Search results for "MOLECULE"
showing 10 items of 5162 documents
UV optical record and electron beam lithography in polymer films
2012
Possibility of UV optical record and electron beam lithography in different type of organic polymer films was studied. Mechanisms of molecular structure changes: photoisomerization, destruction, cross-linking and oxidation have been discussed. The results of UV illumination of polyurethanes, polyacrilates, and some block-copolymers are described. The element analysis of polyisoprene block copolymer was performed before and after UV illumination, and the changes in transmission spectra of the polymer film were measured. The resolution of electron beam lithography on polymer films was studied. In the polyisoprene block copolymer film the oxidation polymerization was ascertain at UV-illuminati…
Simulations of Polymers in Confined Geometries
1991
The properties of flexible polymers moving inside porous structures are believed to be relevant to practical problems such as filtration, gel permeation chromatography, heterogeneous catalysis, oil recuperation, etc.1. Similarly the adsorption of macromolecules on interfaces plays an important role for problems such as adhesion, flocculation and stabilisation of colloid particles, biological membrane function, artificial organs in medicine, etc. 2. Aside from this eventual practical application, the configurational statistics of polymers in such confined geometries is a challenging problem of theoretical physics. The present brief review will be concerned with the study of a single long fle…
Discotic liquid crystals at the air water interface
1991
The monolayer properties of two types of discotic liquid crystals, hexasubstituted triphenylenes 1 and azo derivatives of phloroglucinol 5, were examined. First investigations show that these discotic liquid crystals form stable monolayers. It could be shown that electron acceptors insert into the monolayer of 1. Azo discs display a packing behaviour at the monolayer that is ascribed to a side-on packing of the molecules.
Large Scale Fractionation of Macromolecules
2004
Access to sufficiently large amounts of material with adequate molecular and chemical uniformity from polydisperse natural products or synthetic materials has been a long-standing challenge to polymer scientists. We have developed a broadly applicable preparative fractionation method consisting of a special kind of continuous extraction removing the easier soluble components from the initial product. It is rendered possible by the use of spinning nozzles throught which a concentrated polymer solution is pressed into a liquid of tailored thermodynamic quality. The initially produced jets of the source phase disintegrate rapidly into minute droplets of typically 50 μm diameter. This efficient…
Controlled Synthesis of Linear Polymers with Highly Branched Side Chains by “Hypergrafting”: Poly(4-hydroxy styrene)-graft-hyperbranched Polyglycerol
2012
Linear polymers with hyperbranched side chains are unusual macromolecular structures due to their high number of functional groups in the side chains as well as their potential cylindrical conformation in bulk or solution. In a three-step synthesis combining anionic and oxy-anionic polymerization, hyperbranched polyglycerol was “hypergrafted” from linear poly(4-hydroxy styrene) macroinitiators to yield poly(4-hydroxy styrene)-graft-hyperbranched polyglycerol. Successful grafting with control over molecular weight (10–31 kg·mol–1) and low PDIs (<1.4) was shown by various characterization techniques. All polymers have a high side chain density, due to rapid transfer of the initiating function…
Specialty and advanced polymers by carbocationic macromolecular engineering
1993
This study briefly surveys a variety of new advanced polymeric materials and controlled synthetic processes available by carbocationic macromolecular engineering techniques and having potential commercial interest. These recent developments, mainly by living carbocationic polymerization, have led to new opportunities in polymerization process control, and in designing microstructure, functionality, molecular weight and molecular weight distribution (MWD) and thus properties of a wide variety of unique polymer systems. The fundamentals of these new emerging technologies and the novel materials offered by them, such as macromonomers, telechelics, polymers with pendant functional groups (liqui…
Polymer-polymer interaction parameters in solvent/polymer/polymer ternary systems
1981
Abstract Empirical equations defining the relationships between b23 and χ23 interaction parameters for the ternary systems toluene (1)/poly(dimethylsiloxane), PDMS, (2)/polystyrene, PS, (3) and benzene (1)/PDMS(2)/PS(3) have been determined. The dependences of both interaction parameters on the mean molecular weights of the macromolecular components have also been studied. A single dependence of b23 (or χ23) upon the mean molecular weight is found when both polymeric components have intermediate to high molecular weights. However, that single dependence is not found when the molecular size of polymer (2) is low.
The effect of macromolecular architecture of ethylene copolymers with multi-alkenylsilsesquioxane on morphological, rheological and dynamic mechanica…
2021
Abstract The influence of the degree and the way of incorporation of multi-alkenylsilsesquioxane into the polymer chain on morphological, rheological and dynamic mechanical parameters were determined. It was found that POSS incorporated into the polymer chain was located outside the crystalline structure of lamella in amorphous phase. The incorporation of POSS-6-2 as a pendant group resulted in significant increase of separation of macromolecules. The key factor in rheological and dynamic mechanical behavior of copolymers turned out to be the way of POSS incorporation into the polymer chain. The incorporation of POSS into the polymer chain as a pendant group resulted in decreased relaxation…
Some linear and branched macromolecules by ring-opening polymerization
1993
In the first part the ring-opening polymerization of some macrocyclic ether-acetals is briefly described. Of special interest are acetal polymers with functional groups, for instance C=C-double bonds. Appropriate unsaturated monomers and their polymerizability are discussed. The second part deals with the polymerization of oxazolines, substituted in 2- and/or 4-position. Branched polymers are obtained by copolymerization of 2-ethyl-2-oxazoline with 2-hexyl-2-oxazoline or 2-undecyl-2-oxazoline. The properties of the random copolymers and corresponding block copolymers are compared. By a “mixed mechanism technique” a block copolymer composed of a poly(tert -butyl methacrylate) block and a pol…
Some photochemical transformations of polymers
1969
Abstract Several light-induced reactions of polymers are described. The light-sensitive groups are part of the macromolecules. Photoisomerization of polyvinylbutyral produces a polymer with vinylbutyrate-groups. At exposure to light, furan and benzofuran are added to the carbonyl-groups of polyvinylbenzophenone. Polymers with azido-groups are prepared, which eliminate nitrogen at irradiation. Light-sensitive films can be cast from polymers with o-quinonediazide-groups.