional groups in their side chains. However, the diversity in their functionality is limited due to issues of conservation of functional groups during the polymer formation. Objective: The review focuses on recent progress in the area of synthesis of PHAs functionalized with various reactive as well as bioactive end and side groups. Conclusion: A potent route to resolve the problem of functional group diversity in natural origin PHAs involves post-polymerization modification, where the desired side groups can be created. On the contrary, synthetically produced PHA analogs obtained directly via ring-opening polymerization of β-lactones offer various functionalities at different position throughout the polymer chain. The desired α- and ω-end groups can be introduced into the polymer chain using specific polymerization, initiation or termination strategies, respectively. The preferred side chain functionality is obtained by choosing the appropriate β-lactone monomers bearing respective functional groups. All functional groups may also be subjected to additional chemical modification. The degradation of PHA as a method for producing functional polymers as well as their possible further applications are also discussed.

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.

Sign in / Sign up

Export Citation Format

Share Document